/*
* Copyright (c) 2015, 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
#include "precompiled.hpp"
#include "gc/shared/gcLogPrecious.hpp"
#include "gc/shared/suspendibleThreadSet.hpp"
#include "gc/z/zArray.inline.hpp"
#include "gc/z/zCollectedHeap.hpp"
#include "gc/z/zFuture.inline.hpp"
#include "gc/z/zGlobals.hpp"
#include "gc/z/zLock.inline.hpp"
#include "gc/z/zPage.inline.hpp"
#include "gc/z/zPageAllocator.inline.hpp"
#include "gc/z/zPageCache.hpp"
#include "gc/z/zSafeDelete.inline.hpp"
#include "gc/z/zStat.hpp"
#include "gc/z/zTask.hpp"
#include "gc/z/zUncommitter.hpp"
#include "gc/z/zUnmapper.hpp"
#include "gc/z/zWorkers.hpp"
#include "jfr/jfrEvents.hpp"
#include "logging/log.hpp"
#include "runtime/globals.hpp"
#include "runtime/init.hpp"
#include "runtime/java.hpp"
#include "utilities/debug.hpp"
#include "utilities/globalDefinitions.hpp"
static const ZStatCounter ZCounterAllocationRate("Memory", "Allocation Rate", ZStatUnitBytesPerSecond);
static const ZStatCounter ZCounterPageCacheFlush("Memory", "Page Cache Flush", ZStatUnitBytesPerSecond);
static const ZStatCounter ZCounterDefragment("Memory", "Defragment", ZStatUnitOpsPerSecond);
static const ZStatCriticalPhase ZCriticalPhaseAllocationStall("Allocation Stall");
enum ZPageAllocationStall {
ZPageAllocationStallSuccess,
ZPageAllocationStallFailed,
ZPageAllocationStallStartGC
};
class ZPageAllocation : public StackObj {
friend class ZList<ZPageAllocation>;
private:
const uint8_t _type;
const size_t _size;
const ZAllocationFlags _flags;
const uint32_t _seqnum;
size_t _flushed;
size_t _committed;
ZList<ZPage> _pages;
ZListNode<ZPageAllocation> _node;
ZFuture<ZPageAllocationStall> _stall_result;
public:
ZPageAllocation(uint8_t type, size_t size, ZAllocationFlags flags) :
_type(type),
_size(size),
_flags(flags),
_seqnum(ZGlobalSeqNum),
_flushed(0),
_committed(0),
_pages(),
_node(),
_stall_result() {}
uint8_t type() const {
return _type;
}
size_t size() const {
return _size;
}
ZAllocationFlags flags() const {
return _flags;
}
uint32_t seqnum() const {
return _seqnum;
}
size_t flushed() const {
return _flushed;
}
void set_flushed(size_t flushed) {
_flushed = flushed;
}
size_t committed() const {
return _committed;
}
void set_committed(size_t committed) {
_committed = committed;
}
ZPageAllocationStall wait() {
return _stall_result.get();
}
ZList<ZPage>* pages() {
return &_pages;
}
void satisfy(ZPageAllocationStall result) {
_stall_result.set(result);
}
};
ZPageAllocator::ZPageAllocator(ZWorkers* workers,
size_t min_capacity,
size_t initial_capacity,
size_t max_capacity) :
_lock(),
_cache(),
_virtual(max_capacity),
_physical(max_capacity),
_min_capacity(min_capacity),
_max_capacity(max_capacity),
_current_max_capacity(max_capacity),
_capacity(0),
_claimed(0),
_used(0),
_used_high(0),
_used_low(0),
_reclaimed(0),
_stalled(),
_nstalled(0),
_satisfied(),
_unmapper(new ZUnmapper(this)),
_uncommitter(new ZUncommitter(this)),
_safe_delete(),
_initialized(false) {
if (!_virtual.is_initialized() || !_physical.is_initialized()) {
return;
}
log_info_p(gc, init)("Min Capacity: " SIZE_FORMAT "M", min_capacity / M);
log_info_p(gc, init)("Initial Capacity: " SIZE_FORMAT "M", initial_capacity / M);
log_info_p(gc, init)("Max Capacity: " SIZE_FORMAT "M", max_capacity / M);
if (ZPageSizeMedium > 0) {
log_info_p(gc, init)("Medium Page Size: " SIZE_FORMAT "M", ZPageSizeMedium / M);
} else {
log_info_p(gc, init)("Medium Page Size: N/A");
}
log_info_p(gc, init)("Pre-touch: %s", AlwaysPreTouch ? "Enabled" : "Disabled");
// Warn if system limits could stop us from reaching max capacity
_physical.warn_commit_limits(max_capacity);
// Check if uncommit should and can be enabled
_physical.try_enable_uncommit(min_capacity, max_capacity);
// Pre-map initial capacity
if (!prime_cache(workers, initial_capacity)) {
log_error_p(gc)("Failed to allocate initial Java heap (" SIZE_FORMAT "M)", initial_capacity / M);
return;
}
// Successfully initialized
_initialized = true;
}
class ZPreTouchTask : public ZTask {
private:
const ZPhysicalMemoryManager* const _physical;
volatile uintptr_t _start;
const uintptr_t _end;
public:
ZPreTouchTask(const ZPhysicalMemoryManager* physical, uintptr_t start, uintptr_t end) :
ZTask("ZPreTouchTask"),
_physical(physical),
_start(start),
_end(end) {}
virtual void work() {
for (;;) {
// Get granule offset
const size_t size = ZGranuleSize;
const uintptr_t offset = Atomic::fetch_and_add(&_start, size);
if (offset >= _end) {
// Done
break;
}
// Pre-touch granule
_physical->pretouch(offset, size);
}
}
};
bool ZPageAllocator::prime_cache(ZWorkers* workers, size_t size) {
ZAllocationFlags flags;
flags.set_non_blocking();
flags.set_low_address();
ZPage* const page = alloc_page(ZPageTypeLarge, size, flags);
if (page == NULL) {
return false;
}
if (AlwaysPreTouch) {
// Pre-touch page
ZPreTouchTask task(&_physical, page->start(), page->end());
workers->run_all(&task);
}
free_page(page, false /* reclaimed */);
return true;
}
bool ZPageAllocator::is_initialized() const {
return _initialized;
}
size_t ZPageAllocator::min_capacity() const {
return _min_capacity;
}
size_t ZPageAllocator::max_capacity() const {
return _max_capacity;
}
size_t ZPageAllocator::soft_max_capacity() const {
// Note that SoftMaxHeapSize is a manageable flag
const size_t soft_max_capacity = Atomic::load(&SoftMaxHeapSize);
const size_t current_max_capacity = Atomic::load(&_current_max_capacity);
return MIN2(soft_max_capacity, current_max_capacity);
}
size_t ZPageAllocator::capacity() const {
return Atomic::load(&_capacity);
}
size_t ZPageAllocator::used() const {
return Atomic::load(&_used);
}
size_t ZPageAllocator::unused() const {
const ssize_t capacity = (ssize_t)Atomic::load(&_capacity);
const ssize_t used = (ssize_t)Atomic::load(&_used);
const ssize_t claimed = (ssize_t)Atomic::load(&_claimed);
const ssize_t unused = capacity - used - claimed;
return unused > 0 ? (size_t)unused : 0;
}
ZPageAllocatorStats ZPageAllocator::stats() const {
ZLocker<ZLock> locker(&_lock);
return ZPageAllocatorStats(_min_capacity,
_max_capacity,
soft_max_capacity(),
_capacity,
_used,
_used_high,
_used_low,
_reclaimed);
}
void ZPageAllocator::reset_statistics() {
assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
_reclaimed = 0;
_used_high = _used_low = _used;
_nstalled = 0;
}
size_t ZPageAllocator::increase_capacity(size_t size) {
const size_t increased = MIN2(size, _current_max_capacity - _capacity);
if (increased > 0) {
// Update atomically since we have concurrent readers
Atomic::add(&_capacity, increased);
// Record time of last commit. When allocation, we prefer increasing
// the capacity over flushing the cache. That means there could be
// expired pages in the cache at this time. However, since we are
// increasing the capacity we are obviously in need of committed
// memory and should therefore not be uncommitting memory.
_cache.set_last_commit();
}
return increased;
}
void ZPageAllocator::decrease_capacity(size_t size, bool set_max_capacity) {
// Update atomically since we have concurrent readers
Atomic::sub(&_capacity, size);
if (set_max_capacity) {
// Adjust current max capacity to avoid further attempts to increase capacity
log_error_p(gc)("Forced to lower max Java heap size from "
SIZE_FORMAT "M(%.0f%%) to " SIZE_FORMAT "M(%.0f%%)",
_current_max_capacity / M, percent_of(_current_max_capacity, _max_capacity),
_capacity / M, percent_of(_capacity, _max_capacity));
// Update atomically since we have concurrent readers
Atomic::store(&_current_max_capacity, _capacity);
}
}
void ZPageAllocator::increase_used(size_t size, bool worker_relocation) {
if (worker_relocation) {
// Allocating a page for the purpose of worker relocation has
// a negative contribution to the number of reclaimed bytes.
_reclaimed -= size;
}
// Update atomically since we have concurrent readers
const size_t used = Atomic::add(&_used, size);
if (used > _used_high) {
_used_high = used;
}
}
void ZPageAllocator::decrease_used(size_t size, bool reclaimed) {
// Only pages explicitly released with the reclaimed flag set
// counts as reclaimed bytes. This flag is true when we release
// a page after relocation, and is false when we release a page
// to undo an allocation.
if (reclaimed) {
_reclaimed += size;
}
// Update atomically since we have concurrent readers
const size_t used = Atomic::sub(&_used, size);
if (used < _used_low) {
_used_low = used;
}
}
bool ZPageAllocator::commit_page(ZPage* page) {
// Commit physical memory
return _physical.commit(page->physical_memory());
}
void ZPageAllocator::uncommit_page(ZPage* page) {
if (!ZUncommit) {
return;
}
// Uncommit physical memory
_physical.uncommit(page->physical_memory());
}
void ZPageAllocator::map_page(const ZPage* page) const {
// Map physical memory
_physical.map(page->start(), page->physical_memory());
}
void ZPageAllocator::unmap_page(const ZPage* page) const {
// Unmap physical memory
_physical.unmap(page->start(), page->size());
}
void ZPageAllocator::destroy_page(ZPage* page) {
// Free virtual memory
_virtual.free(page->virtual_memory());
// Free physical memory
_physical.free(page->physical_memory());
// Delete page safely
_safe_delete(page);
}
bool ZPageAllocator::is_alloc_allowed(size_t size) const {
const size_t available = _current_max_capacity - _used - _claimed;
return available >= size;
}
bool ZPageAllocator::alloc_page_common_inner(uint8_t type, size_t size, ZList<ZPage>* pages) {
if (!is_alloc_allowed(size)) {
// Out of memory
return false;
}
// Try allocate from the page cache
ZPage* const page = _cache.alloc_page(type, size);
if (page != NULL) {
// Success
pages->insert_last(page);
return true;
}
// Try increase capacity
const size_t increased = increase_capacity(size);
if (increased < size) {
// Could not increase capacity enough to satisfy the allocation
// completely. Flush the page cache to satisfy the remainder.
const size_t remaining = size - increased;
_cache.flush_for_allocation(remaining, pages);
}
// Success
return true;
}
bool ZPageAllocator::alloc_page_common(ZPageAllocation* allocation) {
const uint8_t type = allocation->type();
const size_t size = allocation->size();
const ZAllocationFlags flags = allocation->flags();
ZList<ZPage>* const pages = allocation->pages();
if (!alloc_page_common_inner(type, size, pages)) {
// Out of memory
return false;
}
// Updated used statistics
increase_used(size, flags.worker_relocation());
// Success
return true;
}
static void check_out_of_memory_during_initialization() {
if (!is_init_completed()) {
vm_exit_during_initialization("java.lang.OutOfMemoryError", "Java heap too small");
}
}
bool ZPageAllocator::alloc_page_stall(ZPageAllocation* allocation) {
ZStatTimer timer(ZCriticalPhaseAllocationStall);
EventZAllocationStall event;
ZPageAllocationStall result;
// We can only block if the VM is fully initialized
check_out_of_memory_during_initialization();
// Increment stalled counter
Atomic::inc(&_nstalled);
do {
// Start asynchronous GC
ZCollectedHeap::heap()->collect(GCCause::_z_allocation_stall);
// Wait for allocation to complete, fail or request a GC
result = allocation->wait();
} while (result == ZPageAllocationStallStartGC);
{
//
// We grab the lock here for two different reasons:
//
// 1) Guard deletion of underlying semaphore. This is a workaround for
// a bug in sem_post() in glibc < 2.21, where it's not safe to destroy
// the semaphore immediately after returning from sem_wait(). The
// reason is that sem_post() can touch the semaphore after a waiting
// thread have returned from sem_wait(). To avoid this race we are
// forcing the waiting thread to acquire/release the lock held by the
// posting thread. https://sourceware.org/bugzilla/show_bug.cgi?id=12674
//
// 2) Guard the list of satisfied pages.
//
ZLocker<ZLock> locker(&_lock);
_satisfied.remove(allocation);
}
// Send event
event.commit(allocation->type(), allocation->size());
return (result == ZPageAllocationStallSuccess);
}
bool ZPageAllocator::alloc_page_or_stall(ZPageAllocation* allocation) {
{
ZLocker<ZLock> locker(&_lock);
if (alloc_page_common(allocation)) {
// Success
return true;
}
// Failed
if (allocation->flags().non_blocking()) {
// Don't stall
return false;
}
// Enqueue allocation request
_stalled.insert_last(allocation);
}
// Stall
return alloc_page_stall(allocation);
}
ZPage* ZPageAllocator::alloc_page_create(ZPageAllocation* allocation) {
const size_t size = allocation->size();
// Allocate virtual memory. To make error handling a lot more straight
// forward, we allocate virtual memory before destroying flushed pages.
// Flushed pages are also unmapped and destroyed asynchronously, so we
// can't immediately reuse that part of the address space anyway.
const ZVirtualMemory vmem = _virtual.alloc(size, allocation->flags().low_address());
if (vmem.is_null()) {
log_error(gc)("Out of address space");
return NULL;
}
ZPhysicalMemory pmem;
size_t flushed = 0;
// Harvest physical memory from flushed pages
ZListRemoveIterator<ZPage> iter(allocation->pages());
for (ZPage* page; iter.next(&page);) {
flushed += page->size();
// Harvest flushed physical memory
ZPhysicalMemory& fmem = page->physical_memory();
pmem.add_segments(fmem);
fmem.remove_segments();
// Unmap and destroy page
_unmapper->unmap_and_destroy_page(page);
}
if (flushed > 0) {
allocation->set_flushed(flushed);
// Update statistics
ZStatInc(ZCounterPageCacheFlush, flushed);
log_debug(gc, heap)("Page Cache Flushed: " SIZE_FORMAT "M", flushed / M);
}
// Allocate any remaining physical memory. Capacity and used has
// already been adjusted, we just need to fetch the memory, which
// is guaranteed to succeed.
if (flushed < size) {
const size_t remaining = size - flushed;
allocation->set_committed(remaining);
_physical.alloc(pmem, remaining);
}
// Create new page
return new ZPage(allocation->type(), vmem, pmem);
}
bool ZPageAllocator::should_defragment(const ZPage* page) const {
// A small page can end up at a high address (second half of the address space)
// if we've split a larger page or we have a constrained address space. To help
// fight address space fragmentation we remap such pages to a lower address, if
// a lower address is available.
return page->type() == ZPageTypeSmall &&
page->start() >= _virtual.reserved() / 2 &&
page->start() > _virtual.lowest_available_address();
}
bool ZPageAllocator::is_alloc_satisfied(ZPageAllocation* allocation) const {
// The allocation is immediately satisfied if the list of pages contains
// exactly one page, with the type and size that was requested. However,
// even if the allocation is immediately satisfied we might still want to
// return false here to force the page to be remapped to fight address
// space fragmentation.
if (allocation->pages()->size() != 1) {
// Not a single page
return false;
}
const ZPage* const page = allocation->pages()->first();
if (page->type() != allocation->type() ||
page->size() != allocation->size()) {
// Wrong type or size
return false;
}
if (should_defragment(page)) {
// Defragment address space
ZStatInc(ZCounterDefragment);
return false;
}
// Allocation immediately satisfied
return true;
}
ZPage* ZPageAllocator::alloc_page_finalize(ZPageAllocation* allocation) {
// Fast path
if (is_alloc_satisfied(allocation)) {
return allocation->pages()->remove_first();
}
// Slow path
ZPage* const page = alloc_page_create(allocation);
if (page == NULL) {
// Out of address space
return NULL;
}
// Commit page
if (commit_page(page)) {
// Success
map_page(page);
return page;
}
// Failed or partially failed. Split of any successfully committed
// part of the page into a new page and insert it into list of pages,
// so that it will be re-inserted into the page cache.
ZPage* const committed_page = page->split_committed();
destroy_page(page);
if (committed_page != NULL) {
map_page(committed_page);
allocation->pages()->insert_last(committed_page);
}
return NULL;
}
void ZPageAllocator::alloc_page_failed(ZPageAllocation* allocation) {
ZLocker<ZLock> locker(&_lock);
size_t freed = 0;
// Free any allocated/flushed pages
ZListRemoveIterator<ZPage> iter(allocation->pages());
for (ZPage* page; iter.next(&page);) {
freed += page->size();
free_page_inner(page, false /* reclaimed */);
}
// Adjust capacity and used to reflect the failed capacity increase
const size_t remaining = allocation->size() - freed;
decrease_used(remaining, false /* reclaimed */);
decrease_capacity(remaining, true /* set_max_capacity */);
// Try satisfy stalled allocations
satisfy_stalled();
}
ZPage* ZPageAllocator::alloc_page(uint8_t type, size_t size, ZAllocationFlags flags) {
EventZPageAllocation event;
retry:
ZPageAllocation allocation(type, size, flags);
// Allocate one or more pages from the page cache. If the allocation
// succeeds but the returned pages don't cover the complete allocation,
// then finalize phase is allowed to allocate the remaining memory
// directly from the physical memory manager. Note that this call might
// block in a safepoint if the non-blocking flag is not set.
if (!alloc_page_or_stall(&allocation)) {
// Out of memory
return NULL;
}
ZPage* const page = alloc_page_finalize(&allocation);
if (page == NULL) {
// Failed to commit or map. Clean up and retry, in the hope that
// we can still allocate by flushing the page cache (more aggressively).
alloc_page_failed(&allocation);
goto retry;
}
// Reset page. This updates the page's sequence number and must
// be done after we potentially blocked in a safepoint (stalled)
// where the global sequence number was updated.
page->reset();
// Update allocation statistics. Exclude worker relocations to avoid
// artificial inflation of the allocation rate during relocation.
if (!flags.worker_relocation() && is_init_completed()) {
// Note that there are two allocation rate counters, which have
// different purposes and are sampled at different frequencies.
const size_t bytes = page->size();
ZStatInc(ZCounterAllocationRate, bytes);
ZStatInc(ZStatAllocRate::counter(), bytes);
}
// Send event
event.commit(type, size, allocation.flushed(), allocation.committed(),
page->physical_memory().nsegments(), flags.non_blocking());
return page;
}
void ZPageAllocator::satisfy_stalled() {
for (;;) {
ZPageAllocation* const allocation = _stalled.first();
if (allocation == NULL) {
// Allocation queue is empty
return;
}
if (!alloc_page_common(allocation)) {
// Allocation could not be satisfied, give up
return;
}
// Allocation succeeded, dequeue and satisfy allocation request.
// Note that we must dequeue the allocation request first, since
// it will immediately be deallocated once it has been satisfied.
_stalled.remove(allocation);
_satisfied.insert_last(allocation);
allocation->satisfy(ZPageAllocationStallSuccess);
}
}
void ZPageAllocator::free_page_inner(ZPage* page, bool reclaimed) {
// Update used statistics
decrease_used(page->size(), reclaimed);
// Set time when last used
page->set_last_used();
// Cache page
_cache.free_page(page);
}
void ZPageAllocator::free_page(ZPage* page, bool reclaimed) {
ZLocker<ZLock> locker(&_lock);
// Free page
free_page_inner(page, reclaimed);
// Try satisfy stalled allocations
satisfy_stalled();
}
void ZPageAllocator::free_pages(const ZArray<ZPage*>* pages, bool reclaimed) {
ZLocker<ZLock> locker(&_lock);
// Free pages
ZArrayIterator<ZPage*> iter(pages);
for (ZPage* page; iter.next(&page);) {
free_page_inner(page, reclaimed);
}
// Try satisfy stalled allocations
satisfy_stalled();
}
size_t ZPageAllocator::uncommit(uint64_t* timeout) {
// We need to join the suspendible thread set while manipulating capacity and
// used, to make sure GC safepoints will have a consistent view. However, when
// ZVerifyViews is enabled we need to join at a broader scope to also make sure
// we don't change the address good mask after pages have been flushed, and
// thereby made invisible to pages_do(), but before they have been unmapped.
SuspendibleThreadSetJoiner joiner(ZVerifyViews);
ZList<ZPage> pages;
size_t flushed;
{
SuspendibleThreadSetJoiner joiner(!ZVerifyViews);
ZLocker<ZLock> locker(&_lock);
// Never uncommit below min capacity. We flush out and uncommit chunks at
// a time (~0.8% of the max capacity, but at least one granule and at most
// 256M), in case demand for memory increases while we are uncommitting.
const size_t retain = MAX2(_used, _min_capacity);
const size_t release = _capacity - retain;
const size_t limit = MIN2(align_up(_current_max_capacity >> 7, ZGranuleSize), 256 * M);
const size_t flush = MIN2(release, limit);
// Flush pages to uncommit
flushed = _cache.flush_for_uncommit(flush, &pages, timeout);
if (flushed == 0) {
// Nothing flushed
return 0;
}
// Record flushed pages as claimed
Atomic::add(&_claimed, flushed);
}
// Unmap, uncommit, and destroy flushed pages
ZListRemoveIterator<ZPage> iter(&pages);
for (ZPage* page; iter.next(&page);) {
unmap_page(page);
uncommit_page(page);
destroy_page(page);
}
{
SuspendibleThreadSetJoiner joiner(!ZVerifyViews);
ZLocker<ZLock> locker(&_lock);
// Adjust claimed and capacity to reflect the uncommit
Atomic::sub(&_claimed, flushed);
decrease_capacity(flushed, false /* set_max_capacity */);
}
return flushed;
}
void ZPageAllocator::enable_deferred_delete() const {
_safe_delete.enable_deferred_delete();
}
void ZPageAllocator::disable_deferred_delete() const {
_safe_delete.disable_deferred_delete();
}
void ZPageAllocator::debug_map_page(const ZPage* page) const {
assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
_physical.debug_map(page->start(), page->physical_memory());
}
void ZPageAllocator::debug_unmap_page(const ZPage* page) const {
assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
_physical.debug_unmap(page->start(), page->size());
}
void ZPageAllocator::pages_do(ZPageClosure* cl) const {
assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
ZListIterator<ZPageAllocation> iter_satisfied(&_satisfied);
for (ZPageAllocation* allocation; iter_satisfied.next(&allocation);) {
ZListIterator<ZPage> iter_pages(allocation->pages());
for (ZPage* page; iter_pages.next(&page);) {
cl->do_page(page);
}
}
_cache.pages_do(cl);
}
bool ZPageAllocator::has_alloc_stalled() const {
return Atomic::load(&_nstalled) != 0;
}
void ZPageAllocator::check_out_of_memory() {
ZLocker<ZLock> locker(&_lock);
// Fail allocation requests that were enqueued before the
// last GC cycle started, otherwise start a new GC cycle.
for (ZPageAllocation* allocation = _stalled.first(); allocation != NULL; allocation = _stalled.first()) {
if (allocation->seqnum() == ZGlobalSeqNum) {
// Start a new GC cycle, keep allocation requests enqueued
allocation->satisfy(ZPageAllocationStallStartGC);
return;
}
// Out of memory, fail allocation request
_stalled.remove(allocation);
_satisfied.insert_last(allocation);
allocation->satisfy(ZPageAllocationStallFailed);
}
}
void ZPageAllocator::threads_do(ThreadClosure* tc) const {
tc->do_thread(_unmapper);
tc->do_thread(_uncommitter);
}
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