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/*
* Copyright (c) 2000, 2020, 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/cardTable.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "gc/shared/gcLogPrecious.hpp"
#include "gc/shared/gc_globals.hpp"
#include "gc/shared/space.inline.hpp"
#include "logging/log.hpp"
#include "memory/virtualspace.hpp"
#include "runtime/java.hpp"
#include "runtime/os.hpp"
#include "services/memTracker.hpp"
#include "utilities/align.hpp"
#if INCLUDE_PARALLELGC
#include "gc/parallel/objectStartArray.hpp"
#endif
uint CardTable::_card_shift = 0;
uint CardTable::_card_size = 0;
uint CardTable::_card_size_in_words = 0;
void CardTable::initialize_card_size() {
assert(UseG1GC || UseParallelGC || UseSerialGC,
"Initialize card size should only be called by card based collectors.");
_card_size = GCCardSizeInBytes;
_card_shift = log2i_exact(_card_size);
_card_size_in_words = _card_size / sizeof(HeapWord);
// Set blockOffsetTable size based on card table entry size
BOTConstants::initialize_bot_size(_card_shift);
#if INCLUDE_PARALLELGC
// Set ObjectStartArray block size based on card table entry size
ObjectStartArray::initialize_block_size(_card_shift);
#endif
log_info_p(gc, init)("CardTable entry size: " UINT32_FORMAT, _card_size);
}
size_t CardTable::compute_byte_map_size(size_t num_bytes) {
assert(_page_size != 0, "uninitialized, check declaration order");
const size_t granularity = os::vm_allocation_granularity();
return align_up(num_bytes, MAX2(_page_size, granularity));
}
CardTable::CardTable(MemRegion whole_heap) :
_whole_heap(whole_heap),
_page_size(os::vm_page_size()),
_byte_map_size(0),
_byte_map(NULL),
_byte_map_base(NULL),
_cur_covered_regions(0),
_covered(MemRegion::create_array(_max_covered_regions, mtGC)),
_committed(MemRegion::create_array(_max_covered_regions, mtGC)),
_guard_region()
{
assert((uintptr_t(_whole_heap.start()) & (_card_size - 1)) == 0, "heap must start at card boundary");
assert((uintptr_t(_whole_heap.end()) & (_card_size - 1)) == 0, "heap must end at card boundary");
}
CardTable::~CardTable() {
MemRegion::destroy_array(_covered, _max_covered_regions);
MemRegion::destroy_array(_committed, _max_covered_regions);
}
void CardTable::initialize() {
size_t num_cards = cards_required(_whole_heap.word_size());
// each card takes 1 byte; + 1 for the guard card
size_t num_bytes = num_cards + 1;
_byte_map_size = compute_byte_map_size(num_bytes);
HeapWord* low_bound = _whole_heap.start();
HeapWord* high_bound = _whole_heap.end();
_cur_covered_regions = 0;
const size_t rs_align = _page_size == (size_t) os::vm_page_size() ? 0 :
MAX2(_page_size, (size_t) os::vm_allocation_granularity());
ReservedSpace heap_rs(_byte_map_size, rs_align, _page_size);
MemTracker::record_virtual_memory_type((address)heap_rs.base(), mtGC);
os::trace_page_sizes("Card Table", num_bytes, num_bytes,
_page_size, heap_rs.base(), heap_rs.size());
if (!heap_rs.is_reserved()) {
vm_exit_during_initialization("Could not reserve enough space for the "
"card marking array");
}
// The assembler store_check code will do an unsigned shift of the oop,
// then add it to _byte_map_base, i.e.
//
// _byte_map = _byte_map_base + (uintptr_t(low_bound) >> card_shift)
_byte_map = (CardValue*) heap_rs.base();
_byte_map_base = _byte_map - (uintptr_t(low_bound) >> _card_shift);
assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
assert(byte_for(high_bound-1) <= &_byte_map[last_valid_index()], "Checking end of map");
CardValue* guard_card = &_byte_map[num_cards];
assert(is_aligned(guard_card, _page_size), "must be on its own OS page");
_guard_region = MemRegion((HeapWord*)guard_card, _page_size);
log_trace(gc, barrier)("CardTable::CardTable: ");
log_trace(gc, barrier)(" &_byte_map[0]: " PTR_FORMAT " &_byte_map[last_valid_index()]: " PTR_FORMAT,
p2i(&_byte_map[0]), p2i(&_byte_map[last_valid_index()]));
log_trace(gc, barrier)(" _byte_map_base: " PTR_FORMAT, p2i(_byte_map_base));
}
int CardTable::find_covering_region_by_base(HeapWord* base) {
int i;
for (i = 0; i < _cur_covered_regions; i++) {
if (_covered[i].start() == base) return i;
if (_covered[i].start() > base) break;
}
// If we didn't find it, create a new one.
assert(_cur_covered_regions < _max_covered_regions,
"too many covered regions");
// Move the ones above up, to maintain sorted order.
for (int j = _cur_covered_regions; j > i; j--) {
_covered[j] = _covered[j-1];
_committed[j] = _committed[j-1];
}
int res = i;
_cur_covered_regions++;
_covered[res].set_start(base);
_covered[res].set_word_size(0);
CardValue* ct_start = byte_for(base);
HeapWord* ct_start_aligned = align_down((HeapWord*)ct_start, _page_size);
_committed[res].set_start(ct_start_aligned);
_committed[res].set_word_size(0);
return res;
}
HeapWord* CardTable::largest_prev_committed_end(int ind) const {
HeapWord* max_end = NULL;
for (int j = 0; j < ind; j++) {
HeapWord* this_end = _committed[j].end();
if (this_end > max_end) max_end = this_end;
}
return max_end;
}
MemRegion CardTable::committed_unique_to_self(int self, MemRegion mr) const {
assert(mr.intersection(_guard_region).is_empty(), "precondition");
MemRegion result = mr;
for (int r = 0; r < _cur_covered_regions; r += 1) {
if (r != self) {
result = result.minus(_committed[r]);
}
}
return result;
}
void CardTable::resize_covered_region(MemRegion new_region) {
// We don't change the start of a region, only the end.
assert(_whole_heap.contains(new_region),
"attempt to cover area not in reserved area");
// collided is true if the expansion would push into another committed region
debug_only(bool collided = false;)
int const ind = find_covering_region_by_base(new_region.start());
MemRegion const old_region = _covered[ind];
assert(old_region.start() == new_region.start(), "just checking");
if (new_region.word_size() != old_region.word_size()) {
// Commit new or uncommit old pages, if necessary.
MemRegion cur_committed = _committed[ind];
// Extend the end of this _committed region
// to cover the end of any lower _committed regions.
// This forms overlapping regions, but never interior regions.
HeapWord* const max_prev_end = largest_prev_committed_end(ind);
if (max_prev_end > cur_committed.end()) {
cur_committed.set_end(max_prev_end);
}
// Align the end up to a page size (starts are already aligned).
HeapWord* new_end = (HeapWord*) byte_after(new_region.last());
HeapWord* new_end_aligned = align_up(new_end, _page_size);
assert(new_end_aligned >= new_end, "align up, but less");
// Check the other regions (excludes "ind") to ensure that
// the new_end_aligned does not intrude onto the committed
// space of another region.
int ri = 0;
for (ri = ind + 1; ri < _cur_covered_regions; ri++) {
if (new_end_aligned > _committed[ri].start()) {
assert(new_end_aligned <= _committed[ri].end(),
"An earlier committed region can't cover a later committed region");
// Any region containing the new end
// should start at or beyond the region found (ind)
// for the new end (committed regions are not expected to
// be proper subsets of other committed regions).
assert(_committed[ri].start() >= _committed[ind].start(),
"New end of committed region is inconsistent");
new_end_aligned = _committed[ri].start();
// new_end_aligned can be equal to the start of its
// committed region (i.e., of "ind") if a second
// region following "ind" also start at the same location
// as "ind".
assert(new_end_aligned >= _committed[ind].start(),
"New end of committed region is before start");
debug_only(collided = true;)
// Should only collide with 1 region
break;
}
}
#ifdef ASSERT
for (++ri; ri < _cur_covered_regions; ri++) {
assert(!_committed[ri].contains(new_end_aligned),
"New end of committed region is in a second committed region");
}
#endif
// The guard page is always committed and should not be committed over.
// "guarded" is used for assertion checking below and recalls the fact
// that the would-be end of the new committed region would have
// penetrated the guard page.
HeapWord* new_end_for_commit = new_end_aligned;
DEBUG_ONLY(bool guarded = false;)
if (new_end_for_commit > _guard_region.start()) {
new_end_for_commit = _guard_region.start();
DEBUG_ONLY(guarded = true;)
}
if (new_end_for_commit > cur_committed.end()) {
// Must commit new pages.
MemRegion const new_committed =
MemRegion(cur_committed.end(), new_end_for_commit);
assert(!new_committed.is_empty(), "Region should not be empty here");
os::commit_memory_or_exit((char*)new_committed.start(),
new_committed.byte_size(), _page_size,
!ExecMem, "card table expansion");
// Use new_end_aligned (as opposed to new_end_for_commit) because
// the cur_committed region may include the guard region.
} else if (new_end_aligned < cur_committed.end()) {
// Must uncommit pages.
MemRegion const uncommit_region =
committed_unique_to_self(ind, MemRegion(new_end_aligned,
cur_committed.end()));
if (!uncommit_region.is_empty()) {
if (!os::uncommit_memory((char*)uncommit_region.start(),
uncommit_region.byte_size())) {
assert(false, "Card table contraction failed");
// The call failed so don't change the end of the
// committed region. This is better than taking the
// VM down.
new_end_aligned = _committed[ind].end();
}
}
}
// In any case, we can reset the end of the current committed entry.
_committed[ind].set_end(new_end_aligned);
#ifdef ASSERT
// Check that the last card in the new region is committed according
// to the tables.
bool covered = false;
for (int cr = 0; cr < _cur_covered_regions; cr++) {
if (_committed[cr].contains(new_end - 1)) {
covered = true;
break;
}
}
assert(covered, "Card for end of new region not committed");
#endif
// The default of 0 is not necessarily clean cards.
CardValue* entry;
if (old_region.last() < _whole_heap.start()) {
entry = byte_for(_whole_heap.start());
} else {
entry = byte_after(old_region.last());
}
assert(index_for(new_region.last()) <= last_valid_index(),
"The guard card will be overwritten");
// This line commented out cleans the newly expanded region and
// not the aligned up expanded region.
// CardValue* const end = byte_after(new_region.last());
CardValue* const end = (CardValue*) new_end_for_commit;
assert((end >= byte_after(new_region.last())) || collided || guarded,
"Expect to be beyond new region unless impacting another region");
// do nothing if we resized downward.
#ifdef ASSERT
for (int ri = 0; ri < _cur_covered_regions; ri++) {
if (ri != ind) {
// The end of the new committed region should not
// be in any existing region unless it matches
// the start of the next region.
assert(!_committed[ri].contains(end) ||
(_committed[ri].start() == (HeapWord*) end),
"Overlapping committed regions");
}
}
#endif
if (entry < end) {
memset(entry, clean_card, pointer_delta(end, entry, sizeof(CardValue)));
}
}
// In any case, the covered size changes.
_covered[ind].set_word_size(new_region.word_size());
log_trace(gc, barrier)("CardTable::resize_covered_region: ");
log_trace(gc, barrier)(" _covered[%d].start(): " PTR_FORMAT " _covered[%d].last(): " PTR_FORMAT,
ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last()));
log_trace(gc, barrier)(" _committed[%d].start(): " PTR_FORMAT " _committed[%d].last(): " PTR_FORMAT,
ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last()));
log_trace(gc, barrier)(" byte_for(start): " PTR_FORMAT " byte_for(last): " PTR_FORMAT,
p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last())));
log_trace(gc, barrier)(" addr_for(start): " PTR_FORMAT " addr_for(last): " PTR_FORMAT,
p2i(addr_for((CardValue*) _committed[ind].start())), p2i(addr_for((CardValue*) _committed[ind].last())));
// Touch the last card of the covered region to show that it
// is committed (or SEGV).
debug_only((void) (*byte_for(_covered[ind].last()));)
}
// Note that these versions are precise! The scanning code has to handle the
// fact that the write barrier may be either precise or imprecise.
void CardTable::dirty_MemRegion(MemRegion mr) {
assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
CardValue* cur = byte_for(mr.start());
CardValue* last = byte_after(mr.last());
while (cur < last) {
*cur = dirty_card;
cur++;
}
}
void CardTable::clear_MemRegion(MemRegion mr) {
// Be conservative: only clean cards entirely contained within the
// region.
CardValue* cur;
if (mr.start() == _whole_heap.start()) {
cur = byte_for(mr.start());
} else {
assert(mr.start() > _whole_heap.start(), "mr is not covered.");
cur = byte_after(mr.start() - 1);
}
CardValue* last = byte_after(mr.last());
memset(cur, clean_card, pointer_delta(last, cur, sizeof(CardValue)));
}
void CardTable::clear(MemRegion mr) {
for (int i = 0; i < _cur_covered_regions; i++) {
MemRegion mri = mr.intersection(_covered[i]);
if (!mri.is_empty()) clear_MemRegion(mri);
}
}
uintx CardTable::ct_max_alignment_constraint() {
// Calculate maximum alignment using GCCardSizeInBytes as card_size hasn't been set yet
return GCCardSizeInBytes * os::vm_page_size();
}
void CardTable::invalidate(MemRegion mr) {
assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
for (int i = 0; i < _cur_covered_regions; i++) {
MemRegion mri = mr.intersection(_covered[i]);
if (!mri.is_empty()) dirty_MemRegion(mri);
}
}
#ifndef PRODUCT
void CardTable::verify_region(MemRegion mr, CardValue val, bool val_equals) {
CardValue* start = byte_for(mr.start());
CardValue* end = byte_for(mr.last());
bool failures = false;
for (CardValue* curr = start; curr <= end; ++curr) {
CardValue curr_val = *curr;
bool failed = (val_equals) ? (curr_val != val) : (curr_val == val);
if (failed) {
if (!failures) {
log_error(gc, verify)("== CT verification failed: [" PTR_FORMAT "," PTR_FORMAT "]", p2i(start), p2i(end));
log_error(gc, verify)("== %sexpecting value: %d", (val_equals) ? "" : "not ", val);
failures = true;
}
log_error(gc, verify)("== card " PTR_FORMAT " [" PTR_FORMAT "," PTR_FORMAT "], val: %d",
p2i(curr), p2i(addr_for(curr)),
p2i((HeapWord*) (((size_t) addr_for(curr)) + _card_size)),
(int) curr_val);
}
}
guarantee(!failures, "there should not have been any failures");
}
void CardTable::verify_not_dirty_region(MemRegion mr) {
verify_region(mr, dirty_card, false /* val_equals */);
}
void CardTable::verify_dirty_region(MemRegion mr) {
verify_region(mr, dirty_card, true /* val_equals */);
}
#endif
void CardTable::print_on(outputStream* st) const {
st->print_cr("Card table byte_map: [" PTR_FORMAT "," PTR_FORMAT "] _byte_map_base: " PTR_FORMAT,
p2i(_byte_map), p2i(_byte_map + _byte_map_size), p2i(_byte_map_base));
}
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