/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
// Portions of this file were originally under the following license:
//
// Copyright (C) 2006-2008 Jason Evans <jasone@FreeBSD.org>.
// All rights reserved.
// Copyright (C) 2007-2017 Mozilla Foundation.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
// notice(s), this list of conditions and the following disclaimer as
// the first lines of this file unmodified other than the possible
// addition of one or more copyright notices.
// 2. Redistributions in binary form must reproduce the above copyright
// notice(s), this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the
// distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
// OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// *****************************************************************************
//
// This allocator implementation is designed to provide scalable performance
// for multi-threaded programs on multi-processor systems. The following
// features are included for this purpose:
//
// + Multiple arenas are used if there are multiple CPUs, which reduces lock
// contention and cache sloshing.
//
// + Cache line sharing between arenas is avoided for internal data
// structures.
//
// + Memory is managed in chunks and runs (chunks can be split into runs),
// rather than as individual pages. This provides a constant-time
// mechanism for associating allocations with particular arenas.
//
// Allocation requests are rounded up to the nearest size class, and no record
// of the original request size is maintained. Allocations are broken into
// categories according to size class. Assuming runtime defaults, the size
// classes in each category are as follows (for x86, x86_64 and Apple Silicon):
//
// |=========================================================|
// | Category | Subcategory | x86 | x86_64 | Mac ARM |
// |---------------------------+---------+---------+---------|
// | Word size | 32 bit | 64 bit | 64 bit |
// | Page size | 4 Kb | 4 Kb | 16 Kb |
// |=========================================================|
// | Small | Quantum-spaced | 16 | 16 | 16 |
// | | | 32 | 32 | 32 |
// | | | 48 | 48 | 48 |
// | | | ... | ... | ... |
// | | | 480 | 480 | 480 |
// | | | 496 | 496 | 496 |
// | |----------------+---------|---------|---------|
// | | Quantum-wide- | 512 | 512 | 512 |
// | | spaced | 768 | 768 | 768 |
// | | | ... | ... | ... |
// | | | 3584 | 3584 | 3584 |
// | | | 3840 | 3840 | 3840 |
// | |----------------+---------|---------|---------|
// | | Sub-page | - | - | 4096 |
// | | | - | - | 8 kB |
// |=========================================================|
// | Large | 4 kB | 4 kB | - |
// | | 8 kB | 8 kB | - |
// | | 12 kB | 12 kB | - |
// | | 16 kB | 16 kB | 16 kB |
// | | ... | ... | - |
// | | 32 kB | 32 kB | 32 kB |
// | | ... | ... | ... |
// | | 1008 kB | 1008 kB | 1008 kB |
// | | 1012 kB | 1012 kB | - |
// | | 1016 kB | 1016 kB | - |
// | | 1020 kB | 1020 kB | - |
// |=========================================================|
// | Huge | 1 MB | 1 MB | 1 MB |
// | | 2 MB | 2 MB | 2 MB |
// | | 3 MB | 3 MB | 3 MB |
// | | ... | ... | ... |
// |=========================================================|
//
// Legend:
// n: Size class exists for this platform.
// -: This size class doesn't exist for this platform.
// ...: Size classes follow a pattern here.
//
// A different mechanism is used for each category:
//
// Small : Each size class is segregated into its own set of runs. Each run
// maintains a bitmap of which regions are free/allocated.
//
// Large : Each allocation is backed by a dedicated run. Metadata are stored
// in the associated arena chunk header maps.
//
// Huge : Each allocation is backed by a dedicated contiguous set of chunks.
// Metadata are stored in a separate red-black tree.
//
// *****************************************************************************
#include "mozmemory_wrap.h"
#include "mozjemalloc.h"
#include "mozjemalloc_types.h"
#include "mozjemalloc_profiling.h"
#include <bit>
#include <cstring>
#include <cerrno>
#include <chrono>
#ifdef XP_WIN
# include <io.h>
# include <windows.h>
#else
# include <sys/mman.h>
# include <unistd.h>
#endif
#ifdef XP_DARWIN
# include <libkern/OSAtomic.h>
# include <mach/mach_init.h>
# include <mach/vm_map.h>
#endif
#include "mozilla/Atomics.h"
#include "mozilla/Assertions.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/DoublyLinkedList.h"
#include "mozilla/HelperMacros.h"
#include "mozilla/Likely.h"
#include "mozilla/Literals.h"
#include "mozilla/MathAlgorithms.h"
#include "mozilla/RandomNum.h"
#include "mozilla/RefPtr.h"
// Note: MozTaggedAnonymousMmap() could call an LD_PRELOADed mmap
// instead of the one defined here; use only MozTagAnonymousMemory().
#include "mozilla/TaggedAnonymousMemory.h"
#include "mozilla/ThreadLocal.h"
#include "mozilla/XorShift128PlusRNG.h"
#include "mozilla/fallible.h"
#include "RadixTree.h"
#include "Arena.h"
#include "BaseAlloc.h"
#include "Chunk.h"
#include "Constants.h"
#include "Extent.h"
#include "Globals.h"
#include "Mutex.h"
#include "PHC.h"
#include "RedBlackTree.h"
#include "Utils.h"
#include "Zero.h"
#if defined(XP_WIN)
# include
"mozmemory_stall.h"
#endif
using
namespace mozilla;
#ifdef MOZJEMALLOC_PROFILING_CALLBACKS
// MallocProfilerCallbacks is refcounted so that one thread cannot destroy it
// while another thread accesses it. This means that clearing this value or
// otherwise dropping a reference to it must not be done while holding an
// arena's lock.
constinit
static RefPtr<MallocProfilerCallbacks> sCallbacks;
#endif
// ***************************************************************************
// MALLOC_DECOMMIT and MALLOC_DOUBLE_PURGE are mutually exclusive.
#if defined(MALLOC_DECOMMIT) &&
defined(MALLOC_DOUBLE_PURGE)
# error MALLOC_DECOMMIT
and MALLOC_DOUBLE_PURGE are mutually exclusive.
#endif
// Set to true once the allocator has been initialized.
#if defined(_MSC_VER) && !
defined(__clang__)
// MSVC may create a static initializer for an Atomic<bool>, which may actually
// run after `malloc_init` has been called once, which triggers multiple
// initializations.
// We work around the problem by not using an Atomic<bool> at all. There is a
// theoretical problem with using `malloc_initialized` non-atomically, but
// practically, this is only true if `malloc_init` is never called before
// threads are created.
static bool malloc_initialized;
#else
// We can rely on Relaxed here because this variable is only ever set when
// holding gInitLock. A thread that still sees it false while another sets it
// true will enter the same lock, synchronize with the former and check the
// flag again under the lock.
static Atomic<
bool, MemoryOrdering::Relaxed> malloc_initialized;
#endif
// This lock must be held while bootstrapping us.
constinit StaticMutex gInitLock MOZ_UNANNOTATED;
// We cannot instantiate
// Atomic<std::chrono::time_point<std::chrono::steady_clock>>
// so we explicitly force timestamps to be uint64_t in ns.
uint64_t GetTimestampNS() {
// On most if not all systems we care about the conversion to ns is a no-op,
// so we prefer to keep the precision here for performance, but let's be
// explicit about it.
return std::chrono::floor<std::chrono::nanoseconds>(
std::chrono::steady_clock::now())
.time_since_epoch()
.count();
}
namespace mozilla {
template <>
struct GetDoublyLinkedListElement<arena_t> {
static DoublyLinkedListElement<arena_t>& Get(arena_t* aThis) {
return aThis->mPurgeListElem;
}
static const DoublyLinkedListElement<arena_t>& Get(
const arena_t* aThis) {
return aThis->mPurgeListElem;
}
};
}
// namespace mozilla
struct ArenaTreeTrait {
static RedBlackTreeNode<arena_t>& GetTreeNode(arena_t* aThis) {
return aThis->mLink;
}
static inline Order Compare(arena_t* aNode, arena_t* aOther) {
MOZ_ASSERT(aNode);
MOZ_ASSERT(aOther);
return CompareInt(aNode->mId, aOther->mId);
}
using SearchKey = arena_id_t;
static inline Order Compare(SearchKey aKey, arena_t* aOther) {
MOZ_ASSERT(aOther);
return CompareInt(aKey, aOther->mId);
}
};
// Bookkeeping for all the arenas used by the allocator.
// Arenas are separated in two categories:
// - "private" arenas, used through the moz_arena_* API
// - all the other arenas: the default arena, and thread-local arenas,
// used by the standard API.
class ArenaCollection {
public:
constexpr ArenaCollection() =
default;
bool Init() MOZ_REQUIRES(gInitLock) MOZ_EXCLUDES(mLock) {
arena_params_t params;
// The main arena allows more dirty pages than the default for other arenas.
params.mMaxDirty = opt_dirty_max;
params.mLabel =
"Default";
mDefaultArena =
mLock.Init() ? CreateArena(
/* aIsPrivate = */ false, ¶ms) : nullptr;
mPurgeListLock.Init();
mIsDeferredPurgeEnabled =
false;
return bool(mDefaultArena);
}
// The requested arena must exist.
inline arena_t* GetById(arena_id_t aArenaId,
bool aIsPrivate)
MOZ_EXCLUDES(mLock);
arena_t* CreateArena(
bool aIsPrivate, arena_params_t* aParams)
MOZ_EXCLUDES(mLock);
void DisposeArena(arena_t* aArena) MOZ_EXCLUDES(mLock) {
// This will not call MayPurge but only unlink the element in case.
// It returns true if we successfully removed the item from the list,
// meaning we have exclusive access to it and can delete it.
bool delete_now = RemoveFromOutstandingPurges(aArena);
{
MutexAutoLock lock(mLock);
Tree& tree =
#ifndef NON_RANDOM_ARENA_IDS
aArena->IsMainThreadOnly() ? mMainThreadArenas :
#endif
mPrivateArenas;
MOZ_RELEASE_ASSERT(tree.Search(aArena->mId),
"Arena not in tree");
tree.Remove(aArena);
mNumOperationsDisposedArenas += aArena->Operations();
}
{
MutexAutoLock lock(aArena->mLock);
if (!aArena->mIsPurgePending) {
// If no purge was pending then we have exclusive access to the
// arena and must delete it.
delete_now = true;
}
else if (!delete_now) {
// The remaining possibility, when we failed to remove the arena from
// the list (because a purging thread alredy did so) then that thread
// will be the last thread holding the arena and is now responsible for
// deleting it.
aArena->mMustDeleteAfterPurge = true;
// Not that it's not possible to have checked the list of pending purges
// BEFORE the arena was added to the list because that would mean that
// an operation on the arena (free or realloc) was running concurrently
// with deletion, which would be a memory error and the assertions in
// the destructor help check for that.
}
}
if (delete_now) {
delete aArena;
}
}
void SetDefaultMaxDirtyPageModifier(int32_t aModifier) {
{
MutexAutoLock lock(mLock);
bool decreased = aModifier < mDefaultMaxDirtyPageModifier;
mDefaultMaxDirtyPageModifier = aModifier;
for (
auto* arena : iter()) {
// We can only update max-dirty for main-thread-only arenas from the
// main thread.
if (!arena->IsMainThreadOnly() || IsOnMainThreadWeak()) {
arena->UpdateMaxDirty();
if (decreased) {
purge_action_t action;
{
MaybeMutexAutoLock arena_lock(arena->mLock);
action = arena->ShouldStartPurge();
}
arena->MayDoOrQueuePurge(action,
"SetDefaultMaxDirtyPageModifier");
}
}
}
}
}
int32_t DefaultMaxDirtyPageModifier() {
return mDefaultMaxDirtyPageModifier; }
using Tree = RedBlackTree<arena_t, ArenaTreeTrait>;
class Iterator {
public:
explicit Iterator(Tree* aTree, Tree* aSecondTree,
Tree* aThirdTree = nullptr)
: mFirstIterator(aTree),
mSecondTree(aSecondTree),
mThirdTree(aThirdTree) {}
class Item {
private:
Iterator& mIter;
arena_t* mArena;
public:
Item(Iterator& aIter, arena_t* aArena) : mIter(aIter), mArena(aArena) {}
bool operator!=(
const Item& aOther)
const {
return mArena != aOther.mArena;
}
arena_t*
operator*()
const {
return mArena; }
const Item&
operator++() {
mArena = mIter.Next();
return *this;
}
};
Item begin() {
// If the first tree is empty calling Next() would access memory out of
// bounds, so advance to the next non-empty tree (or last empty tree).
MaybeNextTree();
return Item(*this, mFirstIterator.Current());
}
Item end() {
return Item(*this, nullptr); }
private:
Tree::Iterator mFirstIterator;
Tree* mSecondTree;
Tree* mThirdTree;
void MaybeNextTree() {
while (!mFirstIterator.NotDone() && mSecondTree) {
mFirstIterator = mSecondTree->iter();
mSecondTree = mThirdTree;
mThirdTree = nullptr;
}
}
arena_t* Next() {
arena_t* arena = mFirstIterator.Next();
if (arena) {
return arena;
}
// Advance to the next tree if we can, if there's no next tree, or the
// next tree is empty then Current() will return nullptr.
MaybeNextTree();
return mFirstIterator.Current();
}
friend Item;
};
Iterator iter() MOZ_REQUIRES(mLock) {
#ifdef NON_RANDOM_ARENA_IDS
return Iterator(&mArenas, &mPrivateArenas);
#else
return Iterator(&mArenas, &mPrivateArenas, &mMainThreadArenas);
#endif
}
inline arena_t* GetDefault() {
return mDefaultArena; }
// Guards the collection of arenas. Must not be acquired while holding
// a single arena's lock or mPurgeListLock.
Mutex mLock MOZ_UNANNOTATED;
// Guards only the list of outstanding purge requests. Can be acquired
// while holding gArenas.mLock, but must not be acquired or held while
// holding or acquiring a single arena's lock.
Mutex mPurgeListLock;
// We're running on the main thread which is set by a call to SetMainThread().
bool IsOnMainThread()
const {
return mMainThreadId.isSome() &&
ThreadIdEqual(mMainThreadId.value(), GetThreadId());
}
// We're running on the main thread or SetMainThread() has never been called.
bool IsOnMainThreadWeak()
const {
return mMainThreadId.isNothing() || IsOnMainThread();
}
// After a fork set the new thread ID in the child.
// This is done as the first thing after a fork, before mLock even re-inits.
void ResetMainThread() MOZ_EXCLUDES(mLock) {
// The post fork handler in the child can run from a MacOS worker thread,
// so we can't set our main thread to it here. Instead we have to clear it.
mMainThreadId = Nothing();
}
void SetMainThread() MOZ_EXCLUDES(mLock) {
MutexAutoLock lock(mLock);
MOZ_ASSERT(mMainThreadId.isNothing());
mMainThreadId = Some(GetThreadId());
}
// This requires the lock to get a consistent count across all the active
// + disposed arenas.
uint64_t OperationsDisposedArenas() MOZ_REQUIRES(mLock) {
return mNumOperationsDisposedArenas;
}
// Enable or disable the lazy purge.
//
// Returns the former state of enablement.
// This is a global setting for all arenas. Changing it may cause an
// immediate purge for all arenas.
bool SetDeferredPurge(
bool aEnable) {
MOZ_ASSERT(IsOnMainThreadWeak());
bool ret = mIsDeferredPurgeEnabled;
{
MutexAutoLock lock(mLock);
mIsDeferredPurgeEnabled = aEnable;
for (
auto* arena : iter()) {
MaybeMutexAutoLock lock(arena->mLock);
arena->mIsDeferredPurgeEnabled = aEnable;
}
}
if (ret != aEnable) {
MayPurgeAll(PurgeIfThreshold, __func__);
}
return ret;
}
bool IsDeferredPurgeEnabled() {
return mIsDeferredPurgeEnabled; }
// Set aside a new purge request for aArena.
void AddToOutstandingPurges(arena_t* aArena) MOZ_EXCLUDES(mPurgeListLock);
// Remove an unhandled purge request for aArena. Returns true if the arena
// was in the list.
bool RemoveFromOutstandingPurges(arena_t* aArena)
MOZ_EXCLUDES(mPurgeListLock);
// Execute all outstanding purge requests, if any.
void MayPurgeAll(PurgeCondition aCond,
const char* aCaller);
// Purge some dirty memory, based on purge requests, returns true if there are
// more to process.
//
// Returns a may_purge_now_result_t with the following meaning:
// Done: Purge has completed for all arenas.
// NeedsMore: There may be some arenas that needs to be purged now.
// WantsLater: There is at least one arena that might want a purge later,
// according to aReuseGraceMS.
//
// Parameters:
// aPeekOnly: If true, check only if there is work to do without doing it.
// aReuseGraceMS: The time to wait with purge after a
// significant re-use happened for an arena.
// aKeepGoing: If this returns false purging will cease.
//
// This could exit for 3 different reasons.
// - There are no more requests (it returns false)
// - There are more requests but aKeepGoing() returned false. (returns true)
// - One arena is completely purged, (returns true).
//
may_purge_now_result_t MayPurgeSteps(
bool aPeekOnly, uint32_t aReuseGraceMS,
const Maybe<std::function<
bool()>>& aKeepGoing);
private:
const static arena_id_t MAIN_THREAD_ARENA_BIT =
0x1;
#ifndef NON_RANDOM_ARENA_IDS
arena_id_t MakeRandArenaId(
bool aIsMainThreadOnly)
const MOZ_REQUIRES(mLock);
#endif
static bool ArenaIdIsMainThreadOnly(arena_id_t aArenaId) {
return aArenaId & MAIN_THREAD_ARENA_BIT;
}
arena_t* mDefaultArena = nullptr;
arena_id_t mLastPublicArenaId MOZ_GUARDED_BY(mLock) =
0;
// Accessing mArenas and mPrivateArenas can only be done while holding mLock.
Tree mArenas MOZ_GUARDED_BY(mLock);
Tree mPrivateArenas MOZ_GUARDED_BY(mLock);
#ifdef NON_RANDOM_ARENA_IDS
// Arena ids are pseudo-obfuscated/deobfuscated based on these values randomly
// initialized on first use.
arena_id_t mArenaIdKey =
0;
int8_t mArenaIdRotation =
0;
#else
// Some mMainThreadArenas accesses to mMainThreadArenas can (and should) elude
// the lock, see GetById().
Tree mMainThreadArenas MOZ_GUARDED_BY(mLock);
#endif
// Set only rarely and then propagated on the same thread to all arenas via
// UpdateMaxDirty(). But also read in ExtraCommitPages on arbitrary threads.
// TODO: Could ExtraCommitPages use arena_t::mMaxDirty instead ?
Atomic<int32_t> mDefaultMaxDirtyPageModifier;
// This is never changed except for forking, and it does not need mLock.
Maybe<ThreadId> mMainThreadId;
// The number of operations that happened in arenas that have since been
// destroyed.
uint64_t mNumOperationsDisposedArenas =
0;
// Linked list of outstanding purges. This list has no particular order.
// It is ok for an arena to be in this list even if mIsPurgePending is false,
// it will just cause an extra round of a (most likely no-op) purge.
// It is not ok to not be in this list but have mIsPurgePending set to true,
// as this would prevent any future purges for this arena (except for during
// MayPurgeStep or Purge).
DoublyLinkedList<arena_t> mOutstandingPurges MOZ_GUARDED_BY(mPurgeListLock);
// Flag if we should defer purge to later. Only ever set when holding the
// collection lock. Read only during arena_t ctor.
Atomic<
bool> mIsDeferredPurgeEnabled;
};
constinit
static ArenaCollection gArenas;
// Protects huge allocation-related data structures.
static Mutex huge_mtx;
// Tree of chunks that are stand-alone huge allocations.
static RedBlackTree<extent_node_t, ExtentTreeTrait> huge
MOZ_GUARDED_BY(huge_mtx);
// Huge allocation statistics.
static size_t huge_allocated MOZ_GUARDED_BY(huge_mtx);
static size_t huge_mapped MOZ_GUARDED_BY(huge_mtx);
static uint64_t huge_operations MOZ_GUARDED_BY(huge_mtx);
// ******
// Arenas.
// The arena associated with the current thread (per
// jemalloc_thread_local_arena) On OSX, __thread/thread_local circles back
// calling malloc to allocate storage on first access on each thread, which
// leads to an infinite loop, but pthread-based TLS somehow doesn't have this
// problem.
#if !
defined(XP_DARWIN)
static MOZ_THREAD_LOCAL(arena_t*) thread_arena;
#else
static detail::ThreadLocal<arena_t*, detail::ThreadLocalKeyStorage>
thread_arena;
#endif
// ***************************************************************************
// Begin forward declarations.
static void huge_dalloc(
void* aPtr, arena_t* aArena);
static bool malloc_init_hard();
#ifndef XP_WIN
# ifdef XP_DARWIN
# define FORK_HOOK
extern "C"
# else
# define FORK_HOOK
static
# endif
FORK_HOOK
void _malloc_prefork(
void);
FORK_HOOK
void _malloc_postfork_parent(
void);
FORK_HOOK
void _malloc_postfork_child(
void);
# ifdef XP_DARWIN
FORK_HOOK
void _malloc_postfork(
void);
# endif
#endif
// End forward declarations.
// ***************************************************************************
// FreeBSD's pthreads implementation calls malloc(3), so the malloc
// implementation has to take pains to avoid infinite recursion during
// initialization.
// Returns whether the allocator was successfully initialized.
static inline bool malloc_init() {
if (!malloc_initialized) {
return malloc_init_hard();
}
return true;
}
#ifdef ANDROID
// Android's pthread.h does not declare pthread_atfork() until SDK 21.
extern "C" MOZ_EXPORT
int pthread_atfork(
void (*)(
void),
void (*)(
void),
void (*)(
void));
#endif
// ***************************************************************************
// Begin Utility functions/macros.
#ifdef MOZJEMALLOC_PROFILING_CALLBACKS
namespace mozilla {
void jemalloc_set_profiler_callbacks(
RefPtr<MallocProfilerCallbacks>&& aCallbacks) {
sCallbacks = aCallbacks;
}
}
// namespace mozilla
#endif
// End Utility functions/macros.
// ***************************************************************************
// Begin arena.
static inline arena_t* thread_local_arena(
bool enabled) {
arena_t* arena;
if (enabled) {
// The arena will essentially be leaked if this function is
// called with `false`, but it doesn't matter at the moment.
// because in practice nothing actually calls this function
// with `false`, except maybe at shutdown.
arena_params_t params;
params.mLabel =
"Thread local";
arena = gArenas.CreateArena(
/* aIsPrivate = */ false, ¶ms);
}
else {
arena = gArenas.GetDefault();
}
thread_arena.set(arena);
return arena;
}
inline void MozJemalloc::jemalloc_thread_local_arena(
bool aEnabled) {
if (malloc_init()) {
thread_local_arena(aEnabled);
}
}
// Choose an arena based on a per-thread value.
static inline arena_t* choose_arena(size_t size) {
arena_t* ret = nullptr;
// We can only use TLS if this is a PIC library, since for the static
// library version, libc's malloc is used by TLS allocation, which
// introduces a bootstrapping issue.
if (size > kMaxQuantumClass) {
// Force the default arena for larger allocations.
ret = gArenas.GetDefault();
}
else {
// Check TLS to see if our thread has requested a pinned arena.
ret = thread_arena.get();
// If ret is non-null, it must not be in the first page.
MOZ_DIAGNOSTIC_ASSERT_IF(ret, (size_t)ret >= gPageSize);
if (!ret) {
// Nothing in TLS. Pin this thread to the default arena.
ret = thread_local_arena(
false);
}
}
MOZ_DIAGNOSTIC_ASSERT(ret);
return ret;
}
inline uint8_t arena_t::FindFreeBitInMask(uint32_t aMask, uint32_t& aRng) {
if (mPRNG != nullptr) {
if (aRng == UINT_MAX) {
aRng = mPRNG->next() %
32;
}
uint8_t bitIndex;
// RotateRight asserts when provided bad input.
aMask = aRng ? RotateRight(aMask, aRng)
: aMask;
// Rotate the mask a random number of slots
bitIndex = static_cast<uint8_t>(std::countr_zero(aMask));
return (bitIndex + aRng) %
32;
}
return static_cast<uint8_t>(std::countr_zero(aMask));
}
inline void* arena_t::ArenaRunRegAlloc(arena_run_t* aRun, arena_bin_t* aBin) {
void* ret;
unsigned i, mask, bit, regind;
uint32_t rndPos = UINT_MAX;
MOZ_DIAGNOSTIC_ASSERT(aRun->mMagic == ARENA_RUN_MAGIC);
MOZ_ASSERT(aRun->mRegionsMinElement < aBin->mRunNumRegionsMask);
// Move the first check outside the loop, so that aRun->mRegionsMinElement can
// be updated unconditionally, without the possibility of updating it
// multiple times.
i = aRun->mRegionsMinElement;
mask = aRun->mRegionsMask[i];
if (mask !=
0) {
bit = FindFreeBitInMask(mask, rndPos);
regind = ((i << (LOG2(
sizeof(
int)) +
3)) + bit);
MOZ_ASSERT(regind < aBin->mRunNumRegions);
ret = (
void*)(((uintptr_t)aRun) + aBin->mRunFirstRegionOffset +
(aBin->mSizeClass * regind));
// Clear bit.
mask ^= (
1U << bit);
aRun->mRegionsMask[i] = mask;
return ret;
}
for (i++; i < aBin->mRunNumRegionsMask; i++) {
mask = aRun->mRegionsMask[i];
if (mask !=
0) {
bit = FindFreeBitInMask(mask, rndPos);
regind = ((i << (LOG2(
sizeof(
int)) +
3)) + bit);
MOZ_ASSERT(regind < aBin->mRunNumRegions);
ret = (
void*)(((uintptr_t)aRun) + aBin->mRunFirstRegionOffset +
(aBin->mSizeClass * regind));
// Clear bit.
mask ^= (
1U << bit);
aRun->mRegionsMask[i] = mask;
// Make a note that nothing before this element
// contains a free region.
aRun->mRegionsMinElement = i;
// Low payoff: + (mask == 0);
return ret;
}
}
// Not reached.
MOZ_DIAGNOSTIC_ASSERT(
0);
return nullptr;
}
static inline void arena_run_reg_dalloc(arena_run_t* run, arena_bin_t* bin,
void* ptr, size_t size) {
uint32_t diff, regind;
unsigned elm, bit;
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
// Avoid doing division with a variable divisor if possible. Using
// actual division here can reduce allocator throughput by over 20%!
diff =
(uint32_t)((uintptr_t)ptr - (uintptr_t)run - bin->mRunFirstRegionOffset);
MOZ_ASSERT(diff <=
(static_cast<
unsigned>(bin->mRunSizePages) << gPageSize2Pow));
regind = diff / bin->mSizeDivisor;
MOZ_DIAGNOSTIC_ASSERT(diff == regind * size);
MOZ_DIAGNOSTIC_ASSERT(regind < bin->mRunNumRegions);
elm = regind >> (LOG2(
sizeof(
int)) +
3);
if (elm < run->mRegionsMinElement) {
run->mRegionsMinElement = elm;
}
bit = regind - (elm << (LOG2(
sizeof(
int)) +
3));
MOZ_RELEASE_ASSERT((run->mRegionsMask[elm] & (
1U << bit)) ==
0,
"Double-free?");
run->mRegionsMask[elm] |= (
1U << bit);
}
#ifndef MALLOC_DECOMMIT
void arena_t::TouchMadvisedPage(arena_chunk_t* aChunk, size_t page) {
// It should be MADVISED because it's part of the same real page.
MOZ_ASSERT(aChunk->mPageMap[page].bits & CHUNK_MAP_MADVISED);
// But it must not have the other flags.
MOZ_ASSERT((aChunk->mPageMap[page].bits &
(CHUNK_MAP_FRESH | CHUNK_MAP_DECOMMITTED | CHUNK_MAP_DIRTY)) ==
0);
// Clear MADVISED and set DIRTY. It's dirty since it may still contain
// data from a previous use.
aChunk->mPageMap[page].bits =
(aChunk->mPageMap[page].bits & ~CHUNK_MAP_MADVISED) | CHUNK_MAP_DIRTY;
// Although this increases the number of dirty pages in the chunk, we
// don't add it to the purge list because these pages can't be purged.
// DallocRun will add it later.
aChunk->mNumDirty++;
mNumDirty++;
mStats.committed++;
mNumMAdvised--;
}
#endif
bool arena_t::SplitAndAllocRun(arena_run_t* aRun, size_t aSize,
bool aLarge,
bool aZero) {
arena_chunk_t* chunk = GetChunkForPtr(aRun);
size_t old_ndirty = chunk->mNumDirty;
size_t run_ind =
(
unsigned)((uintptr_t(aRun) - uintptr_t(chunk)) >> gPageSize2Pow);
size_t total_pages =
(chunk->mPageMap[run_ind].bits & ~gPageSizeMask) >> gPageSize2Pow;
size_t need_pages = (aSize >> gPageSize2Pow);
MOZ_ASSERT(need_pages >
0);
MOZ_ASSERT(need_pages <= total_pages);
size_t rem_pages = total_pages - need_pages;
MOZ_ASSERT((chunk->mPageMap[run_ind].bits & CHUNK_MAP_BUSY) ==
0);
#ifdef MALLOC_DECOMMIT
size_t i =
0;
while (i < need_pages) {
MOZ_ASSERT((chunk->mPageMap[run_ind + i].bits & CHUNK_MAP_BUSY) ==
0);
// Commit decommitted pages if necessary. If a decommitted
// page is encountered, commit all needed adjacent decommitted
// pages in one operation, in order to reduce system call
// overhead.
if (chunk->mPageMap[run_ind + i].bits & CHUNK_MAP_DECOMMITTED) {
// The start of the decommitted area is on a real page boundary.
MOZ_ASSERT((run_ind + i) % gPagesPerRealPage ==
0);
// Advance i+j to just past the index of the last page
// to commit. Clear CHUNK_MAP_DECOMMITTED along the way.
size_t j;
for (j =
0; i + j < need_pages && (chunk->mPageMap[run_ind + i + j].bits &
CHUNK_MAP_DECOMMITTED);
j++) {
// DECOMMITTED, MADVISED and FRESH are mutually exclusive.
MOZ_ASSERT((chunk->mPageMap[run_ind + i + j].bits &
(CHUNK_MAP_FRESH | CHUNK_MAP_MADVISED)) ==
0);
}
// Consider committing more pages to amortise calls to VirtualAlloc.
// This only makes sense at the edge of our run hence the if condition
// here.
if (i + j == need_pages) {
size_t extra_commit = ExtraCommitPages(j, rem_pages);
extra_commit =
PAGES_PER_REAL_PAGE_CEILING(run_ind + i + j + extra_commit) -
run_ind - i - j;
for (; i + j < need_pages + extra_commit &&
(chunk->mPageMap[run_ind + i + j].bits &
CHUNK_MAP_MADVISED_OR_DECOMMITTED);
j++) {
MOZ_ASSERT((chunk->mPageMap[run_ind + i + j].bits &
(CHUNK_MAP_FRESH | CHUNK_MAP_MADVISED)) ==
0);
}
}
// The end of the decommitted area is on a real page boundary.
MOZ_ASSERT((run_ind + i + j) % gPagesPerRealPage ==
0);
if (!pages_commit(
(
void*)(uintptr_t(chunk) + ((run_ind + i) << gPageSize2Pow)),
j << gPageSize2Pow)) {
return false;
}
// pages_commit zeroes pages, so mark them as such if it succeeded.
// That's checked further below to avoid manually zeroing the pages.
for (size_t k =
0; k < j; k++) {
chunk->mPageMap[run_ind + i + k].bits =
(chunk->mPageMap[run_ind + i + k].bits & ~CHUNK_MAP_DECOMMITTED) |
CHUNK_MAP_ZEROED | CHUNK_MAP_FRESH;
}
mNumFresh += j;
i += j;
}
else {
i++;
}
}
#endif
// Keep track of trailing unused pages for later use.
if (rem_pages >
0) {
chunk->mPageMap[run_ind + need_pages].bits =
(rem_pages << gPageSize2Pow) |
(chunk->mPageMap[run_ind + need_pages].bits & gPageSizeMask);
chunk->mPageMap[run_ind + total_pages -
1].bits =
(rem_pages << gPageSize2Pow) |
(chunk->mPageMap[run_ind + total_pages -
1].bits & gPageSizeMask);
mRunsAvail.Insert(&chunk->mPageMap[run_ind + need_pages]);
}
if (chunk->mDirtyRunHint == run_ind) {
chunk->mDirtyRunHint = run_ind + need_pages;
}
#ifndef MALLOC_DECOMMIT
bool first_page_was_madvised =
chunk->mPageMap[run_ind].bits & CHUNK_MAP_MADVISED;
bool last_page_was_madvised =
chunk->mPageMap[run_ind + need_pages -
1].bits & CHUNK_MAP_MADVISED;
#endif
for (size_t i =
0; i < need_pages; i++) {
// Zero if necessary.
if (aZero) {
if ((chunk->mPageMap[run_ind + i].bits & CHUNK_MAP_ZEROED) ==
0) {
memset((
void*)(uintptr_t(chunk) + ((run_ind + i) << gPageSize2Pow)),
0,
gPageSize);
// CHUNK_MAP_ZEROED is cleared below.
}
}
// Update dirty page accounting.
if (chunk->mPageMap[run_ind + i].bits & CHUNK_MAP_DIRTY) {
chunk->mNumDirty--;
mNumDirty--;
// CHUNK_MAP_DIRTY is cleared below.
}
else if (chunk->mPageMap[run_ind + i].bits & CHUNK_MAP_MADVISED) {
mStats.committed++;
mNumMAdvised--;
}
else if (chunk->mPageMap[run_ind + i].bits & CHUNK_MAP_FRESH) {
mStats.committed++;
mNumFresh--;
}
// This bit has already been cleared
MOZ_ASSERT(!(chunk->mPageMap[run_ind + i].bits & CHUNK_MAP_DECOMMITTED));
// Initialize the chunk map. This clears the dirty, zeroed and madvised
// bits, decommitted is cleared above.
if (aLarge) {
chunk->mPageMap[run_ind + i].bits = CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
}
else {
chunk->mPageMap[run_ind + i].bits = size_t(aRun) | CHUNK_MAP_ALLOCATED;
}
}
#ifndef MALLOC_DECOMMIT
// Remove the MADVISED bit from leading and trailing pages that are part of
// the same real pages that we've touched. This may cross into other free
// runs, including busy runs. This is safe because real page boundaries are
// not crossed by either this code or the purging code.
if (first_page_was_madvised) {
for (size_t i = run_ind -
1;
(i & (gPagesPerRealPage -
1)) != (gPagesPerRealPage -
1); i--) {
// This loop will never go beyond into the chunk header or touch the guard
// page because the guard page is always aligned.
MOZ_ASSERT(gChunkHeaderNumPages <= i);
TouchMadvisedPage(chunk, i);
}
}
if (last_page_was_madvised) {
for (size_t i = run_ind + need_pages; (i & (gPagesPerRealPage -
1)) !=
0;
i++) {
// This loop will never go beyond the end of the chunk or touch the guard
// page because the guard page is always aligned.
MOZ_ASSERT(i < gChunkNumPages - gPagesPerRealPage);
TouchMadvisedPage(chunk, i);
}
}
#endif
// Set the run size only in the first element for large runs. This is
// primarily a debugging aid, since the lack of size info for trailing
// pages only matters if the application tries to operate on an
// interior pointer.
if (aLarge) {
chunk->mPageMap[run_ind].bits |= aSize;
}
if (chunk->mNumDirty ==
0 && old_ndirty >
0 && !chunk->mIsPurging &&
mChunksDirty.ElementProbablyInList(chunk)) {
mChunksDirty.remove(chunk);
}
return true;
}
void arena_t::InitChunk(arena_chunk_t* aChunk, size_t aMinCommittedPages) {
new (aChunk) arena_chunk_t(this);
mStats.mapped += kChunkSize;
// Setup the chunk's pages in two phases. First we mark which pages are
// committed & decommitted and perform the decommit. Then we update the map
// to create the runs.
// Clear the bits for the real header pages.
size_t i;
for (i =
0; i < gChunkHeaderNumPages - gPagesPerRealPage; i++) {
aChunk->mPageMap[i].bits =
0;
}
mStats.committed += gChunkHeaderNumPages - gPagesPerRealPage;
// Decommit the last header page (=leading page) as a guard.
MOZ_ASSERT(i % gPagesPerRealPage ==
0);
pages_decommit((
void*)(uintptr_t(aChunk) + (i << gPageSize2Pow)),
gRealPageSize);
for (; i < gChunkHeaderNumPages; i++) {
aChunk->mPageMap[i].bits = CHUNK_MAP_DECOMMITTED;
}
// If MALLOC_DECOMMIT is enabled then commit only the pages we're about to
// use. Otherwise commit all of them.
#ifdef MALLOC_DECOMMIT
// The number of usable pages in the chunk, in other words, the total number
// of pages in the chunk, minus the number of pages in the chunk header
// (including the guard page at the beginning of the chunk), and the number of
// pages for the guard page at the end of the chunk.
size_t chunk_usable_pages =
gChunkNumPages - gChunkHeaderNumPages - gPagesPerRealPage;
size_t n_fresh_pages = PAGES_PER_REAL_PAGE_CEILING(
aMinCommittedPages +
ExtraCommitPages(aMinCommittedPages,
chunk_usable_pages - aMinCommittedPages));
#else
size_t n_fresh_pages =
gChunkNumPages - gPagesPerRealPage - gChunkHeaderNumPages;
#endif
// The committed pages are marked as Fresh. Our caller, SplitAndAllocRun will
// update this when it uses them.
for (size_t j =
0; j < n_fresh_pages; j++) {
aChunk->mPageMap[i + j].bits = CHUNK_MAP_ZEROED | CHUNK_MAP_FRESH;
}
i += n_fresh_pages;
mNumFresh += n_fresh_pages;
#ifndef MALLOC_DECOMMIT
// If MALLOC_DECOMMIT isn't defined then all the pages are fresh and setup in
// the loop above.
MOZ_ASSERT(i == gChunkNumPages - gPagesPerRealPage);
#endif
// If MALLOC_DECOMMIT is defined, then this will decommit the remainder of the
// chunk plus the last page which is a guard page, if it is not defined it
// will only decommit the guard page.
MOZ_ASSERT(i % gPagesPerRealPage ==
0);
pages_decommit((
void*)(uintptr_t(aChunk) + (i << gPageSize2Pow)),
(gChunkNumPages - i) << gPageSize2Pow);
for (; i < gChunkNumPages; i++) {
aChunk->mPageMap[i].bits = CHUNK_MAP_DECOMMITTED;
}
// aMinCommittedPages will create a valid run.
MOZ_ASSERT(aMinCommittedPages >
0);
MOZ_ASSERT(aMinCommittedPages <=
gChunkNumPages - gChunkHeaderNumPages - gPagesPerRealPage);
// Create the run.
aChunk->mPageMap[gChunkHeaderNumPages].bits |= gMaxLargeClass;
aChunk->mPageMap[gChunkNumPages - gPagesPerRealPage -
1].bits |=
gMaxLargeClass;
}
bool arena_t::RemoveChunk(arena_chunk_t* aChunk) {
aChunk->mDying = true;
// If the chunk has busy pages that means that a Purge() is in progress.
// We can't remove the chunk now, instead Purge() will do it.
if (aChunk->mIsPurging) {
return false;
}
if (aChunk->mNumDirty >
0) {
MOZ_ASSERT(aChunk->mArena == this);
if (mChunksDirty.ElementProbablyInList(aChunk)) {
mChunksDirty.remove(aChunk);
}
mNumDirty -= aChunk->mNumDirty;
mStats.committed -= aChunk->mNumDirty;
}
// Count the number of madvised/fresh pages and update the stats.
size_t madvised =
0;
size_t fresh =
0;
for (size_t i = gChunkHeaderNumPages; i < gChunkNumPages - gPagesPerRealPage;
i++) {
MOZ_ASSERT((aChunk->mPageMap[i].bits & CHUNK_MAP_ALLOCATED) ==
0);
MOZ_ASSERT((aChunk->mPageMap[i].bits & CHUNK_MAP_BUSY) ==
0);
if (aChunk->mPageMap[i].bits & CHUNK_MAP_MADVISED) {
madvised++;
}
else if (aChunk->mPageMap[i].bits & CHUNK_MAP_FRESH) {
fresh++;
}
}
mNumMAdvised -= madvised;
mNumFresh -= fresh;
#ifdef MALLOC_DOUBLE_PURGE
if (mChunksMAdvised.ElementProbablyInList(aChunk)) {
mChunksMAdvised.remove(aChunk);
}
#endif
mStats.mapped -= kChunkSize;
mStats.committed -= gChunkHeaderNumPages - gPagesPerRealPage;
return true;
}
arena_chunk_t* arena_t::DemoteChunkToSpare(arena_chunk_t* aChunk) {
if (mSpare) {
if (!RemoveChunk(mSpare)) {
// If we can't remove the spare chunk now purge will finish removing it
// later. Set it to null so that the return below will return null and
// our caller won't delete the chunk before Purge() is finished.
mSpare = nullptr;
}
}
arena_chunk_t* chunk_dealloc = mSpare;
mSpare = aChunk;
return chunk_dealloc;
}
arena_run_t* arena_t::AllocRun(size_t aSize,
bool aLarge,
bool aZero) {
arena_run_t* run;
arena_chunk_map_t* mapelm;
MOZ_ASSERT(aSize <= gMaxLargeClass);
MOZ_ASSERT((aSize & gPageSizeMask) ==
0);
// Search the arena's chunks for the best fit.
mapelm = mRunsAvail.SearchOrNext(aSize);
if (mapelm) {
arena_chunk_t* chunk = GetChunkForPtr(mapelm);
size_t pageind = (uintptr_t(mapelm) - uintptr_t(chunk->mPageMap)) /
sizeof(arena_chunk_map_t);
MOZ_ASSERT((chunk->mPageMap[pageind].bits & CHUNK_MAP_BUSY) ==
0);
run = (arena_run_t*)(uintptr_t(chunk) + (pageind << gPageSize2Pow));
mRunsAvail.Remove(mapelm);
}
else if (mSpare && !mSpare->mIsPurging) {
// Use the spare.
arena_chunk_t* chunk = mSpare;
mSpare = nullptr;
run = (arena_run_t*)(uintptr_t(chunk) +
(gChunkHeaderNumPages << gPageSize2Pow));
MOZ_ASSERT((chunk->mPageMap[gChunkHeaderNumPages].bits & CHUNK_MAP_BUSY) ==
0);
mapelm = &chunk->mPageMap[gChunkHeaderNumPages];
}
else {
// No usable runs. Create a new chunk from which to allocate
// the run.
arena_chunk_t* chunk = (arena_chunk_t*)arena_chunk_alloc(
mChunkAllocator, kChunkSize, kChunkSize);
if (!chunk) {
return nullptr;
}
InitChunk(chunk, aSize >> gPageSize2Pow);
run = (arena_run_t*)(uintptr_t(chunk) +
(gChunkHeaderNumPages << gPageSize2Pow));
mapelm = &chunk->mPageMap[gChunkHeaderNumPages];
}
// Update page map.
if (!SplitAndAllocRun(run, aSize, aLarge, aZero)) {
mRunsAvail.Insert(mapelm);
return nullptr;
}
return run;
}
void arena_t::UpdateMaxDirty() {
MaybeMutexAutoLock lock(mLock);
int32_t modifier = gArenas.DefaultMaxDirtyPageModifier();
if (modifier) {
int32_t arenaOverride =
modifier >
0 ? mMaxDirtyIncreaseOverride : mMaxDirtyDecreaseOverride;
if (arenaOverride) {
modifier = arenaOverride;
}
}
mMaxDirty =
modifier >=
0 ? mMaxDirtyBase << modifier : mMaxDirtyBase >> -modifier;
}
#ifdef MALLOC_DECOMMIT
size_t arena_t::ExtraCommitPages(size_t aReqPages, size_t aRemainingPages) {
const int32_t modifier = gArenas.DefaultMaxDirtyPageModifier();
if (modifier <
0) {
return 0;
}
// The maximum size of the page cache
const size_t max_page_cache = mMaxDirty;
// The current size of the page cache, note that we use mNumFresh +
// mNumMAdvised here but Purge() does not.
const size_t page_cache = mNumDirty + mNumFresh + mNumMAdvised;
if (page_cache > max_page_cache) {
// We're already exceeding our dirty page count even though we're trying
// to allocate. This can happen due to fragmentation. Don't commit
// excess memory since we're probably here due to a larger allocation and
// small amounts of memory are certainly available in the page cache.
return 0;
}
if (modifier >
0) {
// If modifier is > 0 then we want to keep all the pages we can, but don't
// exceed the size of the page cache. The subtraction cannot underflow
// because of the condition above.
return std::min(aRemainingPages, max_page_cache - page_cache);
}
// The rest is arbitrary and involves a some assumptions. I've broken it down
// into simple expressions to document them more clearly.
// Assumption 1: a quarter of mMaxDirty is a sensible "minimum
// target" for the dirty page cache. Likewise 3 quarters is a sensible
// "maximum target". Note that for the maximum we avoid using the whole page
// cache now so that a free that follows this allocation doesn't immeidatly
// call Purge (churning memory).
const size_t min = max_page_cache /
4;
const size_t max =
3 * max_page_cache /
4;
// Assumption 2: Committing 32 pages at a time is sufficient to amortise
// VirtualAlloc costs.
size_t amortisation_threshold =
32;
// extra_pages is the number of additional pages needed to meet
// amortisation_threshold.
size_t extra_pages = aReqPages < amortisation_threshold
? amortisation_threshold - aReqPages
:
0;
// If committing extra_pages isn't enough to hit the minimum target then
// increase it.
if (page_cache + extra_pages < min) {
extra_pages = min - page_cache;
}
else if (page_cache + extra_pages > max) {
// If committing extra_pages would exceed our maximum target then it may
// still be useful to allocate extra pages. One of the reasons this can
// happen could be fragmentation of the cache,
// Therefore reduce the amortisation threshold so that we might allocate
// some extra pages but avoid exceeding the dirty page cache.
amortisation_threshold /=
2;
extra_pages = std::min(aReqPages < amortisation_threshold
? amortisation_threshold - aReqPages
:
0,
max_page_cache - page_cache);
}
// Cap extra_pages to aRemainingPages and adjust aRemainingPages. We will
// commit at least this many extra pages.
extra_pages = std::min(extra_pages, aRemainingPages);
// Finally if commiting a small number of additional pages now can prevent
// a small commit later then try to commit a little more now, provided we
// don't exceed max_page_cache.
if ((aRemainingPages - extra_pages) < amortisation_threshold /
2 &&
(page_cache + aRemainingPages) < max_page_cache) {
return aRemainingPages;
}
return extra_pages;
}
#endif
ArenaPurgeResult arena_t::Purge(
PurgeCondition aCond, PurgeStats& aStats,
const Maybe<std::function<
bool()>>& aKeepGoing) {
arena_chunk_t* chunk = nullptr;
// The first critical section will find a chunk with dirty pages.
{
MaybeMutexAutoLock lock(mLock);
if (mMustDeleteAfterPurge) {
mIsPurgePending =
false;
return Dying;
}
#ifdef MOZ_DEBUG
size_t ndirty =
0;
for (
auto& chunk : mChunksDirty) {
ndirty += chunk.mNumDirty;
}
// Not all dirty chunks are in mChunksDirty as some may not have enough
// dirty pages for purging or might currently be being purged.
MOZ_ASSERT(ndirty <= mNumDirty);
#endif
if (!ShouldContinuePurge(aCond)) {
mIsPurgePending =
false;
return ReachedThresholdOrBusy;
}
// Take a single chunk and attempt to purge some of its dirty pages. The
// loop below will purge memory from the chunk until either:
// * The dirty page count for the arena hits its target,
// * Another thread attempts to delete this chunk, or
// * The chunk has no more dirty pages.
// In any of these cases the loop will break and Purge() will return, which
// means it may return before the arena meets its dirty page count target,
// the return value is used by the caller to call Purge() again where it
// will take the next chunk with dirty pages.
if (mSpare && mSpare->mNumDirty && !mSpare->mIsPurging &&
mChunksDirty.ElementProbablyInList(mSpare)) {
// If the spare chunk has dirty pages then try to purge these first.
//
// They're unlikely to be used in the near future because the spare chunk
// is only used if there's no run in mRunsAvail suitable. mRunsAvail
// never contains runs from the spare chunk.
chunk = mSpare;
mChunksDirty.remove(chunk);
}
else {
if (!mChunksDirty.isEmpty()) {
chunk = mChunksDirty.popFront();
}
}
if (!chunk) {
// We have to clear the flag to preserve the invariant that if Purge()
// returns anything other than NotDone then the flag is clear. If there's
// more purging work to do in other chunks then either other calls to
// Purge() (in other threads) will handle it or we rely on
// ShouldStartPurge() returning true at some point in the future.
mIsPurgePending =
false;
// There are chunks with dirty pages (because mNumDirty > 0 above) but
// they're not in mChunksDirty, they might not have enough dirty pages.
// Or maybe they're busy being purged by other threads.
return ReachedThresholdOrBusy;
}
MOZ_ASSERT(chunk->mNumDirty >
0);
// Mark the chunk as busy so it won't be deleted and remove it from
// mChunksDirty so we're the only thread purging it.
MOZ_ASSERT(!chunk->mIsPurging);
chunk->mIsPurging = true;
aStats.chunks++;
}
// MaybeMutexAutoLock
// True if we should continue purging memory from this arena.
bool continue_purge_arena = true;
// True if we should continue purging memory in this chunk.
bool continue_purge_chunk = true;
// True if at least one Purge operation has occured and therefore we need to
// call FinishPurgingInChunk() before returning.
bool purged_once =
false;
// False if aKeepGoing prevents us from finishing this chunk in one go.
bool keep_going = true;
while (continue_purge_chunk && continue_purge_arena && keep_going) {
// This structure is used to communicate between the two PurgePhase
// functions.
PurgeInfo purge_info(*this, chunk, aStats);
bool chunk_is_dying;
{
// Phase 1: Find pages that need purging.
MaybeMutexAutoLock lock(purge_info.mArena.mLock);
MOZ_ASSERT(chunk->mIsPurging);
if (purge_info.mArena.mMustDeleteAfterPurge) {
chunk->mIsPurging =
false;
purge_info.mArena.mIsPurgePending =
false;
return Dying;
}
continue_purge_chunk = purge_info.FindDirtyPages(purged_once);
continue_purge_arena = purge_info.mArena.ShouldContinuePurge(aCond);
chunk_is_dying = chunk->mDying;
// The code below will exit returning ReachedThresholdOrBusy if these are
// both false, so clear mIsDeferredPurgeNeeded while we still hold the
// lock.
if (!continue_purge_chunk && !continue_purge_arena) {
purge_info.mArena.mIsPurgePending =
false;
}
}
if (!continue_purge_chunk) {
if (chunk_is_dying) {
// Phase one already unlinked the chunk from structures, we just need to
// release the memory.
arena_chunk_dealloc(purge_info.mArena.mChunkAllocator, (
void*)chunk,
kChunkSize);
}
// There's nothing else to do here, our caller may execute Purge() again
// if continue_purge_arena is true.
return continue_purge_arena ? NotDone : ReachedThresholdOrBusy;
}
// Note that even if continue_purge_arena is false, then the purge may still
// continue (as long as continue_purge_chunk is true). It must because the
// pages have already been marked in FindDirtyPages(), then it will exit
// after phase 2.
#ifdef MALLOC_DECOMMIT
pages_decommit(purge_info.DirtyPtr(), purge_info.DirtyLenBytes());
#else
# ifdef XP_SOLARIS
posix_madvise(purge_info.DirtyPtr(), purge_info.DirtyLenBytes(), MADV_FREE);
# else
madvise(purge_info.DirtyPtr(), purge_info.DirtyLenBytes(), MADV_FREE);
# endif
#endif
// Check budget outside any lock, after the madvise/decommit which is the
// potentially expensive operation.
keep_going = aKeepGoing ? (*aKeepGoing)() : true;
arena_chunk_t* chunk_to_release = nullptr;
bool arena_is_dying;
{
// Phase 2: Mark the pages with their final state (madvised or
// decommitted) and fix up any other bookkeeping.
MaybeMutexAutoLock lock(purge_info.mArena.mLock);
MOZ_ASSERT(chunk->mIsPurging);
// We can't early exit if the arena is dying, we have to finish the purge
// (which restores the state so the destructor will check it) and maybe
// release the old spare arena.
arena_is_dying = purge_info.mArena.mMustDeleteAfterPurge;
auto [cpc, ctr] = purge_info.UpdatePagesAndCounts();
continue_purge_chunk = cpc;
chunk_to_release = ctr;
continue_purge_arena = purge_info.mArena.ShouldContinuePurge(aCond);
if (!continue_purge_chunk || !continue_purge_arena || !keep_going) {
// We're going to stop (or pause) purging here so update the chunk's
// bookkeeping to reflect what we did (so far).
purge_info.FinishPurgingInChunk(true, continue_purge_chunk);
// Only clear mIsPurgePending when truly done. Otherwise the arena
// stays marked pending so it gets re-queued for the next purge pass.
if (!continue_purge_arena) {
purge_info.mArena.mIsPurgePending =
false;
}
}
}
// MaybeMutexAutoLock
// Phase 2 can release the spare chunk (not always == chunk) so an extra
// parameter is used to return that chunk.
if (chunk_to_release) {
arena_chunk_dealloc(purge_info.mArena.mChunkAllocator,
(
void*)chunk_to_release, kChunkSize);
}
if (arena_is_dying) {
return Dying;
}
purged_once = true;
}
return continue_purge_arena ? NotDone : ReachedThresholdOrBusy;
}
ArenaPurgeResult arena_t::PurgeLoop(PurgeCondition aCond,
const char* aCaller,
uint32_t aReuseGraceMS,
Maybe<std::function<
bool()>> aKeepGoing) {
PurgeStats purge_stats(mId, mLabel, aCaller);
#ifdef MOZJEMALLOC_PROFILING_CALLBACKS
// We hold our own reference to callbacks for the duration of PurgeLoop to
// make sure it's not released during purging.
RefPtr<MallocProfilerCallbacks> callbacks = sCallbacks;
TimeStamp start;
if (callbacks) {
start = TimeStamp::Now();
}
#endif
uint64_t reuseGraceNS = (uint64_t)aReuseGraceMS *
1000 *
1000;
uint64_t now = aReuseGraceMS ?
0 : GetTimestampNS();
ArenaPurgeResult pr;
do {
pr = Purge(aCond, purge_stats, aKeepGoing);
now = aReuseGraceMS ?
0 : GetTimestampNS();
}
while (
pr == NotDone &&
(!aReuseGraceMS || (now - mLastSignificantReuseNS >= reuseGraceNS)) &&
(!aKeepGoing || (*aKeepGoing)()));
#ifdef MOZJEMALLOC_PROFILING_CALLBACKS
if (callbacks) {
TimeStamp end = TimeStamp::Now();
// We can't hold an arena lock while committing profiler markers.
callbacks->OnPurge(start, end, purge_stats, pr);
}
#endif
return pr;
}
bool arena_t::PurgeInfo::FindDirtyPages(
bool aPurgedOnce) {
// It's possible that the previously dirty pages have now been
// allocated or the chunk is dying.
if (mChunk->mNumDirty ==
0 || mChunk->mDying) {
// Add the chunk to the mChunksMAdvised list if it's had at least one
// madvise.
FinishPurgingInChunk(aPurgedOnce,
false);
return false;
}
// This will locate a span of dirty pages within a single run (unallocated
// runs never have unallocated neighbours). The span of dirty pages may have
// "holes" of clean never-allocated pages. We don't know for sure the
// trade-offs of purging those clean pages. On one hand:
// * This reduces the number of system calls needed
// * This may cause less fragmentation in the kernel's structures, but not
// the CPU's page tables.
// * It's likely that the pages aren't committed by the OS anyway.
// On the other hand:
// * Now accessing those pages will require either pages_commit() or a page
// fault to ensure they're available.
do {
if (!ScanForFirstDirtyPage()) {
FinishPurgingInChunk(aPurgedOnce,
false);
return false;
}
}
while (!ScanForLastDirtyPage());
MOZ_ASSERT(mFreeRunInd >= gChunkHeaderNumPages);
MOZ_ASSERT(mFreeRunInd <= mDirtyInd);
MOZ_ASSERT(mFreeRunLen >
0);
MOZ_ASSERT(mDirtyInd !=
0);
MOZ_ASSERT(mDirtyLen !=
0);
MOZ_ASSERT(mDirtyLen <= mFreeRunLen);
MOZ_ASSERT(mDirtyInd + mDirtyLen <= mFreeRunInd + mFreeRunLen);
MOZ_ASSERT(mDirtyInd % gPagesPerRealPage ==
0);
MOZ_ASSERT(mDirtyLen % gPagesPerRealPage ==
0);
// Count the number of dirty pages and clear their bits.
mDirtyNPages =
0;
for (size_t i =
0; i < mDirtyLen; i++) {
size_t& bits = mChunk->mPageMap[mDirtyInd + i].bits;
if (bits & CHUNK_MAP_DIRTY) {
mDirtyNPages++;
bits ^= CHUNK_MAP_DIRTY;
}
}
MOZ_ASSERT(mDirtyNPages >
0);
MOZ_ASSERT(mDirtyNPages <= mChunk->mNumDirty);
MOZ_ASSERT(mDirtyNPages <= mDirtyLen);
mChunk->mNumDirty -= mDirtyNPages;
mArena.mNumDirty -= mDirtyNPages;
// Mark the run as busy so that another thread freeing memory won't try to
// coalesce it.
mChunk->mPageMap[mFreeRunInd].bits |= CHUNK_MAP_BUSY;
mChunk->mPageMap[FreeRunLastInd()].bits |= CHUNK_MAP_BUSY;
// Before we unlock ensure that no other thread can allocate from these
// pages.
if (mArena.mSpare != mChunk) {
mArena.mRunsAvail.Remove(&mChunk->mPageMap[mFreeRunInd]);
}
return true;
}
// Look for the first dirty page and the run it belongs to.
bool arena_t::PurgeInfo::ScanForFirstDirtyPage() {
// Scan in two nested loops. The outer loop iterates over runs, and the inner
// loop iterates over pages within unallocated runs.
size_t run_pages;
for (size_t run_idx = mChunk->mDirtyRunHint;
run_idx < gChunkNumPages - gPagesPerRealPage; run_idx += run_pages) {
size_t run_bits = mChunk->mPageMap[run_idx].bits;
// We must not find any busy pages because this chunk shouldn't be in
// the dirty list.
MOZ_ASSERT((run_bits & CHUNK_MAP_BUSY) ==
0);
// Determine the run's size, this is used in the loop iteration to move to
// the next run.
if (run_bits & CHUNK_MAP_LARGE || !(run_bits & CHUNK_MAP_ALLOCATED)) {
size_t size = run_bits & ~gPageSizeMask;
run_pages = size >> gPageSize2Pow;
}
else {
arena_run_t* run =
reinterpret_cast<arena_run_t*>(run_bits & ~gPageSizeMask);
MOZ_ASSERT(run == reinterpret_cast<arena_run_t*>(
reinterpret_cast<uintptr_t>(mChunk) +
(run_idx << gPageSize2Pow)));
run_pages = run->mBin->mRunSizePages;
}
MOZ_ASSERT(run_pages >
0);
MOZ_ASSERT(run_idx + run_pages <= gChunkNumPages);
if (run_bits & CHUNK_MAP_ALLOCATED) {
// Allocated runs won't contain dirty pages.
continue;
}
mFreeRunInd = run_idx;
mFreeRunLen = run_pages;
mDirtyInd =
0;
// Scan for dirty pages.
for (size_t page_idx = run_idx; page_idx < run_idx + run_pages;
page_idx++) {
size_t& page_bits = mChunk->mPageMap[page_idx].bits;
// We must not find any busy pages because this chunk shouldn't be in
// the dirty list.
MOZ_ASSERT((page_bits & CHUNK_MAP_BUSY) ==
0);
// gPagesPerRealPage is a power of two, use a bitmask to check if page_idx
// is a multiple.
if ((page_idx & (gPagesPerRealPage -
1)) ==
0) {
// A system call can be aligned here.
mDirtyInd = page_idx;
}
if (page_bits & CHUNK_MAP_DIRTY) {
MOZ_ASSERT((page_bits & CHUNK_MAP_FRESH_MADVISED_OR_DECOMMITTED) ==
0);
MOZ_ASSERT(mChunk->mDirtyRunHint <= run_idx);
mChunk->mDirtyRunHint = run_idx;
if (mDirtyInd) {
return true;
}
// This dirty page occurs before a page we can align on,
// so it can't be purged.
mPurgeStats.pages_unpurgable++;
}
}
}
return false;
}
bool arena_t::PurgeInfo::ScanForLastDirtyPage() {
mDirtyLen =
0;
for (size_t i = FreeRunLastInd(); i >= mDirtyInd; i--) {
size_t& bits = mChunk->mPageMap[i].bits;
// We must not find any busy pages because this chunk shouldn't be in the
// dirty list.
MOZ_ASSERT(!(bits & CHUNK_MAP_BUSY));
// gPagesPerRealPage is a power of two, use a bitmask to check if page_idx
// is a multiple minus one.
if ((i & (gPagesPerRealPage -
1)) == gPagesPerRealPage -
1) {
// A system call can be aligned here.
mDirtyLen = i - mDirtyInd +
1;
}
if (bits & CHUNK_MAP_DIRTY) {
if (mDirtyLen) {
return true;
}
// This dirty page occurs after a page we can align on,
// so it can't be purged.
mPurgeStats.pages_unpurgable++;
}
}
// Advance the dirty page hint so that the next scan will make progress.
mChunk->mDirtyRunHint = FreeRunLastInd() +
1;
return false;
}
std::pair<
bool, arena_chunk_t*> arena_t::PurgeInfo::UpdatePagesAndCounts() {
size_t num_madvised =
0;
size_t num_decommitted =
0;
size_t num_fresh =
0;
for (size_t i =
0; i < mDirtyLen; i++) {
size_t& bits = mChunk->mPageMap[mDirtyInd + i].bits;
// The page must not have the dirty bit set.
MOZ_ASSERT((bits & CHUNK_MAP_DIRTY) ==
0);
#ifdef MALLOC_DECOMMIT
if (bits & CHUNK_MAP_DECOMMITTED) {
num_decommitted++;
}
#else
if (bits & CHUNK_MAP_MADVISED) {
num_madvised++;
}
#endif
else if (bits & CHUNK_MAP_FRESH) {
num_fresh++;
}
// Clear these page status bits.
bits &= ~CHUNK_MAP_FRESH_MADVISED_OR_DECOMMITTED;
// Set the free_operation bit.
#ifdef MALLOC_DECOMMIT
bits |= CHUNK_MAP_DECOMMITTED;
#else
bits |= CHUNK_MAP_MADVISED;
#endif
}
// Remove the CHUNK_MAP_BUSY marks from the run.
#ifdef MOZ_DEBUG
MOZ_ASSERT(mChunk->mPageMap[mFreeRunInd].bits & CHUNK_MAP_BUSY);
MOZ_ASSERT(mChunk->mPageMap[FreeRunLastInd()].bits & CHUNK_MAP_BUSY);
#endif
mChunk->mPageMap[mFreeRunInd].bits &= ~CHUNK_MAP_BUSY;
mChunk->mPageMap[FreeRunLastInd()].bits &= ~CHUNK_MAP_BUSY;
#ifndef MALLOC_DECOMMIT
mArena.mNumMAdvised += mDirtyLen - num_madvised;
#endif
mArena.mNumFresh -= num_fresh;
mArena.mStats.committed -=
mDirtyLen - num_madvised - num_decommitted - num_fresh;
mPurgeStats.pages_dirty += mDirtyNPages;
mPurgeStats.pages_total += mDirtyLen;
mPurgeStats.system_calls++;
// Note that this code can't update the dirty run hint. There may be other
// dirty pages within the same run.
if (mChunk->mDying) {
// A dying chunk doesn't need to be coaleased, it will already have one
// large run.
MOZ_ASSERT(mFreeRunInd == gChunkHeaderNumPages &&
mFreeRunLen ==
gChunkNumPages - gChunkHeaderNumPages - gPagesPerRealPage);
return std::make_pair(
false, mChunk);
}
bool was_empty = mChunk->IsEmpty();
mFreeRunInd =
mArena.TryCoalesce(mChunk, mFreeRunInd, mFreeRunLen, FreeRunLenBytes());
arena_chunk_t* chunk_to_release = nullptr;
if (!was_empty && mChunk->IsEmpty()) {
// This now-empty chunk will become the spare chunk and the spare
// chunk will be returned for deletion.
chunk_to_release = mArena.DemoteChunkToSpare(mChunk);
}
if (mChunk != mArena.mSpare) {
mArena.mRunsAvail.Insert(&mChunk->mPageMap[mFreeRunInd]);
}
return std::make_pair(mChunk->mNumDirty !=
0, chunk_to_release);
}
void arena_t::PurgeInfo::FinishPurgingInChunk(
bool aAddToMAdvised,
bool aAddToDirty) {
// If there's no more purge activity for this chunk then finish up while
// we still have the lock.
MOZ_ASSERT(mChunk->mIsPurging);
mChunk->mIsPurging =
false;
if (mChunk->mDying) {
// Another thread tried to delete this chunk while we weren't holding
// the lock. Now it's our responsibility to finish deleting it.
DebugOnly<
bool> release_chunk = mArena.RemoveChunk(mChunk);
// RemoveChunk() can't return false because mIsPurging was false
// during the call.
MOZ_ASSERT(release_chunk);
return;
}
if (mChunk->mNumDirty !=
0 && aAddToDirty) {
// Put the semi-processed chunk on the front of the queue so that it is
// the first chunk processed next time.
mArena.mChunksDirty.pushFront(mChunk);
}
#ifdef MALLOC_DOUBLE_PURGE
if (aAddToMAdvised) {
// The chunk might already be in the list, but this
// makes sure it's at the front.
if (mArena.mChunksMAdvised.ElementProbablyInList(mChunk)) {
mArena.mChunksMAdvised.remove(mChunk);
}
mArena.mChunksMAdvised.pushFront(mChunk);
}
#endif
}
// run_pages and size make each-other redundant. But we use them both and the
// caller computes both so this function requires both and will assert if they
// are inconsistent.
size_t arena_t::TryCoalesce(arena_chunk_t* aChunk, size_t run_ind,
size_t run_pages, size_t size) {
// Copy in/out parameters to local variables so that we don't need '*'
// operators throughout this code but also so that type checking is stricter
// (references are too easily coerced).
MOZ_ASSERT(size == run_pages << gPageSize2Pow);
// Try to coalesce forward.
if (run_ind + run_pages < gChunkNumPages - gPagesPerRealPage &&
(aChunk->mPageMap[run_ind + run_pages].bits &
(CHUNK_MAP_ALLOCATED | CHUNK_MAP_BUSY)) ==
0) {
size_t nrun_size =
aChunk->mPageMap[run_ind + run_pages].bits & ~gPageSizeMask;
// Remove successor from tree of available runs; the coalesced run is
// inserted later.
mRunsAvail.Remove(&aChunk->mPageMap[run_ind + run_pages]);
size += nrun_size;
run_pages = size >> gPageSize2Pow;
MOZ_DIAGNOSTIC_ASSERT((aChunk->mPageMap[run_ind + run_pages -
1].bits &
~gPageSizeMask) == nrun_size);
aChunk->mPageMap[run_ind].bits =
size | (aChunk->mPageMap[run_ind].bits & gPageSizeMask);
aChunk->mPageMap[run_ind + run_pages -
1].bits =
size | (aChunk->mPageMap[run_ind + run_pages -
1].bits & gPageSizeMask);
}
// Try to coalesce backward.
if (run_ind > gChunkHeaderNumPages &&
(aChunk->mPageMap[run_ind -
1].bits &
(CHUNK_MAP_ALLOCATED | CHUNK_MAP_BUSY)) ==
0) {
size_t prun_size = aChunk->mPageMap[run_ind -
1].bits & ~gPageSizeMask;
run_ind -= prun_size >> gPageSize2Pow;
// Remove predecessor from tree of available runs; the coalesced run is
// inserted later.
mRunsAvail.Remove(&aChunk->mPageMap[run_ind]);
size += prun_size;
run_pages = size >> gPageSize2Pow;
MOZ_DIAGNOSTIC_ASSERT((aChunk->mPageMap[run_ind].bits & ~gPageSizeMask) ==
prun_size);
aChunk->mPageMap[run_ind].bits =
size | (aChunk->mPageMap[run_ind].bits & gPageSizeMask);
aChunk->mPageMap[run_ind + run_pages -
1].bits =
size | (aChunk->mPageMap[run_ind + run_pages -
1].bits & gPageSizeMask);
}
// If the dirty run hint points within the run then the new greater run
// is the run with the lowest index containing dirty pages. So update the
// hint.
if ((aChunk->mDirtyRunHint > run_ind) &&
(aChunk->mDirtyRunHint < run_ind + run_pages)) {
aChunk->mDirtyRunHint = run_ind;
}
return run_ind;
}
arena_chunk_t* arena_t::DallocRun(arena_run_t* aRun,
bool aDirty) {
arena_chunk_t* chunk = GetChunkForPtr(aRun);
size_t run_ind =
(size_t)((uintptr_t(aRun) - uintptr_t(chunk)) >> gPageSize2Pow);
MOZ_DIAGNOSTIC_ASSERT(run_ind >= gChunkHeaderNumPages);
MOZ_RELEASE_ASSERT(run_ind < gChunkNumPages -
1);
size_t size, run_pages;
if ((chunk->mPageMap[run_ind].bits & CHUNK_MAP_LARGE) !=
0) {
size = chunk->mPageMap[run_ind].bits & ~gPageSizeMask;
run_pages = (size >> gPageSize2Pow);
}
else {
run_pages = aRun->mBin->mRunSizePages;
size = run_pages << gPageSize2Pow;
}
// Mark pages as unallocated in the chunk map, at the same time clear all the
// page bits and size information, set the dirty bit if the pages are now
// dirty..
for (size_t i =
0; i < run_pages; i++) {
size_t& bits = chunk->mPageMap[run_ind + i].bits;
// No bits other than ALLOCATED or LARGE may be set.
MOZ_DIAGNOSTIC_ASSERT(
(bits & gPageSizeMask & ~(CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED)) ==
0);
bits = aDirty ? CHUNK_MAP_DIRTY :
0;
}
if (aDirty) {
// One of the reasons we check mIsPurging here is so that we don't add a
// chunk that's currently in the middle of purging to the list, which could
// start a concurrent purge.
if (!chunk->mIsPurging &&
(chunk->mNumDirty ==
0 || !mChunksDirty.ElementProbablyInList(chunk))) {
mChunksDirty.pushBack(chunk);
}
chunk->mNumDirty += run_pages;
mNumDirty += run_pages;
}
chunk->mPageMap[run_ind].bits |= size;
chunk->mPageMap[run_ind + run_pages -
1].bits |= size;
run_ind = TryCoalesce(chunk, run_ind, run_pages, size);
// Now that run_ind is finalised we can update the dirty run hint.
if (aDirty && run_ind < chunk->mDirtyRunHint) {
chunk->mDirtyRunHint = run_ind;
}
// Deallocate chunk if it is now completely unused.
arena_chunk_t* chunk_dealloc = nullptr;
if (chunk->IsEmpty()) {
chunk_dealloc = DemoteChunkToSpare(chunk);
}
else {
// Insert into tree of available runs, now that coalescing is complete.
mRunsAvail.Insert(&chunk->mPageMap[run_ind]);
}
return chunk_dealloc;
}
void arena_t::TrimRunHead(arena_chunk_t* aChunk, arena_run_t* aRun,
size_t aOldSize, size_t aNewSize) {
size_t pageind = (uintptr_t(aRun) - uintptr_t(aChunk)) >> gPageSize2Pow;
size_t head_npages = (aOldSize - aNewSize) >> gPageSize2Pow;
MOZ_ASSERT(aOldSize > aNewSize);
// Update the chunk map so that arena_t::RunDalloc() can treat the
// leading run as separately allocated.
aChunk->mPageMap[pageind].bits =
(aOldSize - aNewSize) | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
aChunk->mPageMap[pageind + head_npages].bits =
aNewSize | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
DebugOnly<arena_chunk_t*> no_chunk = DallocRun(aRun,
false);
// This will never release a chunk as there's still at least one allocated
// run.
MOZ_ASSERT(!no_chunk);
}
void arena_t::TrimRunTail(arena_chunk_t* aChunk, arena_run_t* aRun,
size_t aOldSize, size_t aNewSize,
bool aDirty) {
size_t pageind = (uintptr_t(aRun) - uintptr_t(aChunk)) >> gPageSize2Pow;
size_t npages = aNewSize >> gPageSize2Pow;
MOZ_ASSERT(aOldSize > aNewSize);
// Update the chunk map so that arena_t::RunDalloc() can treat the
// trailing run as separately allocated.
aChunk->mPageMap[pageind].bits =
aNewSize | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
aChunk->mPageMap[pageind + npages].bits =
(aOldSize - aNewSize) | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
DebugOnly<arena_chunk_t*> no_chunk =
DallocRun((arena_run_t*)(uintptr_t(aRun) + aNewSize), aDirty);
// This will never release a chunk as there's still at least one allocated
// run.
MOZ_ASSERT(!no_chunk);
}
arena_run_t* arena_t::GetNewEmptyBinRun(arena_bin_t* aBin) {
arena_run_t* run;
unsigned i, remainder;
// Allocate a new run.
run = AllocRun(static_cast<size_t>(aBin->mRunSizePages) << gPageSize2Pow,
false,
false);
if (!run) {
return nullptr;
}
// Initialize run internals.
run->mBin = aBin;
for (i =
0; i < aBin->mRunNumRegionsMask -
1; i++) {
run->mRegionsMask[i] = UINT_MAX;
}
remainder = aBin->mRunNumRegions & ((
1U << (LOG2(
sizeof(
int)) +
3)) -
1);
if (remainder ==
0) {
run->mRegionsMask[i] = UINT_MAX;
}
else {
// The last element has spare bits that need to be unset.
run->mRegionsMask[i] =
(UINT_MAX >> ((
1U << (LOG2(
sizeof(
int)) +
3)) - remainder));
}
run->mRegionsMinElement =
0;
run->mNumFree = aBin->mRunNumRegions;
#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
run->mMagic = ARENA_RUN_MAGIC;
#endif
// Make sure we continue to use this run for subsequent allocations.
new (&run->mRunListElem) DoublyLinkedListElement<arena_run_t>();
aBin->mNonFullRuns.pushFront(run);
aBin->mNumRuns++;
return run;
}
arena_run_t* arena_t::GetNonFullBinRun(arena_bin_t* aBin) {
auto mrf_head = aBin->mNonFullRuns.begin();
if (mrf_head) {
// Take the head and if we are going to fill it, remove it from our list.
arena_run_t* run = &(*mrf_head);
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
if (run->mNumFree ==
1) {
aBin->mNonFullRuns.remove(run);
}
return run;
}
return GetNewEmptyBinRun(aBin);
}
arena_bin_t::arena_bin_t(SizeClass aSizeClass) : mSizeClass(aSizeClass.Size()) {
size_t try_run_size;
unsigned try_nregs, try_mask_nelms, try_reg0_offset;
// Size of the run header, excluding mRegionsMask.
static const size_t kFixedHeaderSize = offsetof(arena_run_t, mRegionsMask);
MOZ_ASSERT(aSizeClass.Size() <= gMaxBinClass);
try_run_size = gMinimumRunSize;
// Run size expansion loop.
while (true) {
try_nregs = ((try_run_size - kFixedHeaderSize) / mSizeClass) +
1;
// Counter-act try_nregs-- in loop.
// The do..while loop iteratively reduces the number of regions until
// the run header and the regions no longer overlap. A closed formula
// would be quite messy, since there is an interdependency between the
// header's mask length and the number of regions.
do {
try_nregs--;
try_mask_nelms =
(try_nregs >> (LOG2(
sizeof(
int)) +
3)) +
((try_nregs & ((
1U << (LOG2(
sizeof(
int)) +
3)) -
1)) ?
1 :
0);
try_reg0_offset = try_run_size - (try_nregs * mSizeClass);
}
while (kFixedHeaderSize + (
sizeof(
unsigned) * try_mask_nelms) >
try_reg0_offset);
// Try to keep the run overhead below kRunOverhead.
if (Fraction(try_reg0_offset, try_run_size) <= kRunOverhead) {
break;
}
// If the overhead is larger than the size class, it means the size class
// is small and doesn't align very well with the header. It's desirable to
// have smaller run sizes for them, so relax the overhead requirement.
if (try_reg0_offset > mSizeClass) {
if (Fraction(try_reg0_offset, try_run_size) <= kRunRelaxedOverhead) {
break;
}
}
// The run header includes one bit per region of the given size. For sizes
// small enough, the number of regions is large enough that growing the run
// size barely moves the needle for the overhead because of all those bits.
// For example, for a size of 8 bytes, adding 4KiB to the run size adds
// close to 512 bits to the header, which is 64 bytes.
// With such overhead, there is no way to get to the wanted overhead above,
// so we give up if the required size for mRegionsMask more than doubles the
// size of the run header.
if (try_mask_nelms *
sizeof(
unsigned) >= kFixedHeaderSize) {
break;
}
// If next iteration is going to be larger than the largest possible large
// size class, then we didn't find a setup where the overhead is small
// enough, and we can't do better than the current settings, so just use
// that.
if (try_run_size + gPageSize > gMaxLargeClass) {
break;
}
// Try more aggressive settings.
try_run_size += gPageSize;
}
MOZ_ASSERT(kFixedHeaderSize + (
sizeof(
unsigned) * try_mask_nelms) <=
try_reg0_offset);
MOZ_ASSERT((try_mask_nelms << (LOG2(
sizeof(
int)) +
3)) >= try_nregs);
// Our list management would break if mRunNumRegions == 1 and we should use
// a large size class instead, anyways.
MOZ_ASSERT(try_nregs >
1);
// Copy final settings.
MOZ_ASSERT((try_run_size >> gPageSize2Pow) <= UINT8_MAX);
mRunSizePages = static_cast<uint8_t>(try_run_size >> gPageSize2Pow);
mRunNumRegions = try_nregs;
mRunNumRegionsMask = try_mask_nelms;
mRunFirstRegionOffset = try_reg0_offset;
mSizeDivisor = FastDivisor<uint16_t>(aSizeClass.Size(), try_run_size);
}
void arena_t::ResetSmallAllocRandomization() {
if (MOZ_UNLIKELY(opt_randomize_small)) {
MaybeMutexAutoLock lock(mLock);
InitPRNG();
}
mRandomizeSmallAllocations = opt_randomize_small;
}
void arena_t::InitPRNG() {
// Both another thread could race and the code backing RandomUint64
// (arc4random for example) may allocate memory while here, so we must
// ensure to start the mPRNG initialization only once and to not hold
// the lock while initializing.
mIsPRNGInitializing = true;
{
mLock.Unlock();
mozilla::Maybe<uint64_t> prngState1 = mozilla::RandomUint64();
mozilla::Maybe<uint64_t> prngState2 = mozilla::RandomUint64();
mLock.Lock();
mozilla::non_crypto::XorShift128PlusRNG prng(prngState1.valueOr(
0),
prngState2.valueOr(
0));
if (mPRNG) {
*mPRNG = prng;
}
else {
void* backing =
sBaseAlloc.alloc(
sizeof(mozilla::non_crypto::XorShift128PlusRNG));
mPRNG =
new (backing)
mozilla::non_crypto::XorShift128PlusRNG(std::move(prng));
}
}
mIsPRNGInitializing =
false;
}
void* arena_t::MallocSmall(size_t aSize,
bool aZero) {
void* ret;
arena_bin_t* bin;
arena_run_t* run;
SizeClass sizeClass(aSize);
aSize = sizeClass.Size();
switch (sizeClass.Type()) {
case SizeClass::Quantum:
// Although we divide 2 things by kQuantum, the compiler will
// reduce `kMinQuantumClass / kQuantum` to a single constant.
bin = &mBins[(aSize / kQuantum) - (kMinQuantumClass / kQuantum)];
break;
case SizeClass::QuantumWide:
bin = &mBins[kNumQuantumClasses + (aSize / kQuantumWide) -
(kMinQuantumWideClass / kQuantumWide)];
break;
case SizeClass::SubPage:
bin = &mBins[kNumQuantumClasses + kNumQuantumWideClasses +
(FloorLog2(aSize) - LOG2(kMinSubPageClass))];
break;
default:
MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE(
"Unexpected size class type");
}
MOZ_DIAGNOSTIC_ASSERT(aSize == bin->mSizeClass);
size_t num_dirty_before, num_dirty_after;
{
MaybeMutexAutoLock lock(mLock);
#ifdef MOZ_DEBUG
bool isInitializingThread(
false);
#endif
if (MOZ_UNLIKELY(mRandomizeSmallAllocations && mPRNG == nullptr &&
!mIsPRNGInitializing)) {
#ifdef MOZ_DEBUG
isInitializingThread = true;
#endif
InitPRNG();
}
MOZ_ASSERT(!mRandomizeSmallAllocations || mPRNG ||
(mIsPRNGInitializing && !isInitializingThread));
num_dirty_before = mNumDirty;
run = GetNonFullBinRun(bin);
num_dirty_after = mNumDirty;
if (MOZ_UNLIKELY(!run)) {
return nullptr;
}
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
MOZ_DIAGNOSTIC_ASSERT(run->mNumFree >
0);
ret = ArenaRunRegAlloc(run, bin);
MOZ_DIAGNOSTIC_ASSERT(ret);
run->mNumFree--;
if (!ret) {
return nullptr;
}
mStats.allocated_small += aSize;
mStats.operations++;
}
if (num_dirty_after < num_dirty_before) {
NotifySignificantReuse();
}
if (!aZero) {
ApplyZeroOrJunk(ret, aSize);
}
else {
memset(ret,
0, aSize);
}
return ret;
}
void* arena_t::MallocLarge(size_t aSize,
bool aZero) {
void* ret;
// Large allocation.
aSize = PAGE_CEILING(aSize);
size_t num_dirty_before, num_dirty_after;
{
MaybeMutexAutoLock lock(mLock);
num_dirty_before = mNumDirty;
ret = AllocRun(aSize, true, aZero);
num_dirty_after = mNumDirty;
if (!ret) {
return nullptr;
}
mStats.allocated_large += aSize;
mStats.operations++;
}
if (num_dirty_after < num_dirty_before) {
NotifySignificantReuse();
}
if (!aZero) {
ApplyZeroOrJunk(ret, aSize);
}
return ret;
}
void* arena_t::Malloc(size_t aSize,
bool aZero) {
MOZ_DIAGNOSTIC_ASSERT(mMagic == ARENA_MAGIC);
MOZ_ASSERT(aSize !=
0);
if (aSize <= gMaxBinClass) {
return MallocSmall(aSize, aZero);
}
if (aSize <= gMaxLargeClass) {
return MallocLarge(aSize, aZero);
}
return MallocHuge(aSize, aZero);
}
// Only handles large allocations that require more than page alignment.
void* arena_t::PallocLarge(size_t aAlignment, size_t aSize, size_t aAllocSize) {
void* ret;
size_t offset;
arena_chunk_t* chunk;
MOZ_ASSERT((aSize & gPageSizeMask) ==
0);
MOZ_ASSERT((aAlignment & gPageSizeMask) ==
0);
size_t num_dirty_before, num_dirty_after;
{
MaybeMutexAutoLock lock(mLock);
num_dirty_before = mNumDirty;
ret = AllocRun(aAllocSize, true,
false);
if (!ret) {
return nullptr;
}
chunk = GetChunkForPtr(ret);
offset = uintptr_t(ret) & (aAlignment -
1);
MOZ_ASSERT((offset & gPageSizeMask) ==
0);
MOZ_ASSERT(offset < aAllocSize);
if (offset ==
0) {
TrimRunTail(chunk, (arena_run_t*)ret, aAllocSize, aSize,
false);
}
else {
size_t leadsize, trailsize;
leadsize = aAlignment - offset;
if (leadsize >
0) {
TrimRunHead(chunk, (arena_run_t*)ret, aAllocSize,
aAllocSize - leadsize);
ret = (
void*)(uintptr_t(ret) + leadsize);
}
trailsize = aAllocSize - leadsize - aSize;
if (trailsize !=
0) {
// Trim trailing space.
MOZ_ASSERT(trailsize < aAllocSize);
TrimRunTail(chunk, (arena_run_t*)ret, aSize + trailsize, aSize,
false);
}
}
num_dirty_after = mNumDirty;
mStats.allocated_large += aSize;
mStats.operations++;
}
if (num_dirty_after < num_dirty_before) {
NotifySignificantReuse();
}
// Note that since Bug 1488780we don't attempt purge dirty memory on this code
// path. In general there won't be dirty memory above the threshold after an
// allocation, only after free. The exception is if the dirty page threshold
// has changed.
ApplyZeroOrJunk(ret, aSize);
return ret;
}
void* arena_t::Palloc(size_t aAlignment, size_t aSize) {
void* ret;
size_t ceil_size;
// Round size up to the nearest multiple of alignment.
//
// This done, we can take advantage of the fact that for each small
// size class, every object is aligned at the smallest power of two
// that is non-zero in the base two representation of the size. For
// example:
//
// Size | Base 2 | Minimum alignment
// -----+----------+------------------
// 96 | 1100000 | 32
// 144 | 10100000 | 32
// 192 | 11000000 | 64
//
// Depending on runtime settings, it is possible that arena_malloc()
// will further round up to a power of two, but that never causes
// correctness issues.
ceil_size = ALIGNMENT_CEILING(aSize, aAlignment);
// (ceil_size < aSize) protects against the combination of maximal
// alignment and size greater than maximal alignment.
if (ceil_size < aSize) {
// size_t overflow.
return nullptr;
}
if (ceil_size <= gPageSize ||
(aAlignment <= gPageSize && ceil_size <= gMaxLargeClass)) {
ret = Malloc(ceil_size,
false);
}
else {
size_t run_size;
// We can't achieve sub-page alignment, so round up alignment
// permanently; it makes later calculations simpler.
aAlignment = PAGE_CEILING(aAlignment);
ceil_size = PAGE_CEILING(aSize);
// (ceil_size < aSize) protects against very large sizes within
// pagesize of SIZE_T_MAX.
//
// (ceil_size + aAlignment < ceil_size) protects against the
// combination of maximal alignment and ceil_size large enough
// to cause overflow. This is similar to the first overflow
// check above, but it needs to be repeated due to the new
// ceil_size value, which may now be *equal* to maximal
// alignment, whereas before we only detected overflow if the
// original size was *greater* than maximal alignment.
if (ceil_size < aSize || ceil_size + aAlignment < ceil_size) {
// size_t overflow.
return nullptr;
}
// Calculate the size of the over-size run that arena_palloc()
// would need to allocate in order to guarantee the alignment.
if (ceil_size >= aAlignment) {
run_size = ceil_size + aAlignment - gPageSize;
}
else {
// It is possible that (aAlignment << 1) will cause
// overflow, but it doesn't matter because we also
// subtract pagesize, which in the case of overflow
// leaves us with a very large run_size. That causes
// the first conditional below to fail, which means
// that the bogus run_size value never gets used for
// anything important.
run_size = (aAlignment <<
1) - gPageSize;
}
if (run_size <= gMaxLargeClass) {
ret = PallocLarge(aAlignment, ceil_size, run_size);
}
else if (aAlignment <= kChunkSize) {
ret = MallocHuge(ceil_size,
false);
}
else {
ret = PallocHuge(ceil_size, aAlignment,
false);
}
}
MOZ_ASSERT((uintptr_t(ret) & (aAlignment -
1)) ==
0);
return ret;
}
class AllocInfo {
public:
template <
bool Validate =
false>
static inline AllocInfo Get(
const void* aPtr) {
// If the allocator is not initialized, the pointer can't belong to it.
if (Validate && !malloc_initialized) {
return AllocInfo();
}
auto chunk = GetChunkForPtr(aPtr);
if (Validate) {
if (!chunk || !gChunkRTree.Get(chunk)) {
return AllocInfo();
}
}
if (chunk != aPtr) {
MOZ_DIAGNOSTIC_ASSERT(chunk->mArena->mMagic == ARENA_MAGIC);
size_t pageind = (((uintptr_t)aPtr - (uintptr_t)chunk) >> gPageSize2Pow);
return GetInChunk(aPtr, chunk, pageind);
}
// Huge allocation
MutexAutoLock lock(huge_mtx);
extent_node_t* node = huge.Search(chunk);
if (Validate && !node) {
return AllocInfo();
}
return AllocInfo(node->mSize, node);
}
// Get the allocation information for a pointer we know is within a chunk
// (Small or large, not huge).
static inline AllocInfo GetInChunk(
const void* aPtr, arena_chunk_t* aChunk,
size_t pageind) {
size_t mapbits = aChunk->mPageMap[pageind].bits;
MOZ_DIAGNOSTIC_ASSERT((mapbits & CHUNK_MAP_ALLOCATED) !=
0);
size_t size;
if ((mapbits & CHUNK_MAP_LARGE) ==
0) {
arena_run_t* run = (arena_run_t*)(mapbits & ~gPageSizeMask);
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
size = run->mBin->mSizeClass;
}
else {
size = mapbits & ~gPageSizeMask;
MOZ_DIAGNOSTIC_ASSERT(size !=
0);
}
return AllocInfo(size, aChunk);
}
// Validate ptr before assuming that it points to an allocation. Currently,
// the following validation is performed:
//
// + Check that ptr is not nullptr.
//
// + Check that ptr lies within a mapped chunk.
static inline AllocInfo GetValidated(
const void* aPtr) {
return Get<true>(aPtr);
}
AllocInfo() : mSize(
0), mChunk(nullptr) {}
explicit AllocInfo(size_t aSize, arena_chunk_t* aChunk)
: mSize(aSize), mChunk(aChunk) {
MOZ_ASSERT(mSize <= gMaxLargeClass);
}
explicit AllocInfo(size_t aSize, extent_node_t* aNode)
: mSize(aSize), mNode(aNode) {
MOZ_ASSERT(mSize > gMaxLargeClass);
}
size_t Size() {
return mSize; }
arena_t* Arena() {
if (mSize <= gMaxLargeClass) {
return mChunk->mArena;
}
// Best effort detection that we're not trying to access an already
// disposed arena. In the case of a disposed arena, the memory location
// pointed by mNode->mArena is either free (but still a valid memory
// region, per TypedBaseAlloc<arena_t>), in which case its id was reset,
// or has been reallocated for a new region, and its id is very likely
// different (per randomness). In both cases, the id is unlikely to
// match what it was for the disposed arena.
MOZ_RELEASE_ASSERT(mNode->mArenaId == mNode->mArena->mId);
return mNode->mArena;
}
bool IsValid()
const {
return !!mSize; }
private:
size_t mSize;
union {
// Pointer to the chunk associated with the allocation for small
// and large allocations.
arena_chunk_t* mChunk;
// Pointer to the extent node for huge allocations.
extent_node_t* mNode;
};
};
inline void MozJemalloc::jemalloc_ptr_info(
const void* aPtr,
jemalloc_ptr_info_t* aInfo) {
arena_chunk_t* chunk = GetChunkForPtr(aPtr);
// Is the pointer null, or within one chunk's size of null?
// Alternatively, if the allocator is not initialized yet, the pointer
// can't be known.
if (!chunk || !malloc_initialized) {
*aInfo = {TagUnknown, nullptr,
0,
0};
return;
}
// Look for huge allocations before looking for |chunk| in gChunkRTree.
// This is necessary because |chunk| won't be in gChunkRTree if it's
// the second or subsequent chunk in a huge allocation.
extent_node_t* node;
{
MutexAutoLock lock(huge_mtx);
node =
reinterpret_cast<RedBlackTree<extent_node_t, ExtentTreeBoundsTrait>*>(
&huge)
->Search(
const_cast<
void*>(aPtr));
if (node) {
*aInfo = {TagLiveAlloc, node->mAddr, node->mSize, node->mArena->mId};
return;
}
}
// It's not a huge allocation. Check if we have a known chunk.
if (!gChunkRTree.Get(chunk)) {
*aInfo = {TagUnknown, nullptr,
0,
0};
return;
}
MOZ_DIAGNOSTIC_ASSERT(chunk->mArena->mMagic == ARENA_MAGIC);
// Get the page number within the chunk.
size_t pageind = (((uintptr_t)aPtr - (uintptr_t)chunk) >> gPageSize2Pow);
if (pageind < gChunkHeaderNumPages) {
// Within the chunk header.
*aInfo = {TagUnknown, nullptr,
0,
0};
return;
}
size_t mapbits = chunk->mPageMap[pageind].bits;
if (!(mapbits & CHUNK_MAP_ALLOCATED)) {
void* pageaddr = (
void*)(uintptr_t(aPtr) & ~gPageSizeMask);
*aInfo = {TagFreedPage, pageaddr, gPageSize, chunk->mArena->mId};
return;
}
if (mapbits & CHUNK_MAP_LARGE) {
// It's a large allocation. Only the first page of a large
// allocation contains its size, so if the address is not in
// the first page, scan back to find the allocation size.
size_t size;
while (true) {
size = mapbits & ~gPageSizeMask;
if (size !=
0) {
break;
}
// The following two return paths shouldn't occur in
// practice unless there is heap corruption.
pageind--;
MOZ_DIAGNOSTIC_ASSERT(pageind >= gChunkHeaderNumPages);
if (pageind < gChunkHeaderNumPages) {
*aInfo = {TagUnknown, nullptr,
0,
0};
return;
}
mapbits = chunk->mPageMap[pageind].bits;
MOZ_DIAGNOSTIC_ASSERT(mapbits & CHUNK_MAP_LARGE);
if (!(mapbits & CHUNK_MAP_LARGE)) {
*aInfo = {TagUnknown, nullptr,
0,
0};
return;
}
}
void* addr = ((
char*)chunk) + (pageind << gPageSize2Pow);
*aInfo = {TagLiveAlloc, addr, size, chunk->mArena->mId};
return;
}
// It must be a small allocation.
auto run = (arena_run_t*)(mapbits & ~gPageSizeMask);
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
// The allocation size is stored in the run metadata.
size_t size = run->mBin->mSizeClass;
// Address of the first possible pointer in the run after its headers.
uintptr_t reg0_addr = (uintptr_t)run + run->mBin->mRunFirstRegionOffset;
if (aPtr < (
void*)reg0_addr) {
// In the run header.
*aInfo = {TagUnknown, nullptr,
0,
0};
return;
}
// Position in the run.
unsigned regind = ((uintptr_t)aPtr - reg0_addr) / size;
// Pointer to the allocation's base address.
void* addr = (
void*)(reg0_addr + regind * size);
// Check if the allocation has been freed.
unsigned elm = regind >> (LOG2(
sizeof(
int)) +
3);
unsigned bit = regind - (elm << (LOG2(
sizeof(
int)) +
3));
PtrInfoTag tag =
((run->mRegionsMask[elm] & (
1U << bit))) ? TagFreedAlloc : TagLiveAlloc;
*aInfo = {tag, addr, size, chunk->mArena->mId};
}
namespace Debug {
// Helper for debuggers. We don't want it to be inlined and optimized out.
MOZ_NEVER_INLINE jemalloc_ptr_info_t* jemalloc_ptr_info(
const void* aPtr) {
static jemalloc_ptr_info_t info;
MozJemalloc::jemalloc_ptr_info(aPtr, &info);
return &info;
}
}
// namespace Debug
arena_chunk_t* arena_t::DallocSmall(arena_chunk_t* aChunk,
void* aPtr,
arena_chunk_map_t* aMapElm) {
arena_run_t* run;
arena_bin_t* bin;
size_t size;
run = (arena_run_t*)(aMapElm->bits & ~gPageSizeMask);
MOZ_DIAGNOSTIC_ASSERT(run->mMagic == ARENA_RUN_MAGIC);
bin = run->mBin;
size = bin->mSizeClass;
MOZ_DIAGNOSTIC_ASSERT(uintptr_t(aPtr) >=
uintptr_t(run) + bin->mRunFirstRegionOffset);
arena_run_reg_dalloc(run, bin, aPtr, size);
run->mNumFree++;
arena_chunk_t* dealloc_chunk = nullptr;
if (run->mNumFree == bin->mRunNumRegions) {
// This run is entirely freed, remove it from our bin.
#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
run->mMagic =
0;
#endif
MOZ_ASSERT(bin->mNonFullRuns.ElementProbablyInList(run));
bin->mNonFullRuns.remove(run);
dealloc_chunk = DallocRun(run, true);
bin->mNumRuns--;
}
else if (run->mNumFree ==
1) {
// This is first slot we freed from this run, start tracking.
MOZ_ASSERT(!bin->mNonFullRuns.ElementProbablyInList(run));
bin->mNonFullRuns.pushFront(run);
}
// else we just keep the run in mNonFullRuns where it is.
// Note that we could move it to the head of the list here to get a strict
// "most-recently-freed" order, but some of our benchmarks seem to be more
// sensible to the increased overhead that this brings than to the order
// supposedly slightly better for keeping CPU caches warm if we do.
// In general we cannot foresee the future, so any order we choose might
// perform different for different use cases and needs to be balanced with
// the book-keeping overhead via measurements.
mStats.allocated_small -= size;
mStats.operations++;
return dealloc_chunk;
}
arena_chunk_t* arena_t::DallocLarge(arena_chunk_t* aChunk,
void* aPtr) {
MOZ_DIAGNOSTIC_ASSERT((uintptr_t(aPtr) & gPageSizeMask) ==
0);
size_t pageind = (uintptr_t(aPtr) - uintptr_t(aChunk)) >> gPageSize2Pow;
size_t size = aChunk->mPageMap[pageind].bits & ~gPageSizeMask;
mStats.allocated_large -= size;
mStats.operations++;
return DallocRun((arena_run_t*)aPtr, true);
}
static inline void arena_dalloc(
void* aPtr, size_t aOffset, arena_t* aArena) {
MOZ_ASSERT(aPtr);
MOZ_ASSERT(aOffset !=
0);
MOZ_ASSERT(GetChunkOffsetForPtr(aPtr) == aOffset);
auto chunk = (arena_chunk_t*)((uintptr_t)aPtr - aOffset);
auto arena = chunk->mArena;
MOZ_ASSERT(arena);
MOZ_DIAGNOSTIC_ASSERT(arena->mMagic == ARENA_MAGIC);
MOZ_RELEASE_ASSERT(!aArena || arena == aArena);
size_t pageind = aOffset >> gPageSize2Pow;
if (opt_poison) {
AllocInfo info = AllocInfo::GetInChunk(aPtr, chunk, pageind);
MOZ_ASSERT(info.IsValid());
MaybePoison(aPtr, info.Size());
}
arena_chunk_t* chunk_dealloc_delay = nullptr;
purge_action_t purge_action;
{
MOZ_DIAGNOSTIC_ASSERT(arena->mLock.SafeOnThisThread());
MaybeMutexAutoLock lock(arena->mLock);
arena_chunk_map_t* mapelm = &chunk->mPageMap[pageind];
MOZ_RELEASE_ASSERT(
(mapelm->bits &
(CHUNK_MAP_FRESH_MADVISED_OR_DECOMMITTED | CHUNK_MAP_ZEROED)) ==
0,
"Freeing in a page with bad bits.");
MOZ_RELEASE_ASSERT((mapelm->bits & CHUNK_MAP_ALLOCATED) !=
0,
"Double-free?");
if ((mapelm->bits & CHUNK_MAP_LARGE) ==
0) {
// Small allocation.
chunk_dealloc_delay = arena->DallocSmall(chunk, aPtr, mapelm);
}
else {
// Large allocation.
chunk_dealloc_delay = arena->DallocLarge(chunk, aPtr);
}
purge_action = arena->ShouldStartPurge();
}
if (chunk_dealloc_delay) {
arena_chunk_dealloc(arena->mChunkAllocator, (
void*)chunk_dealloc_delay,
kChunkSize);
}
arena->MayDoOrQueuePurge(purge_action,
"arena_dalloc");
}
static inline void idalloc(
void* ptr, arena_t* aArena) {
size_t offset;
MOZ_ASSERT(ptr);
offset = GetChunkOffsetForPtr(ptr);
if (offset !=
0) {
arena_dalloc(ptr, offset, aArena);
}
else {
huge_dalloc(ptr, aArena);
}
}
inline purge_action_t arena_t::ShouldStartPurge() {
if (mNumDirty > mMaxDirty) {
if (!mIsDeferredPurgeEnabled) {
return purge_action_t::PurgeNow;
}
if (mIsPurgePending) {
return purge_action_t::None;
}
mIsPurgePending = true;
return purge_action_t::Queue;
}
return purge_action_t::None;
}
inline void arena_t::MayDoOrQueuePurge(purge_action_t aAction,
const char* aCaller) {
switch (aAction) {
case purge_action_t::Queue:
// Note that this thread committed earlier by setting
// mIsDeferredPurgePending to add us to the list. There is a low
// chance that in the meantime another thread ran Purge() and cleared
// the flag, but that is fine, we'll adjust our bookkeeping when calling
// ShouldStartPurge() or Purge() next time.
gArenas.AddToOutstandingPurges(this);
break;
case purge_action_t::PurgeNow: {
ArenaPurgeResult pr = PurgeLoop(PurgeIfThreshold, aCaller);
// Arenas cannot die here because the caller is still using the arena, if
// they did it'd be a use-after-free: the arena is destroyed but then used
// afterwards.
MOZ_RELEASE_ASSERT(pr != ArenaPurgeResult::Dying);
break;
}
case purge_action_t::None:
// do nothing.
break;
}
}
inline void arena_t::NotifySignificantReuse() {
// Note that there is a chance here for a race between threads calling
// GetTimeStampNS in a different order than writing it to the Atomic,
// resulting in mLastSignificantReuseNS going potentially backwards.
// Our use case is not sensitive to small deviations, the worse that can
// happen is a slightly earlier purge.
mLastSignificantReuseNS = GetTimestampNS();
}
void arena_t::RallocShrinkLarge(arena_chunk_t* aChunk,
void* aPtr, size_t aSize,
size_t aOldSize) {
MOZ_ASSERT(aSize < aOldSize);
// Shrink the run, and make trailing pages available for other
// allocations.
purge_action_t purge_action;
{
MaybeMutexAutoLock lock(mLock);
TrimRunTail(aChunk, (arena_run_t*)aPtr, aOldSize, aSize, true);
mStats.allocated_large -= aOldSize - aSize;
mStats.operations++;
purge_action = ShouldStartPurge();
}
MayDoOrQueuePurge(purge_action,
"RallocShrinkLarge");
}
// Returns whether reallocation was successful.
bool arena_t::RallocGrowLarge(arena_chunk_t* aChunk,
void* aPtr, size_t aSize,
size_t aOldSize) {
size_t pageind = (uintptr_t(aPtr) - uintptr_t(aChunk)) >> gPageSize2Pow;
size_t npages = aOldSize >> gPageSize2Pow;
size_t num_dirty_before, num_dirty_after;
{
MaybeMutexAutoLock lock(mLock);
MOZ_DIAGNOSTIC_ASSERT(aOldSize ==
(aChunk->mPageMap[pageind].bits & ~gPageSizeMask));
// Try to extend the run.
MOZ_ASSERT(aSize > aOldSize);
if (pageind + npages < gChunkNumPages -
1 &&
(aChunk->mPageMap[pageind + npages].bits &
(CHUNK_MAP_ALLOCATED | CHUNK_MAP_BUSY)) ==
0 &&
(aChunk->mPageMap[pageind + npages].bits & ~gPageSizeMask) >=
aSize - aOldSize) {
num_dirty_before = mNumDirty;
// The next run is available and sufficiently large. Split the
// following run, then merge the first part with the existing
// allocation.
mRunsAvail.Remove(&aChunk->mPageMap[pageind + npages]);
if (!SplitAndAllocRun(
(arena_run_t*)(uintptr_t(aChunk) +
((pageind + npages) << gPageSize2Pow)),
aSize - aOldSize, true,
false)) {
mRunsAvail.Insert(&aChunk->mPageMap[pageind + npages]);
return false;
}
aChunk->mPageMap[pageind].bits =
aSize | CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
aChunk->mPageMap[pageind + npages].bits =
CHUNK_MAP_LARGE | CHUNK_MAP_ALLOCATED;
mStats.allocated_large += aSize - aOldSize;
mStats.operations++;
num_dirty_after = mNumDirty;
}
else {
return false;
}
}
if (num_dirty_after < num_dirty_before) {
NotifySignificantReuse();
}
return true;
}
#ifdef XP_DARWIN
# define VM_COPY_MIN kChunkSize
static inline void pages_copy(
void* dest,
const void* src, size_t n) {
MOZ_ASSERT((
void*)((uintptr_t)dest & ~gPageSizeMask) == dest);
MOZ_ASSERT(n >= VM_COPY_MIN);
MOZ_ASSERT((
void*)((uintptr_t)src & ~gPageSizeMask) == src);
kern_return_t r = vm_copy(mach_task_self(), (vm_address_t)src, (vm_size_t)n,
(vm_address_t)dest);
if (r != KERN_SUCCESS) {
MOZ_CRASH(
"vm_copy() failed");
}
}
#endif
void* arena_t::RallocSmallOrLarge(
void* aPtr, size_t aSize, size_t aOldSize) {
void* ret;
size_t copysize;
SizeClass sizeClass(aSize);
// Try to avoid moving the allocation.
if (aOldSize <= gMaxLargeClass && sizeClass.Size() == aOldSize) {
if (aSize < aOldSize) {
MaybePoison((
void*)(uintptr_t(aPtr) + aSize), aOldSize - aSize);
}
return aPtr;
}
if (sizeClass.Type() == SizeClass::Large && aOldSize > gMaxBinClass &&
aOldSize <= gMaxLargeClass) {
arena_chunk_t* chunk = GetChunkForPtr(aPtr);
if (sizeClass.Size() < aOldSize) {
// Fill before shrinking in order to avoid a race.
MaybePoison((
void*)((uintptr_t)aPtr + aSize), aOldSize - aSize);
RallocShrinkLarge(chunk, aPtr, sizeClass.Size(), aOldSize);
return aPtr;
}
if (RallocGrowLarge(chunk, aPtr, sizeClass.Size(), aOldSize)) {
ApplyZeroOrJunk((
void*)((uintptr_t)aPtr + aOldSize), aSize - aOldSize);
return aPtr;
}
}
// If we get here, then aSize and aOldSize are different enough that we
// need to move the object or the run can't be expanded because the memory
// after it is allocated or busy. In that case, fall back to allocating new
// space and copying. Allow non-private arenas to switch arenas.
ret = (mIsPrivate ? this : choose_arena(aSize))->Malloc(aSize,
false);
if (!ret) {
return nullptr;
}
// Junk/zero-filling were already done by arena_t::Malloc().
copysize = (aSize < aOldSize) ? aSize : aOldSize;
#ifdef VM_COPY_MIN
if (copysize >= VM_COPY_MIN) {
pages_copy(ret, aPtr, copysize);
}
else
#endif
{
memcpy(ret, aPtr, copysize);
}
idalloc(aPtr, this);
return ret;
}
void* arena_t::Ralloc(
void* aPtr, size_t aSize, size_t aOldSize) {
MOZ_DIAGNOSTIC_ASSERT(mMagic == ARENA_MAGIC);
MOZ_ASSERT(aPtr);
MOZ_ASSERT(aSize !=
0);
return (aSize <= gMaxLargeClass) ? RallocSmallOrLarge(aPtr, aSize, aOldSize)
: RallocHuge(aPtr, aSize, aOldSize);
}
void* arena_t::
operator new(size_t aCount,
const fallible_t&) noexcept {
MOZ_ASSERT(aCount ==
sizeof(arena_t));
// Ignore aCount, instead allocate axtra space for the trailing array of
// bins.
return sBaseAlloc.alloc(
sizeof(arena_t) +
(
sizeof(arena_bin_t) * NUM_SMALL_CLASSES));
}
arena_t::arena_t(arena_params_t* aParams,
bool aIsPrivate)
: mRandomizeSmallAllocations(opt_randomize_small),
mIsPrivate(aIsPrivate),
// The default maximum amount of dirty pages allowed on arenas is a
// fraction of opt_dirty_max.
mMaxDirtyBase((aParams && aParams->mMaxDirty) ? aParams->mMaxDirty
: (opt_dirty_max /
8)),
mLastSignificantReuseNS(GetTimestampNS()),
mIsDeferredPurgeEnabled(gArenas.IsDeferredPurgeEnabled()),
mChunkAllocator(&gSystemChunkAllocator) {
MaybeMutex::DoLock doLock = MaybeMutex::MUST_LOCK;
if (aParams) {
uint32_t randFlags = aParams->mFlags & ARENA_FLAG_RANDOMIZE_SMALL_MASK;
switch (randFlags) {
case ARENA_FLAG_RANDOMIZE_SMALL_ENABLED:
mRandomizeSmallAllocations = true;
break;
case ARENA_FLAG_RANDOMIZE_SMALL_DISABLED:
mRandomizeSmallAllocations =
false;
break;
case ARENA_FLAG_RANDOMIZE_SMALL_DEFAULT:
default:
break;
}
uint32_t threadFlags = aParams->mFlags & ARENA_FLAG_THREAD_MASK;
if (threadFlags == ARENA_FLAG_THREAD_MAIN_THREAD_ONLY) {
// At the moment we require that any ARENA_FLAG_THREAD_MAIN_THREAD_ONLY
// arenas are created and therefore always accessed by the main thread.
// This is for two reasons:
// * it allows jemalloc_stats to read their statistics (we also require
// that jemalloc_stats is only used on the main thread).
// * Only main-thread or threadsafe arenas can be guanteed to be in a
// consistent state after a fork() from the main thread. If fork()
// occurs off-thread then the new child process cannot use these arenas
// (new children should usually exec() or exit() since other data may
// also be inconsistent).
MOZ_ASSERT(gArenas.IsOnMainThread());
MOZ_ASSERT(aIsPrivate);
doLock = MaybeMutex::AVOID_LOCK_UNSAFE;
}
mMaxDirtyIncreaseOverride = aParams->mMaxDirtyIncreaseOverride;
mMaxDirtyDecreaseOverride = aParams->mMaxDirtyDecreaseOverride;
if (aParams->mLabel) {
// The string may be truncated so always place a null-byte in the last
// position.
strncpy(mLabel, aParams->mLabel, LABEL_MAX_CAPACITY -
1);
mLabel[LABEL_MAX_CAPACITY -
1] =
0;
// If the string was truncated, then replace its end with "..."
if (strlen(aParams->mLabel) >= LABEL_MAX_CAPACITY) {
for (
int i =
0; i <
3; i++) {
mLabel[LABEL_MAX_CAPACITY -
2 - i] =
'.';
}
}
}
if (aParams->mChunkAllocator) {
MOZ_ASSERT(aIsPrivate);
mChunkAllocator = aParams->mChunkAllocator;
}
}
MOZ_RELEASE_ASSERT(mLock.Init(doLock));
UpdateMaxDirty();
// Initialize bins.
SizeClass sizeClass(
1);
unsigned i;
for (i =
0;; i++) {
new (&mBins[i]) arena_bin_t(sizeClass);
// SizeClass doesn't want sizes larger than gMaxBinClass for now.
if (sizeClass.Size() == gMaxBinClass) {
break;
}
sizeClass = sizeClass.Next();
}
MOZ_ASSERT(i == NUM_SMALL_CLASSES -
1);
}
arena_t::~arena_t() {
size_t i;
MaybeMutexAutoLock lock(mLock);
MOZ_RELEASE_ASSERT(!mLink.Left() && !mLink.Right(),
"Arena is still registered");
MOZ_RELEASE_ASSERT(!mStats.allocated_small && !mStats.allocated_large,
"Arena is not empty");
if (mSpare) {
arena_chunk_dealloc(mChunkAllocator, mSpare, kChunkSize);
}
for (i =
0; i < NUM_SMALL_CLASSES; i++) {
MOZ_RELEASE_ASSERT(mBins[i].mNonFullRuns.isEmpty(),
"Bin is not empty");
}
#ifdef MOZ_DEBUG
{
MutexAutoLock lock(huge_mtx);
// This is an expensive check, so we only do it on debug builds.
for (
auto node : huge.iter()) {
MOZ_RELEASE_ASSERT(node->mArenaId != mId,
"Arena has huge allocations");
}
}
#endif
mId =
0;
}
arena_t* ArenaCollection::CreateArena(
bool aIsPrivate,
arena_params_t* aParams) {
arena_t* ret =
new (fallible) arena_t(aParams, aIsPrivate);
if (!ret) {
// Only reached if there is an OOM error.
// OOM here is quite inconvenient to propagate, since dealing with it
// would require a check for failure in the fast path. Instead, punt
// by using the first arena.
// In practice, this is an extremely unlikely failure.
_malloc_message(_getprogname(),
": (malloc) Error initializing arena\n");
return mDefaultArena;
}
MutexAutoLock lock(mLock);
// For public arenas, it's fine to just use incrementing arena id
if (!aIsPrivate) {
ret->mId = mLastPublicArenaId++;
mArenas.Insert(ret);
return ret;
}
#ifdef NON_RANDOM_ARENA_IDS
// For private arenas, slightly obfuscate the id by XORing a key generated
// once, and rotate the bits by an amount also generated once.
if (mArenaIdKey ==
0) {
mozilla::Maybe<uint64_t> maybeRandom = mozilla::RandomUint64();
MOZ_RELEASE_ASSERT(maybeRandom.isSome());
mArenaIdKey = maybeRandom.value();
maybeRandom = mozilla::RandomUint64();
MOZ_RELEASE_ASSERT(maybeRandom.isSome());
mArenaIdRotation = maybeRandom.value() & (
sizeof(
void*) *
8 -
1);
}
arena_id_t id = reinterpret_cast<arena_id_t>(ret) ^ mArenaIdKey;
ret->mId =
(id >> mArenaIdRotation) | (id << (
sizeof(
void*) *
8 - mArenaIdRotation));
mPrivateArenas.Insert(ret);
return ret;
#else
// For private arenas, generate a cryptographically-secure random id for the
// new arena. If an attacker manages to get control of the process, this
// should make it more difficult for them to "guess" the ID of a memory
// arena, stopping them from getting data they may want
Tree& tree = (ret->IsMainThreadOnly()) ? mMainThreadArenas : mPrivateArenas;
arena_id_t arena_id;
do {
arena_id = MakeRandArenaId(ret->IsMainThreadOnly());
// Keep looping until we ensure that the random number we just generated
// isn't already in use by another active arena
}
while (tree.Search(arena_id));
ret->mId = arena_id;
tree.Insert(ret);
return ret;
#endif
}
#ifndef NON_RANDOM_ARENA_IDS
arena_id_t ArenaCollection::MakeRandArenaId(
bool aIsMainThreadOnly)
const {
uint64_t rand;
do {
mozilla::Maybe<uint64_t> maybeRandomId = mozilla::RandomUint64();
MOZ_RELEASE_ASSERT(maybeRandomId.isSome());
rand = maybeRandomId.value();
// Set or clear the least significant bit depending on if this is a
// main-thread-only arena. We use this in GetById.
if (aIsMainThreadOnly) {
rand = rand | MAIN_THREAD_ARENA_BIT;
}
else {
rand = rand & ~MAIN_THREAD_ARENA_BIT;
}
// Avoid 0 as an arena Id. We use 0 for disposed arenas.
}
while (rand ==
0);
return arena_id_t(rand);
}
#endif
// End arena.
// ***************************************************************************
// Begin general internal functions.
// Initialize huge allocation data.
static void huge_init() MOZ_REQUIRES(gInitLock) {
huge_mtx.Init();
MOZ_PUSH_IGNORE_THREAD_SAFETY
huge_allocated =
0;
huge_mapped =
0;
huge_operations =
0;
MOZ_POP_THREAD_SAFETY
}
void* arena_t::MallocHuge(size_t aSize,
bool aZero) {
return PallocHuge(aSize, kChunkSize, aZero);
}
void* arena_t::PallocHuge(size_t aSize, size_t aAlignment,
bool aZero) {
void* ret;
size_t csize;
size_t psize;
extent_node_t* node;
// We're going to configure guard pages in the region between the
// page-aligned size and the chunk-aligned size, so if those are the same
// then we need to force that region into existence.
csize = CHUNK_CEILING(aSize + gRealPageSize);
if (csize < aSize) {
// size is large enough to cause size_t wrap-around.
return nullptr;
}
// Allocate an extent node with which to track the chunk.
node =
new (fallible) extent_node_t();
if (!node) {
return nullptr;
}
// Allocate one or more contiguous chunks for this request.
ret = arena_chunk_alloc(mChunkAllocator, csize, aAlignment);
if (!ret) {
delete node;
return nullptr;
}
psize = REAL_PAGE_CEILING(aSize);
MOZ_ASSERT(psize < csize);
#ifdef MOZ_DEBUG
if (aZero) {
chunk_assert_zero(ret, psize);
}
#endif
// Insert node into huge.
node->mAddr = ret;
node->mSize = psize;
node->mArena = this;
node->mArenaId = mId;
{
MutexAutoLock lock(huge_mtx);
huge.Insert(node);
// Although we allocated space for csize bytes, we indicate that we've
// allocated only psize bytes.
//
// If DECOMMIT is defined, this is a reasonable thing to do, since
// we'll explicitly decommit the bytes in excess of psize.
//
// If DECOMMIT is not defined, then we're relying on the OS to be lazy
// about how it allocates physical pages to mappings. If we never
// touch the pages in excess of psize, the OS won't allocate a physical
// page, and we won't use more than psize bytes of physical memory.
//
// A correct program will only touch memory in excess of how much it
// requested if it first calls malloc_usable_size and finds out how
// much space it has to play with. But because we set node->mSize =
// psize above, malloc_usable_size will return psize, not csize, and
// the program will (hopefully) never touch bytes in excess of psize.
// Thus those bytes won't take up space in physical memory, and we can
// reasonably claim we never "allocated" them in the first place.
huge_allocated += psize;
huge_mapped += csize;
huge_operations++;
}
pages_decommit((
void*)((uintptr_t)ret + psize), csize - psize);
if (!aZero) {
ApplyZeroOrJunk(ret, psize);
}
return ret;
}
void* arena_t::RallocHuge(
void* aPtr, size_t aSize, size_t aOldSize) {
void* ret;
size_t copysize;
// Avoid moving the allocation if the size class would not change.
if (aOldSize > gMaxLargeClass &&
CHUNK_CEILING(aSize + gRealPageSize) ==
CHUNK_CEILING(aOldSize + gRealPageSize)) {
size_t psize = REAL_PAGE_CEILING(aSize);
if (aSize < aOldSize) {
MaybePoison((
void*)((uintptr_t)aPtr + aSize), aOldSize - aSize);
}
if (psize < aOldSize) {
pages_decommit((
void*)((uintptr_t)aPtr + psize), aOldSize - psize);
// Update recorded size.
MutexAutoLock lock(huge_mtx);
extent_node_t* node = huge.Search(aPtr);
MOZ_ASSERT(node);
MOZ_ASSERT(node->mSize == aOldSize);
MOZ_RELEASE_ASSERT(node->mArena == this);
huge_allocated -= aOldSize - psize;
huge_operations++;
// No need to change huge_mapped, because we didn't (un)map anything.
node->mSize = psize;
}
else if (psize > aOldSize) {
if (!pages_commit((
void*)((uintptr_t)aPtr + aOldSize),
psize - aOldSize)) {
return nullptr;
}
// We need to update the recorded size if the size increased,
// so malloc_usable_size doesn't return a value smaller than
// what was requested via realloc().
MutexAutoLock lock(huge_mtx);
extent_node_t* node = huge.Search(aPtr);
MOZ_ASSERT(node);
MOZ_ASSERT(node->mSize == aOldSize);
MOZ_RELEASE_ASSERT(node->mArena == this);
huge_allocated += psize - aOldSize;
huge_operations++;
// No need to change huge_mapped, because we didn't
// (un)map anything.
node->mSize = psize;
}
if (aSize > aOldSize) {
ApplyZeroOrJunk((
void*)((uintptr_t)aPtr + aOldSize), aSize - aOldSize);
}
return aPtr;
}
// If we get here, then aSize and aOldSize are different enough that we
// need to use a different size class. In that case, fall back to allocating
// new space and copying. Allow non-private arenas to switch arenas.
ret = (mIsPrivate ? this : choose_arena(aSize))->MallocHuge(aSize,
false);
if (!ret) {
return nullptr;
}
copysize = (aSize < aOldSize) ? aSize : aOldSize;
#ifdef VM_COPY_MIN
if (copysize >= VM_COPY_MIN) {
pages_copy(ret, aPtr, copysize);
}
else
#endif
{
memcpy(ret, aPtr, copysize);
}
idalloc(aPtr, this);
return ret;
}
static void huge_dalloc(
void* aPtr, arena_t* aArena) {
extent_node_t* node;
size_t mapped =
0;
{
MutexAutoLock lock(huge_mtx);
// Extract from tree of huge allocations.
node = huge.Search(aPtr);
MOZ_RELEASE_ASSERT(node,
"Double-free?");
MOZ_ASSERT(node->mAddr == aPtr);
MOZ_RELEASE_ASSERT(!aArena || node->mArena == aArena);
// See AllocInfo::Arena.
MOZ_RELEASE_ASSERT(node->mArenaId == node->mArena->mId);
huge.Remove(node);
mapped = CHUNK_CEILING(node->mSize + gRealPageSize);
huge_allocated -= node->mSize;
huge_mapped -= mapped;
huge_operations++;
}
// Unmap chunk.
arena_chunk_dealloc(node->mArena->mChunkAllocator, node->mAddr, mapped);
delete node;
}
// Returns whether the allocator was successfully initialized.
static bool malloc_init_hard() {
unsigned i;
const char* opts;
AutoLock<StaticMutex> lock(gInitLock);
if (malloc_initialized) {
// Another thread initialized the allocator before this one
// acquired gInitLock.
return true;
}
if (!thread_arena.init()) {
return true;
}
// Get page size and number of CPUs
const size_t page_size = GetKernelPageSize();
// We assume that the page size is a power of 2.
MOZ_ASSERT(std::has_single_bit(page_size));
#ifdef MALLOC_STATIC_PAGESIZE
if (gRealPageSize % page_size) {
_malloc_message(
_getprogname(),
"Compile-time page size does not divide the runtime one.\n");
MOZ_CRASH();
}
#else
gRealPageSize = page_size;
gPageSize = page_size;
#endif
// Get runtime configuration.
if ((opts = getenv(
"MALLOC_OPTIONS"))) {
for (i =
0; opts[i] !=
'\0'; i++) {
// All options are single letters, some take a *prefix* numeric argument.
// Parse the argument.
unsigned prefix_arg =
0;
while (opts[i] >=
'0' && opts[i] <=
'9') {
prefix_arg *=
10;
prefix_arg += opts[i] -
'0';
i++;
}
switch (opts[i]) {
case 'f':
opt_dirty_max >>= prefix_arg ? prefix_arg :
1;
break;
case 'F':
prefix_arg = prefix_arg ? prefix_arg :
1;
if (opt_dirty_max ==
0) {
opt_dirty_max =
1;
prefix_arg--;
}
opt_dirty_max <<= prefix_arg;
if (opt_dirty_max ==
0) {
// If the shift above overflowed all the bits then clamp the result
// instead. If we started with DIRTY_MAX_DEFAULT then this will
// always be a power of two so choose the maximum power of two that
// fits in a size_t.
opt_dirty_max = size_t(
1) << (
sizeof(size_t) * CHAR_BIT -
1);
}
break;
#ifdef MALLOC_RUNTIME_CONFIG
case 'j':
opt_junk =
false;
break;
case 'J':
opt_junk = true;
break;
case 'q':
// The argument selects how much poisoning to do.
opt_poison = NONE;
break;
case 'Q':
if (opts[i +
1] ==
'Q') {
// Maximum poisoning.
i++;
opt_poison = ALL;
}
else {
opt_poison = SOME;
opt_poison_size = kCacheLineSize * prefix_arg;
}
break;
case 'z':
opt_zero =
false;
break;
case 'Z':
opt_zero = true;
break;
# ifndef MALLOC_STATIC_PAGESIZE
case 'P':
MOZ_ASSERT(gPageSize >=
1_KiB);
MOZ_ASSERT(gPageSize <=
64_KiB);
prefix_arg = prefix_arg ? prefix_arg :
1;
gPageSize <<= prefix_arg;
// We know that if the shift causes gPageSize to be zero then it's
// because it shifted all the bits off. We didn't start with zero.
// Therefore if gPageSize is out of bounds we set it to 64KiB.
if (gPageSize <
1_KiB || gPageSize >
64_KiB) {
gPageSize =
64_KiB;
}
// We also limit gPageSize to be no larger than gRealPageSize, there's
// no reason to support this.
if (gPageSize > gRealPageSize) {
gPageSize = gRealPageSize;
}
break;
case 'p':
MOZ_ASSERT(gPageSize >=
1_KiB);
MOZ_ASSERT(gPageSize <=
64_KiB);
prefix_arg = prefix_arg ? prefix_arg :
1;
gPageSize >>= prefix_arg;
if (gPageSize <
1_KiB) {
gPageSize =
1_KiB;
}
break;
# endif
#endif
case 'r':
opt_randomize_small =
false;
break;
case 'R':
opt_randomize_small = true;
break;
default: {
char cbuf[
2];
cbuf[
0] = opts[i];
cbuf[
1] =
'\0';
_malloc_message(_getprogname(),
": (malloc) Unsupported character "
"in malloc options: '",
cbuf,
"'\n");
}
}
}
}
MOZ_ASSERT(gPageSize <= gRealPageSize);
#ifndef MALLOC_STATIC_PAGESIZE
DefineGlobals();
#endif
gRecycledSize =
0;
chunks_init();
huge_init();
sBaseAlloc.Init();
// Initialize arenas collection here.
if (!gArenas.Init()) {
return false;
}
// Assign the default arena to the initial thread.
thread_arena.set(gArenas.GetDefault());
if (!gChunkRTree.Init()) {
return false;
}
malloc_initialized = true;
// Dummy call so that the function is not removed by dead-code elimination
Debug::jemalloc_ptr_info(nullptr);
#if !
defined(XP_WIN) && !
defined(XP_DARWIN)
// Prevent potential deadlock on malloc locks after fork.
pthread_atfork(_malloc_prefork, _malloc_postfork_parent,
_malloc_postfork_child);
#endif
#ifdef MOZ_PHC
// PHC must be initialised after mozjemalloc.
phc_init();
#endif
return true;
}
// End general internal functions.
// ***************************************************************************
// Begin malloc(3)-compatible functions.
// The BaseAllocator class is a helper class that implements the base allocator
// functions (malloc, calloc, realloc, free, memalign) for a given arena,
// or an appropriately chosen arena (per choose_arena()) when none is given.
struct BaseAllocator {
#define MALLOC_DECL(name, return_type, ...) \
inline return_type name(__VA_ARGS__);
#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
#include "malloc_decls.h"
explicit BaseAllocator(arena_t* aArena) : mArena(aArena) {}
private:
arena_t* mArena;
};
#define MALLOC_DECL(name, return_type, ...) \
inline return_type MozJemalloc::name( \
ARGS_HELPER(TYPED_ARGS,
##__VA_ARGS__)) { \
BaseAllocator allocator(nullptr); \
return allocator.name(ARGS_HELPER(ARGS,
##__VA_ARGS__)); \
}
#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
#include "malloc_decls.h"
inline void* BaseAllocator::malloc(size_t aSize) {
void* ret;
arena_t* arena;
if (!malloc_init()) {
ret = nullptr;
goto RETURN;
}
if (aSize ==
0) {
aSize =
1;
}
// If mArena is non-null, it must not be in the first page.
MOZ_DIAGNOSTIC_ASSERT_IF(mArena, (size_t)mArena >= gPageSize);
arena = mArena ? mArena : choose_arena(aSize);
ret = arena->Malloc(aSize,
/* aZero = */ false);
RETURN:
if (!ret) {
errno = ENOMEM;
}
return ret;
}
inline void* BaseAllocator::memalign(size_t aAlignment, size_t aSize) {
MOZ_ASSERT(((aAlignment -
1) & aAlignment) ==
0);
if (!malloc_init()) {
return nullptr;
}
if (aSize ==
0) {
aSize =
1;
}
aAlignment = aAlignment <
sizeof(
void*) ?
sizeof(
void*) : aAlignment;
arena_t* arena = mArena ? mArena : choose_arena(aSize);
return arena->Palloc(aAlignment, aSize);
}
inline void* BaseAllocator::calloc(size_t aNum, size_t aSize) {
void* ret;
if (malloc_init()) {
CheckedInt<size_t> checkedSize = CheckedInt<size_t>(aNum) * aSize;
if (checkedSize.isValid()) {
size_t allocSize = checkedSize.value();
if (allocSize ==
0) {
allocSize =
1;
}
arena_t* arena = mArena ? mArena : choose_arena(allocSize);
ret = arena->Malloc(allocSize,
/* aZero = */ true);
}
else {
ret = nullptr;
}
}
else {
ret = nullptr;
}
if (!ret) {
errno = ENOMEM;
}
return ret;
}
inline void* BaseAllocator::realloc(
void* aPtr, size_t aSize) {
void* ret;
if (aSize ==
0) {
aSize =
1;
}
if (aPtr) {
MOZ_RELEASE_ASSERT(malloc_initialized);
auto info = AllocInfo::Get(aPtr);
auto arena = info.Arena();
MOZ_RELEASE_ASSERT(!mArena || arena == mArena);
ret = arena->Ralloc(aPtr, aSize, info.Size());
}
else {
if (!malloc_init()) {
ret = nullptr;
}
else {
arena_t* arena = mArena ? mArena : choose_arena(aSize);
ret = arena->Malloc(aSize,
/* aZero = */ false);
}
}
if (!ret) {
errno = ENOMEM;
}
return ret;
}
inline void BaseAllocator::free(
void* aPtr) {
size_t offset;
// A version of idalloc that checks for nullptr pointer.
offset = GetChunkOffsetForPtr(aPtr);
if (offset !=
0) {
MOZ_RELEASE_ASSERT(malloc_initialized);
arena_dalloc(aPtr, offset, mArena);
}
else if (aPtr) {
MOZ_RELEASE_ASSERT(malloc_initialized);
huge_dalloc(aPtr, mArena);
}
}
inline int MozJemalloc::posix_memalign(
void** aMemPtr, size_t aAlignment,
size_t aSize) {
return AlignedAllocator<memalign>::posix_memalign(aMemPtr, aAlignment, aSize);
}
inline void* MozJemalloc::aligned_alloc(size_t aAlignment, size_t aSize) {
return AlignedAllocator<memalign>::aligned_alloc(aAlignment, aSize);
}
inline void* MozJemalloc::valloc(size_t aSize) {
return AlignedAllocator<memalign>::valloc(aSize);
}
// End malloc(3)-compatible functions.
// ***************************************************************************
// Begin non-standard functions.
// This was added by Mozilla for use by SQLite.
inline size_t MozJemalloc::malloc_good_size(size_t aSize) {
if (aSize ==
0) {
aSize = SizeClass(
1).Size();
}
else if (aSize <= gMaxLargeClass) {
// Small or large
aSize = SizeClass(aSize).Size();
}
else {
// Huge. We use PAGE_CEILING to get psize, instead of using
// CHUNK_CEILING to get csize. This ensures that this
// malloc_usable_size(malloc(n)) always matches
// malloc_good_size(n).
aSize = REAL_PAGE_CEILING(aSize);
}
return aSize;
}
inline size_t MozJemalloc::malloc_usable_size(usable_ptr_t aPtr) {
return AllocInfo::GetValidated(aPtr).Size();
}
inline void MozJemalloc::jemalloc_stats_internal(
jemalloc_stats_t* aStats, jemalloc_bin_stats_t* aBinStats) {
size_t non_arena_mapped, chunk_header_size;
if (!aStats) {
return;
}
if (!malloc_init()) {
memset(aStats,
0,
sizeof(*aStats));
return;
}
if (aBinStats) {
memset(aBinStats,
0,
sizeof(jemalloc_bin_stats_t) * NUM_SMALL_CLASSES);
}
// Gather runtime settings.
aStats->opt_junk = opt_junk;
aStats->opt_randomize_small = opt_randomize_small;
aStats->opt_zero = opt_zero;
aStats->quantum = kQuantum;
aStats->quantum_max = kMaxQuantumClass;
aStats->quantum_wide = kQuantumWide;
aStats->quantum_wide_max = kMaxQuantumWideClass;
aStats->subpage_max = gMaxSubPageClass;
aStats->large_max = gMaxLargeClass;
aStats->chunksize = kChunkSize;
aStats->page_size = gPageSize;
aStats->real_page_size = gRealPageSize;
aStats->dirty_max = opt_dirty_max;
aStats->arena_run_header = offsetof(arena_run_t, mRegionsMask);
// Gather current memory usage statistics.
aStats->narenas =
0;
aStats->mapped =
0;
aStats->allocated =
0;
aStats->waste =
0;
aStats->pages_dirty =
0;
aStats->pages_fresh =
0;
aStats->pages_madvised =
0;
aStats->bookkeeping =
0;
aStats->bin_unused =
0;
non_arena_mapped =
0;
// Get huge mapped/allocated.
{
MutexAutoLock lock(huge_mtx);
non_arena_mapped += huge_mapped;
aStats->allocated += huge_allocated;
aStats->num_operations += huge_operations;
MOZ_ASSERT(huge_mapped >= huge_allocated);
}
// Get base mapped/allocated.
auto base_stats = sBaseAlloc.GetStats();
non_arena_mapped += base_stats.mMapped;
aStats->bookkeeping += base_stats.mCommitted;
gArenas.mLock.Lock();
// Stats can only read complete information if its run on the main thread.
MOZ_ASSERT(gArenas.IsOnMainThreadWeak());
// Iterate over arenas.
for (
auto arena : gArenas.iter()) {
// Cannot safely read stats for this arena and therefore stats would be
// incomplete.
MOZ_ASSERT(arena->mLock.SafeOnThisThread());
size_t arena_mapped, arena_allocated, arena_committed, arena_dirty,
arena_fresh, arena_madvised, j, arena_unused, arena_headers;
arena_headers =
0;
arena_unused =
0;
{
MaybeMutexAutoLock lock(arena->mLock);
arena_mapped = arena->mStats.mapped;
// "committed" counts dirty and allocated memory.
arena_committed = arena->mStats.committed << gPageSize2Pow;
arena_allocated =
arena->mStats.allocated_small + arena->mStats.allocated_large;
arena_dirty = arena->mNumDirty << gPageSize2Pow;
arena_fresh = arena->mNumFresh << gPageSize2Pow;
arena_madvised = arena->mNumMAdvised << gPageSize2Pow;
aStats->num_operations += arena->mStats.operations;
for (j =
0; j < NUM_SMALL_CLASSES; j++) {
arena_bin_t* bin = &arena->mBins[j];
size_t bin_unused =
0;
size_t num_non_full_runs =
0;
for (arena_run_t& run : bin->mNonFullRuns) {
MOZ_DIAGNOSTIC_ASSERT(run.mMagic == ARENA_RUN_MAGIC);
MOZ_RELEASE_ASSERT(run.mNumFree >
0 &&
run.mNumFree < bin->mRunNumRegions);
MOZ_RELEASE_ASSERT(run.mBin == bin);
MOZ_RELEASE_ASSERT(bin->mNonFullRuns.ElementIsLinkedWell(&run));
arena_chunk_t* chunk = GetChunkForPtr(&run);
MOZ_RELEASE_ASSERT(chunk->mArena == arena);
bin_unused += run.mNumFree * bin->mSizeClass;
num_non_full_runs++;
}
arena_unused += bin_unused;
arena_headers += bin->mNumRuns * bin->mRunFirstRegionOffset;
if (aBinStats) {
aBinStats[j].size = bin->mSizeClass;
aBinStats[j].num_non_full_runs += num_non_full_runs;
aBinStats[j].num_runs += bin->mNumRuns;
aBinStats[j].bytes_unused += bin_unused;
size_t bytes_per_run = static_cast<size_t>(bin->mRunSizePages)
<< gPageSize2Pow;
aBinStats[j].bytes_total +=
bin->mNumRuns * (bytes_per_run - bin->mRunFirstRegionOffset);
aBinStats[j].bytes_per_run = bytes_per_run;
aBinStats[j].regions_per_run = bin->mRunNumRegions;
}
}
}
MOZ_ASSERT(arena_mapped >= arena_committed);
MOZ_ASSERT(arena_committed >= arena_allocated + arena_dirty);
aStats->mapped += arena_mapped;
aStats->allocated += arena_allocated;
aStats->pages_dirty += arena_dirty;
aStats->pages_fresh += arena_fresh;
aStats->pages_madvised += arena_madvised;
// "waste" is committed memory that is neither dirty nor
// allocated. If you change this definition please update
// memory/replace/logalloc/replay/Replay.cpp's jemalloc_stats calculation of
// committed.
MOZ_ASSERT(arena_committed >=
(arena_allocated + arena_dirty + arena_unused + arena_headers));
aStats->waste += arena_committed - arena_allocated - arena_dirty -
arena_unused - arena_headers;
aStats->bin_unused += arena_unused;
aStats->bookkeeping += arena_headers;
aStats->narenas++;
}
gArenas.mLock.Unlock();
// Account for arena chunk headers in bookkeeping rather than waste.
chunk_header_size =
((aStats->mapped / aStats->chunksize) * (gChunkHeaderNumPages -
1))
<< gPageSize2Pow;
aStats->mapped += non_arena_mapped;
aStats->bookkeeping += chunk_header_size;
aStats->waste -= chunk_header_size;
MOZ_ASSERT(aStats->mapped >= aStats->allocated + aStats->waste +
aStats->pages_dirty + aStats->bookkeeping);
}
inline void MozJemalloc::jemalloc_stats_lite(jemalloc_stats_lite_t* aStats) {
if (!aStats) {
return;
}
if (!malloc_init()) {
memset(aStats,
0,
sizeof(*aStats));
return;
}
aStats->allocated_bytes =
0;
aStats->num_operations =
0;
// Get huge mapped/allocated.
{
MutexAutoLock lock(huge_mtx);
aStats->allocated_bytes += huge_allocated;
aStats->num_operations += huge_operations;
MOZ_ASSERT(huge_mapped >= huge_allocated);
}
{
MutexAutoLock lock(gArenas.mLock);
for (
auto arena : gArenas.iter()) {
// We don't need to lock the arena to access these fields.
aStats->allocated_bytes += arena->AllocatedBytes();
aStats->num_operations += arena->Operations();
}
aStats->num_operations += gArenas.OperationsDisposedArenas();
}
}
inline size_t MozJemalloc::jemalloc_stats_num_bins() {
return NUM_SMALL_CLASSES;
}
inline void MozJemalloc::jemalloc_set_main_thread() {
MOZ_ASSERT(malloc_initialized);
gArenas.SetMainThread();
}
#ifdef MALLOC_DOUBLE_PURGE
// Explicitly remove all of this chunk's MADV_FREE'd pages from memory.
static size_t hard_purge_chunk(arena_chunk_t* aChunk) {
size_t total_npages =
0;
// See similar logic in arena_t::Purge().
for (size_t i = gChunkHeaderNumPages; i < gChunkNumPages; i++) {
// Find all adjacent pages with CHUNK_MAP_MADVISED set.
size_t npages;
for (npages =
0; aChunk->mPageMap[i + npages].bits & CHUNK_MAP_MADVISED &&
i + npages < gChunkNumPages;
npages++) {
// Turn off the page's CHUNK_MAP_MADVISED bit and turn on its
// CHUNK_MAP_FRESH bit.
MOZ_DIAGNOSTIC_ASSERT(!(aChunk->mPageMap[i + npages].bits &
(CHUNK_MAP_FRESH | CHUNK_MAP_DECOMMITTED)));
aChunk->mPageMap[i + npages].bits ^=
(CHUNK_MAP_MADVISED | CHUNK_MAP_FRESH);
}
// We could use mincore to find out which pages are actually
// present, but it's not clear that's better.
if (npages >
0) {
// i and npages should be aligned because they needed to be for the
// purge code that set CHUNK_MAP_MADVISED.
MOZ_ASSERT((i % gPagesPerRealPage) ==
0);
MOZ_ASSERT((npages % gPagesPerRealPage) ==
0);
pages_decommit(((
char*)aChunk) + (i << gPageSize2Pow),
npages << gPageSize2Pow);
(
void)pages_commit(((
char*)aChunk) + (i << gPageSize2Pow),
npages << gPageSize2Pow);
}
total_npages += npages;
i += npages;
}
return total_npages;
}
// Explicitly remove all of this arena's MADV_FREE'd pages from memory.
void arena_t::HardPurge() {
MaybeMutexAutoLock lock(mLock);
while (!mChunksMAdvised.isEmpty()) {
arena_chunk_t* chunk = mChunksMAdvised.popFront();
size_t npages = hard_purge_chunk(chunk);
mNumMAdvised -= npages;
mNumFresh += npages;
}
}
inline void MozJemalloc::jemalloc_purge_freed_pages() {
if (malloc_initialized) {
MutexAutoLock lock(gArenas.mLock);
MOZ_ASSERT(gArenas.IsOnMainThreadWeak());
for (
auto arena : gArenas.iter()) {
arena->HardPurge();
}
}
}
#else // !defined MALLOC_DOUBLE_PURGE
inline void MozJemalloc::jemalloc_purge_freed_pages() {
// Do nothing.
}
#endif // defined MALLOC_DOUBLE_PURGE
inline void MozJemalloc::jemalloc_free_dirty_pages(
void) {
if (malloc_initialized) {
gArenas.MayPurgeAll(PurgeUnconditional, __func__);
}
}
inline void MozJemalloc::jemalloc_free_excess_dirty_pages(
void) {
if (malloc_initialized) {
gArenas.MayPurgeAll(PurgeIfThreshold, __func__);
}
}
inline arena_t* ArenaCollection::GetById(arena_id_t aArenaId,
bool aIsPrivate) {
if (!malloc_initialized) {
return nullptr;
}
#ifdef NON_RANDOM_ARENA_IDS
// This function is never called with aIsPrivate = false, let's make sure it
// doesn't silently change while we're making that assumption below because
// we can't resolve non-private arenas this way.
MOZ_RELEASE_ASSERT(aIsPrivate);
// This function is not expected to be called before at least one private
// arena was created.
// coverity[missing_lock]
MOZ_RELEASE_ASSERT(mArenaIdKey);
arena_id_t id = (aArenaId << mArenaIdRotation) |
(aArenaId >> (
sizeof(
void*) *
8 - mArenaIdRotation));
arena_t* result = reinterpret_cast<arena_t*>(id ^ mArenaIdKey);
#else
Tree* tree = nullptr;
if (aIsPrivate) {
if (ArenaIdIsMainThreadOnly(aArenaId)) {
// The main thread only arenas support lock free access, so it's desirable
// to do GetById without taking mLock either.
//
// Races can occur between writers and writers, or between writers and
// readers. The only writer is the main thread and it will never race
// against itself so we can elude the lock when the main thread is
// reading.
MOZ_ASSERT(IsOnMainThread());
MOZ_PUSH_IGNORE_THREAD_SAFETY
arena_t* result = mMainThreadArenas.Search(aArenaId);
MOZ_POP_THREAD_SAFETY
MOZ_RELEASE_ASSERT(result);
return result;
}
tree = &mPrivateArenas;
}
else {
tree = &mArenas;
}
MutexAutoLock lock(mLock);
arena_t* result = tree->Search(aArenaId);
#endif
MOZ_RELEASE_ASSERT(result);
MOZ_RELEASE_ASSERT(result->mId == aArenaId);
return result;
}
inline arena_id_t MozJemalloc::moz_create_arena_with_params(
arena_params_t* aParams) {
if (malloc_init()) {
arena_t* arena = gArenas.CreateArena(
/* IsPrivate = */ true, aParams);
return arena->mId;
}
return 0;
}
inline void MozJemalloc::moz_dispose_arena(arena_id_t aArenaId) {
arena_t* arena = gArenas.GetById(aArenaId,
/* IsPrivate = */ true);
MOZ_RELEASE_ASSERT(arena);
gArenas.DisposeArena(arena);
}
inline void MozJemalloc::moz_set_max_dirty_page_modifier(int32_t aModifier) {
if (malloc_init()) {
gArenas.SetDefaultMaxDirtyPageModifier(aModifier);
}
}
inline void MozJemalloc::jemalloc_reset_small_alloc_randomization(
bool aRandomizeSmall) {
// When this process got forked by ForkServer then it inherited the existing
// state of mozjemalloc. Specifically, parsing of MALLOC_OPTIONS has already
// been done but it may not reflect anymore the current set of options after
// the fork().
//
// Similar behavior is also present on Android where it is also required to
// perform this step.
//
// Content process will have randomization on small malloc disabled via the
// MALLOC_OPTIONS environment variable set by parent process, missing this
// will lead to serious performance regressions because CPU prefetch will
// break, cf bug 1912262. However on forkserver-forked Content processes, the
// environment is not yet reset when the postfork child handler is being
// called.
//
// This API is here to allow those Content processes (spawned by ForkServer or
// Android service) to notify jemalloc to turn off the randomization on small
// allocations and perform the required reinitialization of already existing
// arena's PRNG. It is important to make sure that the PRNG state is properly
// re-initialized otherwise child processes would share all the same state.
{
AutoLock<StaticMutex> lock(gInitLock);
opt_randomize_small = aRandomizeSmall;
}
MutexAutoLock lock(gArenas.mLock);
for (
auto* arena : gArenas.iter()) {
// We can only initialize the PRNG for main-thread-only arenas from the main
// thread.
if (!arena->IsMainThreadOnly() || gArenas.IsOnMainThreadWeak()) {
arena->ResetSmallAllocRandomization();
}
}
}
inline bool MozJemalloc::moz_enable_deferred_purge(
bool aEnabled) {
return gArenas.SetDeferredPurge(aEnabled);
}
inline may_purge_now_result_t MozJemalloc::moz_may_purge_now(
bool aPeekOnly, uint32_t aReuseGraceMS,
const Maybe<std::function<
bool()>>& aKeepGoing) {
return gArenas.MayPurgeSteps(aPeekOnly, aReuseGraceMS, aKeepGoing);
}
inline void ArenaCollection::AddToOutstandingPurges(arena_t* aArena) {
MOZ_ASSERT(aArena);
// We cannot trust the caller to know whether the element was already added
// from another thread given we have our own lock.
MutexAutoLock lock(mPurgeListLock);
if (!mOutstandingPurges.ElementProbablyInList(aArena)) {
mOutstandingPurges.pushBack(aArena);
}
}
inline bool ArenaCollection::RemoveFromOutstandingPurges(arena_t* aArena) {
MOZ_ASSERT(aArena);
// We cannot trust the caller to know whether the element was already removed
// from another thread given we have our own lock.
MutexAutoLock lock(mPurgeListLock);
if (mOutstandingPurges.ElementProbablyInList(aArena)) {
mOutstandingPurges.remove(aArena);
return true;
}
return false;
}
may_purge_now_result_t ArenaCollection::MayPurgeSteps(
bool aPeekOnly, uint32_t aReuseGraceMS,
const Maybe<std::function<
bool()>>& aKeepGoing) {
// This only works on the main thread because it may process main-thread-only
// arenas.
MOZ_ASSERT(IsOnMainThreadWeak());
uint64_t now = GetTimestampNS();
uint64_t reuseGraceNS = (uint64_t)aReuseGraceMS *
1000 *
1000;
arena_t* found = nullptr;
{
MutexAutoLock lock(mPurgeListLock);
if (mOutstandingPurges.isEmpty()) {
return may_purge_now_result_t::Done;
}
for (arena_t& arena : mOutstandingPurges) {
if (now - arena.mLastSignificantReuseNS >= reuseGraceNS) {
found = &arena;
break;
}
}
if (!found) {
return may_purge_now_result_t::WantsLater;
}
if (aPeekOnly) {
return may_purge_now_result_t::NeedsMore;
}
// We need to avoid the invalid state where mIsDeferredPurgePending is set
// but the arena is not in the list or about to be added. So remove the
// arena from the list before calling Purge().
mOutstandingPurges.remove(found);
}
ArenaPurgeResult pr =
found->PurgeLoop(PurgeIfThreshold, __func__, aReuseGraceMS, aKeepGoing);
if (pr == ArenaPurgeResult::NotDone) {
// If there's more work to do we re-insert the arena into the purge queue.
// If the arena was busy we don't since the other thread that's purging it
// will finish that work.
// Note that after the above Purge() and taking the lock below there's a
// chance another thread may be purging the arena and clear
// mIsDeferredPurgePending. Resulting in the state of being in the list
// with that flag clear. That's okay since the next time a purge occurs
// (and one will because it's in the list) it'll clear the flag and the
// state will be consistent again.
MutexAutoLock lock(mPurgeListLock);
if (!mOutstandingPurges.ElementProbablyInList(found)) {
// Given we want to continue to purge this arena, push it to the front
// to increase the probability to find it fast.
mOutstandingPurges.pushFront(found);
}
}
else if (pr == ArenaPurgeResult::Dying) {
delete found;
}
// Even if there is no other arena that needs work, let the caller just call
// us again and we will do the above checks then and return their result.
// Note that in the current surrounding setting this may (rarely) cause a
// new slice of our idle task runner if we are exceeding idle budget.
return may_purge_now_result_t::NeedsMore;
}
void ArenaCollection::MayPurgeAll(PurgeCondition aCond,
const char* aCaller) {
MutexAutoLock lock(mLock);
for (
auto* arena : iter()) {
// Arenas that are not IsMainThreadOnly can be purged from any thread.
// So we do what we can even if called from another thread.
if (!arena->IsMainThreadOnly() || IsOnMainThreadWeak()) {
RemoveFromOutstandingPurges(arena);
ArenaPurgeResult pr = arena->PurgeLoop(aCond, aCaller);
// No arena can die here because we're holding the arena collection lock.
// Arenas are removed from the collection before setting their mDying
// flag.
MOZ_RELEASE_ASSERT(pr != ArenaPurgeResult::Dying);
}
}
}
#define MALLOC_DECL(name, return_type, ...) \
inline return_type MozJemalloc::moz_arena_
##name( \
arena_id_t aArenaId, ARGS_HELPER(TYPED_ARGS,
##__VA_ARGS__)) { \
BaseAllocator allocator( \
gArenas.GetById(aArenaId,
/* IsPrivate = */ true)); \
return allocator.name(ARGS_HELPER(ARGS,
##__VA_ARGS__)); \
}
#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
#include "malloc_decls.h"
// End non-standard functions.
// ***************************************************************************
#ifndef XP_WIN
// Begin library-private functions, used by threading libraries for protection
// of malloc during fork(). These functions are only called if the program is
// running in threaded mode, so there is no need to check whether the program
// is threaded here.
//
// Note that the only way to keep the main-thread-only arenas in a consistent
// state for the child is if fork is called from the main thread only. Or the
// child must not use them, eg it should call exec(). We attempt to prevent the
// child for accessing these arenas by refusing to re-initialise them.
//
// This is only accessed in the fork handlers while gArenas.mLock is held.
static pthread_t gForkingThread;
# ifdef XP_DARWIN
// This is only accessed in the fork handlers while gArenas.mLock is held.
static pid_t gForkingProcess;
# endif
FORK_HOOK
void _malloc_prefork(
void) MOZ_NO_THREAD_SAFETY_ANALYSIS {
// Acquire all mutexes in a safe order.
gArenas.mLock.Lock();
gForkingThread = pthread_self();
# ifdef XP_DARWIN
gForkingProcess = getpid();
# endif
for (
auto arena : gArenas.iter()) {
if (arena->mLock.LockIsEnabled()) {
arena->mLock.Lock();
}
}
gArenas.mPurgeListLock.Lock();
sBaseAlloc.mMutex.Lock();
huge_mtx.Lock();
}
FORK_HOOK
void _malloc_postfork_parent(
void) MOZ_NO_THREAD_SAFETY_ANALYSIS {
// Release all mutexes, now that fork() has completed.
huge_mtx.Unlock();
sBaseAlloc.mMutex.Unlock();
gArenas.mPurgeListLock.Unlock();
for (
auto arena : gArenas.iter()) {
if (arena->mLock.LockIsEnabled()) {
arena->mLock.Unlock();
}
}
gArenas.mLock.Unlock();
}
FORK_HOOK
void _malloc_postfork_child(
void) {
// Do this before iterating over the arenas.
gArenas.ResetMainThread();
// Reinitialize all mutexes, now that fork() has completed.
huge_mtx.Init();
sBaseAlloc.mMutex.Init();
gArenas.mPurgeListLock.Init();
MOZ_PUSH_IGNORE_THREAD_SAFETY
for (
auto arena : gArenas.iter()) {
arena->mLock.Reinit(gForkingThread);
}
MOZ_POP_THREAD_SAFETY
gArenas.mLock.Init();
}
# ifdef XP_DARWIN
FORK_HOOK
void _malloc_postfork(
void) {
// On MacOS we need to check if this is running in the parent or child
// process.
bool is_in_parent = getpid() == gForkingProcess;
gForkingProcess =
0;
if (is_in_parent) {
_malloc_postfork_parent();
}
else {
_malloc_postfork_child();
}
}
# endif
// XP_DARWIN
#endif // ! XP_WIN
// End library-private functions.
// ***************************************************************************
#ifdef MOZ_REPLACE_MALLOC
// Windows doesn't come with weak imports as they are possible with
// LD_PRELOAD or DYLD_INSERT_LIBRARIES on Linux/OSX. On this platform,
// the replacement functions are defined as variable pointers to the
// function resolved with GetProcAddress() instead of weak definitions
// of functions. On Android, the same needs to happen as well, because
// the Android linker doesn't handle weak linking with non LD_PRELOADed
// libraries, but LD_PRELOADing is not very convenient on Android, with
// the zygote.
# ifdef XP_DARWIN
# define MOZ_REPLACE_WEAK __attribute__((weak_import))
# elif
defined(XP_WIN) ||
defined(ANDROID)
# define MOZ_DYNAMIC_REPLACE_INIT
# define replace_init replace_init_decl
# elif
defined(__GNUC__)
# define MOZ_REPLACE_WEAK __attribute__((weak))
# endif
# include
"replace_malloc.h"
# define MALLOC_DECL(name, return_type, ...) CanonicalMalloc::name,
// The default malloc table, i.e. plain allocations. It never changes. It's
// used by init(), and not used after that.
static const malloc_table_t gDefaultMallocTable = {
# include
"malloc_decls.h"
};
// The malloc table installed by init(). It never changes from that point
// onward. It will be the same as gDefaultMallocTable if no replace-malloc tool
// is enabled at startup.
static malloc_table_t gOriginalMallocTable = {
# include
"malloc_decls.h"
};
// The malloc table installed by jemalloc_replace_dynamic(). (Read the
// comments above that function for more details.)
static malloc_table_t gDynamicMallocTable = {
# include
"malloc_decls.h"
};
// This briefly points to gDefaultMallocTable at startup. After that, it points
// to either gOriginalMallocTable or gDynamicMallocTable. It's atomic to avoid
// races when switching between tables.
static Atomic<malloc_table_t
const*, mozilla::MemoryOrdering::Relaxed>
gMallocTablePtr;
# ifdef MOZ_DYNAMIC_REPLACE_INIT
# undef replace_init
typedef decltype(replace_init_decl) replace_init_impl_t;
static replace_init_impl_t* replace_init = nullptr;
# endif
# ifdef XP_WIN
typedef HMODULE replace_malloc_handle_t;
static replace_malloc_handle_t replace_malloc_handle() {
wchar_t replace_malloc_lib[
1024];
if (GetEnvironmentVariableW(L
"MOZ_REPLACE_MALLOC_LIB", replace_malloc_lib,
std::size(replace_malloc_lib)) >
0) {
return LoadLibraryW(replace_malloc_lib);
}
return nullptr;
}
# define REPLACE_MALLOC_GET_INIT_FUNC(handle) \
(replace_init_impl_t*)GetProcAddress(handle,
"replace_init")
# elif
defined(ANDROID)
# include <dlfcn.h>
typedef void* replace_malloc_handle_t;
static replace_malloc_handle_t replace_malloc_handle() {
const char* replace_malloc_lib = getenv(
"MOZ_REPLACE_MALLOC_LIB");
if (replace_malloc_lib && *replace_malloc_lib) {
return dlopen(replace_malloc_lib, RTLD_LAZY);
}
return nullptr;
}
# define REPLACE_MALLOC_GET_INIT_FUNC(handle) \
(replace_init_impl_t*)dlsym(handle,
"replace_init")
# endif
static void replace_malloc_init_funcs(malloc_table_t*);
# ifdef MOZ_REPLACE_MALLOC_STATIC
extern "C" void logalloc_init(malloc_table_t*, ReplaceMallocBridge**);
extern "C" void dmd_init(malloc_table_t*, ReplaceMallocBridge**);
# endif
void phc_init(malloc_table_t*, ReplaceMallocBridge**);
bool Equals(
const malloc_table_t& aTable1,
const malloc_table_t& aTable2) {
return memcmp(&aTable1, &aTable2,
sizeof(malloc_table_t)) ==
0;
}
// Below is the malloc implementation overriding jemalloc and calling the
// replacement functions if they exist.
static ReplaceMallocBridge* gReplaceMallocBridge = nullptr;
static void init() {
malloc_table_t tempTable = gDefaultMallocTable;
# ifdef MOZ_DYNAMIC_REPLACE_INIT
replace_malloc_handle_t handle = replace_malloc_handle();
if (handle) {
replace_init = REPLACE_MALLOC_GET_INIT_FUNC(handle);
}
# endif
// Set this *before* calling replace_init, otherwise if replace_init calls
// malloc() we'll get an infinite loop.
gMallocTablePtr = &gDefaultMallocTable;
// Pass in the default allocator table so replace functions can copy and use
// it for their allocations. The replace_init() function should modify the
// table if it wants to be active, otherwise leave it unmodified.
if (replace_init) {
replace_init(&tempTable, &gReplaceMallocBridge);
}
# ifdef MOZ_REPLACE_MALLOC_STATIC
if (Equals(tempTable, gDefaultMallocTable)) {
logalloc_init(&tempTable, &gReplaceMallocBridge);
}
# ifdef MOZ_DMD
if (Equals(tempTable, gDefaultMallocTable)) {
dmd_init(&tempTable, &gReplaceMallocBridge);
}
# endif
# endif
if (!Equals(tempTable, gDefaultMallocTable)) {
replace_malloc_init_funcs(&tempTable);
}
gOriginalMallocTable = tempTable;
gMallocTablePtr = &gOriginalMallocTable;
}
// WARNING WARNING WARNING: this function should be used with extreme care. It
// is not as general-purpose as it looks. It is currently used by
// tools/profiler/core/memory_hooks.cpp for counting allocations and probably
// should not be used for any other purpose.
//
// This function allows the original malloc table to be temporarily replaced by
// a different malloc table. Or, if the argument is nullptr, it switches back to
// the original malloc table.
//
// Limitations:
//
// - It is not threadsafe. If multiple threads pass it the same
// `replace_init_func` at the same time, there will be data races writing to
// the malloc_table_t within that function.
//
// - Only one replacement can be installed. No nesting is allowed.
//
// - The new malloc table must be able to free allocations made by the original
// malloc table, and upon removal the original malloc table must be able to
// free allocations made by the new malloc table. This means the new malloc
// table can only do simple things like recording extra information, while
// delegating actual allocation/free operations to the original malloc table.
//
MOZ_JEMALLOC_API
void jemalloc_replace_dynamic(
jemalloc_init_func replace_init_func) {
if (replace_init_func) {
malloc_table_t tempTable = gOriginalMallocTable;
(*replace_init_func)(&tempTable, &gReplaceMallocBridge);
if (!Equals(tempTable, gOriginalMallocTable)) {
replace_malloc_init_funcs(&tempTable);
// Temporarily switch back to the original malloc table. In the
// (supported) non-nested case, this is a no-op. But just in case this is
// a (unsupported) nested call, it makes the overwriting of
// gDynamicMallocTable less racy, because ongoing calls to malloc() and
// friends won't go through gDynamicMallocTable.
gMallocTablePtr = &gOriginalMallocTable;
gDynamicMallocTable = tempTable;
gMallocTablePtr = &gDynamicMallocTable;
// We assume that dynamic replaces don't occur close enough for a
// thread to still have old copies of the table pointer when the 2nd
// replace occurs.
}
}
else {
// Switch back to the original malloc table.
gMallocTablePtr = &gOriginalMallocTable;
}
}
# define MALLOC_DECL(name, return_type, ...) \
inline return_type ReplaceMalloc::name( \
ARGS_HELPER(TYPED_ARGS,
##__VA_ARGS__)) { \
if (MOZ_UNLIKELY(!gMallocTablePtr)) { \
init(); \
} \
return (*gMallocTablePtr).name(ARGS_HELPER(ARGS,
##__VA_ARGS__)); \
}
# include
"malloc_decls.h"
MOZ_JEMALLOC_API
struct ReplaceMallocBridge* get_bridge(
void) {
if (MOZ_UNLIKELY(!gMallocTablePtr)) {
init();
}
return gReplaceMallocBridge;
}
// posix_memalign, aligned_alloc, memalign and valloc all implement some kind
// of aligned memory allocation. For convenience, a replace-malloc library can
// skip defining replace_posix_memalign, replace_aligned_alloc and
// replace_valloc, and default implementations will be automatically derived
// from replace_memalign.
static void replace_malloc_init_funcs(malloc_table_t* table) {
if (table->posix_memalign == CanonicalMalloc::posix_memalign &&
table->memalign != CanonicalMalloc::memalign) {
table->posix_memalign =
AlignedAllocator<ReplaceMalloc::memalign>::posix_memalign;
}
if (table->aligned_alloc == CanonicalMalloc::aligned_alloc &&
table->memalign != CanonicalMalloc::memalign) {
table->aligned_alloc =
AlignedAllocator<ReplaceMalloc::memalign>::aligned_alloc;
}
if (table->valloc == CanonicalMalloc::valloc &&
table->memalign != CanonicalMalloc::memalign) {
table->valloc = AlignedAllocator<ReplaceMalloc::memalign>::valloc;
}
if (table->moz_create_arena_with_params ==
CanonicalMalloc::moz_create_arena_with_params &&
table->malloc != CanonicalMalloc::malloc) {
# define MALLOC_DECL(name, ...) \
table->name = DummyArenaAllocator<ReplaceMalloc>::name;
# define MALLOC_FUNCS MALLOC_FUNCS_ARENA_BASE
# include
"malloc_decls.h"
}
if (table->moz_arena_malloc == CanonicalMalloc::moz_arena_malloc &&
table->malloc != CanonicalMalloc::malloc) {
# define MALLOC_DECL(name, ...) \
table->name = DummyArenaAllocator<ReplaceMalloc>::name;
# define MALLOC_FUNCS MALLOC_FUNCS_ARENA_ALLOC
# include
"malloc_decls.h"
}
}
#endif // MOZ_REPLACE_MALLOC
// ***************************************************************************
// Definition of all the _impl functions
// GENERIC_MALLOC_DECL2_MINGW is only used for the MinGW build, and aliases
// the malloc funcs (e.g. malloc) to the je_ versions. It does not generate
// aliases for the other functions (jemalloc and arena functions).
//
// We do need aliases for the other mozglue.def-redirected functions though,
// these are done at the bottom of mozmemory_wrap.cpp
#define GENERIC_MALLOC_DECL2_MINGW(name, name_impl, return_type, ...) \
return_type name(ARGS_HELPER(TYPED_ARGS,
##__VA_ARGS__)) \
__attribute__((alias(MOZ_STRINGIFY(name_impl))));
#define GENERIC_MALLOC_DECL2(attributes, name, name_impl, return_type, ...) \
return_type name_impl(ARGS_HELPER(TYPED_ARGS,
##__VA_ARGS__)) attributes { \
return DefaultMalloc::name(ARGS_HELPER(ARGS,
##__VA_ARGS__)); \
}
#ifndef __MINGW32__
# define GENERIC_MALLOC_DECL(attributes, name, return_type, ...) \
GENERIC_MALLOC_DECL2(attributes, name, name
##_impl, return_type, \
##__VA_ARGS__)
#else
# define GENERIC_MALLOC_DECL(attributes, name, return_type, ...) \
GENERIC_MALLOC_DECL2(attributes, name, name
##_impl, return_type, \
##__VA_ARGS__) \
GENERIC_MALLOC_DECL2_MINGW(name, name
##_impl, return_type,
##__VA_ARGS__)
#endif
#define NOTHROW_MALLOC_DECL(...) \
MOZ_MEMORY_API MACRO_CALL(GENERIC_MALLOC_DECL, (noexcept(true), __VA_ARGS__))
#define MALLOC_DECL(...) \
MOZ_MEMORY_API MACRO_CALL(GENERIC_MALLOC_DECL, (, __VA_ARGS__))
#define MALLOC_FUNCS MALLOC_FUNCS_MALLOC
#include "malloc_decls.h"
#undef GENERIC_MALLOC_DECL
#define GENERIC_MALLOC_DECL(attributes, name, return_type, ...) \
GENERIC_MALLOC_DECL2(attributes, name, name, return_type,
##__VA_ARGS__)
#define MALLOC_DECL(...) \
MOZ_JEMALLOC_API MACRO_CALL(GENERIC_MALLOC_DECL, (, __VA_ARGS__))
#define MALLOC_FUNCS (MALLOC_FUNCS_JEMALLOC | MALLOC_FUNCS_ARENA)
#include "malloc_decls.h"
// ***************************************************************************
#ifdef HAVE_DLFCN_H
# include <dlfcn.h>
#endif
#if defined(__GLIBC__) && !
defined(__UCLIBC__)
// glibc provides the RTLD_DEEPBIND flag for dlopen which can make it possible
// to inconsistently reference libc's malloc(3)-compatible functions
// (bug 493541).
//
// These definitions interpose hooks in glibc. The functions are actually
// passed an extra argument for the caller return address, which will be
// ignored.
extern "C" {
MOZ_EXPORT
void (*__free_hook)(
void*) = free_impl;
MOZ_EXPORT
void* (*__malloc_hook)(size_t) = malloc_impl;
MOZ_EXPORT
void* (*__realloc_hook)(
void*, size_t) = realloc_impl;
MOZ_EXPORT
void* (*__memalign_hook)(size_t, size_t) = memalign_impl;
}
#elif defined(RTLD_DEEPBIND)
// XXX On systems that support RTLD_GROUP or DF_1_GROUP, do their
// implementations permit similar inconsistencies? Should STV_SINGLETON
// visibility be used for interposition where available?
# error \
"Interposing malloc is unsafe on this system without libc malloc hooks."
#endif
#ifdef XP_WIN
MOZ_EXPORT
void* _recalloc(
void* aPtr, size_t aCount, size_t aSize) {
size_t oldsize = aPtr ? AllocInfo::Get(aPtr).Size() :
0;
CheckedInt<size_t> checkedSize = CheckedInt<size_t>(aCount) * aSize;
if (!checkedSize.isValid()) {
return nullptr;
}
size_t newsize = checkedSize.value();
// In order for all trailing bytes to be zeroed, the caller needs to
// use calloc(), followed by recalloc(). However, the current calloc()
// implementation only zeros the bytes requested, so if recalloc() is
// to work 100% correctly, calloc() will need to change to zero
// trailing bytes.
aPtr = DefaultMalloc::realloc(aPtr, newsize);
if (aPtr && oldsize < newsize) {
memset((
void*)((uintptr_t)aPtr + oldsize),
0, newsize - oldsize);
}
return aPtr;
}
// This impl of _expand doesn't ever actually expand or shrink blocks: it
// simply replies that you may continue using a shrunk block.
MOZ_EXPORT
void* _expand(
void* aPtr, size_t newsize) {
if (AllocInfo::Get(aPtr).Size() >= newsize) {
return aPtr;
}
return nullptr;
}
MOZ_EXPORT size_t _msize(
void* aPtr) {
return DefaultMalloc::malloc_usable_size(aPtr);
}
#endif
#ifdef MOZ_PHC
// Compile PHC and mozjemalloc together so that PHC can inline mozjemalloc.
# include
"PHC.cpp"
#endif
