8227225: ParallelGC: add subspace transitions for young gen for gc+heap=info log lines
Reviewed-by: tschatzl, kbarrett
/*
* Copyright (c) 2005, 2019, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* questions.
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*/
#include "precompiled.hpp"
#include "aot/aotLoader.hpp"
#include "classfile/classLoaderDataGraph.hpp"
#include "classfile/javaClasses.inline.hpp"
#include "classfile/stringTable.hpp"
#include "classfile/symbolTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "code/codeCache.hpp"
#include "gc/parallel/gcTaskManager.hpp"
#include "gc/parallel/parallelArguments.hpp"
#include "gc/parallel/parallelScavengeHeap.inline.hpp"
#include "gc/parallel/parMarkBitMap.inline.hpp"
#include "gc/parallel/pcTasks.hpp"
#include "gc/parallel/psAdaptiveSizePolicy.hpp"
#include "gc/parallel/psCompactionManager.inline.hpp"
#include "gc/parallel/psOldGen.hpp"
#include "gc/parallel/psParallelCompact.inline.hpp"
#include "gc/parallel/psPromotionManager.inline.hpp"
#include "gc/parallel/psScavenge.hpp"
#include "gc/parallel/psYoungGen.hpp"
#include "gc/shared/gcCause.hpp"
#include "gc/shared/gcHeapSummary.hpp"
#include "gc/shared/gcId.hpp"
#include "gc/shared/gcLocker.hpp"
#include "gc/shared/gcTimer.hpp"
#include "gc/shared/gcTrace.hpp"
#include "gc/shared/gcTraceTime.inline.hpp"
#include "gc/shared/isGCActiveMark.hpp"
#include "gc/shared/referencePolicy.hpp"
#include "gc/shared/referenceProcessor.hpp"
#include "gc/shared/referenceProcessorPhaseTimes.hpp"
#include "gc/shared/spaceDecorator.hpp"
#include "gc/shared/weakProcessor.hpp"
#include "logging/log.hpp"
#include "memory/iterator.inline.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "oops/access.inline.hpp"
#include "oops/instanceClassLoaderKlass.inline.hpp"
#include "oops/instanceKlass.inline.hpp"
#include "oops/instanceMirrorKlass.inline.hpp"
#include "oops/methodData.hpp"
#include "oops/objArrayKlass.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/vmThread.hpp"
#include "services/management.hpp"
#include "services/memTracker.hpp"
#include "services/memoryService.hpp"
#include "utilities/align.hpp"
#include "utilities/debug.hpp"
#include "utilities/events.hpp"
#include "utilities/formatBuffer.hpp"
#include "utilities/macros.hpp"
#include "utilities/stack.inline.hpp"
#if INCLUDE_JVMCI
#include "jvmci/jvmci.hpp"
#endif
#include <math.h>
// All sizes are in HeapWords.
const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
const size_t ParallelCompactData::RegionSizeBytes =
RegionSize << LogHeapWordSize;
const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
const size_t ParallelCompactData::Log2BlockSize = 7; // 128 words
const size_t ParallelCompactData::BlockSize = (size_t)1 << Log2BlockSize;
const size_t ParallelCompactData::BlockSizeBytes =
BlockSize << LogHeapWordSize;
const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
const size_t ParallelCompactData::BlockAddrMask = ~BlockAddrOffsetMask;
const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
const size_t ParallelCompactData::Log2BlocksPerRegion =
Log2RegionSize - Log2BlockSize;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::dc_shift = 27;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::los_mask = ~dc_mask;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
const ParallelCompactData::RegionData::region_sz_t
ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
double PSParallelCompact::_dwl_mean;
double PSParallelCompact::_dwl_std_dev;
double PSParallelCompact::_dwl_first_term;
double PSParallelCompact::_dwl_adjustment;
#ifdef ASSERT
bool PSParallelCompact::_dwl_initialized = false;
#endif // #ifdef ASSERT
void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
HeapWord* destination)
{
assert(src_region_idx != 0, "invalid src_region_idx");
assert(partial_obj_size != 0, "invalid partial_obj_size argument");
assert(destination != NULL, "invalid destination argument");
_src_region_idx = src_region_idx;
_partial_obj_size = partial_obj_size;
_destination = destination;
// These fields may not be updated below, so make sure they're clear.
assert(_dest_region_addr == NULL, "should have been cleared");
assert(_first_src_addr == NULL, "should have been cleared");
// Determine the number of destination regions for the partial object.
HeapWord* const last_word = destination + partial_obj_size - 1;
const ParallelCompactData& sd = PSParallelCompact::summary_data();
HeapWord* const beg_region_addr = sd.region_align_down(destination);
HeapWord* const end_region_addr = sd.region_align_down(last_word);
if (beg_region_addr == end_region_addr) {
// One destination region.
_destination_count = 1;
if (end_region_addr == destination) {
// The destination falls on a region boundary, thus the first word of the
// partial object will be the first word copied to the destination region.
_dest_region_addr = end_region_addr;
_first_src_addr = sd.region_to_addr(src_region_idx);
}
} else {
// Two destination regions. When copied, the partial object will cross a
// destination region boundary, so a word somewhere within the partial
// object will be the first word copied to the second destination region.
_destination_count = 2;
_dest_region_addr = end_region_addr;
const size_t ofs = pointer_delta(end_region_addr, destination);
assert(ofs < _partial_obj_size, "sanity");
_first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
}
}
void SplitInfo::clear()
{
_src_region_idx = 0;
_partial_obj_size = 0;
_destination = NULL;
_destination_count = 0;
_dest_region_addr = NULL;
_first_src_addr = NULL;
assert(!is_valid(), "sanity");
}
#ifdef ASSERT
void SplitInfo::verify_clear()
{
assert(_src_region_idx == 0, "not clear");
assert(_partial_obj_size == 0, "not clear");
assert(_destination == NULL, "not clear");
assert(_destination_count == 0, "not clear");
assert(_dest_region_addr == NULL, "not clear");
assert(_first_src_addr == NULL, "not clear");
}
#endif // #ifdef ASSERT
void PSParallelCompact::print_on_error(outputStream* st) {
_mark_bitmap.print_on_error(st);
}
#ifndef PRODUCT
const char* PSParallelCompact::space_names[] = {
"old ", "eden", "from", "to "
};
void PSParallelCompact::print_region_ranges() {
if (!log_develop_is_enabled(Trace, gc, compaction)) {
return;
}
Log(gc, compaction) log;
ResourceMark rm;
LogStream ls(log.trace());
Universe::print_on(&ls);
log.trace("space bottom top end new_top");
log.trace("------ ---------- ---------- ---------- ----------");
for (unsigned int id = 0; id < last_space_id; ++id) {
const MutableSpace* space = _space_info[id].space();
log.trace("%u %s "
SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
id, space_names[id],
summary_data().addr_to_region_idx(space->bottom()),
summary_data().addr_to_region_idx(space->top()),
summary_data().addr_to_region_idx(space->end()),
summary_data().addr_to_region_idx(_space_info[id].new_top()));
}
}
void
print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
{
#define REGION_IDX_FORMAT SIZE_FORMAT_W(7)
#define REGION_DATA_FORMAT SIZE_FORMAT_W(5)
ParallelCompactData& sd = PSParallelCompact::summary_data();
size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
log_develop_trace(gc, compaction)(
REGION_IDX_FORMAT " " PTR_FORMAT " "
REGION_IDX_FORMAT " " PTR_FORMAT " "
REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
i, p2i(c->data_location()), dci, p2i(c->destination()),
c->partial_obj_size(), c->live_obj_size(),
c->data_size(), c->source_region(), c->destination_count());
#undef REGION_IDX_FORMAT
#undef REGION_DATA_FORMAT
}
void
print_generic_summary_data(ParallelCompactData& summary_data,
HeapWord* const beg_addr,
HeapWord* const end_addr)
{
size_t total_words = 0;
size_t i = summary_data.addr_to_region_idx(beg_addr);
const size_t last = summary_data.addr_to_region_idx(end_addr);
HeapWord* pdest = 0;
while (i < last) {
ParallelCompactData::RegionData* c = summary_data.region(i);
if (c->data_size() != 0 || c->destination() != pdest) {
print_generic_summary_region(i, c);
total_words += c->data_size();
pdest = c->destination();
}
++i;
}
log_develop_trace(gc, compaction)("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
}
void
PSParallelCompact::print_generic_summary_data(ParallelCompactData& summary_data,
HeapWord* const beg_addr,
HeapWord* const end_addr) {
::print_generic_summary_data(summary_data,beg_addr, end_addr);
}
void
print_generic_summary_data(ParallelCompactData& summary_data,
SpaceInfo* space_info)
{
if (!log_develop_is_enabled(Trace, gc, compaction)) {
return;
}
for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
const MutableSpace* space = space_info[id].space();
print_generic_summary_data(summary_data, space->bottom(),
MAX2(space->top(), space_info[id].new_top()));
}
}
void
print_initial_summary_data(ParallelCompactData& summary_data,
const MutableSpace* space) {
if (space->top() == space->bottom()) {
return;
}
const size_t region_size = ParallelCompactData::RegionSize;
typedef ParallelCompactData::RegionData RegionData;
HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
const RegionData* c = summary_data.region(end_region - 1);
HeapWord* end_addr = c->destination() + c->data_size();
const size_t live_in_space = pointer_delta(end_addr, space->bottom());
// Print (and count) the full regions at the beginning of the space.
size_t full_region_count = 0;
size_t i = summary_data.addr_to_region_idx(space->bottom());
while (i < end_region && summary_data.region(i)->data_size() == region_size) {
ParallelCompactData::RegionData* c = summary_data.region(i);
log_develop_trace(gc, compaction)(
SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
i, p2i(c->destination()),
c->partial_obj_size(), c->live_obj_size(),
c->data_size(), c->source_region(), c->destination_count());
++full_region_count;
++i;
}
size_t live_to_right = live_in_space - full_region_count * region_size;
double max_reclaimed_ratio = 0.0;
size_t max_reclaimed_ratio_region = 0;
size_t max_dead_to_right = 0;
size_t max_live_to_right = 0;
// Print the 'reclaimed ratio' for regions while there is something live in
// the region or to the right of it. The remaining regions are empty (and
// uninteresting), and computing the ratio will result in division by 0.
while (i < end_region && live_to_right > 0) {
c = summary_data.region(i);
HeapWord* const region_addr = summary_data.region_to_addr(i);
const size_t used_to_right = pointer_delta(space->top(), region_addr);
const size_t dead_to_right = used_to_right - live_to_right;
const double reclaimed_ratio = double(dead_to_right) / live_to_right;
if (reclaimed_ratio > max_reclaimed_ratio) {
max_reclaimed_ratio = reclaimed_ratio;
max_reclaimed_ratio_region = i;
max_dead_to_right = dead_to_right;
max_live_to_right = live_to_right;
}
ParallelCompactData::RegionData* c = summary_data.region(i);
log_develop_trace(gc, compaction)(
SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d"
"%12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
i, p2i(c->destination()),
c->partial_obj_size(), c->live_obj_size(),
c->data_size(), c->source_region(), c->destination_count(),
reclaimed_ratio, dead_to_right, live_to_right);
live_to_right -= c->data_size();
++i;
}
// Any remaining regions are empty. Print one more if there is one.
if (i < end_region) {
ParallelCompactData::RegionData* c = summary_data.region(i);
log_develop_trace(gc, compaction)(
SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
i, p2i(c->destination()),
c->partial_obj_size(), c->live_obj_size(),
c->data_size(), c->source_region(), c->destination_count());
}
log_develop_trace(gc, compaction)("max: " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
max_reclaimed_ratio_region, max_dead_to_right, max_live_to_right, max_reclaimed_ratio);
}
void
print_initial_summary_data(ParallelCompactData& summary_data,
SpaceInfo* space_info) {
if (!log_develop_is_enabled(Trace, gc, compaction)) {
return;
}
unsigned int id = PSParallelCompact::old_space_id;
const MutableSpace* space;
do {
space = space_info[id].space();
print_initial_summary_data(summary_data, space);
} while (++id < PSParallelCompact::eden_space_id);
do {
space = space_info[id].space();
print_generic_summary_data(summary_data, space->bottom(), space->top());
} while (++id < PSParallelCompact::last_space_id);
}
#endif // #ifndef PRODUCT
#ifdef ASSERT
size_t add_obj_count;
size_t add_obj_size;
size_t mark_bitmap_count;
size_t mark_bitmap_size;
#endif // #ifdef ASSERT
ParallelCompactData::ParallelCompactData() :
_region_start(NULL),
DEBUG_ONLY(_region_end(NULL) COMMA)
_region_vspace(NULL),
_reserved_byte_size(0),
_region_data(NULL),
_region_count(0),
_block_vspace(NULL),
_block_data(NULL),
_block_count(0) {}
bool ParallelCompactData::initialize(MemRegion covered_region)
{
_region_start = covered_region.start();
const size_t region_size = covered_region.word_size();
DEBUG_ONLY(_region_end = _region_start + region_size;)
assert(region_align_down(_region_start) == _region_start,
"region start not aligned");
assert((region_size & RegionSizeOffsetMask) == 0,
"region size not a multiple of RegionSize");
bool result = initialize_region_data(region_size) && initialize_block_data();
return result;
}
PSVirtualSpace*
ParallelCompactData::create_vspace(size_t count, size_t element_size)
{
const size_t raw_bytes = count * element_size;
const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
const size_t granularity = os::vm_allocation_granularity();
_reserved_byte_size = align_up(raw_bytes, MAX2(page_sz, granularity));
const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
MAX2(page_sz, granularity);
ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, page_sz, rs.base(),
rs.size());
MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
if (vspace != 0) {
if (vspace->expand_by(_reserved_byte_size)) {
return vspace;
}
delete vspace;
// Release memory reserved in the space.
rs.release();
}
return 0;
}
bool ParallelCompactData::initialize_region_data(size_t region_size)
{
const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
_region_vspace = create_vspace(count, sizeof(RegionData));
if (_region_vspace != 0) {
_region_data = (RegionData*)_region_vspace->reserved_low_addr();
_region_count = count;
return true;
}
return false;
}
bool ParallelCompactData::initialize_block_data()
{
assert(_region_count != 0, "region data must be initialized first");
const size_t count = _region_count << Log2BlocksPerRegion;
_block_vspace = create_vspace(count, sizeof(BlockData));
if (_block_vspace != 0) {
_block_data = (BlockData*)_block_vspace->reserved_low_addr();
_block_count = count;
return true;
}
return false;
}
void ParallelCompactData::clear()
{
memset(_region_data, 0, _region_vspace->committed_size());
memset(_block_data, 0, _block_vspace->committed_size());
}
void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
assert(beg_region <= _region_count, "beg_region out of range");
assert(end_region <= _region_count, "end_region out of range");
assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
const size_t region_cnt = end_region - beg_region;
memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
const size_t beg_block = beg_region * BlocksPerRegion;
const size_t block_cnt = region_cnt * BlocksPerRegion;
memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
}
HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
{
const RegionData* cur_cp = region(region_idx);
const RegionData* const end_cp = region(region_count() - 1);
HeapWord* result = region_to_addr(region_idx);
if (cur_cp < end_cp) {
do {
result += cur_cp->partial_obj_size();
} while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
}
return result;
}
void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
{
const size_t obj_ofs = pointer_delta(addr, _region_start);
const size_t beg_region = obj_ofs >> Log2RegionSize;
const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
DEBUG_ONLY(Atomic::inc(&add_obj_count);)
DEBUG_ONLY(Atomic::add(len, &add_obj_size);)
if (beg_region == end_region) {
// All in one region.
_region_data[beg_region].add_live_obj(len);
return;
}
// First region.
const size_t beg_ofs = region_offset(addr);
_region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
Klass* klass = ((oop)addr)->klass();
// Middle regions--completely spanned by this object.
for (size_t region = beg_region + 1; region < end_region; ++region) {
_region_data[region].set_partial_obj_size(RegionSize);
_region_data[region].set_partial_obj_addr(addr);
}
// Last region.
const size_t end_ofs = region_offset(addr + len - 1);
_region_data[end_region].set_partial_obj_size(end_ofs + 1);
_region_data[end_region].set_partial_obj_addr(addr);
}
void
ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
{
assert(region_offset(beg) == 0, "not RegionSize aligned");
assert(region_offset(end) == 0, "not RegionSize aligned");
size_t cur_region = addr_to_region_idx(beg);
const size_t end_region = addr_to_region_idx(end);
HeapWord* addr = beg;
while (cur_region < end_region) {
_region_data[cur_region].set_destination(addr);
_region_data[cur_region].set_destination_count(0);
_region_data[cur_region].set_source_region(cur_region);
_region_data[cur_region].set_data_location(addr);
// Update live_obj_size so the region appears completely full.
size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
_region_data[cur_region].set_live_obj_size(live_size);
++cur_region;
addr += RegionSize;
}
}
// Find the point at which a space can be split and, if necessary, record the
// split point.
//
// If the current src region (which overflowed the destination space) doesn't
// have a partial object, the split point is at the beginning of the current src
// region (an "easy" split, no extra bookkeeping required).
//
// If the current src region has a partial object, the split point is in the
// region where that partial object starts (call it the split_region). If
// split_region has a partial object, then the split point is just after that
// partial object (a "hard" split where we have to record the split data and
// zero the partial_obj_size field). With a "hard" split, we know that the
// partial_obj ends within split_region because the partial object that caused
// the overflow starts in split_region. If split_region doesn't have a partial
// obj, then the split is at the beginning of split_region (another "easy"
// split).
HeapWord*
ParallelCompactData::summarize_split_space(size_t src_region,
SplitInfo& split_info,
HeapWord* destination,
HeapWord* target_end,
HeapWord** target_next)
{
assert(destination <= target_end, "sanity");
assert(destination + _region_data[src_region].data_size() > target_end,
"region should not fit into target space");
assert(is_region_aligned(target_end), "sanity");
size_t split_region = src_region;
HeapWord* split_destination = destination;
size_t partial_obj_size = _region_data[src_region].partial_obj_size();
if (destination + partial_obj_size > target_end) {
// The split point is just after the partial object (if any) in the
// src_region that contains the start of the object that overflowed the
// destination space.
//
// Find the start of the "overflow" object and set split_region to the
// region containing it.
HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
split_region = addr_to_region_idx(overflow_obj);
// Clear the source_region field of all destination regions whose first word
// came from data after the split point (a non-null source_region field
// implies a region must be filled).
//
// An alternative to the simple loop below: clear during post_compact(),
// which uses memcpy instead of individual stores, and is easy to
// parallelize. (The downside is that it clears the entire RegionData
// object as opposed to just one field.)
//
// post_compact() would have to clear the summary data up to the highest
// address that was written during the summary phase, which would be
//
// max(top, max(new_top, clear_top))
//
// where clear_top is a new field in SpaceInfo. Would have to set clear_top
// to target_end.
const RegionData* const sr = region(split_region);
const size_t beg_idx =
addr_to_region_idx(region_align_up(sr->destination() +
sr->partial_obj_size()));
const size_t end_idx = addr_to_region_idx(target_end);
log_develop_trace(gc, compaction)("split: clearing source_region field in [" SIZE_FORMAT ", " SIZE_FORMAT ")", beg_idx, end_idx);
for (size_t idx = beg_idx; idx < end_idx; ++idx) {
_region_data[idx].set_source_region(0);
}
// Set split_destination and partial_obj_size to reflect the split region.
split_destination = sr->destination();
partial_obj_size = sr->partial_obj_size();
}
// The split is recorded only if a partial object extends onto the region.
if (partial_obj_size != 0) {
_region_data[split_region].set_partial_obj_size(0);
split_info.record(split_region, partial_obj_size, split_destination);
}
// Setup the continuation addresses.
*target_next = split_destination + partial_obj_size;
HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
if (log_develop_is_enabled(Trace, gc, compaction)) {
const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
log_develop_trace(gc, compaction)("%s split: src=" PTR_FORMAT " src_c=" SIZE_FORMAT " pos=" SIZE_FORMAT,
split_type, p2i(source_next), split_region, partial_obj_size);
log_develop_trace(gc, compaction)("%s split: dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT " tn=" PTR_FORMAT,
split_type, p2i(split_destination),
addr_to_region_idx(split_destination),
p2i(*target_next));
if (partial_obj_size != 0) {
HeapWord* const po_beg = split_info.destination();
HeapWord* const po_end = po_beg + split_info.partial_obj_size();
log_develop_trace(gc, compaction)("%s split: po_beg=" PTR_FORMAT " " SIZE_FORMAT " po_end=" PTR_FORMAT " " SIZE_FORMAT,
split_type,
p2i(po_beg), addr_to_region_idx(po_beg),
p2i(po_end), addr_to_region_idx(po_end));
}
}
return source_next;
}
bool ParallelCompactData::summarize(SplitInfo& split_info,
HeapWord* source_beg, HeapWord* source_end,
HeapWord** source_next,
HeapWord* target_beg, HeapWord* target_end,
HeapWord** target_next)
{
HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
log_develop_trace(gc, compaction)(
"sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
"tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
p2i(source_beg), p2i(source_end), p2i(source_next_val),
p2i(target_beg), p2i(target_end), p2i(*target_next));
size_t cur_region = addr_to_region_idx(source_beg);
const size_t end_region = addr_to_region_idx(region_align_up(source_end));
HeapWord *dest_addr = target_beg;
while (cur_region < end_region) {
// The destination must be set even if the region has no data.
_region_data[cur_region].set_destination(dest_addr);
size_t words = _region_data[cur_region].data_size();
if (words > 0) {
// If cur_region does not fit entirely into the target space, find a point
// at which the source space can be 'split' so that part is copied to the
// target space and the rest is copied elsewhere.
if (dest_addr + words > target_end) {
assert(source_next != NULL, "source_next is NULL when splitting");
*source_next = summarize_split_space(cur_region, split_info, dest_addr,
target_end, target_next);
return false;
}
// Compute the destination_count for cur_region, and if necessary, update
// source_region for a destination region. The source_region field is
// updated if cur_region is the first (left-most) region to be copied to a
// destination region.
//
// The destination_count calculation is a bit subtle. A region that has
// data that compacts into itself does not count itself as a destination.
// This maintains the invariant that a zero count means the region is
// available and can be claimed and then filled.
uint destination_count = 0;
if (split_info.is_split(cur_region)) {
// The current region has been split: the partial object will be copied
// to one destination space and the remaining data will be copied to
// another destination space. Adjust the initial destination_count and,
// if necessary, set the source_region field if the partial object will
// cross a destination region boundary.
destination_count = split_info.destination_count();
if (destination_count == 2) {
size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
_region_data[dest_idx].set_source_region(cur_region);
}
}
HeapWord* const last_addr = dest_addr + words - 1;
const size_t dest_region_1 = addr_to_region_idx(dest_addr);
const size_t dest_region_2 = addr_to_region_idx(last_addr);
// Initially assume that the destination regions will be the same and
// adjust the value below if necessary. Under this assumption, if
// cur_region == dest_region_2, then cur_region will be compacted
// completely into itself.
destination_count += cur_region == dest_region_2 ? 0 : 1;
if (dest_region_1 != dest_region_2) {
// Destination regions differ; adjust destination_count.
destination_count += 1;
// Data from cur_region will be copied to the start of dest_region_2.
_region_data[dest_region_2].set_source_region(cur_region);
} else if (region_offset(dest_addr) == 0) {
// Data from cur_region will be copied to the start of the destination
// region.
_region_data[dest_region_1].set_source_region(cur_region);
}
_region_data[cur_region].set_destination_count(destination_count);
_region_data[cur_region].set_data_location(region_to_addr(cur_region));
dest_addr += words;
}
++cur_region;
}
*target_next = dest_addr;
return true;
}
HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr, ParCompactionManager* cm) {
assert(addr != NULL, "Should detect NULL oop earlier");
assert(ParallelScavengeHeap::heap()->is_in(addr), "not in heap");
assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
// Region covering the object.
RegionData* const region_ptr = addr_to_region_ptr(addr);
HeapWord* result = region_ptr->destination();
// If the entire Region is live, the new location is region->destination + the
// offset of the object within in the Region.
// Run some performance tests to determine if this special case pays off. It
// is worth it for pointers into the dense prefix. If the optimization to
// avoid pointer updates in regions that only point to the dense prefix is
// ever implemented, this should be revisited.
if (region_ptr->data_size() == RegionSize) {
result += region_offset(addr);
return result;
}
// Otherwise, the new location is region->destination + block offset + the
// number of live words in the Block that are (a) to the left of addr and (b)
// due to objects that start in the Block.
// Fill in the block table if necessary. This is unsynchronized, so multiple
// threads may fill the block table for a region (harmless, since it is
// idempotent).
if (!region_ptr->blocks_filled()) {
PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
region_ptr->set_blocks_filled();
}
HeapWord* const search_start = block_align_down(addr);
const size_t block_offset = addr_to_block_ptr(addr)->offset();
const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
const size_t live = bitmap->live_words_in_range(cm, search_start, oop(addr));
result += block_offset + live;
DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
return result;
}
#ifdef ASSERT
void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
{
const size_t* const beg = (const size_t*)vspace->committed_low_addr();
const size_t* const end = (const size_t*)vspace->committed_high_addr();
for (const size_t* p = beg; p < end; ++p) {
assert(*p == 0, "not zero");
}
}
void ParallelCompactData::verify_clear()
{
verify_clear(_region_vspace);
verify_clear(_block_vspace);
}
#endif // #ifdef ASSERT
STWGCTimer PSParallelCompact::_gc_timer;
ParallelOldTracer PSParallelCompact::_gc_tracer;
elapsedTimer PSParallelCompact::_accumulated_time;
unsigned int PSParallelCompact::_total_invocations = 0;
unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
jlong PSParallelCompact::_time_of_last_gc = 0;
CollectorCounters* PSParallelCompact::_counters = NULL;
ParMarkBitMap PSParallelCompact::_mark_bitmap;
ParallelCompactData PSParallelCompact::_summary_data;
PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
class PCReferenceProcessor: public ReferenceProcessor {
public:
PCReferenceProcessor(
BoolObjectClosure* is_subject_to_discovery,
BoolObjectClosure* is_alive_non_header) :
ReferenceProcessor(is_subject_to_discovery,
ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
ParallelGCThreads, // mt processing degree
true, // mt discovery
ParallelGCThreads, // mt discovery degree
true, // atomic_discovery
is_alive_non_header) {
}
template<typename T> bool discover(oop obj, ReferenceType type) {
T* referent_addr = (T*) java_lang_ref_Reference::referent_addr_raw(obj);
T heap_oop = RawAccess<>::oop_load(referent_addr);
oop referent = CompressedOops::decode_not_null(heap_oop);
return PSParallelCompact::mark_bitmap()->is_unmarked(referent)
&& ReferenceProcessor::discover_reference(obj, type);
}
virtual bool discover_reference(oop obj, ReferenceType type) {
if (UseCompressedOops) {
return discover<narrowOop>(obj, type);
} else {
return discover<oop>(obj, type);
}
}
};
void PSParallelCompact::post_initialize() {
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
_span_based_discoverer.set_span(heap->reserved_region());
_ref_processor =
new PCReferenceProcessor(&_span_based_discoverer,
&_is_alive_closure); // non-header is alive closure
_counters = new CollectorCounters("Parallel full collection pauses", 1);
// Initialize static fields in ParCompactionManager.
ParCompactionManager::initialize(mark_bitmap());
}
bool PSParallelCompact::initialize() {
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
MemRegion mr = heap->reserved_region();
// Was the old gen get allocated successfully?
if (!heap->old_gen()->is_allocated()) {
return false;
}
initialize_space_info();
initialize_dead_wood_limiter();
if (!_mark_bitmap.initialize(mr)) {
vm_shutdown_during_initialization(
err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
"garbage collection for the requested " SIZE_FORMAT "KB heap.",
_mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
return false;
}
if (!_summary_data.initialize(mr)) {
vm_shutdown_during_initialization(
err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
"garbage collection for the requested " SIZE_FORMAT "KB heap.",
_summary_data.reserved_byte_size()/K, mr.byte_size()/K));
return false;
}
return true;
}
void PSParallelCompact::initialize_space_info()
{
memset(&_space_info, 0, sizeof(_space_info));
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
PSYoungGen* young_gen = heap->young_gen();
_space_info[old_space_id].set_space(heap->old_gen()->object_space());
_space_info[eden_space_id].set_space(young_gen->eden_space());
_space_info[from_space_id].set_space(young_gen->from_space());
_space_info[to_space_id].set_space(young_gen->to_space());
_space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
}
void PSParallelCompact::initialize_dead_wood_limiter()
{
const size_t max = 100;
_dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
_dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
_dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
DEBUG_ONLY(_dwl_initialized = true;)
_dwl_adjustment = normal_distribution(1.0);
}
void
PSParallelCompact::clear_data_covering_space(SpaceId id)
{
// At this point, top is the value before GC, new_top() is the value that will
// be set at the end of GC. The marking bitmap is cleared to top; nothing
// should be marked above top. The summary data is cleared to the larger of
// top & new_top.
MutableSpace* const space = _space_info[id].space();
HeapWord* const bot = space->bottom();
HeapWord* const top = space->top();
HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
_mark_bitmap.clear_range(beg_bit, end_bit);
const size_t beg_region = _summary_data.addr_to_region_idx(bot);
const size_t end_region =
_summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
_summary_data.clear_range(beg_region, end_region);
// Clear the data used to 'split' regions.
SplitInfo& split_info = _space_info[id].split_info();
if (split_info.is_valid()) {
split_info.clear();
}
DEBUG_ONLY(split_info.verify_clear();)
}
void PSParallelCompact::pre_compact()
{
// Update the from & to space pointers in space_info, since they are swapped
// at each young gen gc. Do the update unconditionally (even though a
// promotion failure does not swap spaces) because an unknown number of young
// collections will have swapped the spaces an unknown number of times.
GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
_space_info[from_space_id].set_space(heap->young_gen()->from_space());
_space_info[to_space_id].set_space(heap->young_gen()->to_space());
DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
// Increment the invocation count
heap->increment_total_collections(true);
// We need to track unique mark sweep invocations as well.
_total_invocations++;
heap->print_heap_before_gc();
heap->trace_heap_before_gc(&_gc_tracer);
// Fill in TLABs
heap->ensure_parsability(true); // retire TLABs
if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
Universe::verify("Before GC");
}
// Verify object start arrays
if (VerifyObjectStartArray &&
VerifyBeforeGC) {
heap->old_gen()->verify_object_start_array();
}
DEBUG_ONLY(mark_bitmap()->verify_clear();)
DEBUG_ONLY(summary_data().verify_clear();)
// Have worker threads release resources the next time they run a task.
gc_task_manager()->release_all_resources();
ParCompactionManager::reset_all_bitmap_query_caches();
}
void PSParallelCompact::post_compact()
{
GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
for (unsigned int id = old_space_id; id < last_space_id; ++id) {
// Clear the marking bitmap, summary data and split info.
clear_data_covering_space(SpaceId(id));
// Update top(). Must be done after clearing the bitmap and summary data.
_space_info[id].publish_new_top();
}
MutableSpace* const eden_space = _space_info[eden_space_id].space();
MutableSpace* const from_space = _space_info[from_space_id].space();
MutableSpace* const to_space = _space_info[to_space_id].space();
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
bool eden_empty = eden_space->is_empty();
if (!eden_empty) {
eden_empty = absorb_live_data_from_eden(heap->size_policy(),
heap->young_gen(), heap->old_gen());
}
// Update heap occupancy information which is used as input to the soft ref
// clearing policy at the next gc.
Universe::update_heap_info_at_gc();
bool young_gen_empty = eden_empty && from_space->is_empty() &&
to_space->is_empty();
PSCardTable* ct = heap->card_table();
MemRegion old_mr = heap->old_gen()->reserved();
if (young_gen_empty) {
ct->clear(MemRegion(old_mr.start(), old_mr.end()));
} else {
ct->invalidate(MemRegion(old_mr.start(), old_mr.end()));
}
// Delete metaspaces for unloaded class loaders and clean up loader_data graph
ClassLoaderDataGraph::purge();
MetaspaceUtils::verify_metrics();
heap->prune_scavengable_nmethods();
#if COMPILER2_OR_JVMCI
DerivedPointerTable::update_pointers();
#endif
if (ZapUnusedHeapArea) {
heap->gen_mangle_unused_area();
}
// Update time of last GC
reset_millis_since_last_gc();
}
HeapWord*
PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
bool maximum_compaction)
{
const size_t region_size = ParallelCompactData::RegionSize;
const ParallelCompactData& sd = summary_data();
const MutableSpace* const space = _space_info[id].space();
HeapWord* const top_aligned_up = sd.region_align_up(space->top());
const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
// Skip full regions at the beginning of the space--they are necessarily part
// of the dense prefix.
size_t full_count = 0;
const RegionData* cp;
for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
++full_count;
}
assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
if (maximum_compaction || cp == end_cp || interval_ended) {
_maximum_compaction_gc_num = total_invocations();
return sd.region_to_addr(cp);
}
HeapWord* const new_top = _space_info[id].new_top();
const size_t space_live = pointer_delta(new_top, space->bottom());
const size_t space_used = space->used_in_words();
const size_t space_capacity = space->capacity_in_words();
const double cur_density = double(space_live) / space_capacity;
const double deadwood_density =
(1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
if (TraceParallelOldGCDensePrefix) {
tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
cur_density, deadwood_density, deadwood_goal);
tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
"space_cap=" SIZE_FORMAT,
space_live, space_used,
space_capacity);
}
// XXX - Use binary search?
HeapWord* dense_prefix = sd.region_to_addr(cp);
const RegionData* full_cp = cp;
const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
while (cp < end_cp) {
HeapWord* region_destination = cp->destination();
const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
if (TraceParallelOldGCDensePrefix && Verbose) {
tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
"dp=" PTR_FORMAT " " "cdw=" SIZE_FORMAT_W(8),
sd.region(cp), p2i(region_destination),
p2i(dense_prefix), cur_deadwood);
}
if (cur_deadwood >= deadwood_goal) {
// Found the region that has the correct amount of deadwood to the left.
// This typically occurs after crossing a fairly sparse set of regions, so
// iterate backwards over those sparse regions, looking for the region
// that has the lowest density of live objects 'to the right.'
size_t space_to_left = sd.region(cp) * region_size;
size_t live_to_left = space_to_left - cur_deadwood;
size_t space_to_right = space_capacity - space_to_left;
size_t live_to_right = space_live - live_to_left;
double density_to_right = double(live_to_right) / space_to_right;
while (cp > full_cp) {
--cp;
const size_t prev_region_live_to_right = live_to_right -
cp->data_size();
const size_t prev_region_space_to_right = space_to_right + region_size;
double prev_region_density_to_right =
double(prev_region_live_to_right) / prev_region_space_to_right;
if (density_to_right <= prev_region_density_to_right) {
return dense_prefix;
}
if (TraceParallelOldGCDensePrefix && Verbose) {
tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
"pc_d2r=%10.8f", sd.region(cp), density_to_right,
prev_region_density_to_right);
}
dense_prefix -= region_size;
live_to_right = prev_region_live_to_right;
space_to_right = prev_region_space_to_right;
density_to_right = prev_region_density_to_right;
}
return dense_prefix;
}
dense_prefix += region_size;
++cp;
}
return dense_prefix;
}
#ifndef PRODUCT
void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
const SpaceId id,
const bool maximum_compaction,
HeapWord* const addr)
{
const size_t region_idx = summary_data().addr_to_region_idx(addr);
RegionData* const cp = summary_data().region(region_idx);
const MutableSpace* const space = _space_info[id].space();
HeapWord* const new_top = _space_info[id].new_top();
const size_t space_live = pointer_delta(new_top, space->bottom());
const size_t dead_to_left = pointer_delta(addr, cp->destination());
const size_t space_cap = space->capacity_in_words();
const double dead_to_left_pct = double(dead_to_left) / space_cap;
const size_t live_to_right = new_top - cp->destination();
const size_t dead_to_right = space->top() - addr - live_to_right;
tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
"spl=" SIZE_FORMAT " "
"d2l=" SIZE_FORMAT " d2l%%=%6.4f "
"d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
" ratio=%10.8f",
algorithm, p2i(addr), region_idx,
space_live,
dead_to_left, dead_to_left_pct,
dead_to_right, live_to_right,
double(dead_to_right) / live_to_right);
}
#endif // #ifndef PRODUCT
// Return a fraction indicating how much of the generation can be treated as
// "dead wood" (i.e., not reclaimed). The function uses a normal distribution
// based on the density of live objects in the generation to determine a limit,
// which is then adjusted so the return value is min_percent when the density is
// 1.
//
// The following table shows some return values for a different values of the
// standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
// min_percent is 1.
//
// fraction allowed as dead wood
// -----------------------------------------------------------------
// density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
// ------- ---------- ---------- ---------- ---------- ---------- ----------
// 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
// 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
// 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
// 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
// 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
// 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
// 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
// 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
// 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
// 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
// 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
// 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
// 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
// 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
// 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
// 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
// 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
// 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
// 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
// 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
// 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
{
assert(_dwl_initialized, "uninitialized");
// The raw limit is the value of the normal distribution at x = density.
const double raw_limit = normal_distribution(density);
// Adjust the raw limit so it becomes the minimum when the density is 1.
//
// First subtract the adjustment value (which is simply the precomputed value
// normal_distribution(1.0)); this yields a value of 0 when the density is 1.
// Then add the minimum value, so the minimum is returned when the density is
// 1. Finally, prevent negative values, which occur when the mean is not 0.5.
const double min = double(min_percent) / 100.0;
const double limit = raw_limit - _dwl_adjustment + min;
return MAX2(limit, 0.0);
}
ParallelCompactData::RegionData*
PSParallelCompact::first_dead_space_region(const RegionData* beg,
const RegionData* end)
{
const size_t region_size = ParallelCompactData::RegionSize;
ParallelCompactData& sd = summary_data();
size_t left = sd.region(beg);
size_t right = end > beg ? sd.region(end) - 1 : left;
// Binary search.
while (left < right) {
// Equivalent to (left + right) / 2, but does not overflow.
const size_t middle = left + (right - left) / 2;
RegionData* const middle_ptr = sd.region(middle);
HeapWord* const dest = middle_ptr->destination();
HeapWord* const addr = sd.region_to_addr(middle);
assert(dest != NULL, "sanity");
assert(dest <= addr, "must move left");
if (middle > left && dest < addr) {
right = middle - 1;
} else if (middle < right && middle_ptr->data_size() == region_size) {
left = middle + 1;
} else {
return middle_ptr;
}
}
return sd.region(left);
}
ParallelCompactData::RegionData*
PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
const RegionData* end,
size_t dead_words)
{
ParallelCompactData& sd = summary_data();
size_t left = sd.region(beg);
size_t right = end > beg ? sd.region(end) - 1 : left;
// Binary search.
while (left < right) {
// Equivalent to (left + right) / 2, but does not overflow.
const size_t middle = left + (right - left) / 2;
RegionData* const middle_ptr = sd.region(middle);
HeapWord* const dest = middle_ptr->destination();
HeapWord* const addr = sd.region_to_addr(middle);
assert(dest != NULL, "sanity");
assert(dest <= addr, "must move left");
const size_t dead_to_left = pointer_delta(addr, dest);
if (middle > left && dead_to_left > dead_words) {
right = middle - 1;
} else if (middle < right && dead_to_left < dead_words) {
left = middle + 1;
} else {
return middle_ptr;
}
}
return sd.region(left);
}
// The result is valid during the summary phase, after the initial summarization
// of each space into itself, and before final summarization.
inline double
PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
HeapWord* const bottom,
HeapWord* const top,
HeapWord* const new_top)
{
ParallelCompactData& sd = summary_data();
assert(cp != NULL, "sanity");
assert(bottom != NULL, "sanity");
assert(top != NULL, "sanity");
assert(new_top != NULL, "sanity");
assert(top >= new_top, "summary data problem?");
assert(new_top > bottom, "space is empty; should not be here");
assert(new_top >= cp->destination(), "sanity");
assert(top >= sd.region_to_addr(cp), "sanity");
HeapWord* const destination = cp->destination();
const size_t dense_prefix_live = pointer_delta(destination, bottom);
const size_t compacted_region_live = pointer_delta(new_top, destination);
const size_t compacted_region_used = pointer_delta(top,
sd.region_to_addr(cp));
const size_t reclaimable = compacted_region_used - compacted_region_live;
const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
return double(reclaimable) / divisor;
}
// Return the address of the end of the dense prefix, a.k.a. the start of the
// compacted region. The address is always on a region boundary.
//
// Completely full regions at the left are skipped, since no compaction can
// occur in those regions. Then the maximum amount of dead wood to allow is
// computed, based on the density (amount live / capacity) of the generation;
// the region with approximately that amount of dead space to the left is
// identified as the limit region. Regions between the last completely full
// region and the limit region are scanned and the one that has the best
// (maximum) reclaimed_ratio() is selected.
HeapWord*
PSParallelCompact::compute_dense_prefix(const SpaceId id,
bool maximum_compaction)
{
const size_t region_size = ParallelCompactData::RegionSize;
const ParallelCompactData& sd = summary_data();
const MutableSpace* const space = _space_info[id].space();
HeapWord* const top = space->top();
HeapWord* const top_aligned_up = sd.region_align_up(top);
HeapWord* const new_top = _space_info[id].new_top();
HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
HeapWord* const bottom = space->bottom();
const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
const RegionData* const new_top_cp =
sd.addr_to_region_ptr(new_top_aligned_up);
// Skip full regions at the beginning of the space--they are necessarily part
// of the dense prefix.
const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
space->is_empty(), "no dead space allowed to the left");
assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
"region must have dead space");
// The gc number is saved whenever a maximum compaction is done, and used to
// determine when the maximum compaction interval has expired. This avoids
// successive max compactions for different reasons.
assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
total_invocations() == HeapFirstMaximumCompactionCount;
if (maximum_compaction || full_cp == top_cp || interval_ended) {
_maximum_compaction_gc_num = total_invocations();
return sd.region_to_addr(full_cp);
}
const size_t space_live = pointer_delta(new_top, bottom);
const size_t space_used = space->used_in_words();
const size_t space_capacity = space->capacity_in_words();
const double density = double(space_live) / double(space_capacity);
const size_t min_percent_free = MarkSweepDeadRatio;
const double limiter = dead_wood_limiter(density, min_percent_free);
const size_t dead_wood_max = space_used - space_live;
const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
dead_wood_max);
if (TraceParallelOldGCDensePrefix) {
tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
"space_cap=" SIZE_FORMAT,
space_live, space_used,
space_capacity);
tty->print_cr("dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
"dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
density, min_percent_free, limiter,
dead_wood_max, dead_wood_limit);
}
// Locate the region with the desired amount of dead space to the left.
const RegionData* const limit_cp =
dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
// Scan from the first region with dead space to the limit region and find the
// one with the best (largest) reclaimed ratio.
double best_ratio = 0.0;
const RegionData* best_cp = full_cp;
for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
if (tmp_ratio > best_ratio) {
best_cp = cp;
best_ratio = tmp_ratio;
}
}
return sd.region_to_addr(best_cp);
}
void PSParallelCompact::summarize_spaces_quick()
{
for (unsigned int i = 0; i < last_space_id; ++i) {
const MutableSpace* space = _space_info[i].space();
HeapWord** nta = _space_info[i].new_top_addr();
bool result = _summary_data.summarize(_space_info[i].split_info(),
space->bottom(), space->top(), NULL,
space->bottom(), space->end(), nta);
assert(result, "space must fit into itself");
_space_info[i].set_dense_prefix(space->bottom());
}
}
void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
{
HeapWord* const dense_prefix_end = dense_prefix(id);
const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
// Only enough dead space is filled so that any remaining dead space to the
// left is larger than the minimum filler object. (The remainder is filled
// during the copy/update phase.)
//
// The size of the dead space to the right of the boundary is not a
// concern, since compaction will be able to use whatever space is
// available.
//
// Here '||' is the boundary, 'x' represents a don't care bit and a box
// surrounds the space to be filled with an object.
//
// In the 32-bit VM, each bit represents two 32-bit words:
// +---+
// a) beg_bits: ... x x x | 0 | || 0 x x ...
// end_bits: ... x x x | 0 | || 0 x x ...
// +---+
//
// In the 64-bit VM, each bit represents one 64-bit word:
// +------------+
// b) beg_bits: ... x x x | 0 || 0 | x x ...
// end_bits: ... x x 1 | 0 || 0 | x x ...
// +------------+
// +-------+
// c) beg_bits: ... x x | 0 0 | || 0 x x ...
// end_bits: ... x 1 | 0 0 | || 0 x x ...
// +-------+
// +-----------+
// d) beg_bits: ... x | 0 0 0 | || 0 x x ...
// end_bits: ... 1 | 0 0 0 | || 0 x x ...
// +-----------+
// +-------+
// e) beg_bits: ... 0 0 | 0 0 | || 0 x x ...
// end_bits: ... 0 0 | 0 0 | || 0 x x ...
// +-------+
// Initially assume case a, c or e will apply.
size_t obj_len = CollectedHeap::min_fill_size();
HeapWord* obj_beg = dense_prefix_end - obj_len;
#ifdef _LP64
if (MinObjAlignment > 1) { // object alignment > heap word size
// Cases a, c or e.
} else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
// Case b above.
obj_beg = dense_prefix_end - 1;
} else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
_mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
// Case d above.
obj_beg = dense_prefix_end - 3;
obj_len = 3;
}
#endif // #ifdef _LP64
CollectedHeap::fill_with_object(obj_beg, obj_len);
_mark_bitmap.mark_obj(obj_beg, obj_len);
_summary_data.add_obj(obj_beg, obj_len);
assert(start_array(id) != NULL, "sanity");
start_array(id)->allocate_block(obj_beg);
}
}
void
PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
{
assert(id < last_space_id, "id out of range");
assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
"should have been reset in summarize_spaces_quick()");
const MutableSpace* space = _space_info[id].space();
if (_space_info[id].new_top() != space->bottom()) {
HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
_space_info[id].set_dense_prefix(dense_prefix_end);
#ifndef PRODUCT
if (TraceParallelOldGCDensePrefix) {
print_dense_prefix_stats("ratio", id, maximum_compaction,
dense_prefix_end);
HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
print_dense_prefix_stats("density", id, maximum_compaction, addr);
}
#endif // #ifndef PRODUCT
// Recompute the summary data, taking into account the dense prefix. If
// every last byte will be reclaimed, then the existing summary data which
// compacts everything can be left in place.
if (!maximum_compaction && dense_prefix_end != space->bottom()) {
// If dead space crosses the dense prefix boundary, it is (at least
// partially) filled with a dummy object, marked live and added to the
// summary data. This simplifies the copy/update phase and must be done
// before the final locations of objects are determined, to prevent
// leaving a fragment of dead space that is too small to fill.
fill_dense_prefix_end(id);
// Compute the destination of each Region, and thus each object.
_summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
_summary_data.summarize(_space_info[id].split_info(),
dense_prefix_end, space->top(), NULL,
dense_prefix_end, space->end(),
_space_info[id].new_top_addr());
}
}
if (log_develop_is_enabled(Trace, gc, compaction)) {
const size_t region_size = ParallelCompactData::RegionSize;
HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
HeapWord* const new_top = _space_info[id].new_top();
const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
log_develop_trace(gc, compaction)(
"id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
"dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
"cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
id, space->capacity_in_words(), p2i(dense_prefix_end),
dp_region, dp_words / region_size,
cr_words / region_size, p2i(new_top));
}
}
#ifndef PRODUCT
void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
HeapWord* dst_beg, HeapWord* dst_end,
SpaceId src_space_id,
HeapWord* src_beg, HeapWord* src_end)
{
log_develop_trace(gc, compaction)(
"Summarizing %d [%s] into %d [%s]: "
"src=" PTR_FORMAT "-" PTR_FORMAT " "
SIZE_FORMAT "-" SIZE_FORMAT " "
"dst=" PTR_FORMAT "-" PTR_FORMAT " "
SIZE_FORMAT "-" SIZE_FORMAT,
src_space_id, space_names[src_space_id],
dst_space_id, space_names[dst_space_id],
p2i(src_beg), p2i(src_end),
_summary_data.addr_to_region_idx(src_beg),
_summary_data.addr_to_region_idx(src_end),
p2i(dst_beg), p2i(dst_end),
_summary_data.addr_to_region_idx(dst_beg),
_summary_data.addr_to_region_idx(dst_end));
}
#endif // #ifndef PRODUCT
void PSParallelCompact::summary_phase(ParCompactionManager* cm,
bool maximum_compaction)
{
GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
#ifdef ASSERT
if (TraceParallelOldGCMarkingPhase) {
tty->print_cr("add_obj_count=" SIZE_FORMAT " "
"add_obj_bytes=" SIZE_FORMAT,
add_obj_count, add_obj_size * HeapWordSize);
tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
"mark_bitmap_bytes=" SIZE_FORMAT,
mark_bitmap_count, mark_bitmap_size * HeapWordSize);
}
#endif // #ifdef ASSERT
// Quick summarization of each space into itself, to see how much is live.
summarize_spaces_quick();
log_develop_trace(gc, compaction)("summary phase: after summarizing each space to self");
NOT_PRODUCT(print_region_ranges());
NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
// The amount of live data that will end up in old space (assuming it fits).
size_t old_space_total_live = 0;
for (unsigned int id = old_space_id; id < last_space_id; ++id) {
old_space_total_live += pointer_delta(_space_info[id].new_top(),
_space_info[id].space()->bottom());
}
MutableSpace* const old_space = _space_info[old_space_id].space();
const size_t old_capacity = old_space->capacity_in_words();
if (old_space_total_live > old_capacity) {
// XXX - should also try to expand
maximum_compaction = true;
}
// Old generations.
summarize_space(old_space_id, maximum_compaction);
// Summarize the remaining spaces in the young gen. The initial target space
// is the old gen. If a space does not fit entirely into the target, then the
// remainder is compacted into the space itself and that space becomes the new
// target.
SpaceId dst_space_id = old_space_id;
HeapWord* dst_space_end = old_space->end();
HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
const MutableSpace* space = _space_info[id].space();
const size_t live = pointer_delta(_space_info[id].new_top(),
space->bottom());
const size_t available = pointer_delta(dst_space_end, *new_top_addr);
NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
SpaceId(id), space->bottom(), space->top());)
if (live > 0 && live <= available) {
// All the live data will fit.
bool done = _summary_data.summarize(_space_info[id].split_info(),
space->bottom(), space->top(),
NULL,
*new_top_addr, dst_space_end,
new_top_addr);
assert(done, "space must fit into old gen");
// Reset the new_top value for the space.
_space_info[id].set_new_top(space->bottom());
} else if (live > 0) {
// Attempt to fit part of the source space into the target space.
HeapWord* next_src_addr = NULL;
bool done = _summary_data.summarize(_space_info[id].split_info(),
space->bottom(), space->top(),
&next_src_addr,
*new_top_addr, dst_space_end,
new_top_addr);
assert(!done, "space should not fit into old gen");
assert(next_src_addr != NULL, "sanity");
// The source space becomes the new target, so the remainder is compacted
// within the space itself.
dst_space_id = SpaceId(id);
dst_space_end = space->end();
new_top_addr = _space_info[id].new_top_addr();
NOT_PRODUCT(summary_phase_msg(dst_space_id,
space->bottom(), dst_space_end,
SpaceId(id), next_src_addr, space->top());)
done = _summary_data.summarize(_space_info[id].split_info(),
next_src_addr, space->top(),
NULL,
space->bottom(), dst_space_end,
new_top_addr);
assert(done, "space must fit when compacted into itself");
assert(*new_top_addr <= space->top(), "usage should not grow");
}
}
log_develop_trace(gc, compaction)("Summary_phase: after final summarization");
NOT_PRODUCT(print_region_ranges());
NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
}
// This method should contain all heap-specific policy for invoking a full
// collection. invoke_no_policy() will only attempt to compact the heap; it
// will do nothing further. If we need to bail out for policy reasons, scavenge
// before full gc, or any other specialized behavior, it needs to be added here.
//
// Note that this method should only be called from the vm_thread while at a
// safepoint.
//
// Note that the all_soft_refs_clear flag in the soft ref policy
// may be true because this method can be called without intervening
// activity. For example when the heap space is tight and full measure
// are being taken to free space.
void PSParallelCompact::invoke(bool maximum_heap_compaction) {
assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
assert(Thread::current() == (Thread*)VMThread::vm_thread(),
"should be in vm thread");
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
GCCause::Cause gc_cause = heap->gc_cause();
assert(!heap->is_gc_active(), "not reentrant");
PSAdaptiveSizePolicy* policy = heap->size_policy();
IsGCActiveMark mark;
if (ScavengeBeforeFullGC) {
PSScavenge::invoke_no_policy();
}
const bool clear_all_soft_refs =
heap->soft_ref_policy()->should_clear_all_soft_refs();
PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
maximum_heap_compaction);
}
// This method contains no policy. You should probably
// be calling invoke() instead.
bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
assert(ref_processor() != NULL, "Sanity");
if (GCLocker::check_active_before_gc()) {
return false;
}
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
GCIdMark gc_id_mark;
_gc_timer.register_gc_start();
_gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
TimeStamp marking_start;
TimeStamp compaction_start;
TimeStamp collection_exit;
GCCause::Cause gc_cause = heap->gc_cause();
PSYoungGen* young_gen = heap->young_gen();
PSOldGen* old_gen = heap->old_gen();
PSAdaptiveSizePolicy* size_policy = heap->size_policy();
// The scope of casr should end after code that can change
// SoftRefPolicy::_should_clear_all_soft_refs.
ClearedAllSoftRefs casr(maximum_heap_compaction,
heap->soft_ref_policy());
if (ZapUnusedHeapArea) {
// Save information needed to minimize mangling
heap->record_gen_tops_before_GC();
}
// Make sure data structures are sane, make the heap parsable, and do other
// miscellaneous bookkeeping.
pre_compact();
const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
// Get the compaction manager reserved for the VM thread.
ParCompactionManager* const vmthread_cm =
ParCompactionManager::manager_array(gc_task_manager()->workers());
{
ResourceMark rm;
HandleMark hm;
// Set the number of GC threads to be used in this collection
gc_task_manager()->set_active_gang();
gc_task_manager()->task_idle_workers();
GCTraceCPUTime tcpu;
GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause, true);
heap->pre_full_gc_dump(&_gc_timer);
TraceCollectorStats tcs(counters());
TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause);
if (log_is_enabled(Debug, gc, heap, exit)) {
accumulated_time()->start();
}
// Let the size policy know we're starting
size_policy->major_collection_begin();
#if COMPILER2_OR_JVMCI
DerivedPointerTable::clear();
#endif
ref_processor()->enable_discovery();
ref_processor()->setup_policy(maximum_heap_compaction);
bool marked_for_unloading = false;
marking_start.update();
marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
bool max_on_system_gc = UseMaximumCompactionOnSystemGC
&& GCCause::is_user_requested_gc(gc_cause);
summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
#if COMPILER2_OR_JVMCI
assert(DerivedPointerTable::is_active(), "Sanity");
DerivedPointerTable::set_active(false);
#endif
// adjust_roots() updates Universe::_intArrayKlassObj which is
// needed by the compaction for filling holes in the dense prefix.
adjust_roots(vmthread_cm);
compaction_start.update();
compact();
// Reset the mark bitmap, summary data, and do other bookkeeping. Must be
// done before resizing.
post_compact();
// Let the size policy know we're done
size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
if (UseAdaptiveSizePolicy) {
log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
// Don't check if the size_policy is ready here. Let
// the size_policy check that internally.
if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
// Swap the survivor spaces if from_space is empty. The
// resize_young_gen() called below is normally used after
// a successful young GC and swapping of survivor spaces;
// otherwise, it will fail to resize the young gen with
// the current implementation.
if (young_gen->from_space()->is_empty()) {
young_gen->from_space()->clear(SpaceDecorator::Mangle);
young_gen->swap_spaces();
}
// Calculate optimal free space amounts
assert(young_gen->max_size() >
young_gen->from_space()->capacity_in_bytes() +
young_gen->to_space()->capacity_in_bytes(),
"Sizes of space in young gen are out-of-bounds");
size_t young_live = young_gen->used_in_bytes();
size_t eden_live = young_gen->eden_space()->used_in_bytes();
size_t old_live = old_gen->used_in_bytes();
size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
size_t max_old_gen_size = old_gen->max_gen_size();
size_t max_eden_size = young_gen->max_size() -
young_gen->from_space()->capacity_in_bytes() -
young_gen->to_space()->capacity_in_bytes();
// Used for diagnostics
size_policy->clear_generation_free_space_flags();
size_policy->compute_generations_free_space(young_live,
eden_live,
old_live,
cur_eden,
max_old_gen_size,
max_eden_size,
true /* full gc*/);
size_policy->check_gc_overhead_limit(eden_live,
max_old_gen_size,
max_eden_size,
true /* full gc*/,
gc_cause,
heap->soft_ref_policy());
size_policy->decay_supplemental_growth(true /* full gc*/);
heap->resize_old_gen(
size_policy->calculated_old_free_size_in_bytes());
heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
size_policy->calculated_survivor_size_in_bytes());
}
log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
}
if (UsePerfData) {
PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
counters->update_counters();
counters->update_old_capacity(old_gen->capacity_in_bytes());
counters->update_young_capacity(young_gen->capacity_in_bytes());
}
heap->resize_all_tlabs();
// Resize the metaspace capacity after a collection
MetaspaceGC::compute_new_size();
if (log_is_enabled(Debug, gc, heap, exit)) {
accumulated_time()->stop();
}
heap->print_heap_change(pre_gc_values);
// Track memory usage and detect low memory
MemoryService::track_memory_usage();
heap->update_counters();
gc_task_manager()->release_idle_workers();
heap->post_full_gc_dump(&_gc_timer);
}
#ifdef ASSERT
for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
ParCompactionManager* const cm =
ParCompactionManager::manager_array(int(i));
assert(cm->marking_stack()->is_empty(), "should be empty");
assert(cm->region_stack()->is_empty(), "Region stack " SIZE_FORMAT " is not empty", i);
}
#endif // ASSERT
if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
Universe::verify("After GC");
}
// Re-verify object start arrays
if (VerifyObjectStartArray &&
VerifyAfterGC) {
old_gen->verify_object_start_array();
}
if (ZapUnusedHeapArea) {
old_gen->object_space()->check_mangled_unused_area_complete();
}
NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
collection_exit.update();
heap->print_heap_after_gc();
heap->trace_heap_after_gc(&_gc_tracer);
log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
marking_start.ticks(), compaction_start.ticks(),
collection_exit.ticks());
gc_task_manager()->print_task_time_stamps();
#ifdef TRACESPINNING
ParallelTaskTerminator::print_termination_counts();
#endif
AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
_gc_timer.register_gc_end();
_gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
_gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
return true;
}
bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
PSYoungGen* young_gen,
PSOldGen* old_gen) {
MutableSpace* const eden_space = young_gen->eden_space();
assert(!eden_space->is_empty(), "eden must be non-empty");
assert(young_gen->virtual_space()->alignment() ==
old_gen->virtual_space()->alignment(), "alignments do not match");
// We also return false when it's a heterogenous heap because old generation cannot absorb data from eden
// when it is allocated on different memory (example, nv-dimm) than young.
if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary) ||
ParallelArguments::is_heterogeneous_heap()) {
return false;
}
// Both generations must be completely committed.
if (young_gen->virtual_space()->uncommitted_size() != 0) {
return false;
}
if (old_gen->virtual_space()->uncommitted_size() != 0) {
return false;
}
// Figure out how much to take from eden. Include the average amount promoted
// in the total; otherwise the next young gen GC will simply bail out to a
// full GC.
const size_t alignment = old_gen->virtual_space()->alignment();
const size_t eden_used = eden_space->used_in_bytes();
const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
const size_t absorb_size = align_up(eden_used + promoted, alignment);
const size_t eden_capacity = eden_space->capacity_in_bytes();
if (absorb_size >= eden_capacity) {
return false; // Must leave some space in eden.
}
const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
if (new_young_size < young_gen->min_gen_size()) {
return false; // Respect young gen minimum size.
}
log_trace(gc, ergo, heap)(" absorbing " SIZE_FORMAT "K: "
"eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
"from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
"young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
absorb_size / K,
eden_capacity / K, (eden_capacity - absorb_size) / K,
young_gen->from_space()->used_in_bytes() / K,
young_gen->to_space()->used_in_bytes() / K,
young_gen->capacity_in_bytes() / K, new_young_size / K);
// Fill the unused part of the old gen.
MutableSpace* const old_space = old_gen->object_space();
HeapWord* const unused_start = old_space->top();
size_t const unused_words = pointer_delta(old_space->end(), unused_start);
if (unused_words > 0) {
if (unused_words < CollectedHeap::min_fill_size()) {
return false; // If the old gen cannot be filled, must give up.
}
CollectedHeap::fill_with_objects(unused_start, unused_words);
}
// Take the live data from eden and set both top and end in the old gen to
// eden top. (Need to set end because reset_after_change() mangles the region
// from end to virtual_space->high() in debug builds).
HeapWord* const new_top = eden_space->top();
old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
absorb_size);
young_gen->reset_after_change();
old_space->set_top(new_top);
old_space->set_end(new_top);
old_gen->reset_after_change();
// Update the object start array for the filler object and the data from eden.
ObjectStartArray* const start_array = old_gen->start_array();
for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
start_array->allocate_block(p);
}
// Could update the promoted average here, but it is not typically updated at
// full GCs and the value to use is unclear. Something like
//
// cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
size_policy->set_bytes_absorbed_from_eden(absorb_size);
return true;
}
GCTaskManager* const PSParallelCompact::gc_task_manager() {
assert(ParallelScavengeHeap::gc_task_manager() != NULL,
"shouldn't return NULL");
return ParallelScavengeHeap::gc_task_manager();
}
class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
private:
GCTaskQueue* _q;
public:
PCAddThreadRootsMarkingTaskClosure(GCTaskQueue* q) : _q(q) { }
void do_thread(Thread* t) {
_q->enqueue(new ThreadRootsMarkingTask(t));
}
};
void PSParallelCompact::marking_phase(ParCompactionManager* cm,
bool maximum_heap_compaction,
ParallelOldTracer *gc_tracer) {
// Recursively traverse all live objects and mark them
GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
uint parallel_gc_threads = heap->gc_task_manager()->workers();
uint active_gc_threads = heap->gc_task_manager()->active_workers();
TaskQueueSetSuper* qset = ParCompactionManager::stack_array();
TaskTerminator terminator(active_gc_threads, qset);
PCMarkAndPushClosure mark_and_push_closure(cm);
ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
// Need new claim bits before marking starts.
ClassLoaderDataGraph::clear_claimed_marks();
{
GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
ParallelScavengeHeap::ParStrongRootsScope psrs;
GCTaskQueue* q = GCTaskQueue::create();
q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
// We scan the thread roots in parallel
PCAddThreadRootsMarkingTaskClosure cl(q);
Threads::java_threads_and_vm_thread_do(&cl);
q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data));
q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
if (active_gc_threads > 1) {
for (uint j = 0; j < active_gc_threads; j++) {
q->enqueue(new StealMarkingTask(terminator.terminator()));
}
}
gc_task_manager()->execute_and_wait(q);
}
// Process reference objects found during marking
{
GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
ReferenceProcessorStats stats;
ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
if (ref_processor()->processing_is_mt()) {
ref_processor()->set_active_mt_degree(active_gc_threads);
RefProcTaskExecutor task_executor;
stats = ref_processor()->process_discovered_references(
is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
&task_executor, &pt);
} else {
stats = ref_processor()->process_discovered_references(
is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
&pt);
}
gc_tracer->report_gc_reference_stats(stats);
pt.print_all_references();
}
// This is the point where the entire marking should have completed.
assert(cm->marking_stacks_empty(), "Marking should have completed");
{
GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
WeakProcessor::weak_oops_do(is_alive_closure(), &do_nothing_cl);
}
{
GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
// Follow system dictionary roots and unload classes.
bool purged_class = SystemDictionary::do_unloading(&_gc_timer);
// Unload nmethods.
CodeCache::do_unloading(is_alive_closure(), purged_class);
// Prune dead klasses from subklass/sibling/implementor lists.
Klass::clean_weak_klass_links(purged_class);
// Clean JVMCI metadata handles.
JVMCI_ONLY(JVMCI::do_unloading(purged_class));
}
_gc_tracer.report_object_count_after_gc(is_alive_closure());
}
void PSParallelCompact::adjust_roots(ParCompactionManager* cm) {
// Adjust the pointers to reflect the new locations
GCTraceTime(Info, gc, phases) tm("Adjust Roots", &_gc_timer);
// Need new claim bits when tracing through and adjusting pointers.
ClassLoaderDataGraph::clear_claimed_marks();
PCAdjustPointerClosure oop_closure(cm);
// General strong roots.
Universe::oops_do(&oop_closure);
JNIHandles::oops_do(&oop_closure); // Global (strong) JNI handles
Threads::oops_do(&oop_closure, NULL);
ObjectSynchronizer::oops_do(&oop_closure);
Management::oops_do(&oop_closure);
JvmtiExport::oops_do(&oop_closure);
SystemDictionary::oops_do(&oop_closure);
CLDToOopClosure cld_closure(&oop_closure, ClassLoaderData::_claim_strong);
ClassLoaderDataGraph::cld_do(&cld_closure);
// Now adjust pointers in remaining weak roots. (All of which should
// have been cleared if they pointed to non-surviving objects.)
WeakProcessor::oops_do(&oop_closure);
CodeBlobToOopClosure adjust_from_blobs(&oop_closure, CodeBlobToOopClosure::FixRelocations);
CodeCache::blobs_do(&adjust_from_blobs);
AOT_ONLY(AOTLoader::oops_do(&oop_closure);)
ref_processor()->weak_oops_do(&oop_closure);
// Roots were visited so references into the young gen in roots
// may have been scanned. Process them also.
// Should the reference processor have a span that excludes
// young gen objects?
PSScavenge::reference_processor()->weak_oops_do(&oop_closure);
}
// Helper class to print 8 region numbers per line and then print the total at the end.
class FillableRegionLogger : public StackObj {
private:
Log(gc, compaction) log;
static const int LineLength = 8;
size_t _regions[LineLength];
int _next_index;
bool _enabled;
size_t _total_regions;
public:
FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
~FillableRegionLogger() {
log.trace(SIZE_FORMAT " initially fillable regions", _total_regions);
}
void print_line() {
if (!_enabled || _next_index == 0) {
return;
}
FormatBuffer<> line("Fillable: ");
for (int i = 0; i < _next_index; i++) {
line.append(" " SIZE_FORMAT_W(7), _regions[i]);
}
log.trace("%s", line.buffer());
_next_index = 0;
}
void handle(size_t region) {
if (!_enabled) {
return;
}
_regions[_next_index++] = region;
if (_next_index == LineLength) {
print_line();
}
_total_regions++;
}
};
void PSParallelCompact::prepare_region_draining_tasks(GCTaskQueue* q,
uint parallel_gc_threads)
{
GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
// Find the threads that are active
unsigned int which = 0;
// Find all regions that are available (can be filled immediately) and
// distribute them to the thread stacks. The iteration is done in reverse
// order (high to low) so the regions will be removed in ascending order.
const ParallelCompactData& sd = PSParallelCompact::summary_data();
which = 0;
// id + 1 is used to test termination so unsigned can
// be used with an old_space_id == 0.
FillableRegionLogger region_logger;
for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
SpaceInfo* const space_info = _space_info + id;
MutableSpace* const space = space_info->space();
HeapWord* const new_top = space_info->new_top();
const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
const size_t end_region =
sd.addr_to_region_idx(sd.region_align_up(new_top));
for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
if (sd.region(cur)->claim_unsafe()) {
ParCompactionManager* cm = ParCompactionManager::manager_array(which);
cm->region_stack()->push(cur);
region_logger.handle(cur);
// Assign regions to tasks in round-robin fashion.
if (++which == parallel_gc_threads) {
which = 0;
}
}
}
region_logger.print_line();
}
}
#define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
uint parallel_gc_threads) {
GCTraceTime(Trace, gc, phases) tm("Dense Prefix Task Setup", &_gc_timer);
ParallelCompactData& sd = PSParallelCompact::summary_data();
// Iterate over all the spaces adding tasks for updating
// regions in the dense prefix. Assume that 1 gc thread
// will work on opening the gaps and the remaining gc threads
// will work on the dense prefix.
unsigned int space_id;
for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
const MutableSpace* const space = _space_info[space_id].space();
if (dense_prefix_end == space->bottom()) {
// There is no dense prefix for this space.
continue;
}
// The dense prefix is before this region.
size_t region_index_end_dense_prefix =
sd.addr_to_region_idx(dense_prefix_end);
RegionData* const dense_prefix_cp =
sd.region(region_index_end_dense_prefix);
assert(dense_prefix_end == space->end() ||
dense_prefix_cp->available() ||
dense_prefix_cp->claimed(),
"The region after the dense prefix should always be ready to fill");
size_t region_index_start = sd.addr_to_region_idx(space->bottom());
// Is there dense prefix work?
size_t total_dense_prefix_regions =
region_index_end_dense_prefix - region_index_start;
// How many regions of the dense prefix should be given to
// each thread?
if (total_dense_prefix_regions > 0) {
uint tasks_for_dense_prefix = 1;
if (total_dense_prefix_regions <=
(parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
// Don't over partition. This assumes that
// PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
// so there are not many regions to process.
tasks_for_dense_prefix = parallel_gc_threads;
} else {
// Over partition
tasks_for_dense_prefix = parallel_gc_threads *
PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
}
size_t regions_per_thread = total_dense_prefix_regions /
tasks_for_dense_prefix;
// Give each thread at least 1 region.
if (regions_per_thread == 0) {
regions_per_thread = 1;
}
for (uint k = 0; k < tasks_for_dense_prefix; k++) {
if (region_index_start >= region_index_end_dense_prefix) {
break;
}
// region_index_end is not processed
size_t region_index_end = MIN2(region_index_start + regions_per_thread,
region_index_end_dense_prefix);
q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
region_index_start,
region_index_end));
region_index_start = region_index_end;
}
}
// This gets any part of the dense prefix that did not
// fit evenly.
if (region_index_start < region_index_end_dense_prefix) {
q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
region_index_start,
region_index_end_dense_prefix));
}
}
}
void PSParallelCompact::enqueue_region_stealing_tasks(
GCTaskQueue* q,
ParallelTaskTerminator* terminator_ptr,
uint parallel_gc_threads) {
GCTraceTime(Trace, gc, phases) tm("Steal Task Setup", &_gc_timer);
// Once a thread has drained it's stack, it should try to steal regions from
// other threads.
for (uint j = 0; j < parallel_gc_threads; j++) {
q->enqueue(new CompactionWithStealingTask(terminator_ptr));
}
}
#ifdef ASSERT
// Write a histogram of the number of times the block table was filled for a
// region.
void PSParallelCompact::write_block_fill_histogram()
{
if (!log_develop_is_enabled(Trace, gc, compaction)) {
return;
}
Log(gc, compaction) log;
ResourceMark rm;
LogStream ls(log.trace());
outputStream* out = &ls;
typedef ParallelCompactData::RegionData rd_t;
ParallelCompactData& sd = summary_data();
for (unsigned int id = old_space_id; id < last_space_id; ++id) {
MutableSpace* const spc = _space_info[id].space();
if (spc->bottom() != spc->top()) {
const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
size_t histo[5] = { 0, 0, 0, 0, 0 };
const size_t histo_len = sizeof(histo) / sizeof(size_t);
const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
for (const rd_t* cur = beg; cur < end; ++cur) {
++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
}
out->print("Block fill histogram: %u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
for (size_t i = 0; i < histo_len; ++i) {
out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
histo[i], 100.0 * histo[i] / region_cnt);
}
out->cr();
}
}
}
#endif // #ifdef ASSERT
void PSParallelCompact::compact() {
GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
PSOldGen* old_gen = heap->old_gen();
old_gen->start_array()->reset();
uint parallel_gc_threads = heap->gc_task_manager()->workers();
uint active_gc_threads = heap->gc_task_manager()->active_workers();
TaskQueueSetSuper* qset = ParCompactionManager::region_array();
TaskTerminator terminator(active_gc_threads, qset);
GCTaskQueue* q = GCTaskQueue::create();
prepare_region_draining_tasks(q, active_gc_threads);
enqueue_dense_prefix_tasks(q, active_gc_threads);
enqueue_region_stealing_tasks(q, terminator.terminator(), active_gc_threads);
{
GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
gc_task_manager()->execute_and_wait(q);
#ifdef ASSERT
// Verify that all regions have been processed before the deferred updates.
for (unsigned int id = old_space_id; id < last_space_id; ++id) {
verify_complete(SpaceId(id));
}
#endif
}
{
// Update the deferred objects, if any. Any compaction manager can be used.
GCTraceTime(Trace, gc, phases) tm("Deferred Updates", &_gc_timer);
ParCompactionManager* cm = ParCompactionManager::manager_array(0);
for (unsigned int id = old_space_id; id < last_space_id; ++id) {
update_deferred_objects(cm, SpaceId(id));
}
}
DEBUG_ONLY(write_block_fill_histogram());
}
#ifdef ASSERT
void PSParallelCompact::verify_complete(SpaceId space_id) {
// All Regions between space bottom() to new_top() should be marked as filled
// and all Regions between new_top() and top() should be available (i.e.,
// should have been emptied).
ParallelCompactData& sd = summary_data();
SpaceInfo si = _space_info[space_id];
HeapWord* new_top_addr = sd.region_align_up(si.new_top());
HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
bool issued_a_warning = false;
size_t cur_region;
for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
const RegionData* const c = sd.region(cur_region);
if (!c->completed()) {
log_warning(gc)("region " SIZE_FORMAT " not filled: destination_count=%u",
cur_region, c->destination_count());
issued_a_warning = true;
}
}
for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
const RegionData* const c = sd.region(cur_region);
if (!c->available()) {
log_warning(gc)("region " SIZE_FORMAT " not empty: destination_count=%u",
cur_region, c->destination_count());
issued_a_warning = true;
}
}
if (issued_a_warning) {
print_region_ranges();
}
}
#endif // #ifdef ASSERT
inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
_start_array->allocate_block(addr);
compaction_manager()->update_contents(oop(addr));
}
// Update interior oops in the ranges of regions [beg_region, end_region).
void
PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
SpaceId space_id,
size_t beg_region,
size_t end_region) {
ParallelCompactData& sd = summary_data();
ParMarkBitMap* const mbm = mark_bitmap();
HeapWord* beg_addr = sd.region_to_addr(beg_region);
HeapWord* const end_addr = sd.region_to_addr(end_region);
assert(beg_region <= end_region, "bad region range");
assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
#ifdef ASSERT
// Claim the regions to avoid triggering an assert when they are marked as
// filled.
for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
}
#endif // #ifdef ASSERT
if (beg_addr != space(space_id)->bottom()) {
// Find the first live object or block of dead space that *starts* in this
// range of regions. If a partial object crosses onto the region, skip it;
// it will be marked for 'deferred update' when the object head is
// processed. If dead space crosses onto the region, it is also skipped; it
// will be filled when the prior region is processed. If neither of those
// apply, the first word in the region is the start of a live object or dead
// space.
assert(beg_addr > space(space_id)->bottom(), "sanity");
const RegionData* const cp = sd.region(beg_region);
if (cp->partial_obj_size() != 0) {
beg_addr = sd.partial_obj_end(beg_region);
} else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
}
}
if (beg_addr < end_addr) {
// A live object or block of dead space starts in this range of Regions.
HeapWord* const dense_prefix_end = dense_prefix(space_id);
// Create closures and iterate.
UpdateOnlyClosure update_closure(mbm, cm, space_id);
FillClosure fill_closure(cm, space_id);
ParMarkBitMap::IterationStatus status;
status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
dense_prefix_end);
if (status == ParMarkBitMap::incomplete) {
update_closure.do_addr(update_closure.source());
}
}
// Mark the regions as filled.
RegionData* const beg_cp = sd.region(beg_region);
RegionData* const end_cp = sd.region(end_region);
for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
cp->set_completed();
}
}
// Return the SpaceId for the space containing addr. If addr is not in the
// heap, last_space_id is returned. In debug mode it expects the address to be
// in the heap and asserts such.
PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
for (unsigned int id = old_space_id; id < last_space_id; ++id) {
if (_space_info[id].space()->contains(addr)) {
return SpaceId(id);
}
}
assert(false, "no space contains the addr");
return last_space_id;
}
void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
SpaceId id) {
assert(id < last_space_id, "bad space id");
ParallelCompactData& sd = summary_data();
const SpaceInfo* const space_info = _space_info + id;
ObjectStartArray* const start_array = space_info->start_array();
const MutableSpace* const space = space_info->space();
assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
HeapWord* const beg_addr = space_info->dense_prefix();
HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
const RegionData* cur_region;
for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
HeapWord* const addr = cur_region->deferred_obj_addr();
if (addr != NULL) {
if (start_array != NULL) {
start_array->allocate_block(addr);
}
cm->update_contents(oop(addr));
assert(oopDesc::is_oop_or_null(oop(addr)), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr)));
}
}
}
// Skip over count live words starting from beg, and return the address of the
// next live word. Unless marked, the word corresponding to beg is assumed to
// be dead. Callers must either ensure beg does not correspond to the middle of
// an object, or account for those live words in some other way. Callers must
// also ensure that there are enough live words in the range [beg, end) to skip.
HeapWord*
PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
{
assert(count > 0, "sanity");
ParMarkBitMap* m = mark_bitmap();
idx_t bits_to_skip = m->words_to_bits(count);
idx_t cur_beg = m->addr_to_bit(beg);
const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
do {
cur_beg = m->find_obj_beg(cur_beg, search_end);
idx_t cur_end = m->find_obj_end(cur_beg, search_end);
const size_t obj_bits = cur_end - cur_beg + 1;
if (obj_bits > bits_to_skip) {
return m->bit_to_addr(cur_beg + bits_to_skip);
}
bits_to_skip -= obj_bits;
cur_beg = cur_end + 1;
} while (bits_to_skip > 0);
// Skipping the desired number of words landed just past the end of an object.
// Find the start of the next object.
cur_beg = m->find_obj_beg(cur_beg, search_end);
assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
return m->bit_to_addr(cur_beg);
}
HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
SpaceId src_space_id,
size_t src_region_idx)
{
assert(summary_data().is_region_aligned(dest_addr), "not aligned");
const SplitInfo& split_info = _space_info[src_space_id].split_info();
if (split_info.dest_region_addr() == dest_addr) {
// The partial object ending at the split point contains the first word to
// be copied to dest_addr.
return split_info.first_src_addr();
}
const ParallelCompactData& sd = summary_data();
ParMarkBitMap* const bitmap = mark_bitmap();
const size_t RegionSize = ParallelCompactData::RegionSize;
assert(sd.is_region_aligned(dest_addr), "not aligned");
const RegionData* const src_region_ptr = sd.region(src_region_idx);
const size_t partial_obj_size = src_region_ptr->partial_obj_size();
HeapWord* const src_region_destination = src_region_ptr->destination();
assert(dest_addr >= src_region_destination, "wrong src region");
assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
HeapWord* const src_region_end = src_region_beg + RegionSize;
HeapWord* addr = src_region_beg;
if (dest_addr == src_region_destination) {
// Return the first live word in the source region.
if (partial_obj_size == 0) {
addr = bitmap->find_obj_beg(addr, src_region_end);
assert(addr < src_region_end, "no objects start in src region");
}
return addr;
}
// Must skip some live data.
size_t words_to_skip = dest_addr - src_region_destination;
assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
if (partial_obj_size >= words_to_skip) {
// All the live words to skip are part of the partial object.
addr += words_to_skip;
if (partial_obj_size == words_to_skip) {
// Find the first live word past the partial object.
addr = bitmap->find_obj_beg(addr, src_region_end);
assert(addr < src_region_end, "wrong src region");
}
return addr;
}
// Skip over the partial object (if any).
if (partial_obj_size != 0) {
words_to_skip -= partial_obj_size;
addr += partial_obj_size;
}
// Skip over live words due to objects that start in the region.
addr = skip_live_words(addr, src_region_end, words_to_skip);
assert(addr < src_region_end, "wrong src region");
return addr;
}
void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
SpaceId src_space_id,
size_t beg_region,
HeapWord* end_addr)
{
ParallelCompactData& sd = summary_data();
#ifdef ASSERT
MutableSpace* const src_space = _space_info[src_space_id].space();
HeapWord* const beg_addr = sd.region_to_addr(beg_region);
assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
"src_space_id does not match beg_addr");
assert(src_space->contains(end_addr) || end_addr == src_space->end(),
"src_space_id does not match end_addr");
#endif // #ifdef ASSERT
RegionData* const beg = sd.region(beg_region);
RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
// Regions up to new_top() are enqueued if they become available.
HeapWord* const new_top = _space_info[src_space_id].new_top();
RegionData* const enqueue_end =
sd.addr_to_region_ptr(sd.region_align_up(new_top));
for (RegionData* cur = beg; cur < end; ++cur) {
assert(cur->data_size() > 0, "region must have live data");
cur->decrement_destination_count();
if (cur < enqueue_end && cur->available() && cur->claim()) {
cm->push_region(sd.region(cur));
}
}
}
size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
SpaceId& src_space_id,
HeapWord*& src_space_top,
HeapWord* end_addr)
{
typedef ParallelCompactData::RegionData RegionData;
ParallelCompactData& sd = PSParallelCompact::summary_data();
const size_t region_size = ParallelCompactData::RegionSize;
size_t src_region_idx = 0;
// Skip empty regions (if any) up to the top of the space.
HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
const RegionData* const top_region_ptr =
sd.addr_to_region_ptr(top_aligned_up);
while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
++src_region_ptr;
}
if (src_region_ptr < top_region_ptr) {
// The next source region is in the current space. Update src_region_idx
// and the source address to match src_region_ptr.
src_region_idx = sd.region(src_region_ptr);
HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
if (src_region_addr > closure.source()) {
closure.set_source(src_region_addr);
}
return src_region_idx;
}
// Switch to a new source space and find the first non-empty region.
unsigned int space_id = src_space_id + 1;
assert(space_id < last_space_id, "not enough spaces");
HeapWord* const destination = closure.destination();
do {
MutableSpace* space = _space_info[space_id].space();
HeapWord* const bottom = space->bottom();
const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
// Iterate over the spaces that do not compact into themselves.
if (bottom_cp->destination() != bottom) {
HeapWord* const top_aligned_up = sd.region_align_up(space->top());
const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
if (src_cp->live_obj_size() > 0) {
// Found it.
assert(src_cp->destination() == destination,
"first live obj in the space must match the destination");
assert(src_cp->partial_obj_size() == 0,
"a space cannot begin with a partial obj");
src_space_id = SpaceId(space_id);
src_space_top = space->top();
const size_t src_region_idx = sd.region(src_cp);
closure.set_source(sd.region_to_addr(src_region_idx));
return src_region_idx;
} else {
assert(src_cp->data_size() == 0, "sanity");
}
}
}
} while (++space_id < last_space_id);
assert(false, "no source region was found");
return 0;
}
void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
{
typedef ParMarkBitMap::IterationStatus IterationStatus;
const size_t RegionSize = ParallelCompactData::RegionSize;
ParMarkBitMap* const bitmap = mark_bitmap();
ParallelCompactData& sd = summary_data();
RegionData* const region_ptr = sd.region(region_idx);
// Get the items needed to construct the closure.
HeapWord* dest_addr = sd.region_to_addr(region_idx);
SpaceId dest_space_id = space_id(dest_addr);
ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
HeapWord* new_top = _space_info[dest_space_id].new_top();
assert(dest_addr < new_top, "sanity");
const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
// Get the source region and related info.
size_t src_region_idx = region_ptr->source_region();
SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
HeapWord* src_space_top = _space_info[src_space_id].space()->top();
MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
// Adjust src_region_idx to prepare for decrementing destination counts (the
// destination count is not decremented when a region is copied to itself).
if (src_region_idx == region_idx) {
src_region_idx += 1;
}
if (bitmap->is_unmarked(closure.source())) {
// The first source word is in the middle of an object; copy the remainder
// of the object or as much as will fit. The fact that pointer updates were
// deferred will be noted when the object header is processed.
HeapWord* const old_src_addr = closure.source();
closure.copy_partial_obj();
if (closure.is_full()) {
decrement_destination_counts(cm, src_space_id, src_region_idx,
closure.source());
region_ptr->set_deferred_obj_addr(NULL);
region_ptr->set_completed();
return;
}
HeapWord* const end_addr = sd.region_align_down(closure.source());
if (sd.region_align_down(old_src_addr) != end_addr) {
// The partial object was copied from more than one source region.
decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
// Move to the next source region, possibly switching spaces as well. All
// args except end_addr may be modified.
src_region_idx = next_src_region(closure, src_space_id, src_space_top,
end_addr);
}
}
do {
HeapWord* const cur_addr = closure.source();
HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
src_space_top);
IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
if (status == ParMarkBitMap::incomplete) {
// The last obj that starts in the source region does not end in the
// region.
assert(closure.source() < end_addr, "sanity");
HeapWord* const obj_beg = closure.source();
HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
src_space_top);
HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
if (obj_end < range_end) {
// The end was found; the entire object will fit.
status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
assert(status != ParMarkBitMap::would_overflow, "sanity");
} else {
// The end was not found; the object will not fit.
assert(range_end < src_space_top, "obj cannot cross space boundary");
status = ParMarkBitMap::would_overflow;
}
}
if (status == ParMarkBitMap::would_overflow) {
// The last object did not fit. Note that interior oop updates were
// deferred, then copy enough of the object to fill the region.
region_ptr->set_deferred_obj_addr(closure.destination());
status = closure.copy_until_full(); // copies from closure.source()
decrement_destination_counts(cm, src_space_id, src_region_idx,
closure.source());
region_ptr->set_completed();
return;
}
if (status == ParMarkBitMap::full) {
decrement_destination_counts(cm, src_space_id, src_region_idx,
closure.source());
region_ptr->set_deferred_obj_addr(NULL);
region_ptr->set_completed();
return;
}
decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
// Move to the next source region, possibly switching spaces as well. All
// args except end_addr may be modified.
src_region_idx = next_src_region(closure, src_space_id, src_space_top,
end_addr);
} while (true);
}
void PSParallelCompact::fill_blocks(size_t region_idx)
{
// Fill in the block table elements for the specified region. Each block
// table element holds the number of live words in the region that are to the
// left of the first object that starts in the block. Thus only blocks in
// which an object starts need to be filled.
//
// The algorithm scans the section of the bitmap that corresponds to the
// region, keeping a running total of the live words. When an object start is
// found, if it's the first to start in the block that contains it, the
// current total is written to the block table element.
const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
const size_t RegionSize = ParallelCompactData::RegionSize;
ParallelCompactData& sd = summary_data();
const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
if (partial_obj_size >= RegionSize) {
return; // No objects start in this region.
}
// Ensure the first loop iteration decides that the block has changed.
size_t cur_block = sd.block_count();
const ParMarkBitMap* const bitmap = mark_bitmap();
const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
assert((size_t)1 << Log2BitsPerBlock ==
bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
size_t live_bits = bitmap->words_to_bits(partial_obj_size);
beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
while (beg_bit < range_end) {
const size_t new_block = beg_bit >> Log2BitsPerBlock;
if (new_block != cur_block) {
cur_block = new_block;
sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
}
const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
if (end_bit < range_end - 1) {
live_bits += end_bit - beg_bit + 1;
beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
} else {
return;
}
}
}
void
PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
const MutableSpace* sp = space(space_id);
if (sp->is_empty()) {
return;
}
ParallelCompactData& sd = PSParallelCompact::summary_data();
ParMarkBitMap* const bitmap = mark_bitmap();
HeapWord* const dp_addr = dense_prefix(space_id);
HeapWord* beg_addr = sp->bottom();
HeapWord* end_addr = sp->top();
assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
const size_t beg_region = sd.addr_to_region_idx(beg_addr);
const size_t dp_region = sd.addr_to_region_idx(dp_addr);
if (beg_region < dp_region) {
update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
}
// The destination of the first live object that starts in the region is one
// past the end of the partial object entering the region (if any).
HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
HeapWord* const new_top = _space_info[space_id].new_top();
assert(new_top >= dest_addr, "bad new_top value");
const size_t words = pointer_delta(new_top, dest_addr);
if (words > 0) {
ObjectStartArray* start_array = _space_info[space_id].start_array();
MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
ParMarkBitMap::IterationStatus status;
status = bitmap->iterate(&closure, dest_addr, end_addr);
assert(status == ParMarkBitMap::full, "iteration not complete");
assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
"live objects skipped because closure is full");
}
}
jlong PSParallelCompact::millis_since_last_gc() {
// We need a monotonically non-decreasing time in ms but
// os::javaTimeMillis() does not guarantee monotonicity.
jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
jlong ret_val = now - _time_of_last_gc;
// XXX See note in genCollectedHeap::millis_since_last_gc().
if (ret_val < 0) {
NOT_PRODUCT(log_warning(gc)("time warp: " JLONG_FORMAT, ret_val);)
return 0;
}
return ret_val;
}
void PSParallelCompact::reset_millis_since_last_gc() {
// We need a monotonically non-decreasing time in ms but
// os::javaTimeMillis() does not guarantee monotonicity.
_time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
}
ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
{
if (source() != destination()) {
DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
Copy::aligned_conjoint_words(source(), destination(), words_remaining());
}
update_state(words_remaining());
assert(is_full(), "sanity");
return ParMarkBitMap::full;
}
void MoveAndUpdateClosure::copy_partial_obj()
{
size_t words = words_remaining();
HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
if (end_addr < range_end) {
words = bitmap()->obj_size(source(), end_addr);
}
// This test is necessary; if omitted, the pointer updates to a partial object
// that crosses the dense prefix boundary could be overwritten.
if (source() != destination()) {
DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
Copy::aligned_conjoint_words(source(), destination(), words);
}
update_state(words);
}
ParMarkBitMapClosure::IterationStatus
MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
assert(destination() != NULL, "sanity");
assert(bitmap()->obj_size(addr) == words, "bad size");
_source = addr;
assert(PSParallelCompact::summary_data().calc_new_pointer(source(), compaction_manager()) ==
destination(), "wrong destination");
if (words > words_remaining()) {
return ParMarkBitMap::would_overflow;
}
// The start_array must be updated even if the object is not moving.
if (_start_array != NULL) {
_start_array->allocate_block(destination());
}
if (destination() != source()) {
DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
Copy::aligned_conjoint_words(source(), destination(), words);
}
oop moved_oop = (oop) destination();
compaction_manager()->update_contents(moved_oop);
assert(oopDesc::is_oop_or_null(moved_oop), "Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop));
update_state(words);
assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
}
UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
ParCompactionManager* cm,
PSParallelCompact::SpaceId space_id) :
ParMarkBitMapClosure(mbm, cm),
_space_id(space_id),
_start_array(PSParallelCompact::start_array(space_id))
{
}
// Updates the references in the object to their new values.
ParMarkBitMapClosure::IterationStatus
UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
do_addr(addr);
return ParMarkBitMap::incomplete;
}
FillClosure::FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :
ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),
_start_array(PSParallelCompact::start_array(space_id))
{
assert(space_id == PSParallelCompact::old_space_id,
"cannot use FillClosure in the young gen");
}
ParMarkBitMapClosure::IterationStatus
FillClosure::do_addr(HeapWord* addr, size_t size) {
CollectedHeap::fill_with_objects(addr, size);
HeapWord* const end = addr + size;
do {
_start_array->allocate_block(addr);
addr += oop(addr)->size();
} while (addr < end);
return ParMarkBitMap::incomplete;
}