/*
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* 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.
*
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* 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
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*/
#include "precompiled.hpp"
#include "gc/cms/cmsHeap.hpp"
#include "gc/cms/cmsLockVerifier.hpp"
#include "gc/cms/compactibleFreeListSpace.hpp"
#include "gc/cms/concurrentMarkSweepGeneration.inline.hpp"
#include "gc/cms/concurrentMarkSweepThread.hpp"
#include "gc/shared/blockOffsetTable.inline.hpp"
#include "gc/shared/collectedHeap.inline.hpp"
#include "gc/shared/genOopClosures.inline.hpp"
#include "gc/shared/space.inline.hpp"
#include "gc/shared/spaceDecorator.hpp"
#include "logging/log.hpp"
#include "logging/logStream.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/binaryTreeDictionary.inline.hpp"
#include "memory/iterator.inline.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "oops/access.inline.hpp"
#include "oops/compressedOops.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/globals.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/init.hpp"
#include "runtime/java.hpp"
#include "runtime/orderAccess.hpp"
#include "runtime/vmThread.hpp"
#include "utilities/align.hpp"
#include "utilities/copy.hpp"
// Specialize for AdaptiveFreeList which tries to avoid
// splitting a chunk of a size that is under populated in favor of
// an over populated size. The general get_better_list() just returns
// the current list.
template <>
TreeList<FreeChunk, AdaptiveFreeList<FreeChunk> >*
TreeList<FreeChunk, AdaptiveFreeList<FreeChunk> >::get_better_list(
BinaryTreeDictionary<FreeChunk, ::AdaptiveFreeList<FreeChunk> >* dictionary) {
// A candidate chunk has been found. If it is already under
// populated, get a chunk associated with the hint for this
// chunk.
TreeList<FreeChunk, ::AdaptiveFreeList<FreeChunk> >* curTL = this;
if (curTL->surplus() <= 0) {
/* Use the hint to find a size with a surplus, and reset the hint. */
TreeList<FreeChunk, ::AdaptiveFreeList<FreeChunk> >* hintTL = this;
while (hintTL->hint() != 0) {
assert(hintTL->hint() > hintTL->size(),
"hint points in the wrong direction");
hintTL = dictionary->find_list(hintTL->hint());
assert(curTL != hintTL, "Infinite loop");
if (hintTL == NULL ||
hintTL == curTL /* Should not happen but protect against it */ ) {
// No useful hint. Set the hint to NULL and go on.
curTL->set_hint(0);
break;
}
assert(hintTL->size() > curTL->size(), "hint is inconsistent");
if (hintTL->surplus() > 0) {
// The hint led to a list that has a surplus. Use it.
// Set the hint for the candidate to an overpopulated
// size.
curTL->set_hint(hintTL->size());
// Change the candidate.
curTL = hintTL;
break;
}
}
}
return curTL;
}
void AFLBinaryTreeDictionary::dict_census_update(size_t size, bool split, bool birth) {
TreeList<FreeChunk, AdaptiveFreeList<FreeChunk> >* nd = find_list(size);
if (nd) {
if (split) {
if (birth) {
nd->increment_split_births();
nd->increment_surplus();
} else {
nd->increment_split_deaths();
nd->decrement_surplus();
}
} else {
if (birth) {
nd->increment_coal_births();
nd->increment_surplus();
} else {
nd->increment_coal_deaths();
nd->decrement_surplus();
}
}
}
// A list for this size may not be found (nd == 0) if
// This is a death where the appropriate list is now
// empty and has been removed from the list.
// This is a birth associated with a LinAB. The chunk
// for the LinAB is not in the dictionary.
}
bool AFLBinaryTreeDictionary::coal_dict_over_populated(size_t size) {
if (FLSAlwaysCoalesceLarge) return true;
TreeList<FreeChunk, AdaptiveFreeList<FreeChunk> >* list_of_size = find_list(size);
// None of requested size implies overpopulated.
return list_of_size == NULL || list_of_size->coal_desired() <= 0 ||
list_of_size->count() > list_of_size->coal_desired();
}
// For each list in the tree, calculate the desired, desired
// coalesce, count before sweep, and surplus before sweep.
class BeginSweepClosure : public AscendTreeCensusClosure<FreeChunk, AdaptiveFreeList<FreeChunk> > {
double _percentage;
float _inter_sweep_current;
float _inter_sweep_estimate;
float _intra_sweep_estimate;
public:
BeginSweepClosure(double p, float inter_sweep_current,
float inter_sweep_estimate,
float intra_sweep_estimate) :
_percentage(p),
_inter_sweep_current(inter_sweep_current),
_inter_sweep_estimate(inter_sweep_estimate),
_intra_sweep_estimate(intra_sweep_estimate) { }
void do_list(AdaptiveFreeList<FreeChunk>* fl) {
double coalSurplusPercent = _percentage;
fl->compute_desired(_inter_sweep_current, _inter_sweep_estimate, _intra_sweep_estimate);
fl->set_coal_desired((ssize_t)((double)fl->desired() * coalSurplusPercent));
fl->set_before_sweep(fl->count());
fl->set_bfr_surp(fl->surplus());
}
};
void AFLBinaryTreeDictionary::begin_sweep_dict_census(double coalSurplusPercent,
float inter_sweep_current, float inter_sweep_estimate, float intra_sweep_estimate) {
BeginSweepClosure bsc(coalSurplusPercent, inter_sweep_current,
inter_sweep_estimate,
intra_sweep_estimate);
bsc.do_tree(root());
}
// Calculate surpluses for the lists in the tree.
class setTreeSurplusClosure : public AscendTreeCensusClosure<FreeChunk, AdaptiveFreeList<FreeChunk> > {
double percentage;
public:
setTreeSurplusClosure(double v) { percentage = v; }
void do_list(AdaptiveFreeList<FreeChunk>* fl) {
double splitSurplusPercent = percentage;
fl->set_surplus(fl->count() -
(ssize_t)((double)fl->desired() * splitSurplusPercent));
}
};
void AFLBinaryTreeDictionary::set_tree_surplus(double splitSurplusPercent) {
setTreeSurplusClosure sts(splitSurplusPercent);
sts.do_tree(root());
}
// Set hints for the lists in the tree.
class setTreeHintsClosure : public DescendTreeCensusClosure<FreeChunk, AdaptiveFreeList<FreeChunk> > {
size_t hint;
public:
setTreeHintsClosure(size_t v) { hint = v; }
void do_list(AdaptiveFreeList<FreeChunk>* fl) {
fl->set_hint(hint);
assert(fl->hint() == 0 || fl->hint() > fl->size(),
"Current hint is inconsistent");
if (fl->surplus() > 0) {
hint = fl->size();
}
}
};
void AFLBinaryTreeDictionary::set_tree_hints(void) {
setTreeHintsClosure sth(0);
sth.do_tree(root());
}
// Save count before previous sweep and splits and coalesces.
class clearTreeCensusClosure : public AscendTreeCensusClosure<FreeChunk, AdaptiveFreeList<FreeChunk> > {
void do_list(AdaptiveFreeList<FreeChunk>* fl) {
fl->set_prev_sweep(fl->count());
fl->set_coal_births(0);
fl->set_coal_deaths(0);
fl->set_split_births(0);
fl->set_split_deaths(0);
}
};
void AFLBinaryTreeDictionary::clear_tree_census(void) {
clearTreeCensusClosure ctc;
ctc.do_tree(root());
}
// Do reporting and post sweep clean up.
void AFLBinaryTreeDictionary::end_sweep_dict_census(double splitSurplusPercent) {
// Does walking the tree 3 times hurt?
set_tree_surplus(splitSurplusPercent);
set_tree_hints();
LogTarget(Trace, gc, freelist, stats) log;
if (log.is_enabled()) {
LogStream out(log);
report_statistics(&out);
}
clear_tree_census();
}
// Print census information - counts, births, deaths, etc.
// for each list in the tree. Also print some summary
// information.
class PrintTreeCensusClosure : public AscendTreeCensusClosure<FreeChunk, AdaptiveFreeList<FreeChunk> > {
int _print_line;
size_t _total_free;
AdaptiveFreeList<FreeChunk> _total;
public:
PrintTreeCensusClosure() {
_print_line = 0;
_total_free = 0;
}
AdaptiveFreeList<FreeChunk>* total() { return &_total; }
size_t total_free() { return _total_free; }
void do_list(AdaptiveFreeList<FreeChunk>* fl) {
LogStreamHandle(Debug, gc, freelist, census) out;
if (++_print_line >= 40) {
AdaptiveFreeList<FreeChunk>::print_labels_on(&out, "size");
_print_line = 0;
}
fl->print_on(&out);
_total_free += fl->count() * fl->size() ;
total()->set_count( total()->count() + fl->count() );
total()->set_bfr_surp( total()->bfr_surp() + fl->bfr_surp() );
total()->set_surplus( total()->split_deaths() + fl->surplus() );
total()->set_desired( total()->desired() + fl->desired() );
total()->set_prev_sweep( total()->prev_sweep() + fl->prev_sweep() );
total()->set_before_sweep(total()->before_sweep() + fl->before_sweep());
total()->set_coal_births( total()->coal_births() + fl->coal_births() );
total()->set_coal_deaths( total()->coal_deaths() + fl->coal_deaths() );
total()->set_split_births(total()->split_births() + fl->split_births());
total()->set_split_deaths(total()->split_deaths() + fl->split_deaths());
}
};
void AFLBinaryTreeDictionary::print_dict_census(outputStream* st) const {
st->print_cr("BinaryTree");
AdaptiveFreeList<FreeChunk>::print_labels_on(st, "size");
PrintTreeCensusClosure ptc;
ptc.do_tree(root());
AdaptiveFreeList<FreeChunk>* total = ptc.total();
AdaptiveFreeList<FreeChunk>::print_labels_on(st, " ");
total->print_on(st, "TOTAL\t");
st->print_cr("total_free(words): " SIZE_FORMAT_W(16) " growth: %8.5f deficit: %8.5f",
ptc.total_free(),
(double)(total->split_births() + total->coal_births()
- total->split_deaths() - total->coal_deaths())
/(total->prev_sweep() != 0 ? (double)total->prev_sweep() : 1.0),
(double)(total->desired() - total->count())
/(total->desired() != 0 ? (double)total->desired() : 1.0));
}
/////////////////////////////////////////////////////////////////////////
//// CompactibleFreeListSpace
/////////////////////////////////////////////////////////////////////////
// highest ranked free list lock rank
int CompactibleFreeListSpace::_lockRank = Mutex::leaf + 3;
// Defaults are 0 so things will break badly if incorrectly initialized.
size_t CompactibleFreeListSpace::IndexSetStart = 0;
size_t CompactibleFreeListSpace::IndexSetStride = 0;
size_t CompactibleFreeListSpace::_min_chunk_size_in_bytes = 0;
size_t MinChunkSize = 0;
void CompactibleFreeListSpace::set_cms_values() {
// Set CMS global values
assert(MinChunkSize == 0, "already set");
// MinChunkSize should be a multiple of MinObjAlignment and be large enough
// for chunks to contain a FreeChunk.
_min_chunk_size_in_bytes = align_up(sizeof(FreeChunk), MinObjAlignmentInBytes);
MinChunkSize = _min_chunk_size_in_bytes / BytesPerWord;
assert(IndexSetStart == 0 && IndexSetStride == 0, "already set");
IndexSetStart = MinChunkSize;
IndexSetStride = MinObjAlignment;
}
// Constructor
CompactibleFreeListSpace::CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr) :
_rescan_task_size(CardTable::card_size_in_words * BitsPerWord *
CMSRescanMultiple),
_marking_task_size(CardTable::card_size_in_words * BitsPerWord *
CMSConcMarkMultiple),
_bt(bs, mr),
_collector(NULL),
// free list locks are in the range of values taken by _lockRank
// This range currently is [_leaf+2, _leaf+3]
// Note: this requires that CFLspace c'tors
// are called serially in the order in which the locks are
// are acquired in the program text. This is true today.
_freelistLock(_lockRank--, "CompactibleFreeListSpace_lock", true,
Monitor::_safepoint_check_never),
_preconsumptionDirtyCardClosure(NULL),
_parDictionaryAllocLock(Mutex::leaf - 1, // == rank(ExpandHeap_lock) - 1
"CompactibleFreeListSpace_dict_par_lock", true,
Monitor::_safepoint_check_never)
{
assert(sizeof(FreeChunk) / BytesPerWord <= MinChunkSize,
"FreeChunk is larger than expected");
_bt.set_space(this);
initialize(mr, SpaceDecorator::Clear, SpaceDecorator::Mangle);
_dictionary = new AFLBinaryTreeDictionary(mr);
assert(_dictionary != NULL, "CMS dictionary initialization");
// The indexed free lists are initially all empty and are lazily
// filled in on demand. Initialize the array elements to NULL.
initializeIndexedFreeListArray();
_smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc,
SmallForLinearAlloc);
// CMSIndexedFreeListReplenish should be at least 1
CMSIndexedFreeListReplenish = MAX2((uintx)1, CMSIndexedFreeListReplenish);
_promoInfo.setSpace(this);
if (UseCMSBestFit) {
_fitStrategy = FreeBlockBestFitFirst;
} else {
_fitStrategy = FreeBlockStrategyNone;
}
check_free_list_consistency();
// Initialize locks for parallel case.
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
_indexedFreeListParLocks[i] = new Mutex(Mutex::leaf - 1, // == ExpandHeap_lock - 1
"a freelist par lock", true, Mutex::_safepoint_check_never);
DEBUG_ONLY(
_indexedFreeList[i].set_protecting_lock(_indexedFreeListParLocks[i]);
)
}
_dictionary->set_par_lock(&_parDictionaryAllocLock);
_used_stable = 0;
}
// Like CompactibleSpace forward() but always calls cross_threshold() to
// update the block offset table. Removed initialize_threshold call because
// CFLS does not use a block offset array for contiguous spaces.
HeapWord* CompactibleFreeListSpace::forward(oop q, size_t size,
CompactPoint* cp, HeapWord* compact_top) {
// q is alive
// First check if we should switch compaction space
assert(this == cp->space, "'this' should be current compaction space.");
size_t compaction_max_size = pointer_delta(end(), compact_top);
assert(adjustObjectSize(size) == cp->space->adjust_object_size_v(size),
"virtual adjustObjectSize_v() method is not correct");
size_t adjusted_size = adjustObjectSize(size);
assert(compaction_max_size >= MinChunkSize || compaction_max_size == 0,
"no small fragments allowed");
assert(minimum_free_block_size() == MinChunkSize,
"for de-virtualized reference below");
// Can't leave a nonzero size, residual fragment smaller than MinChunkSize
if (adjusted_size + MinChunkSize > compaction_max_size &&
adjusted_size != compaction_max_size) {
do {
// switch to next compaction space
cp->space->set_compaction_top(compact_top);
cp->space = cp->space->next_compaction_space();
if (cp->space == NULL) {
cp->gen = CMSHeap::heap()->young_gen();
assert(cp->gen != NULL, "compaction must succeed");
cp->space = cp->gen->first_compaction_space();
assert(cp->space != NULL, "generation must have a first compaction space");
}
compact_top = cp->space->bottom();
cp->space->set_compaction_top(compact_top);
// The correct adjusted_size may not be the same as that for this method
// (i.e., cp->space may no longer be "this" so adjust the size again.
// Use the virtual method which is not used above to save the virtual
// dispatch.
adjusted_size = cp->space->adjust_object_size_v(size);
compaction_max_size = pointer_delta(cp->space->end(), compact_top);
assert(cp->space->minimum_free_block_size() == 0, "just checking");
} while (adjusted_size > compaction_max_size);
}
// store the forwarding pointer into the mark word
if ((HeapWord*)q != compact_top) {
q->forward_to(oop(compact_top));
assert(q->is_gc_marked(), "encoding the pointer should preserve the mark");
} else {
// if the object isn't moving we can just set the mark to the default
// mark and handle it specially later on.
q->init_mark_raw();
assert(q->forwardee() == NULL, "should be forwarded to NULL");
}
compact_top += adjusted_size;
// we need to update the offset table so that the beginnings of objects can be
// found during scavenge. Note that we are updating the offset table based on
// where the object will be once the compaction phase finishes.
// Always call cross_threshold(). A contiguous space can only call it when
// the compaction_top exceeds the current threshold but not for an
// non-contiguous space.
cp->threshold =
cp->space->cross_threshold(compact_top - adjusted_size, compact_top);
return compact_top;
}
// A modified copy of OffsetTableContigSpace::cross_threshold() with _offsets -> _bt
// and use of single_block instead of alloc_block. The name here is not really
// appropriate - maybe a more general name could be invented for both the
// contiguous and noncontiguous spaces.
HeapWord* CompactibleFreeListSpace::cross_threshold(HeapWord* start, HeapWord* the_end) {
_bt.single_block(start, the_end);
return end();
}
// Initialize them to NULL.
void CompactibleFreeListSpace::initializeIndexedFreeListArray() {
for (size_t i = 0; i < IndexSetSize; i++) {
// Note that on platforms where objects are double word aligned,
// the odd array elements are not used. It is convenient, however,
// to map directly from the object size to the array element.
_indexedFreeList[i].reset(IndexSetSize);
_indexedFreeList[i].set_size(i);
assert(_indexedFreeList[i].count() == 0, "reset check failed");
assert(_indexedFreeList[i].head() == NULL, "reset check failed");
assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
}
}
size_t CompactibleFreeListSpace::obj_size(const HeapWord* addr) const {
return adjustObjectSize(oop(addr)->size());
}
void CompactibleFreeListSpace::resetIndexedFreeListArray() {
for (size_t i = 1; i < IndexSetSize; i++) {
assert(_indexedFreeList[i].size() == (size_t) i,
"Indexed free list sizes are incorrect");
_indexedFreeList[i].reset(IndexSetSize);
assert(_indexedFreeList[i].count() == 0, "reset check failed");
assert(_indexedFreeList[i].head() == NULL, "reset check failed");
assert(_indexedFreeList[i].tail() == NULL, "reset check failed");
assert(_indexedFreeList[i].hint() == IndexSetSize, "reset check failed");
}
}
void CompactibleFreeListSpace::reset(MemRegion mr) {
resetIndexedFreeListArray();
dictionary()->reset();
if (BlockOffsetArrayUseUnallocatedBlock) {
assert(end() == mr.end(), "We are compacting to the bottom of CMS gen");
// Everything's allocated until proven otherwise.
_bt.set_unallocated_block(end());
}
if (!mr.is_empty()) {
assert(mr.word_size() >= MinChunkSize, "Chunk size is too small");
_bt.single_block(mr.start(), mr.word_size());
FreeChunk* fc = (FreeChunk*) mr.start();
fc->set_size(mr.word_size());
if (mr.word_size() >= IndexSetSize ) {
returnChunkToDictionary(fc);
} else {
_bt.verify_not_unallocated((HeapWord*)fc, fc->size());
_indexedFreeList[mr.word_size()].return_chunk_at_head(fc);
}
coalBirth(mr.word_size());
}
_promoInfo.reset();
_smallLinearAllocBlock._ptr = NULL;
_smallLinearAllocBlock._word_size = 0;
}
void CompactibleFreeListSpace::reset_after_compaction() {
// Reset the space to the new reality - one free chunk.
MemRegion mr(compaction_top(), end());
reset(mr);
// Now refill the linear allocation block(s) if possible.
refillLinearAllocBlocksIfNeeded();
}
// Walks the entire dictionary, returning a coterminal
// chunk, if it exists. Use with caution since it involves
// a potentially complete walk of a potentially large tree.
FreeChunk* CompactibleFreeListSpace::find_chunk_at_end() {
assert_lock_strong(&_freelistLock);
return dictionary()->find_chunk_ends_at(end());
}
#ifndef PRODUCT
void CompactibleFreeListSpace::initializeIndexedFreeListArrayReturnedBytes() {
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
_indexedFreeList[i].allocation_stats()->set_returned_bytes(0);
}
}
size_t CompactibleFreeListSpace::sumIndexedFreeListArrayReturnedBytes() {
size_t sum = 0;
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
sum += _indexedFreeList[i].allocation_stats()->returned_bytes();
}
return sum;
}
size_t CompactibleFreeListSpace::totalCountInIndexedFreeLists() const {
size_t count = 0;
for (size_t i = IndexSetStart; i < IndexSetSize; i++) {
debug_only(
ssize_t total_list_count = 0;
for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
fc = fc->next()) {
total_list_count++;
}
assert(total_list_count == _indexedFreeList[i].count(),
"Count in list is incorrect");
)
count += _indexedFreeList[i].count();
}
return count;
}
size_t CompactibleFreeListSpace::totalCount() {
size_t num = totalCountInIndexedFreeLists();
num += dictionary()->total_count();
if (_smallLinearAllocBlock._word_size != 0) {
num++;
}
return num;
}
#endif
bool CompactibleFreeListSpace::is_free_block(const HeapWord* p) const {
FreeChunk* fc = (FreeChunk*) p;
return fc->is_free();
}
size_t CompactibleFreeListSpace::used() const {
return capacity() - free();
}
size_t CompactibleFreeListSpace::used_stable() const {
return _used_stable;
}
void CompactibleFreeListSpace::recalculate_used_stable() {
_used_stable = used();
}
size_t CompactibleFreeListSpace::free() const {
// "MT-safe, but not MT-precise"(TM), if you will: i.e.
// if you do this while the structures are in flux you
// may get an approximate answer only; for instance
// because there is concurrent allocation either
// directly by mutators or for promotion during a GC.
// It's "MT-safe", however, in the sense that you are guaranteed
// not to crash and burn, for instance, because of walking
// pointers that could disappear as you were walking them.
// The approximation is because the various components
// that are read below are not read atomically (and
// further the computation of totalSizeInIndexedFreeLists()
// is itself a non-atomic computation. The normal use of
// this is during a resize operation at the end of GC
// and at that time you are guaranteed to get the
// correct actual value. However, for instance, this is
// also read completely asynchronously by the "perf-sampler"
// that supports jvmstat, and you are apt to see the values
// flicker in such cases.
assert(_dictionary != NULL, "No _dictionary?");
return (_dictionary->total_chunk_size(DEBUG_ONLY(freelistLock())) +
totalSizeInIndexedFreeLists() +
_smallLinearAllocBlock._word_size) * HeapWordSize;
}
size_t CompactibleFreeListSpace::max_alloc_in_words() const {
assert(_dictionary != NULL, "No _dictionary?");
assert_locked();
size_t res = _dictionary->max_chunk_size();
res = MAX2(res, MIN2(_smallLinearAllocBlock._word_size,
(size_t) SmallForLinearAlloc - 1));
// XXX the following could potentially be pretty slow;
// should one, pessimistically for the rare cases when res
// calculated above is less than IndexSetSize,
// just return res calculated above? My reasoning was that
// those cases will be so rare that the extra time spent doesn't
// really matter....
// Note: do not change the loop test i >= res + IndexSetStride
// to i > res below, because i is unsigned and res may be zero.
for (size_t i = IndexSetSize - 1; i >= res + IndexSetStride;
i -= IndexSetStride) {
if (_indexedFreeList[i].head() != NULL) {
assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
return i;
}
}
return res;
}
void LinearAllocBlock::print_on(outputStream* st) const {
st->print_cr(" LinearAllocBlock: ptr = " PTR_FORMAT ", word_size = " SIZE_FORMAT
", refillsize = " SIZE_FORMAT ", allocation_size_limit = " SIZE_FORMAT,
p2i(_ptr), _word_size, _refillSize, _allocation_size_limit);
}
void CompactibleFreeListSpace::print_on(outputStream* st) const {
st->print_cr("COMPACTIBLE FREELIST SPACE");
st->print_cr(" Space:");
Space::print_on(st);
st->print_cr("promoInfo:");
_promoInfo.print_on(st);
st->print_cr("_smallLinearAllocBlock");
_smallLinearAllocBlock.print_on(st);
// dump_memory_block(_smallLinearAllocBlock->_ptr, 128);
st->print_cr(" _fitStrategy = %s", BOOL_TO_STR(_fitStrategy));
}
void CompactibleFreeListSpace::print_indexed_free_lists(outputStream* st)
const {
reportIndexedFreeListStatistics(st);
st->print_cr("Layout of Indexed Freelists");
st->print_cr("---------------------------");
AdaptiveFreeList<FreeChunk>::print_labels_on(st, "size");
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
_indexedFreeList[i].print_on(st);
for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL; fc = fc->next()) {
st->print_cr("\t[" PTR_FORMAT "," PTR_FORMAT ") %s",
p2i(fc), p2i((HeapWord*)fc + i),
fc->cantCoalesce() ? "\t CC" : "");
}
}
}
void CompactibleFreeListSpace::print_promo_info_blocks(outputStream* st)
const {
_promoInfo.print_on(st);
}
void CompactibleFreeListSpace::print_dictionary_free_lists(outputStream* st)
const {
_dictionary->report_statistics(st);
st->print_cr("Layout of Freelists in Tree");
st->print_cr("---------------------------");
_dictionary->print_free_lists(st);
}
class BlkPrintingClosure: public BlkClosure {
const CMSCollector* _collector;
const CompactibleFreeListSpace* _sp;
const CMSBitMap* _live_bit_map;
const bool _post_remark;
outputStream* _st;
public:
BlkPrintingClosure(const CMSCollector* collector,
const CompactibleFreeListSpace* sp,
const CMSBitMap* live_bit_map,
outputStream* st):
_collector(collector),
_sp(sp),
_live_bit_map(live_bit_map),
_post_remark(collector->abstract_state() > CMSCollector::FinalMarking),
_st(st) { }
size_t do_blk(HeapWord* addr);
};
size_t BlkPrintingClosure::do_blk(HeapWord* addr) {
size_t sz = _sp->block_size_no_stall(addr, _collector);
assert(sz != 0, "Should always be able to compute a size");
if (_sp->block_is_obj(addr)) {
const bool dead = _post_remark && !_live_bit_map->isMarked(addr);
_st->print_cr(PTR_FORMAT ": %s object of size " SIZE_FORMAT "%s",
p2i(addr),
dead ? "dead" : "live",
sz,
(!dead && CMSPrintObjectsInDump) ? ":" : ".");
if (CMSPrintObjectsInDump && !dead) {
oop(addr)->print_on(_st);
_st->print_cr("--------------------------------------");
}
} else { // free block
_st->print_cr(PTR_FORMAT ": free block of size " SIZE_FORMAT "%s",
p2i(addr), sz, CMSPrintChunksInDump ? ":" : ".");
if (CMSPrintChunksInDump) {
((FreeChunk*)addr)->print_on(_st);
_st->print_cr("--------------------------------------");
}
}
return sz;
}
void CompactibleFreeListSpace::dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st) {
st->print_cr("=========================");
st->print_cr("Block layout in CMS Heap:");
st->print_cr("=========================");
BlkPrintingClosure bpcl(c, this, c->markBitMap(), st);
blk_iterate(&bpcl);
st->print_cr("=======================================");
st->print_cr("Order & Layout of Promotion Info Blocks");
st->print_cr("=======================================");
print_promo_info_blocks(st);
st->print_cr("===========================");
st->print_cr("Order of Indexed Free Lists");
st->print_cr("=========================");
print_indexed_free_lists(st);
st->print_cr("=================================");
st->print_cr("Order of Free Lists in Dictionary");
st->print_cr("=================================");
print_dictionary_free_lists(st);
}
void CompactibleFreeListSpace::reportFreeListStatistics(const char* title) const {
assert_lock_strong(&_freelistLock);
Log(gc, freelist, stats) log;
if (!log.is_debug()) {
return;
}
log.debug("%s", title);
LogStream out(log.debug());
_dictionary->report_statistics(&out);
if (log.is_trace()) {
LogStream trace_out(log.trace());
reportIndexedFreeListStatistics(&trace_out);
size_t total_size = totalSizeInIndexedFreeLists() +
_dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
log.trace(" free=" SIZE_FORMAT " frag=%1.4f", total_size, flsFrag());
}
}
void CompactibleFreeListSpace::reportIndexedFreeListStatistics(outputStream* st) const {
assert_lock_strong(&_freelistLock);
st->print_cr("Statistics for IndexedFreeLists:");
st->print_cr("--------------------------------");
size_t total_size = totalSizeInIndexedFreeLists();
size_t free_blocks = numFreeBlocksInIndexedFreeLists();
st->print_cr("Total Free Space: " SIZE_FORMAT, total_size);
st->print_cr("Max Chunk Size: " SIZE_FORMAT, maxChunkSizeInIndexedFreeLists());
st->print_cr("Number of Blocks: " SIZE_FORMAT, free_blocks);
if (free_blocks != 0) {
st->print_cr("Av. Block Size: " SIZE_FORMAT, total_size/free_blocks);
}
}
size_t CompactibleFreeListSpace::numFreeBlocksInIndexedFreeLists() const {
size_t res = 0;
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
debug_only(
ssize_t recount = 0;
for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
fc = fc->next()) {
recount += 1;
}
assert(recount == _indexedFreeList[i].count(),
"Incorrect count in list");
)
res += _indexedFreeList[i].count();
}
return res;
}
size_t CompactibleFreeListSpace::maxChunkSizeInIndexedFreeLists() const {
for (size_t i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
if (_indexedFreeList[i].head() != NULL) {
assert(_indexedFreeList[i].count() != 0, "Inconsistent FreeList");
return (size_t)i;
}
}
return 0;
}
void CompactibleFreeListSpace::set_end(HeapWord* value) {
HeapWord* prevEnd = end();
assert(prevEnd != value, "unnecessary set_end call");
assert(prevEnd == NULL || !BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
"New end is below unallocated block");
_end = value;
if (prevEnd != NULL) {
// Resize the underlying block offset table.
_bt.resize(pointer_delta(value, bottom()));
if (value <= prevEnd) {
assert(!BlockOffsetArrayUseUnallocatedBlock || value >= unallocated_block(),
"New end is below unallocated block");
} else {
// Now, take this new chunk and add it to the free blocks.
// Note that the BOT has not yet been updated for this block.
size_t newFcSize = pointer_delta(value, prevEnd);
// Add the block to the free lists, if possible coalescing it
// with the last free block, and update the BOT and census data.
addChunkToFreeListsAtEndRecordingStats(prevEnd, newFcSize);
}
}
}
class FreeListSpaceDCTOC : public FilteringDCTOC {
CompactibleFreeListSpace* _cfls;
CMSCollector* _collector;
bool _parallel;
protected:
// Override.
#define walk_mem_region_with_cl_DECL(ClosureType) \
virtual void walk_mem_region_with_cl(MemRegion mr, \
HeapWord* bottom, HeapWord* top, \
ClosureType* cl); \
void walk_mem_region_with_cl_par(MemRegion mr, \
HeapWord* bottom, HeapWord* top, \
ClosureType* cl); \
void walk_mem_region_with_cl_nopar(MemRegion mr, \
HeapWord* bottom, HeapWord* top, \
ClosureType* cl)
walk_mem_region_with_cl_DECL(OopIterateClosure);
walk_mem_region_with_cl_DECL(FilteringClosure);
public:
FreeListSpaceDCTOC(CompactibleFreeListSpace* sp,
CMSCollector* collector,
OopIterateClosure* cl,
CardTable::PrecisionStyle precision,
HeapWord* boundary,
bool parallel) :
FilteringDCTOC(sp, cl, precision, boundary),
_cfls(sp), _collector(collector), _parallel(parallel) {}
};
// We de-virtualize the block-related calls below, since we know that our
// space is a CompactibleFreeListSpace.
#define FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(ClosureType) \
void FreeListSpaceDCTOC::walk_mem_region_with_cl(MemRegion mr, \
HeapWord* bottom, \
HeapWord* top, \
ClosureType* cl) { \
if (_parallel) { \
walk_mem_region_with_cl_par(mr, bottom, top, cl); \
} else { \
walk_mem_region_with_cl_nopar(mr, bottom, top, cl); \
} \
} \
void FreeListSpaceDCTOC::walk_mem_region_with_cl_par(MemRegion mr, \
HeapWord* bottom, \
HeapWord* top, \
ClosureType* cl) { \
/* Skip parts that are before "mr", in case "block_start" sent us \
back too far. */ \
HeapWord* mr_start = mr.start(); \
size_t bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
HeapWord* next = bottom + bot_size; \
while (next < mr_start) { \
bottom = next; \
bot_size = _cfls->CompactibleFreeListSpace::block_size(bottom); \
next = bottom + bot_size; \
} \
\
while (bottom < top) { \
if (_cfls->CompactibleFreeListSpace::block_is_obj(bottom) && \
!_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
oop(bottom)) && \
!_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
size_t word_sz = oop(bottom)->oop_iterate_size(cl, mr); \
bottom += _cfls->adjustObjectSize(word_sz); \
} else { \
bottom += _cfls->CompactibleFreeListSpace::block_size(bottom); \
} \
} \
} \
void FreeListSpaceDCTOC::walk_mem_region_with_cl_nopar(MemRegion mr, \
HeapWord* bottom, \
HeapWord* top, \
ClosureType* cl) { \
/* Skip parts that are before "mr", in case "block_start" sent us \
back too far. */ \
HeapWord* mr_start = mr.start(); \
size_t bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
HeapWord* next = bottom + bot_size; \
while (next < mr_start) { \
bottom = next; \
bot_size = _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
next = bottom + bot_size; \
} \
\
while (bottom < top) { \
if (_cfls->CompactibleFreeListSpace::block_is_obj_nopar(bottom) && \
!_cfls->CompactibleFreeListSpace::obj_allocated_since_save_marks( \
oop(bottom)) && \
!_collector->CMSCollector::is_dead_obj(oop(bottom))) { \
size_t word_sz = oop(bottom)->oop_iterate_size(cl, mr); \
bottom += _cfls->adjustObjectSize(word_sz); \
} else { \
bottom += _cfls->CompactibleFreeListSpace::block_size_nopar(bottom); \
} \
} \
}
// (There are only two of these, rather than N, because the split is due
// only to the introduction of the FilteringClosure, a local part of the
// impl of this abstraction.)
FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(OopIterateClosure)
FreeListSpaceDCTOC__walk_mem_region_with_cl_DEFN(FilteringClosure)
DirtyCardToOopClosure*
CompactibleFreeListSpace::new_dcto_cl(OopIterateClosure* cl,
CardTable::PrecisionStyle precision,
HeapWord* boundary,
bool parallel) {
return new FreeListSpaceDCTOC(this, _collector, cl, precision, boundary, parallel);
}
// Note on locking for the space iteration functions:
// since the collector's iteration activities are concurrent with
// allocation activities by mutators, absent a suitable mutual exclusion
// mechanism the iterators may go awry. For instance a block being iterated
// may suddenly be allocated or divided up and part of it allocated and
// so on.
// Apply the given closure to each block in the space.
void CompactibleFreeListSpace::blk_iterate_careful(BlkClosureCareful* cl) {
assert_lock_strong(freelistLock());
HeapWord *cur, *limit;
for (cur = bottom(), limit = end(); cur < limit;
cur += cl->do_blk_careful(cur));
}
// Apply the given closure to each block in the space.
void CompactibleFreeListSpace::blk_iterate(BlkClosure* cl) {
assert_lock_strong(freelistLock());
HeapWord *cur, *limit;
for (cur = bottom(), limit = end(); cur < limit;
cur += cl->do_blk(cur));
}
// Apply the given closure to each oop in the space.
void CompactibleFreeListSpace::oop_iterate(OopIterateClosure* cl) {
assert_lock_strong(freelistLock());
HeapWord *cur, *limit;
size_t curSize;
for (cur = bottom(), limit = end(); cur < limit;
cur += curSize) {
curSize = block_size(cur);
if (block_is_obj(cur)) {
oop(cur)->oop_iterate(cl);
}
}
}
// NOTE: In the following methods, in order to safely be able to
// apply the closure to an object, we need to be sure that the
// object has been initialized. We are guaranteed that an object
// is initialized if we are holding the Heap_lock with the
// world stopped.
void CompactibleFreeListSpace::verify_objects_initialized() const {
if (is_init_completed()) {
assert_locked_or_safepoint(Heap_lock);
if (Universe::is_fully_initialized()) {
guarantee(SafepointSynchronize::is_at_safepoint(),
"Required for objects to be initialized");
}
} // else make a concession at vm start-up
}
// Apply the given closure to each object in the space
void CompactibleFreeListSpace::object_iterate(ObjectClosure* blk) {
assert_lock_strong(freelistLock());
NOT_PRODUCT(verify_objects_initialized());
HeapWord *cur, *limit;
size_t curSize;
for (cur = bottom(), limit = end(); cur < limit;
cur += curSize) {
curSize = block_size(cur);
if (block_is_obj(cur)) {
blk->do_object(oop(cur));
}
}
}
// Apply the given closure to each live object in the space
// The usage of CompactibleFreeListSpace
// by the ConcurrentMarkSweepGeneration for concurrent GC's allows
// objects in the space with references to objects that are no longer
// valid. For example, an object may reference another object
// that has already been sweep up (collected). This method uses
// obj_is_alive() to determine whether it is safe to apply the closure to
// an object. See obj_is_alive() for details on how liveness of an
// object is decided.
void CompactibleFreeListSpace::safe_object_iterate(ObjectClosure* blk) {
assert_lock_strong(freelistLock());
NOT_PRODUCT(verify_objects_initialized());
HeapWord *cur, *limit;
size_t curSize;
for (cur = bottom(), limit = end(); cur < limit;
cur += curSize) {
curSize = block_size(cur);
if (block_is_obj(cur) && obj_is_alive(cur)) {
blk->do_object(oop(cur));
}
}
}
void CompactibleFreeListSpace::object_iterate_mem(MemRegion mr,
UpwardsObjectClosure* cl) {
assert_locked(freelistLock());
NOT_PRODUCT(verify_objects_initialized());
assert(!mr.is_empty(), "Should be non-empty");
// We use MemRegion(bottom(), end()) rather than used_region() below
// because the two are not necessarily equal for some kinds of
// spaces, in particular, certain kinds of free list spaces.
// We could use the more complicated but more precise:
// MemRegion(used_region().start(), align_up(used_region().end(), CardSize))
// but the slight imprecision seems acceptable in the assertion check.
assert(MemRegion(bottom(), end()).contains(mr),
"Should be within used space");
HeapWord* prev = cl->previous(); // max address from last time
if (prev >= mr.end()) { // nothing to do
return;
}
// This assert will not work when we go from cms space to perm
// space, and use same closure. Easy fix deferred for later. XXX YSR
// assert(prev == NULL || contains(prev), "Should be within space");
bool last_was_obj_array = false;
HeapWord *blk_start_addr, *region_start_addr;
if (prev > mr.start()) {
region_start_addr = prev;
blk_start_addr = prev;
// The previous invocation may have pushed "prev" beyond the
// last allocated block yet there may be still be blocks
// in this region due to a particular coalescing policy.
// Relax the assertion so that the case where the unallocated
// block is maintained and "prev" is beyond the unallocated
// block does not cause the assertion to fire.
assert((BlockOffsetArrayUseUnallocatedBlock &&
(!is_in(prev))) ||
(blk_start_addr == block_start(region_start_addr)), "invariant");
} else {
region_start_addr = mr.start();
blk_start_addr = block_start(region_start_addr);
}
HeapWord* region_end_addr = mr.end();
MemRegion derived_mr(region_start_addr, region_end_addr);
while (blk_start_addr < region_end_addr) {
const size_t size = block_size(blk_start_addr);
if (block_is_obj(blk_start_addr)) {
last_was_obj_array = cl->do_object_bm(oop(blk_start_addr), derived_mr);
} else {
last_was_obj_array = false;
}
blk_start_addr += size;
}
if (!last_was_obj_array) {
assert((bottom() <= blk_start_addr) && (blk_start_addr <= end()),
"Should be within (closed) used space");
assert(blk_start_addr > prev, "Invariant");
cl->set_previous(blk_start_addr); // min address for next time
}
}
// Callers of this iterator beware: The closure application should
// be robust in the face of uninitialized objects and should (always)
// return a correct size so that the next addr + size below gives us a
// valid block boundary. [See for instance,
// ScanMarkedObjectsAgainCarefullyClosure::do_object_careful()
// in ConcurrentMarkSweepGeneration.cpp.]
HeapWord*
CompactibleFreeListSpace::object_iterate_careful_m(MemRegion mr,
ObjectClosureCareful* cl) {
assert_lock_strong(freelistLock());
// Can't use used_region() below because it may not necessarily
// be the same as [bottom(),end()); although we could
// use [used_region().start(),align_up(used_region().end(),CardSize)),
// that appears too cumbersome, so we just do the simpler check
// in the assertion below.
assert(!mr.is_empty() && MemRegion(bottom(),end()).contains(mr),
"mr should be non-empty and within used space");
HeapWord *addr, *end;
size_t size;
for (addr = block_start_careful(mr.start()), end = mr.end();
addr < end; addr += size) {
FreeChunk* fc = (FreeChunk*)addr;
if (fc->is_free()) {
// Since we hold the free list lock, which protects direct
// allocation in this generation by mutators, a free object
// will remain free throughout this iteration code.
size = fc->size();
} else {
// Note that the object need not necessarily be initialized,
// because (for instance) the free list lock does NOT protect
// object initialization. The closure application below must
// therefore be correct in the face of uninitialized objects.
size = cl->do_object_careful_m(oop(addr), mr);
if (size == 0) {
// An unparsable object found. Signal early termination.
return addr;
}
}
}
return NULL;
}
HeapWord* CompactibleFreeListSpace::block_start_const(const void* p) const {
NOT_PRODUCT(verify_objects_initialized());
return _bt.block_start(p);
}
HeapWord* CompactibleFreeListSpace::block_start_careful(const void* p) const {
return _bt.block_start_careful(p);
}
size_t CompactibleFreeListSpace::block_size(const HeapWord* p) const {
NOT_PRODUCT(verify_objects_initialized());
// This must be volatile, or else there is a danger that the compiler
// will compile the code below into a sometimes-infinite loop, by keeping
// the value read the first time in a register.
while (true) {
// We must do this until we get a consistent view of the object.
if (FreeChunk::indicatesFreeChunk(p)) {
volatile FreeChunk* fc = (volatile FreeChunk*)p;
size_t res = fc->size();
// Bugfix for systems with weak memory model (PPC64/IA64). The
// block's free bit was set and we have read the size of the
// block. Acquire and check the free bit again. If the block is
// still free, the read size is correct.
OrderAccess::acquire();
// If the object is still a free chunk, return the size, else it
// has been allocated so try again.
if (FreeChunk::indicatesFreeChunk(p)) {
assert(res != 0, "Block size should not be 0");
return res;
}
} else {
// Ensure klass read before size.
Klass* k = oop(p)->klass_or_null_acquire();
if (k != NULL) {
assert(k->is_klass(), "Should really be klass oop.");
oop o = (oop)p;
assert(oopDesc::is_oop(o, true /* ignore mark word */), "Should be an oop.");
size_t res = o->size_given_klass(k);
res = adjustObjectSize(res);
assert(res != 0, "Block size should not be 0");
return res;
}
}
}
}
// TODO: Now that is_parsable is gone, we should combine these two functions.
// A variant of the above that uses the Printezis bits for
// unparsable but allocated objects. This avoids any possible
// stalls waiting for mutators to initialize objects, and is
// thus potentially faster than the variant above. However,
// this variant may return a zero size for a block that is
// under mutation and for which a consistent size cannot be
// inferred without stalling; see CMSCollector::block_size_if_printezis_bits().
size_t CompactibleFreeListSpace::block_size_no_stall(HeapWord* p,
const CMSCollector* c)
const {
assert(MemRegion(bottom(), end()).contains(p), "p not in space");
// This must be volatile, or else there is a danger that the compiler
// will compile the code below into a sometimes-infinite loop, by keeping
// the value read the first time in a register.
DEBUG_ONLY(uint loops = 0;)
while (true) {
// We must do this until we get a consistent view of the object.
if (FreeChunk::indicatesFreeChunk(p)) {
volatile FreeChunk* fc = (volatile FreeChunk*)p;
size_t res = fc->size();
// Bugfix for systems with weak memory model (PPC64/IA64). The
// free bit of the block was set and we have read the size of
// the block. Acquire and check the free bit again. If the
// block is still free, the read size is correct.
OrderAccess::acquire();
if (FreeChunk::indicatesFreeChunk(p)) {
assert(res != 0, "Block size should not be 0");
assert(loops == 0, "Should be 0");
return res;
}
} else {
// Ensure klass read before size.
Klass* k = oop(p)->klass_or_null_acquire();
if (k != NULL) {
assert(k->is_klass(), "Should really be klass oop.");
oop o = (oop)p;
assert(oopDesc::is_oop(o), "Should be an oop");
size_t res = o->size_given_klass(k);
res = adjustObjectSize(res);
assert(res != 0, "Block size should not be 0");
return res;
} else {
// May return 0 if P-bits not present.
return c->block_size_if_printezis_bits(p);
}
}
assert(loops == 0, "Can loop at most once");
DEBUG_ONLY(loops++;)
}
}
size_t CompactibleFreeListSpace::block_size_nopar(const HeapWord* p) const {
NOT_PRODUCT(verify_objects_initialized());
assert(MemRegion(bottom(), end()).contains(p), "p not in space");
FreeChunk* fc = (FreeChunk*)p;
if (fc->is_free()) {
return fc->size();
} else {
// Ignore mark word because this may be a recently promoted
// object whose mark word is used to chain together grey
// objects (the last one would have a null value).
assert(oopDesc::is_oop(oop(p), true), "Should be an oop");
return adjustObjectSize(oop(p)->size());
}
}
// This implementation assumes that the property of "being an object" is
// stable. But being a free chunk may not be (because of parallel
// promotion.)
bool CompactibleFreeListSpace::block_is_obj(const HeapWord* p) const {
FreeChunk* fc = (FreeChunk*)p;
assert(is_in_reserved(p), "Should be in space");
if (FreeChunk::indicatesFreeChunk(p)) return false;
Klass* k = oop(p)->klass_or_null_acquire();
if (k != NULL) {
// Ignore mark word because it may have been used to
// chain together promoted objects (the last one
// would have a null value).
assert(oopDesc::is_oop(oop(p), true), "Should be an oop");
return true;
} else {
return false; // Was not an object at the start of collection.
}
}
// Check if the object is alive. This fact is checked either by consulting
// the main marking bitmap in the sweeping phase or, if it's a permanent
// generation and we're not in the sweeping phase, by checking the
// perm_gen_verify_bit_map where we store the "deadness" information if
// we did not sweep the perm gen in the most recent previous GC cycle.
bool CompactibleFreeListSpace::obj_is_alive(const HeapWord* p) const {
assert(SafepointSynchronize::is_at_safepoint() || !is_init_completed(),
"Else races are possible");
assert(block_is_obj(p), "The address should point to an object");
// If we're sweeping, we use object liveness information from the main bit map
// for both perm gen and old gen.
// We don't need to lock the bitmap (live_map or dead_map below), because
// EITHER we are in the middle of the sweeping phase, and the
// main marking bit map (live_map below) is locked,
// OR we're in other phases and perm_gen_verify_bit_map (dead_map below)
// is stable, because it's mutated only in the sweeping phase.
// NOTE: This method is also used by jmap where, if class unloading is
// off, the results can return "false" for legitimate perm objects,
// when we are not in the midst of a sweeping phase, which can result
// in jmap not reporting certain perm gen objects. This will be moot
// if/when the perm gen goes away in the future.
if (_collector->abstract_state() == CMSCollector::Sweeping) {
CMSBitMap* live_map = _collector->markBitMap();
return live_map->par_isMarked((HeapWord*) p);
}
return true;
}
bool CompactibleFreeListSpace::block_is_obj_nopar(const HeapWord* p) const {
FreeChunk* fc = (FreeChunk*)p;
assert(is_in_reserved(p), "Should be in space");
assert(_bt.block_start(p) == p, "Should be a block boundary");
if (!fc->is_free()) {
// Ignore mark word because it may have been used to
// chain together promoted objects (the last one
// would have a null value).
assert(oopDesc::is_oop(oop(p), true), "Should be an oop");
return true;
}
return false;
}
// "MT-safe but not guaranteed MT-precise" (TM); you may get an
// approximate answer if you don't hold the freelistlock when you call this.
size_t CompactibleFreeListSpace::totalSizeInIndexedFreeLists() const {
size_t size = 0;
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
debug_only(
// We may be calling here without the lock in which case we
// won't do this modest sanity check.
if (freelistLock()->owned_by_self()) {
size_t total_list_size = 0;
for (FreeChunk* fc = _indexedFreeList[i].head(); fc != NULL;
fc = fc->next()) {
total_list_size += i;
}
assert(total_list_size == i * _indexedFreeList[i].count(),
"Count in list is incorrect");
}
)
size += i * _indexedFreeList[i].count();
}
return size;
}
HeapWord* CompactibleFreeListSpace::par_allocate(size_t size) {
MutexLocker x(freelistLock(), Mutex::_no_safepoint_check_flag);
return allocate(size);
}
HeapWord*
CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlockRemainder(size_t size) {
return getChunkFromLinearAllocBlockRemainder(&_smallLinearAllocBlock, size);
}
HeapWord* CompactibleFreeListSpace::allocate(size_t size) {
assert_lock_strong(freelistLock());
HeapWord* res = NULL;
assert(size == adjustObjectSize(size),
"use adjustObjectSize() before calling into allocate()");
res = allocate_adaptive_freelists(size);
if (res != NULL) {
// check that res does lie in this space!
assert(is_in_reserved(res), "Not in this space!");
assert(is_aligned((void*)res), "alignment check");
FreeChunk* fc = (FreeChunk*)res;
fc->markNotFree();
assert(!fc->is_free(), "shouldn't be marked free");
assert(oop(fc)->klass_or_null() == NULL, "should look uninitialized");
// Verify that the block offset table shows this to
// be a single block, but not one which is unallocated.
_bt.verify_single_block(res, size);
_bt.verify_not_unallocated(res, size);
// mangle a just allocated object with a distinct pattern.
debug_only(fc->mangleAllocated(size));
}
// During GC we do not need to recalculate the stable used value for
// every allocation in old gen. It is done once at the end of GC instead
// for performance reasons.
if (!CMSHeap::heap()->is_gc_active()) {
recalculate_used_stable();
}
return res;
}
HeapWord* CompactibleFreeListSpace::allocate_adaptive_freelists(size_t size) {
assert_lock_strong(freelistLock());
HeapWord* res = NULL;
assert(size == adjustObjectSize(size),
"use adjustObjectSize() before calling into allocate()");
// Strategy
// if small
// exact size from small object indexed list if small
// small or large linear allocation block (linAB) as appropriate
// take from lists of greater sized chunks
// else
// dictionary
// small or large linear allocation block if it has the space
// Try allocating exact size from indexTable first
if (size < IndexSetSize) {
res = (HeapWord*) getChunkFromIndexedFreeList(size);
if(res != NULL) {
assert(res != (HeapWord*)_indexedFreeList[size].head(),
"Not removed from free list");
// no block offset table adjustment is necessary on blocks in
// the indexed lists.
// Try allocating from the small LinAB
} else if (size < _smallLinearAllocBlock._allocation_size_limit &&
(res = getChunkFromSmallLinearAllocBlock(size)) != NULL) {
// if successful, the above also adjusts block offset table
// Note that this call will refill the LinAB to
// satisfy the request. This is different that
// evm.
// Don't record chunk off a LinAB? smallSplitBirth(size);
} else {
// Raid the exact free lists larger than size, even if they are not
// overpopulated.
res = (HeapWord*) getChunkFromGreater(size);
}
} else {
// Big objects get allocated directly from the dictionary.
res = (HeapWord*) getChunkFromDictionaryExact(size);
if (res == NULL) {
// Try hard not to fail since an allocation failure will likely
// trigger a synchronous GC. Try to get the space from the
// allocation blocks.
res = getChunkFromSmallLinearAllocBlockRemainder(size);
}
}
return res;
}
// A worst-case estimate of the space required (in HeapWords) to expand the heap
// when promoting obj.
size_t CompactibleFreeListSpace::expansionSpaceRequired(size_t obj_size) const {
// Depending on the object size, expansion may require refilling either a
// bigLAB or a smallLAB plus refilling a PromotionInfo object. MinChunkSize
// is added because the dictionary may over-allocate to avoid fragmentation.
size_t space = obj_size;
space += _promoInfo.refillSize() + 2 * MinChunkSize;
return space;
}
FreeChunk* CompactibleFreeListSpace::getChunkFromGreater(size_t numWords) {
FreeChunk* ret;
assert(numWords >= MinChunkSize, "Size is less than minimum");
assert(linearAllocationWouldFail() || bestFitFirst(),
"Should not be here");
size_t i;
size_t currSize = numWords + MinChunkSize;
assert(is_object_aligned(currSize), "currSize should be aligned");
for (i = currSize; i < IndexSetSize; i += IndexSetStride) {
AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
if (fl->head()) {
ret = getFromListGreater(fl, numWords);
assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
return ret;
}
}
currSize = MAX2((size_t)SmallForDictionary,
(size_t)(numWords + MinChunkSize));
/* Try to get a chunk that satisfies request, while avoiding
fragmentation that can't be handled. */
{
ret = dictionary()->get_chunk(currSize);
if (ret != NULL) {
assert(ret->size() - numWords >= MinChunkSize,
"Chunk is too small");
_bt.allocated((HeapWord*)ret, ret->size());
/* Carve returned chunk. */
(void) splitChunkAndReturnRemainder(ret, numWords);
/* Label this as no longer a free chunk. */
assert(ret->is_free(), "This chunk should be free");
ret->link_prev(NULL);
}
assert(ret == NULL || ret->is_free(), "Should be returning a free chunk");
return ret;
}
ShouldNotReachHere();
}
bool CompactibleFreeListSpace::verifyChunkInIndexedFreeLists(FreeChunk* fc) const {
assert(fc->size() < IndexSetSize, "Size of chunk is too large");
return _indexedFreeList[fc->size()].verify_chunk_in_free_list(fc);
}
bool CompactibleFreeListSpace::verify_chunk_is_linear_alloc_block(FreeChunk* fc) const {
assert((_smallLinearAllocBlock._ptr != (HeapWord*)fc) ||
(_smallLinearAllocBlock._word_size == fc->size()),
"Linear allocation block shows incorrect size");
return ((_smallLinearAllocBlock._ptr == (HeapWord*)fc) &&
(_smallLinearAllocBlock._word_size == fc->size()));
}
// Check if the purported free chunk is present either as a linear
// allocation block, the size-indexed table of (smaller) free blocks,
// or the larger free blocks kept in the binary tree dictionary.
bool CompactibleFreeListSpace::verify_chunk_in_free_list(FreeChunk* fc) const {
if (verify_chunk_is_linear_alloc_block(fc)) {
return true;
} else if (fc->size() < IndexSetSize) {
return verifyChunkInIndexedFreeLists(fc);
} else {
return dictionary()->verify_chunk_in_free_list(fc);
}
}
#ifndef PRODUCT
void CompactibleFreeListSpace::assert_locked() const {
CMSLockVerifier::assert_locked(freelistLock(), parDictionaryAllocLock());
}
void CompactibleFreeListSpace::assert_locked(const Mutex* lock) const {
CMSLockVerifier::assert_locked(lock);
}
#endif
FreeChunk* CompactibleFreeListSpace::allocateScratch(size_t size) {
// In the parallel case, the main thread holds the free list lock
// on behalf the parallel threads.
FreeChunk* fc;
{
// If GC is parallel, this might be called by several threads.
// This should be rare enough that the locking overhead won't affect
// the sequential code.
MutexLocker x(parDictionaryAllocLock(),
Mutex::_no_safepoint_check_flag);
fc = getChunkFromDictionary(size);
}
if (fc != NULL) {
fc->dontCoalesce();
assert(fc->is_free(), "Should be free, but not coalescable");
// Verify that the block offset table shows this to
// be a single block, but not one which is unallocated.
_bt.verify_single_block((HeapWord*)fc, fc->size());
_bt.verify_not_unallocated((HeapWord*)fc, fc->size());
}
return fc;
}
oop CompactibleFreeListSpace::promote(oop obj, size_t obj_size) {
assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
assert_locked();
// if we are tracking promotions, then first ensure space for
// promotion (including spooling space for saving header if necessary).
// then allocate and copy, then track promoted info if needed.
// When tracking (see PromotionInfo::track()), the mark word may
// be displaced and in this case restoration of the mark word
// occurs in the (oop_since_save_marks_)iterate phase.
if (_promoInfo.tracking() && !_promoInfo.ensure_spooling_space()) {
return NULL;
}
// Call the allocate(size_t, bool) form directly to avoid the
// additional call through the allocate(size_t) form. Having
// the compile inline the call is problematic because allocate(size_t)
// is a virtual method.
HeapWord* res = allocate(adjustObjectSize(obj_size));
if (res != NULL) {
Copy::aligned_disjoint_words((HeapWord*)obj, res, obj_size);
// if we should be tracking promotions, do so.
if (_promoInfo.tracking()) {
_promoInfo.track((PromotedObject*)res);
}
}
return oop(res);
}
HeapWord*
CompactibleFreeListSpace::getChunkFromSmallLinearAllocBlock(size_t size) {
assert_locked();
assert(size >= MinChunkSize, "minimum chunk size");
assert(size < _smallLinearAllocBlock._allocation_size_limit,
"maximum from smallLinearAllocBlock");
return getChunkFromLinearAllocBlock(&_smallLinearAllocBlock, size);
}
HeapWord*
CompactibleFreeListSpace::getChunkFromLinearAllocBlock(LinearAllocBlock *blk,
size_t size) {
assert_locked();
assert(size >= MinChunkSize, "too small");
HeapWord* res = NULL;
// Try to do linear allocation from blk, making sure that
if (blk->_word_size == 0) {
// We have probably been unable to fill this either in the prologue or
// when it was exhausted at the last linear allocation. Bail out until
// next time.
assert(blk->_ptr == NULL, "consistency check");
return NULL;
}
assert(blk->_word_size != 0 && blk->_ptr != NULL, "consistency check");
res = getChunkFromLinearAllocBlockRemainder(blk, size);
if (res != NULL) return res;
// about to exhaust this linear allocation block
if (blk->_word_size == size) { // exactly satisfied
res = blk->_ptr;
_bt.allocated(res, blk->_word_size);
} else if (size + MinChunkSize <= blk->_refillSize) {
size_t sz = blk->_word_size;
// Update _unallocated_block if the size is such that chunk would be
// returned to the indexed free list. All other chunks in the indexed
// free lists are allocated from the dictionary so that _unallocated_block
// has already been adjusted for them. Do it here so that the cost
// for all chunks added back to the indexed free lists.
if (sz < SmallForDictionary) {
_bt.allocated(blk->_ptr, sz);
}
// Return the chunk that isn't big enough, and then refill below.
addChunkToFreeLists(blk->_ptr, sz);
split_birth(sz);
// Don't keep statistics on adding back chunk from a LinAB.
} else {
// A refilled block would not satisfy the request.
return NULL;
}
blk->_ptr = NULL; blk->_word_size = 0;
refillLinearAllocBlock(blk);
assert(blk->_ptr == NULL || blk->_word_size >= size + MinChunkSize,
"block was replenished");
if (res != NULL) {
split_birth(size);
repairLinearAllocBlock(blk);
} else if (blk->_ptr != NULL) {
res = blk->_ptr;
size_t blk_size = blk->_word_size;
blk->_word_size -= size;
blk->_ptr += size;
split_birth(size);
repairLinearAllocBlock(blk);
// Update BOT last so that other (parallel) GC threads see a consistent
// view of the BOT and free blocks.
// Above must occur before BOT is updated below.
OrderAccess::storestore();
_bt.split_block(res, blk_size, size); // adjust block offset table
}
return res;
}
HeapWord* CompactibleFreeListSpace::getChunkFromLinearAllocBlockRemainder(
LinearAllocBlock* blk,
size_t size) {
assert_locked();
assert(size >= MinChunkSize, "too small");
HeapWord* res = NULL;
// This is the common case. Keep it simple.
if (blk->_word_size >= size + MinChunkSize) {
assert(blk->_ptr != NULL, "consistency check");
res = blk->_ptr;
// Note that the BOT is up-to-date for the linAB before allocation. It
// indicates the start of the linAB. The split_block() updates the
// BOT for the linAB after the allocation (indicates the start of the
// next chunk to be allocated).
size_t blk_size = blk->_word_size;
blk->_word_size -= size;
blk->_ptr += size;
split_birth(size);
repairLinearAllocBlock(blk);
// Update BOT last so that other (parallel) GC threads see a consistent
// view of the BOT and free blocks.
// Above must occur before BOT is updated below.
OrderAccess::storestore();
_bt.split_block(res, blk_size, size); // adjust block offset table
_bt.allocated(res, size);
}
return res;
}
FreeChunk*
CompactibleFreeListSpace::getChunkFromIndexedFreeList(size_t size) {
assert_locked();
assert(size < SmallForDictionary, "just checking");
FreeChunk* res;
res = _indexedFreeList[size].get_chunk_at_head();
if (res == NULL) {
res = getChunkFromIndexedFreeListHelper(size);
}
_bt.verify_not_unallocated((HeapWord*) res, size);
assert(res == NULL || res->size() == size, "Incorrect block size");
return res;
}
FreeChunk*
CompactibleFreeListSpace::getChunkFromIndexedFreeListHelper(size_t size,
bool replenish) {
assert_locked();
FreeChunk* fc = NULL;
if (size < SmallForDictionary) {
assert(_indexedFreeList[size].head() == NULL ||
_indexedFreeList[size].surplus() <= 0,
"List for this size should be empty or under populated");
// Try best fit in exact lists before replenishing the list
if (!bestFitFirst() || (fc = bestFitSmall(size)) == NULL) {
// Replenish list.
//
// Things tried that failed.
// Tried allocating out of the two LinAB's first before
// replenishing lists.
// Tried small linAB of size 256 (size in indexed list)
// and replenishing indexed lists from the small linAB.
//
FreeChunk* newFc = NULL;
const size_t replenish_size = CMSIndexedFreeListReplenish * size;
if (replenish_size < SmallForDictionary) {
// Do not replenish from an underpopulated size.
if (_indexedFreeList[replenish_size].surplus() > 0 &&
_indexedFreeList[replenish_size].head() != NULL) {
newFc = _indexedFreeList[replenish_size].get_chunk_at_head();
} else if (bestFitFirst()) {
newFc = bestFitSmall(replenish_size);
}
}
if (newFc == NULL && replenish_size > size) {
assert(CMSIndexedFreeListReplenish > 1, "ctl pt invariant");
newFc = getChunkFromIndexedFreeListHelper(replenish_size, false);
}
// Note: The stats update re split-death of block obtained above
// will be recorded below precisely when we know we are going to
// be actually splitting it into more than one pieces below.
if (newFc != NULL) {
if (replenish || CMSReplenishIntermediate) {
// Replenish this list and return one block to caller.
size_t i;
FreeChunk *curFc, *nextFc;
size_t num_blk = newFc->size() / size;
assert(num_blk >= 1, "Smaller than requested?");
assert(newFc->size() % size == 0, "Should be integral multiple of request");
if (num_blk > 1) {
// we are sure we will be splitting the block just obtained
// into multiple pieces; record the split-death of the original
splitDeath(replenish_size);
}
// carve up and link blocks 0, ..., num_blk - 2
// The last chunk is not added to the lists but is returned as the
// free chunk.
for (curFc = newFc, nextFc = (FreeChunk*)((HeapWord*)curFc + size),
i = 0;
i < (num_blk - 1);
curFc = nextFc, nextFc = (FreeChunk*)((HeapWord*)nextFc + size),
i++) {
curFc->set_size(size);
// Don't record this as a return in order to try and
// determine the "returns" from a GC.
_bt.verify_not_unallocated((HeapWord*) fc, size);
_indexedFreeList[size].return_chunk_at_tail(curFc, false);
_bt.mark_block((HeapWord*)curFc, size);
split_birth(size);
// Don't record the initial population of the indexed list
// as a split birth.
}
// check that the arithmetic was OK above
assert((HeapWord*)nextFc == (HeapWord*)newFc + num_blk*size,
"inconsistency in carving newFc");
curFc->set_size(size);
_bt.mark_block((HeapWord*)curFc, size);
split_birth(size);
fc = curFc;
} else {
// Return entire block to caller
fc = newFc;
}
}
}
} else {
// Get a free chunk from the free chunk dictionary to be returned to
// replenish the indexed free list.
fc = getChunkFromDictionaryExact(size);
}
// assert(fc == NULL || fc->is_free(), "Should be returning a free chunk");
return fc;
}
FreeChunk*
CompactibleFreeListSpace::getChunkFromDictionary(size_t size) {
assert_locked();
FreeChunk* fc = _dictionary->get_chunk(size);
if (fc == NULL) {
return NULL;
}
_bt.allocated((HeapWord*)fc, fc->size());
if (fc->size() >= size + MinChunkSize) {
fc = splitChunkAndReturnRemainder(fc, size);
}
assert(fc->size() >= size, "chunk too small");
assert(fc->size() < size + MinChunkSize, "chunk too big");
_bt.verify_single_block((HeapWord*)fc, fc->size());
return fc;
}
FreeChunk*
CompactibleFreeListSpace::getChunkFromDictionaryExact(size_t size) {
assert_locked();
FreeChunk* fc = _dictionary->get_chunk(size);
if (fc == NULL) {
return fc;
}
_bt.allocated((HeapWord*)fc, fc->size());
if (fc->size() == size) {
_bt.verify_single_block((HeapWord*)fc, size);
return fc;
}
assert(fc->size() > size, "get_chunk() guarantee");
if (fc->size() < size + MinChunkSize) {
// Return the chunk to the dictionary and go get a bigger one.
returnChunkToDictionary(fc);
fc = _dictionary->get_chunk(size + MinChunkSize);
if (fc == NULL) {
return NULL;
}
_bt.allocated((HeapWord*)fc, fc->size());
}
assert(fc->size() >= size + MinChunkSize, "tautology");
fc = splitChunkAndReturnRemainder(fc, size);
assert(fc->size() == size, "chunk is wrong size");
_bt.verify_single_block((HeapWord*)fc, size);
return fc;
}
void
CompactibleFreeListSpace::returnChunkToDictionary(FreeChunk* chunk) {
assert_locked();
size_t size = chunk->size();
_bt.verify_single_block((HeapWord*)chunk, size);
// adjust _unallocated_block downward, as necessary
_bt.freed((HeapWord*)chunk, size);
_dictionary->return_chunk(chunk);
#ifndef PRODUCT
if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >* tc = TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::as_TreeChunk(chunk);
TreeList<FreeChunk, AdaptiveFreeList<FreeChunk> >* tl = tc->list();
tl->verify_stats();
}
#endif // PRODUCT
}
void
CompactibleFreeListSpace::returnChunkToFreeList(FreeChunk* fc) {
assert_locked();
size_t size = fc->size();
_bt.verify_single_block((HeapWord*) fc, size);
_bt.verify_not_unallocated((HeapWord*) fc, size);
_indexedFreeList[size].return_chunk_at_tail(fc);
#ifndef PRODUCT
if (CMSCollector::abstract_state() != CMSCollector::Sweeping) {
_indexedFreeList[size].verify_stats();
}
#endif // PRODUCT
}
// Add chunk to end of last block -- if it's the largest
// block -- and update BOT and census data. We would
// of course have preferred to coalesce it with the
// last block, but it's currently less expensive to find the
// largest block than it is to find the last.
void
CompactibleFreeListSpace::addChunkToFreeListsAtEndRecordingStats(
HeapWord* chunk, size_t size) {
// check that the chunk does lie in this space!
assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
// One of the parallel gc task threads may be here
// whilst others are allocating.
Mutex* lock = &_parDictionaryAllocLock;
FreeChunk* ec;
{
MutexLocker x(lock, Mutex::_no_safepoint_check_flag);
ec = dictionary()->find_largest_dict(); // get largest block
if (ec != NULL && ec->end() == (uintptr_t*) chunk) {
// It's a coterminal block - we can coalesce.
size_t old_size = ec->size();
coalDeath(old_size);
removeChunkFromDictionary(ec);
size += old_size;
} else {
ec = (FreeChunk*)chunk;
}
}
ec->set_size(size);
debug_only(ec->mangleFreed(size));
if (size < SmallForDictionary) {
lock = _indexedFreeListParLocks[size];
}
MutexLocker x(lock, Mutex::_no_safepoint_check_flag);
addChunkAndRepairOffsetTable((HeapWord*)ec, size, true);
// record the birth under the lock since the recording involves
// manipulation of the list on which the chunk lives and
// if the chunk is allocated and is the last on the list,
// the list can go away.
coalBirth(size);
}
void
CompactibleFreeListSpace::addChunkToFreeLists(HeapWord* chunk,
size_t size) {
// check that the chunk does lie in this space!
assert(chunk != NULL && is_in_reserved(chunk), "Not in this space!");
assert_locked();
_bt.verify_single_block(chunk, size);
FreeChunk* fc = (FreeChunk*) chunk;
fc->set_size(size);
debug_only(fc->mangleFreed(size));
if (size < SmallForDictionary) {
returnChunkToFreeList(fc);
} else {
returnChunkToDictionary(fc);
}
}
void
CompactibleFreeListSpace::addChunkAndRepairOffsetTable(HeapWord* chunk,
size_t size, bool coalesced) {
assert_locked();
assert(chunk != NULL, "null chunk");
if (coalesced) {
// repair BOT
_bt.single_block(chunk, size);
}
addChunkToFreeLists(chunk, size);
}
// We _must_ find the purported chunk on our free lists;
// we assert if we don't.
void
CompactibleFreeListSpace::removeFreeChunkFromFreeLists(FreeChunk* fc) {
size_t size = fc->size();
assert_locked();
debug_only(verifyFreeLists());
if (size < SmallForDictionary) {
removeChunkFromIndexedFreeList(fc);
} else {
removeChunkFromDictionary(fc);
}
_bt.verify_single_block((HeapWord*)fc, size);
debug_only(verifyFreeLists());
}
void
CompactibleFreeListSpace::removeChunkFromDictionary(FreeChunk* fc) {
size_t size = fc->size();
assert_locked();
assert(fc != NULL, "null chunk");
_bt.verify_single_block((HeapWord*)fc, size);
_dictionary->remove_chunk(fc);
// adjust _unallocated_block upward, as necessary
_bt.allocated((HeapWord*)fc, size);
}
void
CompactibleFreeListSpace::removeChunkFromIndexedFreeList(FreeChunk* fc) {
assert_locked();
size_t size = fc->size();
_bt.verify_single_block((HeapWord*)fc, size);
NOT_PRODUCT(
if (FLSVerifyIndexTable) {
verifyIndexedFreeList(size);
}
)
_indexedFreeList[size].remove_chunk(fc);
NOT_PRODUCT(
if (FLSVerifyIndexTable) {
verifyIndexedFreeList(size);
}
)
}
FreeChunk* CompactibleFreeListSpace::bestFitSmall(size_t numWords) {
/* A hint is the next larger size that has a surplus.
Start search at a size large enough to guarantee that
the excess is >= MIN_CHUNK. */
size_t start = align_object_size(numWords + MinChunkSize);
if (start < IndexSetSize) {
AdaptiveFreeList<FreeChunk>* it = _indexedFreeList;
size_t hint = _indexedFreeList[start].hint();
while (hint < IndexSetSize) {
assert(is_object_aligned(hint), "hint should be aligned");
AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[hint];
if (fl->surplus() > 0 && fl->head() != NULL) {
// Found a list with surplus, reset original hint
// and split out a free chunk which is returned.
_indexedFreeList[start].set_hint(hint);
FreeChunk* res = getFromListGreater(fl, numWords);
assert(res == NULL || res->is_free(),
"Should be returning a free chunk");
return res;
}
hint = fl->hint(); /* keep looking */
}
/* None found. */
it[start].set_hint(IndexSetSize);
}
return NULL;
}
/* Requires fl->size >= numWords + MinChunkSize */
FreeChunk* CompactibleFreeListSpace::getFromListGreater(AdaptiveFreeList<FreeChunk>* fl,
size_t numWords) {
FreeChunk *curr = fl->head();
size_t oldNumWords = curr->size();
assert(numWords >= MinChunkSize, "Word size is too small");
assert(curr != NULL, "List is empty");
assert(oldNumWords >= numWords + MinChunkSize,
"Size of chunks in the list is too small");
fl->remove_chunk(curr);
// recorded indirectly by splitChunkAndReturnRemainder -
// smallSplit(oldNumWords, numWords);
FreeChunk* new_chunk = splitChunkAndReturnRemainder(curr, numWords);
// Does anything have to be done for the remainder in terms of
// fixing the card table?
assert(new_chunk == NULL || new_chunk->is_free(),
"Should be returning a free chunk");
return new_chunk;
}
FreeChunk*
CompactibleFreeListSpace::splitChunkAndReturnRemainder(FreeChunk* chunk,
size_t new_size) {
assert_locked();
size_t size = chunk->size();
assert(size > new_size, "Split from a smaller block?");
assert(is_aligned(chunk), "alignment problem");
assert(size == adjustObjectSize(size), "alignment problem");
size_t rem_sz = size - new_size;
assert(rem_sz == adjustObjectSize(rem_sz), "alignment problem");
assert(rem_sz >= MinChunkSize, "Free chunk smaller than minimum");
FreeChunk* ffc = (FreeChunk*)((HeapWord*)chunk + new_size);
assert(is_aligned(ffc), "alignment problem");
ffc->set_size(rem_sz);
ffc->link_next(NULL);
ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
// Above must occur before BOT is updated below.
// adjust block offset table
OrderAccess::storestore();
assert(chunk->is_free() && ffc->is_free(), "Error");
_bt.split_block((HeapWord*)chunk, chunk->size(), new_size);
if (rem_sz < SmallForDictionary) {
// The freeList lock is held, but multiple GC task threads might be executing in parallel.
bool is_par = Thread::current()->is_GC_task_thread();
if (is_par) _indexedFreeListParLocks[rem_sz]->lock_without_safepoint_check();
returnChunkToFreeList(ffc);
split(size, rem_sz);
if (is_par) _indexedFreeListParLocks[rem_sz]->unlock();
} else {
returnChunkToDictionary(ffc);
split(size, rem_sz);
}
chunk->set_size(new_size);
return chunk;
}
void
CompactibleFreeListSpace::sweep_completed() {
// Now that space is probably plentiful, refill linear
// allocation blocks as needed.
refillLinearAllocBlocksIfNeeded();
}
void
CompactibleFreeListSpace::gc_prologue() {
assert_locked();
reportFreeListStatistics("Before GC:");
refillLinearAllocBlocksIfNeeded();
}
void
CompactibleFreeListSpace::gc_epilogue() {
assert_locked();
assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
_promoInfo.stopTrackingPromotions();
repairLinearAllocationBlocks();
reportFreeListStatistics("After GC:");
}
// Iteration support, mostly delegated from a CMS generation
void CompactibleFreeListSpace::save_marks() {
assert(Thread::current()->is_VM_thread(),
"Global variable should only be set when single-threaded");
// Mark the "end" of the used space at the time of this call;
// note, however, that promoted objects from this point
// on are tracked in the _promoInfo below.
set_saved_mark_word(unallocated_block());
#ifdef ASSERT
// Check the sanity of save_marks() etc.
MemRegion ur = used_region();
MemRegion urasm = used_region_at_save_marks();
assert(ur.contains(urasm),
" Error at save_marks(): [" PTR_FORMAT "," PTR_FORMAT ")"
" should contain [" PTR_FORMAT "," PTR_FORMAT ")",
p2i(ur.start()), p2i(ur.end()), p2i(urasm.start()), p2i(urasm.end()));
#endif
// inform allocator that promotions should be tracked.
assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
_promoInfo.startTrackingPromotions();
}
bool CompactibleFreeListSpace::no_allocs_since_save_marks() {
assert(_promoInfo.tracking(), "No preceding save_marks?");
return _promoInfo.noPromotions();
}
bool CompactibleFreeListSpace::linearAllocationWouldFail() const {
return _smallLinearAllocBlock._word_size == 0;
}
void CompactibleFreeListSpace::repairLinearAllocationBlocks() {
// Fix up linear allocation blocks to look like free blocks
repairLinearAllocBlock(&_smallLinearAllocBlock);
}
void CompactibleFreeListSpace::repairLinearAllocBlock(LinearAllocBlock* blk) {
assert_locked();
if (blk->_ptr != NULL) {
assert(blk->_word_size != 0 && blk->_word_size >= MinChunkSize,
"Minimum block size requirement");
FreeChunk* fc = (FreeChunk*)(blk->_ptr);
fc->set_size(blk->_word_size);
fc->link_prev(NULL); // mark as free
fc->dontCoalesce();
assert(fc->is_free(), "just marked it free");
assert(fc->cantCoalesce(), "just marked it uncoalescable");
}
}
void CompactibleFreeListSpace::refillLinearAllocBlocksIfNeeded() {
assert_locked();
if (_smallLinearAllocBlock._ptr == NULL) {
assert(_smallLinearAllocBlock._word_size == 0,
"Size of linAB should be zero if the ptr is NULL");
// Reset the linAB refill and allocation size limit.
_smallLinearAllocBlock.set(0, 0, 1024*SmallForLinearAlloc, SmallForLinearAlloc);
}
refillLinearAllocBlockIfNeeded(&_smallLinearAllocBlock);
}
void
CompactibleFreeListSpace::refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk) {
assert_locked();
assert((blk->_ptr == NULL && blk->_word_size == 0) ||
(blk->_ptr != NULL && blk->_word_size >= MinChunkSize),
"blk invariant");
if (blk->_ptr == NULL) {
refillLinearAllocBlock(blk);
}
}
void
CompactibleFreeListSpace::refillLinearAllocBlock(LinearAllocBlock* blk) {
assert_locked();
assert(blk->_word_size == 0 && blk->_ptr == NULL,
"linear allocation block should be empty");
FreeChunk* fc;
if (blk->_refillSize < SmallForDictionary &&
(fc = getChunkFromIndexedFreeList(blk->_refillSize)) != NULL) {
// A linAB's strategy might be to use small sizes to reduce
// fragmentation but still get the benefits of allocation from a
// linAB.
} else {
fc = getChunkFromDictionary(blk->_refillSize);
}
if (fc != NULL) {
blk->_ptr = (HeapWord*)fc;
blk->_word_size = fc->size();
fc->dontCoalesce(); // to prevent sweeper from sweeping us up
}
}
// Support for compaction
void CompactibleFreeListSpace::prepare_for_compaction(CompactPoint* cp) {
scan_and_forward(this, cp);
// Prepare_for_compaction() uses the space between live objects
// so that later phase can skip dead space quickly. So verification
// of the free lists doesn't work after.
}
void CompactibleFreeListSpace::adjust_pointers() {
// In other versions of adjust_pointers(), a bail out
// based on the amount of live data in the generation
// (i.e., if 0, bail out) may be used.
// Cannot test used() == 0 here because the free lists have already
// been mangled by the compaction.
scan_and_adjust_pointers(this);
// See note about verification in prepare_for_compaction().
}
void CompactibleFreeListSpace::compact() {
scan_and_compact(this);
}
// Fragmentation metric = 1 - [sum of (fbs**2) / (sum of fbs)**2]
// where fbs is free block sizes
double CompactibleFreeListSpace::flsFrag() const {
size_t itabFree = totalSizeInIndexedFreeLists();
double frag = 0.0;
size_t i;
for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
double sz = i;
frag += _indexedFreeList[i].count() * (sz * sz);
}
double totFree = itabFree +
_dictionary->total_chunk_size(DEBUG_ONLY(freelistLock()));
if (totFree > 0) {
frag = ((frag + _dictionary->sum_of_squared_block_sizes()) /
(totFree * totFree));
frag = (double)1.0 - frag;
} else {
assert(frag == 0.0, "Follows from totFree == 0");
}
return frag;
}
void CompactibleFreeListSpace::beginSweepFLCensus(
float inter_sweep_current,
float inter_sweep_estimate,
float intra_sweep_estimate) {
assert_locked();
size_t i;
for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[i];
log_trace(gc, freelist)("size[" SIZE_FORMAT "] : ", i);
fl->compute_desired(inter_sweep_current, inter_sweep_estimate, intra_sweep_estimate);
fl->set_coal_desired((ssize_t)((double)fl->desired() * CMSSmallCoalSurplusPercent));
fl->set_before_sweep(fl->count());
fl->set_bfr_surp(fl->surplus());
}
_dictionary->begin_sweep_dict_census(CMSLargeCoalSurplusPercent,
inter_sweep_current,
inter_sweep_estimate,
intra_sweep_estimate);
}
void CompactibleFreeListSpace::setFLSurplus() {
assert_locked();
size_t i;
for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
fl->set_surplus(fl->count() -
(ssize_t)((double)fl->desired() * CMSSmallSplitSurplusPercent));
}
}
void CompactibleFreeListSpace::setFLHints() {
assert_locked();
size_t i;
size_t h = IndexSetSize;
for (i = IndexSetSize - 1; i != 0; i -= IndexSetStride) {
AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
fl->set_hint(h);
if (fl->surplus() > 0) {
h = i;
}
}
}
void CompactibleFreeListSpace::clearFLCensus() {
assert_locked();
size_t i;
for (i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
fl->set_prev_sweep(fl->count());
fl->set_coal_births(0);
fl->set_coal_deaths(0);
fl->set_split_births(0);
fl->set_split_deaths(0);
}
}
void CompactibleFreeListSpace::endSweepFLCensus(size_t sweep_count) {
log_debug(gc, freelist)("CMS: Large block " PTR_FORMAT, p2i(dictionary()->find_largest_dict()));
setFLSurplus();
setFLHints();
printFLCensus(sweep_count);
clearFLCensus();
assert_locked();
_dictionary->end_sweep_dict_census(CMSLargeSplitSurplusPercent);
}
bool CompactibleFreeListSpace::coalOverPopulated(size_t size) {
if (size < SmallForDictionary) {
AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
return (fl->coal_desired() < 0) ||
((int)fl->count() > fl->coal_desired());
} else {
return dictionary()->coal_dict_over_populated(size);
}
}
void CompactibleFreeListSpace::smallCoalBirth(size_t size) {
assert(size < SmallForDictionary, "Size too large for indexed list");
AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
fl->increment_coal_births();
fl->increment_surplus();
}
void CompactibleFreeListSpace::smallCoalDeath(size_t size) {
assert(size < SmallForDictionary, "Size too large for indexed list");
AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
fl->increment_coal_deaths();
fl->decrement_surplus();
}
void CompactibleFreeListSpace::coalBirth(size_t size) {
if (size < SmallForDictionary) {
smallCoalBirth(size);
} else {
dictionary()->dict_census_update(size,
false /* split */,
true /* birth */);
}
}
void CompactibleFreeListSpace::coalDeath(size_t size) {
if(size < SmallForDictionary) {
smallCoalDeath(size);
} else {
dictionary()->dict_census_update(size,
false /* split */,
false /* birth */);
}
}
void CompactibleFreeListSpace::smallSplitBirth(size_t size) {
assert(size < SmallForDictionary, "Size too large for indexed list");
AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
fl->increment_split_births();
fl->increment_surplus();
}
void CompactibleFreeListSpace::smallSplitDeath(size_t size) {
assert(size < SmallForDictionary, "Size too large for indexed list");
AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[size];
fl->increment_split_deaths();
fl->decrement_surplus();
}
void CompactibleFreeListSpace::split_birth(size_t size) {
if (size < SmallForDictionary) {
smallSplitBirth(size);
} else {
dictionary()->dict_census_update(size,
true /* split */,
true /* birth */);
}
}
void CompactibleFreeListSpace::splitDeath(size_t size) {
if (size < SmallForDictionary) {
smallSplitDeath(size);
} else {
dictionary()->dict_census_update(size,
true /* split */,
false /* birth */);
}
}
void CompactibleFreeListSpace::split(size_t from, size_t to1) {
size_t to2 = from - to1;
splitDeath(from);
split_birth(to1);
split_birth(to2);
}
void CompactibleFreeListSpace::print() const {
print_on(tty);
}
void CompactibleFreeListSpace::prepare_for_verify() {
assert_locked();
repairLinearAllocationBlocks();
// Verify that the SpoolBlocks look like free blocks of
// appropriate sizes... To be done ...
}
class VerifyAllBlksClosure: public BlkClosure {
private:
const CompactibleFreeListSpace* _sp;
const MemRegion _span;
HeapWord* _last_addr;
size_t _last_size;
bool _last_was_obj;
bool _last_was_live;
public:
VerifyAllBlksClosure(const CompactibleFreeListSpace* sp,
MemRegion span) : _sp(sp), _span(span),
_last_addr(NULL), _last_size(0),
_last_was_obj(false), _last_was_live(false) { }
virtual size_t do_blk(HeapWord* addr) {
size_t res;
bool was_obj = false;
bool was_live = false;
if (_sp->block_is_obj(addr)) {
was_obj = true;
oop p = oop(addr);
guarantee(oopDesc::is_oop(p), "Should be an oop");
res = _sp->adjustObjectSize(p->size());
if (_sp->obj_is_alive(addr)) {
was_live = true;
oopDesc::verify(p);
}
} else {
FreeChunk* fc = (FreeChunk*)addr;
res = fc->size();
if (FLSVerifyLists && !fc->cantCoalesce()) {
guarantee(_sp->verify_chunk_in_free_list(fc),
"Chunk should be on a free list");
}
}
if (res == 0) {
Log(gc, verify) log;
log.error("Livelock: no rank reduction!");
log.error(" Current: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n"
" Previous: addr = " PTR_FORMAT ", size = " SIZE_FORMAT ", obj = %s, live = %s \n",
p2i(addr), res, was_obj ?"true":"false", was_live ?"true":"false",
p2i(_last_addr), _last_size, _last_was_obj?"true":"false", _last_was_live?"true":"false");
LogStream ls(log.error());
_sp->print_on(&ls);
guarantee(false, "Verification failed.");
}
_last_addr = addr;
_last_size = res;
_last_was_obj = was_obj;
_last_was_live = was_live;
return res;
}
};
class VerifyAllOopsClosure: public BasicOopIterateClosure {
private:
const CMSCollector* _collector;
const CompactibleFreeListSpace* _sp;
const MemRegion _span;
const bool _past_remark;
const CMSBitMap* _bit_map;
protected:
void do_oop(void* p, oop obj) {
if (_span.contains(obj)) { // the interior oop points into CMS heap
if (!_span.contains(p)) { // reference from outside CMS heap
// Should be a valid object; the first disjunct below allows
// us to sidestep an assertion in block_is_obj() that insists
// that p be in _sp. Note that several generations (and spaces)
// are spanned by _span (CMS heap) above.
guarantee(!_sp->is_in_reserved(obj) ||
_sp->block_is_obj((HeapWord*)obj),
"Should be an object");
guarantee(oopDesc::is_oop(obj), "Should be an oop");
oopDesc::verify(obj);
if (_past_remark) {
// Remark has been completed, the object should be marked
_bit_map->isMarked((HeapWord*)obj);
}
} else { // reference within CMS heap
if (_past_remark) {
// Remark has been completed -- so the referent should have
// been marked, if referring object is.
if (_bit_map->isMarked(_collector->block_start(p))) {
guarantee(_bit_map->isMarked((HeapWord*)obj), "Marking error?");
}
}
}
} else if (_sp->is_in_reserved(p)) {
// the reference is from FLS, and points out of FLS
guarantee(oopDesc::is_oop(obj), "Should be an oop");
oopDesc::verify(obj);
}
}
template <class T> void do_oop_work(T* p) {
T heap_oop = RawAccess<>::oop_load(p);
if (!CompressedOops::is_null(heap_oop)) {
oop obj = CompressedOops::decode_not_null(heap_oop);
do_oop(p, obj);
}
}
public:
VerifyAllOopsClosure(const CMSCollector* collector,
const CompactibleFreeListSpace* sp, MemRegion span,
bool past_remark, CMSBitMap* bit_map) :
_collector(collector), _sp(sp), _span(span),
_past_remark(past_remark), _bit_map(bit_map) { }
virtual void do_oop(oop* p) { VerifyAllOopsClosure::do_oop_work(p); }
virtual void do_oop(narrowOop* p) { VerifyAllOopsClosure::do_oop_work(p); }
};
void CompactibleFreeListSpace::verify() const {
assert_lock_strong(&_freelistLock);
verify_objects_initialized();
MemRegion span = _collector->_span;
bool past_remark = (_collector->abstract_state() ==
CMSCollector::Sweeping);
ResourceMark rm;
HandleMark hm;
// Check integrity of CFL data structures
_promoInfo.verify();
_dictionary->verify();
if (FLSVerifyIndexTable) {
verifyIndexedFreeLists();
}
// Check integrity of all objects and free blocks in space
{
VerifyAllBlksClosure cl(this, span);
((CompactibleFreeListSpace*)this)->blk_iterate(&cl); // cast off const
}
// Check that all references in the heap to FLS
// are to valid objects in FLS or that references in
// FLS are to valid objects elsewhere in the heap
if (FLSVerifyAllHeapReferences)
{
VerifyAllOopsClosure cl(_collector, this, span, past_remark,
_collector->markBitMap());
// Iterate over all oops in the heap.
CMSHeap::heap()->oop_iterate(&cl);
}
if (VerifyObjectStartArray) {
// Verify the block offset table
_bt.verify();
}
}
#ifndef PRODUCT
void CompactibleFreeListSpace::verifyFreeLists() const {
if (FLSVerifyLists) {
_dictionary->verify();
verifyIndexedFreeLists();
} else {
if (FLSVerifyDictionary) {
_dictionary->verify();
}
if (FLSVerifyIndexTable) {
verifyIndexedFreeLists();
}
}
}
#endif
void CompactibleFreeListSpace::verifyIndexedFreeLists() const {
size_t i = 0;
for (; i < IndexSetStart; i++) {
guarantee(_indexedFreeList[i].head() == NULL, "should be NULL");
}
for (; i < IndexSetSize; i++) {
verifyIndexedFreeList(i);
}
}
void CompactibleFreeListSpace::verifyIndexedFreeList(size_t size) const {
FreeChunk* fc = _indexedFreeList[size].head();
FreeChunk* tail = _indexedFreeList[size].tail();
size_t num = _indexedFreeList[size].count();
size_t n = 0;
guarantee(((size >= IndexSetStart) && (size % IndexSetStride == 0)) || fc == NULL,
"Slot should have been empty");
for (; fc != NULL; fc = fc->next(), n++) {
guarantee(fc->size() == size, "Size inconsistency");
guarantee(fc->is_free(), "!free?");
guarantee(fc->next() == NULL || fc->next()->prev() == fc, "Broken list");
guarantee((fc->next() == NULL) == (fc == tail), "Incorrect tail");
}
guarantee(n == num, "Incorrect count");
}
#ifndef PRODUCT
void CompactibleFreeListSpace::check_free_list_consistency() const {
assert((TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::min_size() <= IndexSetSize),
"Some sizes can't be allocated without recourse to"
" linear allocation buffers");
assert((TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >::min_size()*HeapWordSize == sizeof(TreeChunk<FreeChunk, AdaptiveFreeList<FreeChunk> >)),
"else MIN_TREE_CHUNK_SIZE is wrong");
assert(IndexSetStart != 0, "IndexSetStart not initialized");
assert(IndexSetStride != 0, "IndexSetStride not initialized");
}
#endif
void CompactibleFreeListSpace::printFLCensus(size_t sweep_count) const {
assert_lock_strong(&_freelistLock);
LogTarget(Debug, gc, freelist, census) log;
if (!log.is_enabled()) {
return;
}
AdaptiveFreeList<FreeChunk> total;
log.print("end sweep# " SIZE_FORMAT, sweep_count);
ResourceMark rm;
LogStream ls(log);
outputStream* out = &ls;
AdaptiveFreeList<FreeChunk>::print_labels_on(out, "size");
size_t total_free = 0;
for (size_t i = IndexSetStart; i < IndexSetSize; i += IndexSetStride) {
const AdaptiveFreeList<FreeChunk> *fl = &_indexedFreeList[i];
total_free += fl->count() * fl->size();
if (i % (40*IndexSetStride) == 0) {
AdaptiveFreeList<FreeChunk>::print_labels_on(out, "size");
}
fl->print_on(out);
total.set_bfr_surp( total.bfr_surp() + fl->bfr_surp() );
total.set_surplus( total.surplus() + fl->surplus() );
total.set_desired( total.desired() + fl->desired() );
total.set_prev_sweep( total.prev_sweep() + fl->prev_sweep() );
total.set_before_sweep(total.before_sweep() + fl->before_sweep());
total.set_count( total.count() + fl->count() );
total.set_coal_births( total.coal_births() + fl->coal_births() );
total.set_coal_deaths( total.coal_deaths() + fl->coal_deaths() );
total.set_split_births(total.split_births() + fl->split_births());
total.set_split_deaths(total.split_deaths() + fl->split_deaths());
}
total.print_on(out, "TOTAL");
log.print("Total free in indexed lists " SIZE_FORMAT " words", total_free);
log.print("growth: %8.5f deficit: %8.5f",
(double)(total.split_births()+total.coal_births()-total.split_deaths()-total.coal_deaths())/
(total.prev_sweep() != 0 ? (double)total.prev_sweep() : 1.0),
(double)(total.desired() - total.count())/(total.desired() != 0 ? (double)total.desired() : 1.0));
_dictionary->print_dict_census(out);
}
///////////////////////////////////////////////////////////////////////////
// CompactibleFreeListSpaceLAB
///////////////////////////////////////////////////////////////////////////
#define VECTOR_257(x) \
/* 1 2 3 4 5 6 7 8 9 1x 11 12 13 14 15 16 17 18 19 2x 21 22 23 24 25 26 27 28 29 3x 31 32 */ \
{ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, \
x }
// Initialize with default setting for CMS, _not_
// generic OldPLABSize, whose static default is different; if overridden at the
// command-line, this will get reinitialized via a call to
// modify_initialization() below.
AdaptiveWeightedAverage CompactibleFreeListSpaceLAB::_blocks_to_claim[] =
VECTOR_257(AdaptiveWeightedAverage(OldPLABWeight, (float)CompactibleFreeListSpaceLAB::_default_dynamic_old_plab_size));
size_t CompactibleFreeListSpaceLAB::_global_num_blocks[] = VECTOR_257(0);
uint CompactibleFreeListSpaceLAB::_global_num_workers[] = VECTOR_257(0);
CompactibleFreeListSpaceLAB::CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls) :
_cfls(cfls)
{
assert(CompactibleFreeListSpace::IndexSetSize == 257, "Modify VECTOR_257() macro above");
for (size_t i = CompactibleFreeListSpace::IndexSetStart;
i < CompactibleFreeListSpace::IndexSetSize;
i += CompactibleFreeListSpace::IndexSetStride) {
_indexedFreeList[i].set_size(i);
_num_blocks[i] = 0;
}
}
static bool _CFLS_LAB_modified = false;
void CompactibleFreeListSpaceLAB::modify_initialization(size_t n, unsigned wt) {
assert(!_CFLS_LAB_modified, "Call only once");
_CFLS_LAB_modified = true;
for (size_t i = CompactibleFreeListSpace::IndexSetStart;
i < CompactibleFreeListSpace::IndexSetSize;
i += CompactibleFreeListSpace::IndexSetStride) {
_blocks_to_claim[i].modify(n, wt, true /* force */);
}
}
HeapWord* CompactibleFreeListSpaceLAB::alloc(size_t word_sz) {
FreeChunk* res;
assert(word_sz == _cfls->adjustObjectSize(word_sz), "Error");
if (word_sz >= CompactibleFreeListSpace::IndexSetSize) {
// This locking manages sync with other large object allocations.
MutexLocker x(_cfls->parDictionaryAllocLock(),
Mutex::_no_safepoint_check_flag);
res = _cfls->getChunkFromDictionaryExact(word_sz);
if (res == NULL) return NULL;
} else {
AdaptiveFreeList<FreeChunk>* fl = &_indexedFreeList[word_sz];
if (fl->count() == 0) {
// Attempt to refill this local free list.
get_from_global_pool(word_sz, fl);
// If it didn't work, give up.
if (fl->count() == 0) return NULL;
}
res = fl->get_chunk_at_head();
assert(res != NULL, "Why was count non-zero?");
}
res->markNotFree();
assert(!res->is_free(), "shouldn't be marked free");
assert(oop(res)->klass_or_null() == NULL, "should look uninitialized");
// mangle a just allocated object with a distinct pattern.
debug_only(res->mangleAllocated(word_sz));
return (HeapWord*)res;
}
// Get a chunk of blocks of the right size and update related
// book-keeping stats
void CompactibleFreeListSpaceLAB::get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl) {
// Get the #blocks we want to claim
size_t n_blks = (size_t)_blocks_to_claim[word_sz].average();
assert(n_blks > 0, "Error");
assert(ResizeOldPLAB || n_blks == OldPLABSize, "Error");
// In some cases, when the application has a phase change,
// there may be a sudden and sharp shift in the object survival
// profile, and updating the counts at the end of a scavenge
// may not be quick enough, giving rise to large scavenge pauses
// during these phase changes. It is beneficial to detect such
// changes on-the-fly during a scavenge and avoid such a phase-change
// pothole. The following code is a heuristic attempt to do that.
// It is protected by a product flag until we have gained
// enough experience with this heuristic and fine-tuned its behavior.
// WARNING: This might increase fragmentation if we overreact to
// small spikes, so some kind of historical smoothing based on
// previous experience with the greater reactivity might be useful.
// Lacking sufficient experience, CMSOldPLABResizeQuicker is disabled by
// default.
if (ResizeOldPLAB && CMSOldPLABResizeQuicker) {
//
// On a 32-bit VM, the denominator can become zero because of integer overflow,
// which is why there is a cast to double.
//
size_t multiple = (size_t) (_num_blocks[word_sz]/(((double)CMSOldPLABToleranceFactor)*CMSOldPLABNumRefills*n_blks));
n_blks += CMSOldPLABReactivityFactor*multiple*n_blks;
n_blks = MIN2(n_blks, CMSOldPLABMax);
}
assert(n_blks > 0, "Error");
_cfls->par_get_chunk_of_blocks(word_sz, n_blks, fl);
// Update stats table entry for this block size
_num_blocks[word_sz] += fl->count();
}
void CompactibleFreeListSpaceLAB::compute_desired_plab_size() {
for (size_t i = CompactibleFreeListSpace::IndexSetStart;
i < CompactibleFreeListSpace::IndexSetSize;
i += CompactibleFreeListSpace::IndexSetStride) {
assert((_global_num_workers[i] == 0) == (_global_num_blocks[i] == 0),
"Counter inconsistency");
if (_global_num_workers[i] > 0) {
// Need to smooth wrt historical average
if (ResizeOldPLAB) {
_blocks_to_claim[i].sample(
MAX2(CMSOldPLABMin,
MIN2(CMSOldPLABMax,
_global_num_blocks[i]/_global_num_workers[i]/CMSOldPLABNumRefills)));
}
// Reset counters for next round
_global_num_workers[i] = 0;
_global_num_blocks[i] = 0;
log_trace(gc, plab)("[" SIZE_FORMAT "]: " SIZE_FORMAT, i, (size_t)_blocks_to_claim[i].average());
}
}
}
// If this is changed in the future to allow parallel
// access, one would need to take the FL locks and,
// depending on how it is used, stagger access from
// parallel threads to reduce contention.
void CompactibleFreeListSpaceLAB::retire(int tid) {
// We run this single threaded with the world stopped;
// so no need for locks and such.
NOT_PRODUCT(Thread* t = Thread::current();)
assert(Thread::current()->is_VM_thread(), "Error");
for (size_t i = CompactibleFreeListSpace::IndexSetStart;
i < CompactibleFreeListSpace::IndexSetSize;
i += CompactibleFreeListSpace::IndexSetStride) {
assert(_num_blocks[i] >= (size_t)_indexedFreeList[i].count(),
"Can't retire more than what we obtained");
if (_num_blocks[i] > 0) {
size_t num_retire = _indexedFreeList[i].count();
assert(_num_blocks[i] > num_retire, "Should have used at least one");
{
// MutexLocker x(_cfls->_indexedFreeListParLocks[i],
// Mutex::_no_safepoint_check_flag);
// Update globals stats for num_blocks used
_global_num_blocks[i] += (_num_blocks[i] - num_retire);
_global_num_workers[i]++;
assert(_global_num_workers[i] <= ParallelGCThreads, "Too big");
if (num_retire > 0) {
_cfls->_indexedFreeList[i].prepend(&_indexedFreeList[i]);
// Reset this list.
_indexedFreeList[i] = AdaptiveFreeList<FreeChunk>();
_indexedFreeList[i].set_size(i);
}
}
log_trace(gc, plab)("%d[" SIZE_FORMAT "]: " SIZE_FORMAT "/" SIZE_FORMAT "/" SIZE_FORMAT,
tid, i, num_retire, _num_blocks[i], (size_t)_blocks_to_claim[i].average());
// Reset stats for next round
_num_blocks[i] = 0;
}
}
}
// Used by par_get_chunk_of_blocks() for the chunks from the
// indexed_free_lists. Looks for a chunk with size that is a multiple
// of "word_sz" and if found, splits it into "word_sz" chunks and add
// to the free list "fl". "n" is the maximum number of chunks to
// be added to "fl".
bool CompactibleFreeListSpace:: par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
// We'll try all multiples of word_sz in the indexed set, starting with
// word_sz itself and, if CMSSplitIndexedFreeListBlocks, try larger multiples,
// then try getting a big chunk and splitting it.
{
bool found;
int k;
size_t cur_sz;
for (k = 1, cur_sz = k * word_sz, found = false;
(cur_sz < CompactibleFreeListSpace::IndexSetSize) &&
(CMSSplitIndexedFreeListBlocks || k <= 1);
k++, cur_sz = k * word_sz) {
AdaptiveFreeList<FreeChunk> fl_for_cur_sz; // Empty.
fl_for_cur_sz.set_size(cur_sz);
{
MutexLocker x(_indexedFreeListParLocks[cur_sz],
Mutex::_no_safepoint_check_flag);
AdaptiveFreeList<FreeChunk>* gfl = &_indexedFreeList[cur_sz];
if (gfl->count() != 0) {
// nn is the number of chunks of size cur_sz that
// we'd need to split k-ways each, in order to create
// "n" chunks of size word_sz each.
const size_t nn = MAX2(n/k, (size_t)1);
gfl->getFirstNChunksFromList(nn, &fl_for_cur_sz);
found = true;
if (k > 1) {
// Update split death stats for the cur_sz-size blocks list:
// we increment the split death count by the number of blocks
// we just took from the cur_sz-size blocks list and which
// we will be splitting below.
ssize_t deaths = gfl->split_deaths() +
fl_for_cur_sz.count();
gfl->set_split_deaths(deaths);
}
}
}
// Now transfer fl_for_cur_sz to fl. Common case, we hope, is k = 1.
if (found) {
if (k == 1) {
fl->prepend(&fl_for_cur_sz);
} else {
// Divide each block on fl_for_cur_sz up k ways.
FreeChunk* fc;
while ((fc = fl_for_cur_sz.get_chunk_at_head()) != NULL) {
// Must do this in reverse order, so that anybody attempting to
// access the main chunk sees it as a single free block until we
// change it.
size_t fc_size = fc->size();
assert(fc->is_free(), "Error");
for (int i = k-1; i >= 0; i--) {
FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
assert((i != 0) ||
((fc == ffc) && ffc->is_free() &&
(ffc->size() == k*word_sz) && (fc_size == word_sz)),
"Counting error");
ffc->set_size(word_sz);
ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
ffc->link_next(NULL);
// Above must occur before BOT is updated below.
OrderAccess::storestore();
// splitting from the right, fc_size == i * word_sz
_bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
fc_size -= word_sz;
assert(fc_size == i*word_sz, "Error");
_bt.verify_not_unallocated((HeapWord*)ffc, word_sz);
_bt.verify_single_block((HeapWord*)fc, fc_size);
_bt.verify_single_block((HeapWord*)ffc, word_sz);
// Push this on "fl".
fl->return_chunk_at_head(ffc);
}
// TRAP
assert(fl->tail()->next() == NULL, "List invariant.");
}
}
// Update birth stats for this block size.
size_t num = fl->count();
MutexLocker x(_indexedFreeListParLocks[word_sz],
Mutex::_no_safepoint_check_flag);
ssize_t births = _indexedFreeList[word_sz].split_births() + num;
_indexedFreeList[word_sz].set_split_births(births);
return true;
}
}
return found;
}
}
FreeChunk* CompactibleFreeListSpace::get_n_way_chunk_to_split(size_t word_sz, size_t n) {
FreeChunk* fc = NULL;
FreeChunk* rem_fc = NULL;
size_t rem;
{
MutexLocker x(parDictionaryAllocLock(),
Mutex::_no_safepoint_check_flag);
while (n > 0) {
fc = dictionary()->get_chunk(MAX2(n * word_sz, _dictionary->min_size()));
if (fc != NULL) {
break;
} else {
n--;
}
}
if (fc == NULL) return NULL;
// Otherwise, split up that block.
assert((ssize_t)n >= 1, "Control point invariant");
assert(fc->is_free(), "Error: should be a free block");
_bt.verify_single_block((HeapWord*)fc, fc->size());
const size_t nn = fc->size() / word_sz;
n = MIN2(nn, n);
assert((ssize_t)n >= 1, "Control point invariant");
rem = fc->size() - n * word_sz;
// If there is a remainder, and it's too small, allocate one fewer.
if (rem > 0 && rem < MinChunkSize) {
n--; rem += word_sz;
}
// Note that at this point we may have n == 0.
assert((ssize_t)n >= 0, "Control point invariant");
// If n is 0, the chunk fc that was found is not large
// enough to leave a viable remainder. We are unable to
// allocate even one block. Return fc to the
// dictionary and return, leaving "fl" empty.
if (n == 0) {
returnChunkToDictionary(fc);
return NULL;
}
_bt.allocated((HeapWord*)fc, fc->size(), true /* reducing */); // update _unallocated_blk
dictionary()->dict_census_update(fc->size(),
true /*split*/,
false /*birth*/);
// First return the remainder, if any.
// Note that we hold the lock until we decide if we're going to give
// back the remainder to the dictionary, since a concurrent allocation
// may otherwise see the heap as empty. (We're willing to take that
// hit if the block is a small block.)
if (rem > 0) {
size_t prefix_size = n * word_sz;
rem_fc = (FreeChunk*)((HeapWord*)fc + prefix_size);
rem_fc->set_size(rem);
rem_fc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
rem_fc->link_next(NULL);
// Above must occur before BOT is updated below.
assert((ssize_t)n > 0 && prefix_size > 0 && rem_fc > fc, "Error");
OrderAccess::storestore();
_bt.split_block((HeapWord*)fc, fc->size(), prefix_size);
assert(fc->is_free(), "Error");
fc->set_size(prefix_size);
if (rem >= IndexSetSize) {
returnChunkToDictionary(rem_fc);
dictionary()->dict_census_update(rem, true /*split*/, true /*birth*/);
rem_fc = NULL;
}
// Otherwise, return it to the small list below.
}
}
if (rem_fc != NULL) {
MutexLocker x(_indexedFreeListParLocks[rem],
Mutex::_no_safepoint_check_flag);
_bt.verify_not_unallocated((HeapWord*)rem_fc, rem_fc->size());
_indexedFreeList[rem].return_chunk_at_head(rem_fc);
smallSplitBirth(rem);
}
assert(n * word_sz == fc->size(),
"Chunk size " SIZE_FORMAT " is not exactly splittable by "
SIZE_FORMAT " sized chunks of size " SIZE_FORMAT,
fc->size(), n, word_sz);
return fc;
}
void CompactibleFreeListSpace:: par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t targetted_number_of_chunks, AdaptiveFreeList<FreeChunk>* fl) {
FreeChunk* fc = get_n_way_chunk_to_split(word_sz, targetted_number_of_chunks);
if (fc == NULL) {
return;
}
size_t n = fc->size() / word_sz;
assert((ssize_t)n > 0, "Consistency");
// Now do the splitting up.
// Must do this in reverse order, so that anybody attempting to
// access the main chunk sees it as a single free block until we
// change it.
size_t fc_size = n * word_sz;
// All but first chunk in this loop
for (ssize_t i = n-1; i > 0; i--) {
FreeChunk* ffc = (FreeChunk*)((HeapWord*)fc + i * word_sz);
ffc->set_size(word_sz);
ffc->link_prev(NULL); // Mark as a free block for other (parallel) GC threads.
ffc->link_next(NULL);
// Above must occur before BOT is updated below.
OrderAccess::storestore();
// splitting from the right, fc_size == (n - i + 1) * wordsize
_bt.mark_block((HeapWord*)ffc, word_sz, true /* reducing */);
fc_size -= word_sz;
_bt.verify_not_unallocated((HeapWord*)ffc, ffc->size());
_bt.verify_single_block((HeapWord*)ffc, ffc->size());
_bt.verify_single_block((HeapWord*)fc, fc_size);
// Push this on "fl".
fl->return_chunk_at_head(ffc);
}
// First chunk
assert(fc->is_free() && fc->size() == n*word_sz, "Error: should still be a free block");
// The blocks above should show their new sizes before the first block below
fc->set_size(word_sz);
fc->link_prev(NULL); // idempotent wrt free-ness, see assert above
fc->link_next(NULL);
_bt.verify_not_unallocated((HeapWord*)fc, fc->size());
_bt.verify_single_block((HeapWord*)fc, fc->size());
fl->return_chunk_at_head(fc);
assert((ssize_t)n > 0 && (ssize_t)n == fl->count(), "Incorrect number of blocks");
{
// Update the stats for this block size.
MutexLocker x(_indexedFreeListParLocks[word_sz],
Mutex::_no_safepoint_check_flag);
const ssize_t births = _indexedFreeList[word_sz].split_births() + n;
_indexedFreeList[word_sz].set_split_births(births);
// ssize_t new_surplus = _indexedFreeList[word_sz].surplus() + n;
// _indexedFreeList[word_sz].set_surplus(new_surplus);
}
// TRAP
assert(fl->tail()->next() == NULL, "List invariant.");
}
void CompactibleFreeListSpace:: par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl) {
assert(fl->count() == 0, "Precondition.");
assert(word_sz < CompactibleFreeListSpace::IndexSetSize,
"Precondition");
if (par_get_chunk_of_blocks_IFL(word_sz, n, fl)) {
// Got it
return;
}
// Otherwise, we'll split a block from the dictionary.
par_get_chunk_of_blocks_dictionary(word_sz, n, fl);
}
const size_t CompactibleFreeListSpace::max_flag_size_for_task_size() const {
const size_t ergo_max = _old_gen->reserved().word_size() / (CardTable::card_size_in_words * BitsPerWord);
return ergo_max;
}
// Set up the space's par_seq_tasks structure for work claiming
// for parallel rescan. See CMSParRemarkTask where this is currently used.
// XXX Need to suitably abstract and generalize this and the next
// method into one.
void
CompactibleFreeListSpace::
initialize_sequential_subtasks_for_rescan(int n_threads) {
// The "size" of each task is fixed according to rescan_task_size.
assert(n_threads > 0, "Unexpected n_threads argument");
const size_t task_size = rescan_task_size();
size_t n_tasks = (used_region().word_size() + task_size - 1)/task_size;
assert((n_tasks == 0) == used_region().is_empty(), "n_tasks incorrect");
assert(n_tasks == 0 ||
((used_region().start() + (n_tasks - 1)*task_size < used_region().end()) &&
(used_region().start() + n_tasks*task_size >= used_region().end())),
"n_tasks calculation incorrect");
SequentialSubTasksDone* pst = conc_par_seq_tasks();
assert(!pst->valid(), "Clobbering existing data?");
// Sets the condition for completion of the subtask (how many threads
// need to finish in order to be done).
pst->set_n_threads(n_threads);
pst->set_n_tasks((int)n_tasks);
}
// Set up the space's par_seq_tasks structure for work claiming
// for parallel concurrent marking. See CMSConcMarkTask where this is currently used.
void
CompactibleFreeListSpace::
initialize_sequential_subtasks_for_marking(int n_threads,
HeapWord* low) {
// The "size" of each task is fixed according to rescan_task_size.
assert(n_threads > 0, "Unexpected n_threads argument");
const size_t task_size = marking_task_size();
assert(task_size > CardTable::card_size_in_words &&
(task_size % CardTable::card_size_in_words == 0),
"Otherwise arithmetic below would be incorrect");
MemRegion span = _old_gen->reserved();
if (low != NULL) {
if (span.contains(low)) {
// Align low down to a card boundary so that
// we can use block_offset_careful() on span boundaries.
HeapWord* aligned_low = align_down(low, CardTable::card_size);
// Clip span prefix at aligned_low
span = span.intersection(MemRegion(aligned_low, span.end()));
} else if (low > span.end()) {
span = MemRegion(low, low); // Null region
} // else use entire span
}
assert(span.is_empty() ||
((uintptr_t)span.start() % CardTable::card_size == 0),
"span should start at a card boundary");
size_t n_tasks = (span.word_size() + task_size - 1)/task_size;
assert((n_tasks == 0) == span.is_empty(), "Inconsistency");
assert(n_tasks == 0 ||
((span.start() + (n_tasks - 1)*task_size < span.end()) &&
(span.start() + n_tasks*task_size >= span.end())),
"n_tasks calculation incorrect");
SequentialSubTasksDone* pst = conc_par_seq_tasks();
assert(!pst->valid(), "Clobbering existing data?");
// Sets the condition for completion of the subtask (how many threads
// need to finish in order to be done).
pst->set_n_threads(n_threads);
pst->set_n_tasks((int)n_tasks);
}