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third-party-mirror/openjdk/jdk25u/refs/heads/master/./src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp
blob: 87c4943b2383377b5d1491b596cfbd4c88c5b8cf [file] [edit]
/*
* Copyright (c) 2016, 2021, Red Hat, Inc. All rights reserved.
* Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
* Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
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*/
#include "gc/shared/tlab_globals.hpp"
#include "gc/shenandoah/shenandoahAffiliation.hpp"
#include "gc/shenandoah/shenandoahFreeSet.hpp"
#include "gc/shenandoah/shenandoahHeap.inline.hpp"
#include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
#include "gc/shenandoah/shenandoahOldGeneration.hpp"
#include "gc/shenandoah/shenandoahSimpleBitMap.hpp"
#include "gc/shenandoah/shenandoahSimpleBitMap.inline.hpp"
#include "gc/shenandoah/shenandoahYoungGeneration.hpp"
#include "logging/logStream.hpp"
#include "memory/resourceArea.hpp"
#include "runtime/orderAccess.hpp"
static const char* partition_name(ShenandoahFreeSetPartitionId t) {
switch (t) {
case ShenandoahFreeSetPartitionId::NotFree: return "NotFree";
case ShenandoahFreeSetPartitionId::Mutator: return "Mutator";
case ShenandoahFreeSetPartitionId::Collector: return "Collector";
case ShenandoahFreeSetPartitionId::OldCollector: return "OldCollector";
default:
ShouldNotReachHere();
return "Unrecognized";
}
}
class ShenandoahLeftRightIterator {
private:
idx_t _idx;
idx_t _end;
ShenandoahRegionPartitions* _partitions;
ShenandoahFreeSetPartitionId _partition;
public:
explicit ShenandoahLeftRightIterator(ShenandoahRegionPartitions* partitions, ShenandoahFreeSetPartitionId partition, bool use_empty = false)
: _idx(0), _end(0), _partitions(partitions), _partition(partition) {
_idx = use_empty ? _partitions->leftmost_empty(_partition) : _partitions->leftmost(_partition);
_end = use_empty ? _partitions->rightmost_empty(_partition) : _partitions->rightmost(_partition);
}
bool has_next() const {
if (_idx <= _end) {
assert(_partitions->in_free_set(_partition, _idx), "Boundaries or find_last_set_bit failed: %zd", _idx);
return true;
}
return false;
}
idx_t current() const {
return _idx;
}
idx_t next() {
_idx = _partitions->find_index_of_next_available_region(_partition, _idx + 1);
return current();
}
};
class ShenandoahRightLeftIterator {
private:
idx_t _idx;
idx_t _end;
ShenandoahRegionPartitions* _partitions;
ShenandoahFreeSetPartitionId _partition;
public:
explicit ShenandoahRightLeftIterator(ShenandoahRegionPartitions* partitions, ShenandoahFreeSetPartitionId partition, bool use_empty = false)
: _idx(0), _end(0), _partitions(partitions), _partition(partition) {
_idx = use_empty ? _partitions->rightmost_empty(_partition) : _partitions->rightmost(_partition);
_end = use_empty ? _partitions->leftmost_empty(_partition) : _partitions->leftmost(_partition);
}
bool has_next() const {
if (_idx >= _end) {
assert(_partitions->in_free_set(_partition, _idx), "Boundaries or find_last_set_bit failed: %zd", _idx);
return true;
}
return false;
}
idx_t current() const {
return _idx;
}
idx_t next() {
_idx = _partitions->find_index_of_previous_available_region(_partition, _idx - 1);
return current();
}
};
#ifndef PRODUCT
void ShenandoahRegionPartitions::dump_bitmap() const {
log_debug(gc)("Mutator range [%zd, %zd], Collector range [%zd, %zd"
"], Old Collector range [%zd, %zd]",
_leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)],
_rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)],
_leftmosts[int(ShenandoahFreeSetPartitionId::Collector)],
_rightmosts[int(ShenandoahFreeSetPartitionId::Collector)],
_leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)],
_rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)]);
log_debug(gc)("Empty Mutator range [%zd, %zd"
"], Empty Collector range [%zd, %zd"
"], Empty Old Collecto range [%zd, %zd]",
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)],
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)],
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)]);
log_debug(gc)("%6s: %18s %18s %18s %18s", "index", "Mutator Bits", "Collector Bits", "Old Collector Bits", "NotFree Bits");
dump_bitmap_range(0, _max-1);
}
void ShenandoahRegionPartitions::dump_bitmap_range(idx_t start_region_idx, idx_t end_region_idx) const {
assert((start_region_idx >= 0) && (start_region_idx < (idx_t) _max), "precondition");
assert((end_region_idx >= 0) && (end_region_idx < (idx_t) _max), "precondition");
idx_t aligned_start = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].aligned_index(start_region_idx);
idx_t aligned_end = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].aligned_index(end_region_idx);
idx_t alignment = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].alignment();
while (aligned_start <= aligned_end) {
dump_bitmap_row(aligned_start);
aligned_start += alignment;
}
}
void ShenandoahRegionPartitions::dump_bitmap_row(idx_t region_idx) const {
assert((region_idx >= 0) && (region_idx < (idx_t) _max), "precondition");
idx_t aligned_idx = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].aligned_index(region_idx);
uintx mutator_bits = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].bits_at(aligned_idx);
uintx collector_bits = _membership[int(ShenandoahFreeSetPartitionId::Collector)].bits_at(aligned_idx);
uintx old_collector_bits = _membership[int(ShenandoahFreeSetPartitionId::OldCollector)].bits_at(aligned_idx);
uintx free_bits = mutator_bits | collector_bits | old_collector_bits;
uintx notfree_bits = ~free_bits;
log_debug(gc)("%6zd : " SIZE_FORMAT_X_0 " 0x" SIZE_FORMAT_X_0 " 0x" SIZE_FORMAT_X_0 " 0x" SIZE_FORMAT_X_0,
aligned_idx, mutator_bits, collector_bits, old_collector_bits, notfree_bits);
}
#endif
ShenandoahRegionPartitions::ShenandoahRegionPartitions(size_t max_regions, ShenandoahFreeSet* free_set) :
_max(max_regions),
_region_size_bytes(ShenandoahHeapRegion::region_size_bytes()),
_free_set(free_set),
_membership{ ShenandoahSimpleBitMap(max_regions), ShenandoahSimpleBitMap(max_regions) , ShenandoahSimpleBitMap(max_regions) }
{
make_all_regions_unavailable();
}
inline bool ShenandoahFreeSet::can_allocate_from(ShenandoahHeapRegion *r) const {
return r->is_empty() || (r->is_trash() && !_heap->is_concurrent_weak_root_in_progress());
}
inline bool ShenandoahFreeSet::can_allocate_from(size_t idx) const {
ShenandoahHeapRegion* r = _heap->get_region(idx);
return can_allocate_from(r);
}
inline size_t ShenandoahFreeSet::alloc_capacity(ShenandoahHeapRegion *r) const {
if (r->is_trash()) {
// This would be recycled on allocation path
return ShenandoahHeapRegion::region_size_bytes();
} else {
return r->free();
}
}
inline size_t ShenandoahFreeSet::alloc_capacity(size_t idx) const {
ShenandoahHeapRegion* r = _heap->get_region(idx);
return alloc_capacity(r);
}
inline bool ShenandoahFreeSet::has_alloc_capacity(ShenandoahHeapRegion *r) const {
return alloc_capacity(r) > 0;
}
inline idx_t ShenandoahRegionPartitions::leftmost(ShenandoahFreeSetPartitionId which_partition) const {
assert (which_partition < NumPartitions, "selected free partition must be valid");
idx_t idx = _leftmosts[int(which_partition)];
if (idx >= _max) {
return _max;
} else {
// Cannot assert that membership[which_partition.is_set(idx) because this helper method may be used
// to query the original value of leftmost when leftmost must be adjusted because the interval representing
// which_partition is shrinking after the region that used to be leftmost is retired.
return idx;
}
}
inline idx_t ShenandoahRegionPartitions::rightmost(ShenandoahFreeSetPartitionId which_partition) const {
assert (which_partition < NumPartitions, "selected free partition must be valid");
idx_t idx = _rightmosts[int(which_partition)];
// Cannot assert that membership[which_partition.is_set(idx) because this helper method may be used
// to query the original value of leftmost when leftmost must be adjusted because the interval representing
// which_partition is shrinking after the region that used to be leftmost is retired.
return idx;
}
void ShenandoahRegionPartitions::make_all_regions_unavailable() {
shenandoah_assert_heaplocked();
for (size_t partition_id = 0; partition_id < IntNumPartitions; partition_id++) {
_membership[partition_id].clear_all();
_leftmosts[partition_id] = _max;
_rightmosts[partition_id] = -1;
_leftmosts_empty[partition_id] = _max;
_rightmosts_empty[partition_id] = -1;;
_capacity[partition_id] = 0;
_used[partition_id] = 0;
_available[partition_id] = FreeSetUnderConstruction;
}
_region_counts[int(ShenandoahFreeSetPartitionId::Mutator)] = _region_counts[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
}
void ShenandoahRegionPartitions::establish_mutator_intervals(idx_t mutator_leftmost, idx_t mutator_rightmost,
idx_t mutator_leftmost_empty, idx_t mutator_rightmost_empty,
size_t mutator_region_count, size_t mutator_used) {
shenandoah_assert_heaplocked();
_leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_leftmost;
_rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_rightmost;
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_leftmost_empty;
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_rightmost_empty;
_region_counts[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_region_count;
_used[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_used;
_capacity[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_region_count * _region_size_bytes;
_available[int(ShenandoahFreeSetPartitionId::Mutator)] =
_capacity[int(ShenandoahFreeSetPartitionId::Mutator)] - _used[int(ShenandoahFreeSetPartitionId::Mutator)];
_leftmosts[int(ShenandoahFreeSetPartitionId::Collector)] = _max;
_rightmosts[int(ShenandoahFreeSetPartitionId::Collector)] = -1;
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)] = _max;
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)] = -1;
_region_counts[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
_used[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
_capacity[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
_available[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
}
void ShenandoahRegionPartitions::establish_old_collector_intervals(idx_t old_collector_leftmost, idx_t old_collector_rightmost,
idx_t old_collector_leftmost_empty,
idx_t old_collector_rightmost_empty,
size_t old_collector_region_count, size_t old_collector_used) {
shenandoah_assert_heaplocked();
_leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_leftmost;
_rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_rightmost;
_leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_leftmost_empty;
_rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_rightmost_empty;
_region_counts[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_region_count;
_used[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_used;
_capacity[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_region_count * _region_size_bytes;
_available[int(ShenandoahFreeSetPartitionId::OldCollector)] =
_capacity[int(ShenandoahFreeSetPartitionId::OldCollector)] - _used[int(ShenandoahFreeSetPartitionId::OldCollector)];
}
void ShenandoahRegionPartitions::increase_used(ShenandoahFreeSetPartitionId which_partition, size_t bytes) {
shenandoah_assert_heaplocked();
assert (which_partition < NumPartitions, "Partition must be valid");
_used[int(which_partition)] += bytes;
_available[int(which_partition)] -= bytes;
assert (_used[int(which_partition)] <= _capacity[int(which_partition)],
"Must not use (%zu) more than capacity (%zu) after increase by %zu",
_used[int(which_partition)], _capacity[int(which_partition)], bytes);
}
inline void ShenandoahRegionPartitions::shrink_interval_if_range_modifies_either_boundary(
ShenandoahFreeSetPartitionId partition, idx_t low_idx, idx_t high_idx) {
assert((low_idx <= high_idx) && (low_idx >= 0) && (high_idx < _max), "Range must span legal index values");
if (low_idx == leftmost(partition)) {
assert (!_membership[int(partition)].is_set(low_idx), "Do not shrink interval if region not removed");
if (high_idx + 1 == _max) {
_leftmosts[int(partition)] = _max;
} else {
_leftmosts[int(partition)] = find_index_of_next_available_region(partition, high_idx + 1);
}
if (_leftmosts_empty[int(partition)] < _leftmosts[int(partition)]) {
// This gets us closer to where we need to be; we'll scan further when leftmosts_empty is requested.
_leftmosts_empty[int(partition)] = _leftmosts[int(partition)];
}
}
if (high_idx == _rightmosts[int(partition)]) {
assert (!_membership[int(partition)].is_set(high_idx), "Do not shrink interval if region not removed");
if (low_idx == 0) {
_rightmosts[int(partition)] = -1;
} else {
_rightmosts[int(partition)] = find_index_of_previous_available_region(partition, low_idx - 1);
}
if (_rightmosts_empty[int(partition)] > _rightmosts[int(partition)]) {
// This gets us closer to where we need to be; we'll scan further when rightmosts_empty is requested.
_rightmosts_empty[int(partition)] = _rightmosts[int(partition)];
}
}
if (_leftmosts[int(partition)] > _rightmosts[int(partition)]) {
_leftmosts[int(partition)] = _max;
_rightmosts[int(partition)] = -1;
_leftmosts_empty[int(partition)] = _max;
_rightmosts_empty[int(partition)] = -1;
}
}
inline void ShenandoahRegionPartitions::shrink_interval_if_boundary_modified(ShenandoahFreeSetPartitionId partition, idx_t idx) {
shrink_interval_if_range_modifies_either_boundary(partition, idx, idx);
}
inline void ShenandoahRegionPartitions::expand_interval_if_boundary_modified(ShenandoahFreeSetPartitionId partition,
idx_t idx, size_t region_available) {
if (_leftmosts[int(partition)] > idx) {
_leftmosts[int(partition)] = idx;
}
if (_rightmosts[int(partition)] < idx) {
_rightmosts[int(partition)] = idx;
}
if (region_available == _region_size_bytes) {
if (_leftmosts_empty[int(partition)] > idx) {
_leftmosts_empty[int(partition)] = idx;
}
if (_rightmosts_empty[int(partition)] < idx) {
_rightmosts_empty[int(partition)] = idx;
}
}
}
void ShenandoahRegionPartitions::retire_range_from_partition(
ShenandoahFreeSetPartitionId partition, idx_t low_idx, idx_t high_idx) {
// Note: we may remove from free partition even if region is not entirely full, such as when available < PLAB::min_size()
assert ((low_idx < _max) && (high_idx < _max), "Both indices are sane: %zu and %zu < %zu",
low_idx, high_idx, _max);
assert (partition < NumPartitions, "Cannot remove from free partitions if not already free");
for (idx_t idx = low_idx; idx <= high_idx; idx++) {
assert (in_free_set(partition, idx), "Must be in partition to remove from partition");
_membership[int(partition)].clear_bit(idx);
}
_region_counts[int(partition)] -= high_idx + 1 - low_idx;
shrink_interval_if_range_modifies_either_boundary(partition, low_idx, high_idx);
}
void ShenandoahRegionPartitions::retire_from_partition(ShenandoahFreeSetPartitionId partition, idx_t idx, size_t used_bytes) {
// Note: we may remove from free partition even if region is not entirely full, such as when available < PLAB::min_size()
assert (idx < _max, "index is sane: %zu < %zu", idx, _max);
assert (partition < NumPartitions, "Cannot remove from free partitions if not already free");
assert (in_free_set(partition, idx), "Must be in partition to remove from partition");
if (used_bytes < _region_size_bytes) {
// Count the alignment pad remnant of memory as used when we retire this region
increase_used(partition, _region_size_bytes - used_bytes);
}
_membership[int(partition)].clear_bit(idx);
shrink_interval_if_boundary_modified(partition, idx);
_region_counts[int(partition)]--;
}
void ShenandoahRegionPartitions::make_free(idx_t idx, ShenandoahFreeSetPartitionId which_partition, size_t available) {
shenandoah_assert_heaplocked();
assert (idx < _max, "index is sane: %zu < %zu", idx, _max);
assert (membership(idx) == ShenandoahFreeSetPartitionId::NotFree, "Cannot make free if already free");
assert (which_partition < NumPartitions, "selected free partition must be valid");
assert (available <= _region_size_bytes, "Available cannot exceed region size");
_membership[int(which_partition)].set_bit(idx);
_capacity[int(which_partition)] += _region_size_bytes;
_used[int(which_partition)] += _region_size_bytes - available;
_available[int(which_partition)] += available;
expand_interval_if_boundary_modified(which_partition, idx, available);
_region_counts[int(which_partition)]++;
}
bool ShenandoahRegionPartitions::is_mutator_partition(ShenandoahFreeSetPartitionId p) {
return (p == ShenandoahFreeSetPartitionId::Mutator);
}
bool ShenandoahRegionPartitions::is_young_collector_partition(ShenandoahFreeSetPartitionId p) {
return (p == ShenandoahFreeSetPartitionId::Collector);
}
bool ShenandoahRegionPartitions::is_old_collector_partition(ShenandoahFreeSetPartitionId p) {
return (p == ShenandoahFreeSetPartitionId::OldCollector);
}
bool ShenandoahRegionPartitions::available_implies_empty(size_t available_in_region) {
return (available_in_region == _region_size_bytes);
}
void ShenandoahRegionPartitions::move_from_partition_to_partition(idx_t idx, ShenandoahFreeSetPartitionId orig_partition,
ShenandoahFreeSetPartitionId new_partition, size_t available) {
ShenandoahHeapRegion* r = ShenandoahHeap::heap()->get_region(idx);
shenandoah_assert_heaplocked();
assert (idx < _max, "index is sane: %zu < %zu", idx, _max);
assert (orig_partition < NumPartitions, "Original partition must be valid");
assert (new_partition < NumPartitions, "New partition must be valid");
assert (available <= _region_size_bytes, "Available cannot exceed region size");
assert (_membership[int(orig_partition)].is_set(idx), "Cannot move from partition unless in partition");
assert ((r != nullptr) && ((r->is_trash() && (available == _region_size_bytes)) ||
(r->used() + available == _region_size_bytes)),
"Used: %zu + available: %zu should equal region size: %zu",
ShenandoahHeap::heap()->get_region(idx)->used(), available, _region_size_bytes);
// Expected transitions:
// During rebuild: Mutator => Collector
// Mutator empty => Collector
// Mutator empty => OldCollector
// During flip_to_gc: Mutator empty => Collector
// Mutator empty => OldCollector
// At start of update refs: Collector => Mutator
// OldCollector Empty => Mutator
assert ((is_mutator_partition(orig_partition) && is_young_collector_partition(new_partition)) ||
(is_mutator_partition(orig_partition) &&
available_implies_empty(available) && is_old_collector_partition(new_partition)) ||
(is_young_collector_partition(orig_partition) && is_mutator_partition(new_partition)) ||
(is_old_collector_partition(orig_partition)
&& available_implies_empty(available) && is_mutator_partition(new_partition)),
"Unexpected movement between partitions, available: %zu, _region_size_bytes: %zu"
", orig_partition: %s, new_partition: %s",
available, _region_size_bytes, partition_name(orig_partition), partition_name(new_partition));
size_t used = _region_size_bytes - available;
assert (_used[int(orig_partition)] >= used,
"Orig partition used: %zu must exceed moved used: %zu within region %zd",
_used[int(orig_partition)], used, idx);
_membership[int(orig_partition)].clear_bit(idx);
_membership[int(new_partition)].set_bit(idx);
_capacity[int(orig_partition)] -= _region_size_bytes;
_used[int(orig_partition)] -= used;
_available[int(orig_partition)] -= available;
shrink_interval_if_boundary_modified(orig_partition, idx);
_capacity[int(new_partition)] += _region_size_bytes;;
_used[int(new_partition)] += used;
_available[int(new_partition)] += available;
expand_interval_if_boundary_modified(new_partition, idx, available);
_region_counts[int(orig_partition)]--;
_region_counts[int(new_partition)]++;
}
const char* ShenandoahRegionPartitions::partition_membership_name(idx_t idx) const {
return partition_name(membership(idx));
}
inline ShenandoahFreeSetPartitionId ShenandoahRegionPartitions::membership(idx_t idx) const {
assert (idx < _max, "index is sane: %zu < %zu", idx, _max);
ShenandoahFreeSetPartitionId result = ShenandoahFreeSetPartitionId::NotFree;
for (uint partition_id = 0; partition_id < UIntNumPartitions; partition_id++) {
if (_membership[partition_id].is_set(idx)) {
assert(result == ShenandoahFreeSetPartitionId::NotFree, "Region should reside in only one partition");
result = (ShenandoahFreeSetPartitionId) partition_id;
}
}
return result;
}
#ifdef ASSERT
inline bool ShenandoahRegionPartitions::partition_id_matches(idx_t idx, ShenandoahFreeSetPartitionId test_partition) const {
assert (idx < _max, "index is sane: %zu < %zu", idx, _max);
assert (test_partition < ShenandoahFreeSetPartitionId::NotFree, "must be a valid partition");
return membership(idx) == test_partition;
}
#endif
inline bool ShenandoahRegionPartitions::is_empty(ShenandoahFreeSetPartitionId which_partition) const {
assert (which_partition < NumPartitions, "selected free partition must be valid");
return (leftmost(which_partition) > rightmost(which_partition));
}
inline idx_t ShenandoahRegionPartitions::find_index_of_next_available_region(
ShenandoahFreeSetPartitionId which_partition, idx_t start_index) const {
idx_t rightmost_idx = rightmost(which_partition);
idx_t leftmost_idx = leftmost(which_partition);
if ((rightmost_idx < leftmost_idx) || (start_index > rightmost_idx)) return _max;
if (start_index < leftmost_idx) {
start_index = leftmost_idx;
}
idx_t result = _membership[int(which_partition)].find_first_set_bit(start_index, rightmost_idx + 1);
if (result > rightmost_idx) {
result = _max;
}
assert (result >= start_index, "Requires progress");
return result;
}
inline idx_t ShenandoahRegionPartitions::find_index_of_previous_available_region(
ShenandoahFreeSetPartitionId which_partition, idx_t last_index) const {
idx_t rightmost_idx = rightmost(which_partition);
idx_t leftmost_idx = leftmost(which_partition);
// if (leftmost_idx == max) then (last_index < leftmost_idx)
if (last_index < leftmost_idx) return -1;
if (last_index > rightmost_idx) {
last_index = rightmost_idx;
}
idx_t result = _membership[int(which_partition)].find_last_set_bit(-1, last_index);
if (result < leftmost_idx) {
result = -1;
}
assert (result <= last_index, "Requires progress");
return result;
}
inline idx_t ShenandoahRegionPartitions::find_index_of_next_available_cluster_of_regions(
ShenandoahFreeSetPartitionId which_partition, idx_t start_index, size_t cluster_size) const {
idx_t rightmost_idx = rightmost(which_partition);
idx_t leftmost_idx = leftmost(which_partition);
if ((rightmost_idx < leftmost_idx) || (start_index > rightmost_idx)) return _max;
idx_t result = _membership[int(which_partition)].find_first_consecutive_set_bits(start_index, rightmost_idx + 1, cluster_size);
if (result > rightmost_idx) {
result = _max;
}
assert (result >= start_index, "Requires progress");
return result;
}
inline idx_t ShenandoahRegionPartitions::find_index_of_previous_available_cluster_of_regions(
ShenandoahFreeSetPartitionId which_partition, idx_t last_index, size_t cluster_size) const {
idx_t leftmost_idx = leftmost(which_partition);
// if (leftmost_idx == max) then (last_index < leftmost_idx)
if (last_index < leftmost_idx) return -1;
idx_t result = _membership[int(which_partition)].find_last_consecutive_set_bits(leftmost_idx - 1, last_index, cluster_size);
if (result <= leftmost_idx) {
result = -1;
}
assert (result <= last_index, "Requires progress");
return result;
}
idx_t ShenandoahRegionPartitions::leftmost_empty(ShenandoahFreeSetPartitionId which_partition) {
assert (which_partition < NumPartitions, "selected free partition must be valid");
idx_t max_regions = _max;
if (_leftmosts_empty[int(which_partition)] == _max) {
return _max;
}
for (idx_t idx = find_index_of_next_available_region(which_partition, _leftmosts_empty[int(which_partition)]);
idx < max_regions; ) {
assert(in_free_set(which_partition, idx), "Boundaries or find_last_set_bit failed: %zd", idx);
if (_free_set->alloc_capacity(idx) == _region_size_bytes) {
_leftmosts_empty[int(which_partition)] = idx;
return idx;
}
idx = find_index_of_next_available_region(which_partition, idx + 1);
}
_leftmosts_empty[int(which_partition)] = _max;
_rightmosts_empty[int(which_partition)] = -1;
return _max;
}
idx_t ShenandoahRegionPartitions::rightmost_empty(ShenandoahFreeSetPartitionId which_partition) {
assert (which_partition < NumPartitions, "selected free partition must be valid");
if (_rightmosts_empty[int(which_partition)] < 0) {
return -1;
}
for (idx_t idx = find_index_of_previous_available_region(which_partition, _rightmosts_empty[int(which_partition)]);
idx >= 0; ) {
assert(in_free_set(which_partition, idx), "Boundaries or find_last_set_bit failed: %zd", idx);
if (_free_set->alloc_capacity(idx) == _region_size_bytes) {
_rightmosts_empty[int(which_partition)] = idx;
return idx;
}
idx = find_index_of_previous_available_region(which_partition, idx - 1);
}
_leftmosts_empty[int(which_partition)] = _max;
_rightmosts_empty[int(which_partition)] = -1;
return -1;
}
#ifdef ASSERT
void ShenandoahRegionPartitions::assert_bounds() {
idx_t leftmosts[UIntNumPartitions];
idx_t rightmosts[UIntNumPartitions];
idx_t empty_leftmosts[UIntNumPartitions];
idx_t empty_rightmosts[UIntNumPartitions];
for (uint i = 0; i < UIntNumPartitions; i++) {
leftmosts[i] = _max;
empty_leftmosts[i] = _max;
rightmosts[i] = -1;
empty_rightmosts[i] = -1;
}
for (idx_t i = 0; i < _max; i++) {
ShenandoahFreeSetPartitionId partition = membership(i);
switch (partition) {
case ShenandoahFreeSetPartitionId::NotFree:
break;
case ShenandoahFreeSetPartitionId::Mutator:
case ShenandoahFreeSetPartitionId::Collector:
case ShenandoahFreeSetPartitionId::OldCollector:
{
size_t capacity = _free_set->alloc_capacity(i);
bool is_empty = (capacity == _region_size_bytes);
assert(capacity > 0, "free regions must have allocation capacity");
if (i < leftmosts[int(partition)]) {
leftmosts[int(partition)] = i;
}
if (is_empty && (i < empty_leftmosts[int(partition)])) {
empty_leftmosts[int(partition)] = i;
}
if (i > rightmosts[int(partition)]) {
rightmosts[int(partition)] = i;
}
if (is_empty && (i > empty_rightmosts[int(partition)])) {
empty_rightmosts[int(partition)] = i;
}
break;
}
default:
ShouldNotReachHere();
}
}
// Performance invariants. Failing these would not break the free partition, but performance would suffer.
assert (leftmost(ShenandoahFreeSetPartitionId::Mutator) <= _max,
"leftmost in bounds: %zd < %zd", leftmost(ShenandoahFreeSetPartitionId::Mutator), _max);
assert (rightmost(ShenandoahFreeSetPartitionId::Mutator) < _max,
"rightmost in bounds: %zd < %zd", rightmost(ShenandoahFreeSetPartitionId::Mutator), _max);
assert (leftmost(ShenandoahFreeSetPartitionId::Mutator) == _max
|| partition_id_matches(leftmost(ShenandoahFreeSetPartitionId::Mutator), ShenandoahFreeSetPartitionId::Mutator),
"leftmost region should be free: %zd", leftmost(ShenandoahFreeSetPartitionId::Mutator));
assert (leftmost(ShenandoahFreeSetPartitionId::Mutator) == _max
|| partition_id_matches(rightmost(ShenandoahFreeSetPartitionId::Mutator), ShenandoahFreeSetPartitionId::Mutator),
"rightmost region should be free: %zd", rightmost(ShenandoahFreeSetPartitionId::Mutator));
// If Mutator partition is empty, leftmosts will both equal max, rightmosts will both equal zero.
// Likewise for empty region partitions.
idx_t beg_off = leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
idx_t end_off = rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
assert (beg_off >= leftmost(ShenandoahFreeSetPartitionId::Mutator),
"free regions before the leftmost: %zd, bound %zd",
beg_off, leftmost(ShenandoahFreeSetPartitionId::Mutator));
assert (end_off <= rightmost(ShenandoahFreeSetPartitionId::Mutator),
"free regions past the rightmost: %zd, bound %zd",
end_off, rightmost(ShenandoahFreeSetPartitionId::Mutator));
beg_off = empty_leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
end_off = empty_rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
assert (beg_off >= leftmost_empty(ShenandoahFreeSetPartitionId::Mutator),
"free empty regions before the leftmost: %zd, bound %zd",
beg_off, leftmost_empty(ShenandoahFreeSetPartitionId::Mutator));
assert (end_off <= rightmost_empty(ShenandoahFreeSetPartitionId::Mutator),
"free empty regions past the rightmost: %zd, bound %zd",
end_off, rightmost_empty(ShenandoahFreeSetPartitionId::Mutator));
// Performance invariants. Failing these would not break the free partition, but performance would suffer.
assert (leftmost(ShenandoahFreeSetPartitionId::Collector) <= _max, "leftmost in bounds: %zd < %zd",
leftmost(ShenandoahFreeSetPartitionId::Collector), _max);
assert (rightmost(ShenandoahFreeSetPartitionId::Collector) < _max, "rightmost in bounds: %zd < %zd",
rightmost(ShenandoahFreeSetPartitionId::Collector), _max);
assert (leftmost(ShenandoahFreeSetPartitionId::Collector) == _max
|| partition_id_matches(leftmost(ShenandoahFreeSetPartitionId::Collector), ShenandoahFreeSetPartitionId::Collector),
"leftmost region should be free: %zd", leftmost(ShenandoahFreeSetPartitionId::Collector));
assert (leftmost(ShenandoahFreeSetPartitionId::Collector) == _max
|| partition_id_matches(rightmost(ShenandoahFreeSetPartitionId::Collector), ShenandoahFreeSetPartitionId::Collector),
"rightmost region should be free: %zd", rightmost(ShenandoahFreeSetPartitionId::Collector));
// If Collector partition is empty, leftmosts will both equal max, rightmosts will both equal zero.
// Likewise for empty region partitions.
beg_off = leftmosts[int(ShenandoahFreeSetPartitionId::Collector)];
end_off = rightmosts[int(ShenandoahFreeSetPartitionId::Collector)];
assert (beg_off >= leftmost(ShenandoahFreeSetPartitionId::Collector),
"free regions before the leftmost: %zd, bound %zd",
beg_off, leftmost(ShenandoahFreeSetPartitionId::Collector));
assert (end_off <= rightmost(ShenandoahFreeSetPartitionId::Collector),
"free regions past the rightmost: %zd, bound %zd",
end_off, rightmost(ShenandoahFreeSetPartitionId::Collector));
beg_off = empty_leftmosts[int(ShenandoahFreeSetPartitionId::Collector)];
end_off = empty_rightmosts[int(ShenandoahFreeSetPartitionId::Collector)];
assert (beg_off >= _leftmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
"free empty regions before the leftmost: %zd, bound %zd",
beg_off, leftmost_empty(ShenandoahFreeSetPartitionId::Collector));
assert (end_off <= _rightmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
"free empty regions past the rightmost: %zd, bound %zd",
end_off, rightmost_empty(ShenandoahFreeSetPartitionId::Collector));
// Performance invariants. Failing these would not break the free partition, but performance would suffer.
assert (leftmost(ShenandoahFreeSetPartitionId::OldCollector) <= _max, "leftmost in bounds: %zd < %zd",
leftmost(ShenandoahFreeSetPartitionId::OldCollector), _max);
assert (rightmost(ShenandoahFreeSetPartitionId::OldCollector) < _max, "rightmost in bounds: %zd < %zd",
rightmost(ShenandoahFreeSetPartitionId::OldCollector), _max);
assert (leftmost(ShenandoahFreeSetPartitionId::OldCollector) == _max
|| partition_id_matches(leftmost(ShenandoahFreeSetPartitionId::OldCollector),
ShenandoahFreeSetPartitionId::OldCollector),
"leftmost region should be free: %zd", leftmost(ShenandoahFreeSetPartitionId::OldCollector));
assert (leftmost(ShenandoahFreeSetPartitionId::OldCollector) == _max
|| partition_id_matches(rightmost(ShenandoahFreeSetPartitionId::OldCollector),
ShenandoahFreeSetPartitionId::OldCollector),
"rightmost region should be free: %zd", rightmost(ShenandoahFreeSetPartitionId::OldCollector));
// If OldCollector partition is empty, leftmosts will both equal max, rightmosts will both equal zero.
// Likewise for empty region partitions.
beg_off = leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
end_off = rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
assert (beg_off >= leftmost(ShenandoahFreeSetPartitionId::OldCollector),
"free regions before the leftmost: %zd, bound %zd",
beg_off, leftmost(ShenandoahFreeSetPartitionId::OldCollector));
assert (end_off <= rightmost(ShenandoahFreeSetPartitionId::OldCollector),
"free regions past the rightmost: %zd, bound %zd",
end_off, rightmost(ShenandoahFreeSetPartitionId::OldCollector));
beg_off = empty_leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
end_off = empty_rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
assert (beg_off >= _leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
"free empty regions before the leftmost: %zd, bound %zd",
beg_off, leftmost_empty(ShenandoahFreeSetPartitionId::OldCollector));
assert (end_off <= _rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
"free empty regions past the rightmost: %zd, bound %zd",
end_off, rightmost_empty(ShenandoahFreeSetPartitionId::OldCollector));
}
#endif
ShenandoahFreeSet::ShenandoahFreeSet(ShenandoahHeap* heap, size_t max_regions) :
_heap(heap),
_partitions(max_regions, this),
_alloc_bias_weight(0)
{
clear_internal();
}
void ShenandoahFreeSet::add_promoted_in_place_region_to_old_collector(ShenandoahHeapRegion* region) {
shenandoah_assert_heaplocked();
size_t plab_min_size_in_bytes = ShenandoahGenerationalHeap::heap()->plab_min_size() * HeapWordSize;
size_t idx = region->index();
size_t capacity = alloc_capacity(region);
assert(_partitions.membership(idx) == ShenandoahFreeSetPartitionId::NotFree,
"Regions promoted in place should have been excluded from Mutator partition");
if (capacity >= plab_min_size_in_bytes) {
_partitions.make_free(idx, ShenandoahFreeSetPartitionId::OldCollector, capacity);
_heap->old_generation()->augment_promoted_reserve(capacity);
}
}
HeapWord* ShenandoahFreeSet::allocate_from_partition_with_affiliation(ShenandoahAffiliation affiliation,
ShenandoahAllocRequest& req, bool& in_new_region) {
shenandoah_assert_heaplocked();
ShenandoahFreeSetPartitionId which_partition = req.is_old()? ShenandoahFreeSetPartitionId::OldCollector: ShenandoahFreeSetPartitionId::Collector;
if (_partitions.alloc_from_left_bias(which_partition)) {
ShenandoahLeftRightIterator iterator(&_partitions, which_partition, affiliation == ShenandoahAffiliation::FREE);
return allocate_with_affiliation(iterator, affiliation, req, in_new_region);
} else {
ShenandoahRightLeftIterator iterator(&_partitions, which_partition, affiliation == ShenandoahAffiliation::FREE);
return allocate_with_affiliation(iterator, affiliation, req, in_new_region);
}
}
template<typename Iter>
HeapWord* ShenandoahFreeSet::allocate_with_affiliation(Iter& iterator, ShenandoahAffiliation affiliation, ShenandoahAllocRequest& req, bool& in_new_region) {
for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
ShenandoahHeapRegion* r = _heap->get_region(idx);
if (r->affiliation() == affiliation) {
HeapWord* result = try_allocate_in(r, req, in_new_region);
if (result != nullptr) {
return result;
}
}
}
log_debug(gc, free)("Could not allocate collector region with affiliation: %s for request " PTR_FORMAT,
shenandoah_affiliation_name(affiliation), p2i(&req));
return nullptr;
}
HeapWord* ShenandoahFreeSet::allocate_single(ShenandoahAllocRequest& req, bool& in_new_region) {
shenandoah_assert_heaplocked();
// Scan the bitmap looking for a first fit.
//
// Leftmost and rightmost bounds provide enough caching to walk bitmap efficiently. Normally,
// we would find the region to allocate at right away.
//
// Allocations are biased: GC allocations are taken from the high end of the heap. Regular (and TLAB)
// mutator allocations are taken from the middle of heap, below the memory reserved for Collector.
// Humongous mutator allocations are taken from the bottom of the heap.
//
// Free set maintains mutator and collector partitions. Normally, each allocates only from its partition,
// except in special cases when the collector steals regions from the mutator partition.
// Overwrite with non-zero (non-null) values only if necessary for allocation bookkeeping.
switch (req.type()) {
case ShenandoahAllocRequest::_alloc_tlab:
case ShenandoahAllocRequest::_alloc_shared:
case ShenandoahAllocRequest::_alloc_cds:
return allocate_for_mutator(req, in_new_region);
case ShenandoahAllocRequest::_alloc_gclab:
case ShenandoahAllocRequest::_alloc_plab:
case ShenandoahAllocRequest::_alloc_shared_gc:
return allocate_for_collector(req, in_new_region);
default:
ShouldNotReachHere();
}
return nullptr;
}
HeapWord* ShenandoahFreeSet::allocate_for_mutator(ShenandoahAllocRequest &req, bool &in_new_region) {
update_allocation_bias();
if (_partitions.is_empty(ShenandoahFreeSetPartitionId::Mutator)) {
// There is no recovery. Mutator does not touch collector view at all.
return nullptr;
}
// Try to allocate in the mutator view
if (_partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Mutator)) {
// Allocate from low to high memory. This keeps the range of fully empty regions more tightly packed.
// Note that the most recently allocated regions tend not to be evacuated in a given GC cycle. So this
// tends to accumulate "fragmented" uncollected regions in high memory.
ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
return allocate_from_regions(iterator, req, in_new_region);
}
// Allocate from high to low memory. This preserves low memory for humongous allocations.
ShenandoahRightLeftIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
return allocate_from_regions(iterator, req, in_new_region);
}
void ShenandoahFreeSet::update_allocation_bias() {
if (_alloc_bias_weight-- <= 0) {
// We have observed that regions not collected in previous GC cycle tend to congregate at one end or the other
// of the heap. Typically, these are the more recently engaged regions and the objects in these regions have not
// yet had a chance to die (and/or are treated as floating garbage). If we use the same allocation bias on each
// GC pass, these "most recently" engaged regions for GC pass N will also be the "most recently" engaged regions
// for GC pass N+1, and the relatively large amount of live data and/or floating garbage introduced
// during the most recent GC pass may once again prevent the region from being collected. We have found that
// alternating the allocation behavior between GC passes improves evacuation performance by 3-7% on certain
// benchmarks. In the best case, this has the effect of consuming these partially consumed regions before
// the start of the next mark cycle so all of their garbage can be efficiently reclaimed.
//
// First, finish consuming regions that are already partially consumed so as to more tightly limit ranges of
// available regions. Other potential benefits:
// 1. Eventual collection set has fewer regions because we have packed newly allocated objects into fewer regions
// 2. We preserve the "empty" regions longer into the GC cycle, reducing likelihood of allocation failures
// late in the GC cycle.
idx_t non_empty_on_left = (_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Mutator)
- _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator));
idx_t non_empty_on_right = (_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator)
- _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Mutator));
_partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Mutator, (non_empty_on_right < non_empty_on_left));
_alloc_bias_weight = INITIAL_ALLOC_BIAS_WEIGHT;
}
}
template<typename Iter>
HeapWord* ShenandoahFreeSet::allocate_from_regions(Iter& iterator, ShenandoahAllocRequest &req, bool &in_new_region) {
for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
ShenandoahHeapRegion* r = _heap->get_region(idx);
size_t min_size = (req.type() == ShenandoahAllocRequest::_alloc_tlab) ? req.min_size() : req.size();
if (alloc_capacity(r) >= min_size * HeapWordSize) {
HeapWord* result = try_allocate_in(r, req, in_new_region);
if (result != nullptr) {
return result;
}
}
}
return nullptr;
}
HeapWord* ShenandoahFreeSet::allocate_for_collector(ShenandoahAllocRequest &req, bool &in_new_region) {
// Fast-path: try to allocate in the collector view first
HeapWord* result;
result = allocate_from_partition_with_affiliation(req.affiliation(), req, in_new_region);
if (result != nullptr) {
return result;
}
bool allow_new_region = can_allocate_in_new_region(req);
if (allow_new_region) {
// Try a free region that is dedicated to GC allocations.
result = allocate_from_partition_with_affiliation(ShenandoahAffiliation::FREE, req, in_new_region);
if (result != nullptr) {
return result;
}
}
// No dice. Can we borrow space from mutator view?
if (!ShenandoahEvacReserveOverflow) {
return nullptr;
}
if (!allow_new_region && req.is_old() && (_heap->young_generation()->free_unaffiliated_regions() > 0)) {
// This allows us to flip a mutator region to old_collector
allow_new_region = true;
}
// We should expand old-gen if this can prevent an old-gen evacuation failure. We don't care so much about
// promotion failures since they can be mitigated in a subsequent GC pass. Would be nice to know if this
// allocation request is for evacuation or promotion. Individual threads limit their use of PLAB memory for
// promotions, so we already have an assurance that any additional memory set aside for old-gen will be used
// only for old-gen evacuations.
if (allow_new_region) {
// Try to steal an empty region from the mutator view.
result = try_allocate_from_mutator(req, in_new_region);
}
// This is it. Do not try to mix mutator and GC allocations, because adjusting region UWM
// due to GC allocations would expose unparsable mutator allocations.
return result;
}
bool ShenandoahFreeSet::can_allocate_in_new_region(const ShenandoahAllocRequest& req) {
if (!_heap->mode()->is_generational()) {
return true;
}
assert(req.is_old() || req.is_young(), "Should request affiliation");
return (req.is_old() && _heap->old_generation()->free_unaffiliated_regions() > 0)
|| (req.is_young() && _heap->young_generation()->free_unaffiliated_regions() > 0);
}
HeapWord* ShenandoahFreeSet::try_allocate_from_mutator(ShenandoahAllocRequest& req, bool& in_new_region) {
// The collector prefers to keep longer lived regions toward the right side of the heap, so it always
// searches for regions from right to left here.
ShenandoahRightLeftIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator, true);
for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
ShenandoahHeapRegion* r = _heap->get_region(idx);
if (can_allocate_from(r)) {
if (req.is_old()) {
if (!flip_to_old_gc(r)) {
continue;
}
} else {
flip_to_gc(r);
}
// Region r is entirely empty. If try_allocate_in fails on region r, something else is really wrong.
// Don't bother to retry with other regions.
log_debug(gc, free)("Flipped region %zu to gc for request: " PTR_FORMAT, idx, p2i(&req));
return try_allocate_in(r, req, in_new_region);
}
}
return nullptr;
}
// This work method takes an argument corresponding to the number of bytes
// free in a region, and returns the largest amount in heapwords that can be allocated
// such that both of the following conditions are satisfied:
//
// 1. it is a multiple of card size
// 2. any remaining shard may be filled with a filler object
//
// The idea is that the allocation starts and ends at card boundaries. Because
// a region ('s end) is card-aligned, the remainder shard that must be filled is
// at the start of the free space.
//
// This is merely a helper method to use for the purpose of such a calculation.
size_t ShenandoahFreeSet::get_usable_free_words(size_t free_bytes) const {
// e.g. card_size is 512, card_shift is 9, min_fill_size() is 8
// free is 514
// usable_free is 512, which is decreased to 0
size_t usable_free = (free_bytes / CardTable::card_size()) << CardTable::card_shift();
assert(usable_free <= free_bytes, "Sanity check");
if ((free_bytes != usable_free) && (free_bytes - usable_free < ShenandoahHeap::min_fill_size() * HeapWordSize)) {
// After aligning to card multiples, the remainder would be smaller than
// the minimum filler object, so we'll need to take away another card's
// worth to construct a filler object.
if (usable_free >= CardTable::card_size()) {
usable_free -= CardTable::card_size();
} else {
assert(usable_free == 0, "usable_free is a multiple of card_size and card_size > min_fill_size");
}
}
return usable_free / HeapWordSize;
}
// Given a size argument, which is a multiple of card size, a request struct
// for a PLAB, and an old region, return a pointer to the allocated space for
// a PLAB which is card-aligned and where any remaining shard in the region
// has been suitably filled by a filler object.
// It is assumed (and assertion-checked) that such an allocation is always possible.
HeapWord* ShenandoahFreeSet::allocate_aligned_plab(size_t size, ShenandoahAllocRequest& req, ShenandoahHeapRegion* r) {
assert(_heap->mode()->is_generational(), "PLABs are only for generational mode");
assert(r->is_old(), "All PLABs reside in old-gen");
assert(!req.is_mutator_alloc(), "PLABs should not be allocated by mutators.");
assert(is_aligned(size, CardTable::card_size_in_words()), "Align by design");
HeapWord* result = r->allocate_aligned(size, req, CardTable::card_size());
assert(result != nullptr, "Allocation cannot fail");
assert(r->top() <= r->end(), "Allocation cannot span end of region");
assert(is_aligned(result, CardTable::card_size_in_words()), "Align by design");
return result;
}
HeapWord* ShenandoahFreeSet::try_allocate_in(ShenandoahHeapRegion* r, ShenandoahAllocRequest& req, bool& in_new_region) {
assert (has_alloc_capacity(r), "Performance: should avoid full regions on this path: %zu", r->index());
if (_heap->is_concurrent_weak_root_in_progress() && r->is_trash()) {
// We cannot use this region for allocation when weak roots are in progress because the collector may need
// to reference unmarked oops during concurrent classunloading. The collector also needs accurate marking
// information to determine which weak handles need to be null'd out. If the region is recycled before weak
// roots processing has finished, weak root processing may fail to null out a handle into a trashed region.
// This turns the handle into a dangling pointer and will crash or corrupt the heap.
return nullptr;
}
HeapWord* result = nullptr;
r->try_recycle_under_lock();
in_new_region = r->is_empty();
if (in_new_region) {
log_debug(gc, free)("Using new region (%zu) for %s (" PTR_FORMAT ").",
r->index(), ShenandoahAllocRequest::alloc_type_to_string(req.type()), p2i(&req));
assert(!r->is_affiliated(), "New region %zu should be unaffiliated", r->index());
r->set_affiliation(req.affiliation());
if (r->is_old()) {
// Any OLD region allocated during concurrent coalesce-and-fill does not need to be coalesced and filled because
// all objects allocated within this region are above TAMS (and thus are implicitly marked). In case this is an
// OLD region and concurrent preparation for mixed evacuations visits this region before the start of the next
// old-gen concurrent mark (i.e. this region is allocated following the start of old-gen concurrent mark but before
// concurrent preparations for mixed evacuations are completed), we mark this region as not requiring any
// coalesce-and-fill processing.
r->end_preemptible_coalesce_and_fill();
_heap->old_generation()->clear_cards_for(r);
}
_heap->generation_for(r->affiliation())->increment_affiliated_region_count();
#ifdef ASSERT
ShenandoahMarkingContext* const ctx = _heap->marking_context();
assert(ctx->top_at_mark_start(r) == r->bottom(), "Newly established allocation region starts with TAMS equal to bottom");
assert(ctx->is_bitmap_range_within_region_clear(ctx->top_bitmap(r), r->end()), "Bitmap above top_bitmap() must be clear");
#endif
log_debug(gc, free)("Using new region (%zu) for %s (" PTR_FORMAT ").",
r->index(), ShenandoahAllocRequest::alloc_type_to_string(req.type()), p2i(&req));
} else {
assert(r->is_affiliated(), "Region %zu that is not new should be affiliated", r->index());
if (r->affiliation() != req.affiliation()) {
assert(_heap->mode()->is_generational(), "Request for %s from %s region should only happen in generational mode.",
req.affiliation_name(), r->affiliation_name());
return nullptr;
}
}
// req.size() is in words, r->free() is in bytes.
if (req.is_lab_alloc()) {
size_t adjusted_size = req.size();
size_t free = r->free(); // free represents bytes available within region r
if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
// This is a PLAB allocation
assert(_heap->mode()->is_generational(), "PLABs are only for generational mode");
assert(_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, r->index()),
"PLABS must be allocated in old_collector_free regions");
// Need to assure that plabs are aligned on multiple of card region
// Convert free from unaligned bytes to aligned number of words
size_t usable_free = get_usable_free_words(free);
if (adjusted_size > usable_free) {
adjusted_size = usable_free;
}
adjusted_size = align_down(adjusted_size, CardTable::card_size_in_words());
if (adjusted_size >= req.min_size()) {
result = allocate_aligned_plab(adjusted_size, req, r);
assert(result != nullptr, "allocate must succeed");
req.set_actual_size(adjusted_size);
} else {
// Otherwise, leave result == nullptr because the adjusted size is smaller than min size.
log_trace(gc, free)("Failed to shrink PLAB request (%zu) in region %zu to %zu"
" because min_size() is %zu", req.size(), r->index(), adjusted_size, req.min_size());
}
} else {
// This is a GCLAB or a TLAB allocation
// Convert free from unaligned bytes to aligned number of words
free = align_down(free >> LogHeapWordSize, MinObjAlignment);
if (adjusted_size > free) {
adjusted_size = free;
}
if (adjusted_size >= req.min_size()) {
result = r->allocate(adjusted_size, req);
assert (result != nullptr, "Allocation must succeed: free %zu, actual %zu", free, adjusted_size);
req.set_actual_size(adjusted_size);
} else {
log_trace(gc, free)("Failed to shrink TLAB or GCLAB request (%zu) in region %zu to %zu"
" because min_size() is %zu", req.size(), r->index(), adjusted_size, req.min_size());
}
}
} else {
size_t size = req.size();
result = r->allocate(size, req);
if (result != nullptr) {
// Record actual allocation size
req.set_actual_size(size);
}
}
if (result != nullptr) {
// Allocation successful, bump stats:
if (req.is_mutator_alloc()) {
assert(req.is_young(), "Mutator allocations always come from young generation.");
_partitions.increase_used(ShenandoahFreeSetPartitionId::Mutator, req.actual_size() * HeapWordSize);
} else {
assert(req.is_gc_alloc(), "Should be gc_alloc since req wasn't mutator alloc");
// For GC allocations, we advance update_watermark because the objects relocated into this memory during
// evacuation are not updated during evacuation. For both young and old regions r, it is essential that all
// PLABs be made parsable at the end of evacuation. This is enabled by retiring all plabs at end of evacuation.
r->set_update_watermark(r->top());
if (r->is_old()) {
_partitions.increase_used(ShenandoahFreeSetPartitionId::OldCollector, req.actual_size() * HeapWordSize);
assert(req.type() != ShenandoahAllocRequest::_alloc_gclab, "old-gen allocations use PLAB or shared allocation");
// for plabs, we'll sort the difference between evac and promotion usage when we retire the plab
} else {
_partitions.increase_used(ShenandoahFreeSetPartitionId::Collector, req.actual_size() * HeapWordSize);
}
}
}
static const size_t min_capacity = (size_t) (ShenandoahHeapRegion::region_size_bytes() * (1.0 - 1.0 / ShenandoahEvacWaste));
size_t ac = alloc_capacity(r);
if (((result == nullptr) && (ac < min_capacity)) || (alloc_capacity(r) < PLAB::min_size() * HeapWordSize)) {
// Regardless of whether this allocation succeeded, if the remaining memory is less than PLAB:min_size(), retire this region.
// Note that retire_from_partition() increases used to account for waste.
// Also, if this allocation request failed and the consumed within this region * ShenandoahEvacWaste > region size,
// then retire the region so that subsequent searches can find available memory more quickly.
size_t idx = r->index();
ShenandoahFreeSetPartitionId orig_partition;
if (req.is_mutator_alloc()) {
orig_partition = ShenandoahFreeSetPartitionId::Mutator;
} else if (req.type() == ShenandoahAllocRequest::_alloc_gclab) {
orig_partition = ShenandoahFreeSetPartitionId::Collector;
} else if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
orig_partition = ShenandoahFreeSetPartitionId::OldCollector;
} else {
assert(req.type() == ShenandoahAllocRequest::_alloc_shared_gc, "Unexpected allocation type");
if (req.is_old()) {
orig_partition = ShenandoahFreeSetPartitionId::OldCollector;
} else {
orig_partition = ShenandoahFreeSetPartitionId::Collector;
}
}
_partitions.retire_from_partition(orig_partition, idx, r->used());
_partitions.assert_bounds();
}
return result;
}
HeapWord* ShenandoahFreeSet::allocate_contiguous(ShenandoahAllocRequest& req, bool is_humongous) {
assert(req.is_mutator_alloc(), "All contiguous allocations are performed by mutator");
shenandoah_assert_heaplocked();
size_t words_size = req.size();
idx_t num = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
assert(req.is_young(), "Humongous regions always allocated in YOUNG");
ShenandoahGeneration* generation = _heap->generation_for(req.affiliation());
// Check if there are enough regions left to satisfy allocation.
if (num > (idx_t) _partitions.count(ShenandoahFreeSetPartitionId::Mutator)) {
return nullptr;
}
idx_t start_range = _partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Mutator);
idx_t end_range = _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Mutator) + 1;
idx_t last_possible_start = end_range - num;
// Find the continuous interval of $num regions, starting from $beg and ending in $end,
// inclusive. Contiguous allocations are biased to the beginning.
idx_t beg = _partitions.find_index_of_next_available_cluster_of_regions(ShenandoahFreeSetPartitionId::Mutator,
start_range, num);
if (beg > last_possible_start) {
// Hit the end, goodbye
return nullptr;
}
idx_t end = beg;
while (true) {
// We've confirmed num contiguous regions belonging to Mutator partition, so no need to confirm membership.
// If region is not completely free, the current [beg; end] is useless, and we may fast-forward. If we can extend
// the existing range, we can exploit that certain regions are already known to be in the Mutator free set.
while (!can_allocate_from(_heap->get_region(end))) {
// region[end] is not empty, so we restart our search after region[end]
idx_t slide_delta = end + 1 - beg;
if (beg + slide_delta > last_possible_start) {
// no room to slide
return nullptr;
}
for (idx_t span_end = beg + num; slide_delta > 0; slide_delta--) {
if (!_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, span_end)) {
beg = _partitions.find_index_of_next_available_cluster_of_regions(ShenandoahFreeSetPartitionId::Mutator,
span_end + 1, num);
break;
} else {
beg++;
span_end++;
}
}
// Here, either beg identifies a range of num regions all of which are in the Mutator free set, or beg > last_possible_start
if (beg > last_possible_start) {
// Hit the end, goodbye
return nullptr;
}
end = beg;
}
if ((end - beg + 1) == num) {
// found the match
break;
}
end++;
}
size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
// Initialize regions:
for (idx_t i = beg; i <= end; i++) {
ShenandoahHeapRegion* r = _heap->get_region(i);
r->try_recycle_under_lock();
assert(i == beg || _heap->get_region(i - 1)->index() + 1 == r->index(), "Should be contiguous");
assert(r->is_empty(), "Should be empty");
r->set_affiliation(req.affiliation());
if (is_humongous) {
if (i == beg) {
r->make_humongous_start();
} else {
r->make_humongous_cont();
}
} else {
r->make_regular_allocation(req.affiliation());
}
// Trailing region may be non-full, record the remainder there
size_t used_words;
if ((i == end) && (remainder != 0)) {
used_words = remainder;
} else {
used_words = ShenandoahHeapRegion::region_size_words();
}
r->set_update_watermark(r->bottom());
r->set_top(r->bottom() + used_words);
}
generation->increase_affiliated_region_count(num);
if (remainder != 0) {
// Record this remainder as allocation waste
_heap->notify_mutator_alloc_words(ShenandoahHeapRegion::region_size_words() - remainder, true);
}
size_t total_used = 0;
if (is_humongous) {
// Humongous allocation retires all regions at once: no allocation is possible anymore.
_partitions.retire_range_from_partition(ShenandoahFreeSetPartitionId::Mutator, beg, end);
total_used = ShenandoahHeapRegion::region_size_bytes() * num;
} else {
// Non-humongous allocation retires only the regions that cannot be used for allocation anymore.
for (idx_t i = beg; i <= end; i++) {
ShenandoahHeapRegion* r = _heap->get_region(i);
if (r->free() < PLAB::min_size() * HeapWordSize) {
_partitions.retire_from_partition(ShenandoahFreeSetPartitionId::Mutator, i, r->used());
}
total_used += r->used();
}
}
_partitions.increase_used(ShenandoahFreeSetPartitionId::Mutator, total_used);
_partitions.assert_bounds();
req.set_actual_size(words_size);
if (remainder != 0 && is_humongous) {
req.set_waste(ShenandoahHeapRegion::region_size_words() - remainder);
}
return _heap->get_region(beg)->bottom();
}
class ShenandoahRecycleTrashedRegionClosure final : public ShenandoahHeapRegionClosure {
public:
ShenandoahRecycleTrashedRegionClosure(): ShenandoahHeapRegionClosure() {}
void heap_region_do(ShenandoahHeapRegion* r) {
r->try_recycle();
}
bool is_thread_safe() {
return true;
}
};
void ShenandoahFreeSet::recycle_trash() {
// lock is not non-reentrant, check we don't have it
shenandoah_assert_not_heaplocked();
ShenandoahHeap* heap = ShenandoahHeap::heap();
heap->assert_gc_workers(heap->workers()->active_workers());
ShenandoahRecycleTrashedRegionClosure closure;
heap->parallel_heap_region_iterate(&closure);
}
bool ShenandoahFreeSet::flip_to_old_gc(ShenandoahHeapRegion* r) {
const size_t idx = r->index();
assert(_partitions.partition_id_matches(idx, ShenandoahFreeSetPartitionId::Mutator), "Should be in mutator view");
assert(can_allocate_from(r), "Should not be allocated");
ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
const size_t region_capacity = alloc_capacity(r);
bool transferred = gen_heap->generation_sizer()->transfer_to_old(1);
if (transferred) {
_partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
ShenandoahFreeSetPartitionId::OldCollector, region_capacity);
_partitions.assert_bounds();
_heap->old_generation()->augment_evacuation_reserve(region_capacity);
return true;
}
if (_heap->young_generation()->free_unaffiliated_regions() == 0 && _heap->old_generation()->free_unaffiliated_regions() > 0) {
// Old has free unaffiliated regions, but it couldn't use them for allocation (likely because they
// are trash and weak roots are in process). In this scenario, we aren't really stealing from the
// mutator (they have nothing to steal), but they do have a usable region in their partition. What
// we want to do here is swap that region from the mutator partition with one from the old collector
// partition.
// 1. Find a temporarily unusable trash region in the old collector partition
ShenandoahRightLeftIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::OldCollector, true);
idx_t unusable_trash = -1;
for (unusable_trash = iterator.current(); iterator.has_next(); unusable_trash = iterator.next()) {
const ShenandoahHeapRegion* region = _heap->get_region(unusable_trash);
if (region->is_trash() && _heap->is_concurrent_weak_root_in_progress()) {
break;
}
}
if (unusable_trash != -1) {
const size_t unusable_capacity = alloc_capacity(unusable_trash);
// 2. Move the (temporarily) unusable trash region we found to the mutator partition
_partitions.move_from_partition_to_partition(unusable_trash,
ShenandoahFreeSetPartitionId::OldCollector,
ShenandoahFreeSetPartitionId::Mutator, unusable_capacity);
// 3. Move this usable region from the mutator partition to the old collector partition
_partitions.move_from_partition_to_partition(idx,
ShenandoahFreeSetPartitionId::Mutator,
ShenandoahFreeSetPartitionId::OldCollector, region_capacity);
_partitions.assert_bounds();
// 4. Do not adjust capacities for generations, we just swapped the regions that have already
// been accounted for. However, we should adjust the evacuation reserves as those may have changed.
shenandoah_assert_heaplocked();
const size_t reserve = _heap->old_generation()->get_evacuation_reserve();
_heap->old_generation()->set_evacuation_reserve(reserve - unusable_capacity + region_capacity);
return true;
}
}
// We can't take this region young because it has no free unaffiliated regions (transfer failed).
return false;
}
void ShenandoahFreeSet::flip_to_gc(ShenandoahHeapRegion* r) {
size_t idx = r->index();
assert(_partitions.partition_id_matches(idx, ShenandoahFreeSetPartitionId::Mutator), "Should be in mutator view");
assert(can_allocate_from(r), "Should not be allocated");
size_t ac = alloc_capacity(r);
_partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
ShenandoahFreeSetPartitionId::Collector, ac);
_partitions.assert_bounds();
// We do not ensure that the region is no longer trash, relying on try_allocate_in(), which always comes next,
// to recycle trash before attempting to allocate anything in the region.
}
void ShenandoahFreeSet::clear() {
clear_internal();
}
void ShenandoahFreeSet::clear_internal() {
shenandoah_assert_heaplocked();
_partitions.make_all_regions_unavailable();
_alloc_bias_weight = 0;
_partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Mutator, true);
_partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Collector, false);
_partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::OldCollector, false);
}
void ShenandoahFreeSet::find_regions_with_alloc_capacity(size_t &young_cset_regions, size_t &old_cset_regions,
size_t &first_old_region, size_t &last_old_region,
size_t &old_region_count) {
clear_internal();
first_old_region = _heap->num_regions();
last_old_region = 0;
old_region_count = 0;
old_cset_regions = 0;
young_cset_regions = 0;
size_t region_size_bytes = _partitions.region_size_bytes();
size_t max_regions = _partitions.max_regions();
size_t mutator_leftmost = max_regions;
size_t mutator_rightmost = 0;
size_t mutator_leftmost_empty = max_regions;
size_t mutator_rightmost_empty = 0;
size_t mutator_regions = 0;
size_t mutator_used = 0;
size_t old_collector_leftmost = max_regions;
size_t old_collector_rightmost = 0;
size_t old_collector_leftmost_empty = max_regions;
size_t old_collector_rightmost_empty = 0;
size_t old_collector_regions = 0;
size_t old_collector_used = 0;
size_t num_regions = _heap->num_regions();
for (size_t idx = 0; idx < num_regions; idx++) {
ShenandoahHeapRegion* region = _heap->get_region(idx);
if (region->is_trash()) {
// Trashed regions represent regions that had been in the collection partition but have not yet been "cleaned up".
// The cset regions are not "trashed" until we have finished update refs.
if (region->is_old()) {
old_cset_regions++;
} else {
assert(region->is_young(), "Trashed region should be old or young");
young_cset_regions++;
}
} else if (region->is_old()) {
// count both humongous and regular regions, but don't count trash (cset) regions.
old_region_count++;
if (first_old_region > idx) {
first_old_region = idx;
}
last_old_region = idx;
}
if (region->is_alloc_allowed() || region->is_trash()) {
assert(!region->is_cset(), "Shouldn't be adding cset regions to the free set");
// Do not add regions that would almost surely fail allocation
size_t ac = alloc_capacity(region);
if (ac > PLAB::min_size() * HeapWordSize) {
if (region->is_trash() || !region->is_old()) {
// Both young and old collected regions (trashed) are placed into the Mutator set
_partitions.raw_assign_membership(idx, ShenandoahFreeSetPartitionId::Mutator);
if (idx < mutator_leftmost) {
mutator_leftmost = idx;
}
if (idx > mutator_rightmost) {
mutator_rightmost = idx;
}
if (ac == region_size_bytes) {
if (idx < mutator_leftmost_empty) {
mutator_leftmost_empty = idx;
}
if (idx > mutator_rightmost_empty) {
mutator_rightmost_empty = idx;
}
}
mutator_regions++;
mutator_used += (region_size_bytes - ac);
} else {
// !region->is_trash() && region is_old()
_partitions.raw_assign_membership(idx, ShenandoahFreeSetPartitionId::OldCollector);
if (idx < old_collector_leftmost) {
old_collector_leftmost = idx;
}
if (idx > old_collector_rightmost) {
old_collector_rightmost = idx;
}
if (ac == region_size_bytes) {
if (idx < old_collector_leftmost_empty) {
old_collector_leftmost_empty = idx;
}
if (idx > old_collector_rightmost_empty) {
old_collector_rightmost_empty = idx;
}
}
old_collector_regions++;
old_collector_used += (region_size_bytes - ac);
}
}
}
}
log_debug(gc, free)(" At end of prep_to_rebuild, mutator_leftmost: %zu"
", mutator_rightmost: %zu"
", mutator_leftmost_empty: %zu"
", mutator_rightmost_empty: %zu"
", mutator_regions: %zu"
", mutator_used: %zu",
mutator_leftmost, mutator_rightmost, mutator_leftmost_empty, mutator_rightmost_empty,
mutator_regions, mutator_used);
log_debug(gc, free)(" old_collector_leftmost: %zu"
", old_collector_rightmost: %zu"
", old_collector_leftmost_empty: %zu"
", old_collector_rightmost_empty: %zu"
", old_collector_regions: %zu"
", old_collector_used: %zu",
old_collector_leftmost, old_collector_rightmost, old_collector_leftmost_empty, old_collector_rightmost_empty,
old_collector_regions, old_collector_used);
idx_t rightmost_idx = (mutator_leftmost == max_regions)? -1: (idx_t) mutator_rightmost;
idx_t rightmost_empty_idx = (mutator_leftmost_empty == max_regions)? -1: (idx_t) mutator_rightmost_empty;
_partitions.establish_mutator_intervals(mutator_leftmost, rightmost_idx, mutator_leftmost_empty, rightmost_empty_idx,
mutator_regions, mutator_used);
rightmost_idx = (old_collector_leftmost == max_regions)? -1: (idx_t) old_collector_rightmost;
rightmost_empty_idx = (old_collector_leftmost_empty == max_regions)? -1: (idx_t) old_collector_rightmost_empty;
_partitions.establish_old_collector_intervals(old_collector_leftmost, rightmost_idx, old_collector_leftmost_empty,
rightmost_empty_idx, old_collector_regions, old_collector_used);
log_debug(gc, free)(" After find_regions_with_alloc_capacity(), Mutator range [%zd, %zd],"
" Old Collector range [%zd, %zd]",
_partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
_partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector));
}
// Returns number of regions transferred, adds transferred bytes to var argument bytes_transferred
size_t ShenandoahFreeSet::transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId which_collector,
size_t max_xfer_regions,
size_t& bytes_transferred) {
shenandoah_assert_heaplocked();
const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
size_t transferred_regions = 0;
ShenandoahLeftRightIterator iterator(&_partitions, which_collector, true);
for (idx_t idx = iterator.current(); transferred_regions < max_xfer_regions && iterator.has_next(); idx = iterator.next()) {
// Note: can_allocate_from() denotes that region is entirely empty
if (can_allocate_from(idx)) {
_partitions.move_from_partition_to_partition(idx, which_collector, ShenandoahFreeSetPartitionId::Mutator, region_size_bytes);
transferred_regions++;
bytes_transferred += region_size_bytes;
}
}
return transferred_regions;
}
// Returns number of regions transferred, adds transferred bytes to var argument bytes_transferred
size_t ShenandoahFreeSet::transfer_non_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId which_collector,
size_t max_xfer_regions,
size_t& bytes_transferred) {
shenandoah_assert_heaplocked();
size_t transferred_regions = 0;
ShenandoahLeftRightIterator iterator(&_partitions, which_collector, false);
for (idx_t idx = iterator.current(); transferred_regions < max_xfer_regions && iterator.has_next(); idx = iterator.next()) {
size_t ac = alloc_capacity(idx);
if (ac > 0) {
_partitions.move_from_partition_to_partition(idx, which_collector, ShenandoahFreeSetPartitionId::Mutator, ac);
transferred_regions++;
bytes_transferred += ac;
}
}
return transferred_regions;
}
void ShenandoahFreeSet::move_regions_from_collector_to_mutator(size_t max_xfer_regions) {
size_t collector_xfer = 0;
size_t old_collector_xfer = 0;
// Process empty regions within the Collector free partition
if ((max_xfer_regions > 0) &&
(_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Collector)
<= _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Collector))) {
ShenandoahHeapLocker locker(_heap->lock());
max_xfer_regions -=
transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::Collector, max_xfer_regions,
collector_xfer);
}
// Process empty regions within the OldCollector free partition
if ((max_xfer_regions > 0) &&
(_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::OldCollector)
<= _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::OldCollector))) {
ShenandoahHeapLocker locker(_heap->lock());
size_t old_collector_regions =
transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::OldCollector, max_xfer_regions,
old_collector_xfer);
max_xfer_regions -= old_collector_regions;
if (old_collector_regions > 0) {
ShenandoahGenerationalHeap::cast(_heap)->generation_sizer()->transfer_to_young(old_collector_regions);
}
}
// If there are any non-empty regions within Collector partition, we can also move them to the Mutator free partition
if ((max_xfer_regions > 0) && (_partitions.leftmost(ShenandoahFreeSetPartitionId::Collector)
<= _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector))) {
ShenandoahHeapLocker locker(_heap->lock());
max_xfer_regions -=
transfer_non_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::Collector, max_xfer_regions,
collector_xfer);
}
size_t total_xfer = collector_xfer + old_collector_xfer;
log_info(gc, ergo)("At start of update refs, moving %zu%s to Mutator free set from Collector Reserve ("
"%zu%s) and from Old Collector Reserve (%zu%s)",
byte_size_in_proper_unit(total_xfer), proper_unit_for_byte_size(total_xfer),
byte_size_in_proper_unit(collector_xfer), proper_unit_for_byte_size(collector_xfer),
byte_size_in_proper_unit(old_collector_xfer), proper_unit_for_byte_size(old_collector_xfer));
}
// Overwrite arguments to represent the amount of memory in each generation that is about to be recycled
void ShenandoahFreeSet::prepare_to_rebuild(size_t &young_cset_regions, size_t &old_cset_regions,
size_t &first_old_region, size_t &last_old_region, size_t &old_region_count) {
shenandoah_assert_heaplocked();
// This resets all state information, removing all regions from all sets.
clear();
log_debug(gc, free)("Rebuilding FreeSet");
// This places regions that have alloc_capacity into the old_collector set if they identify as is_old() or the
// mutator set otherwise. All trashed (cset) regions are affiliated young and placed in mutator set.
find_regions_with_alloc_capacity(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count);
}
void ShenandoahFreeSet::establish_generation_sizes(size_t young_region_count, size_t old_region_count) {
assert(young_region_count + old_region_count == ShenandoahHeap::heap()->num_regions(), "Sanity");
if (ShenandoahHeap::heap()->mode()->is_generational()) {
ShenandoahGenerationalHeap* heap = ShenandoahGenerationalHeap::heap();
ShenandoahOldGeneration* old_gen = heap->old_generation();
ShenandoahYoungGeneration* young_gen = heap->young_generation();
size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
size_t original_old_capacity = old_gen->max_capacity();
size_t new_old_capacity = old_region_count * region_size_bytes;
size_t new_young_capacity = young_region_count * region_size_bytes;
old_gen->set_capacity(new_old_capacity);
young_gen->set_capacity(new_young_capacity);
if (new_old_capacity > original_old_capacity) {
size_t region_count = (new_old_capacity - original_old_capacity) / region_size_bytes;
log_info(gc, ergo)("Transfer %zu region(s) from %s to %s, yielding increased size: " PROPERFMT,
region_count, young_gen->name(), old_gen->name(), PROPERFMTARGS(new_old_capacity));
} else if (new_old_capacity < original_old_capacity) {
size_t region_count = (original_old_capacity - new_old_capacity) / region_size_bytes;
log_info(gc, ergo)("Transfer %zu region(s) from %s to %s, yielding increased size: " PROPERFMT,
region_count, old_gen->name(), young_gen->name(), PROPERFMTARGS(new_young_capacity));
}
// This balances generations, so clear any pending request to balance.
old_gen->set_region_balance(0);
}
}
void ShenandoahFreeSet::finish_rebuild(size_t young_cset_regions, size_t old_cset_regions, size_t old_region_count,
bool have_evacuation_reserves) {
shenandoah_assert_heaplocked();
size_t young_reserve(0), old_reserve(0);
if (_heap->mode()->is_generational()) {
compute_young_and_old_reserves(young_cset_regions, old_cset_regions, have_evacuation_reserves,
young_reserve, old_reserve);
} else {
young_reserve = (_heap->max_capacity() / 100) * ShenandoahEvacReserve;
old_reserve = 0;
}
// Move some of the mutator regions in the Collector and OldCollector partitions in order to satisfy
// young_reserve and old_reserve.
reserve_regions(young_reserve, old_reserve, old_region_count);
size_t young_region_count = _heap->num_regions() - old_region_count;
establish_generation_sizes(young_region_count, old_region_count);
establish_old_collector_alloc_bias();
_partitions.assert_bounds();
log_status();
}
void ShenandoahFreeSet::compute_young_and_old_reserves(size_t young_cset_regions, size_t old_cset_regions,
bool have_evacuation_reserves,
size_t& young_reserve_result, size_t& old_reserve_result) const {
shenandoah_assert_generational();
const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
ShenandoahOldGeneration* const old_generation = _heap->old_generation();
size_t old_available = old_generation->available();
size_t old_unaffiliated_regions = old_generation->free_unaffiliated_regions();
ShenandoahYoungGeneration* const young_generation = _heap->young_generation();
size_t young_capacity = young_generation->max_capacity();
size_t young_unaffiliated_regions = young_generation->free_unaffiliated_regions();
// Add in the regions we anticipate to be freed by evacuation of the collection set
old_unaffiliated_regions += old_cset_regions;
young_unaffiliated_regions += young_cset_regions;
// Consult old-region balance to make adjustments to current generation capacities and availability.
// The generation region transfers take place after we rebuild.
const ssize_t old_region_balance = old_generation->get_region_balance();
if (old_region_balance != 0) {
#ifdef ASSERT
if (old_region_balance > 0) {
assert(old_region_balance <= checked_cast<ssize_t>(old_unaffiliated_regions), "Cannot transfer regions that are affiliated");
} else {
assert(0 - old_region_balance <= checked_cast<ssize_t>(young_unaffiliated_regions), "Cannot transfer regions that are affiliated");
}
#endif
ssize_t xfer_bytes = old_region_balance * checked_cast<ssize_t>(region_size_bytes);
old_available -= xfer_bytes;
old_unaffiliated_regions -= old_region_balance;
young_capacity += xfer_bytes;
young_unaffiliated_regions += old_region_balance;
}
// All allocations taken from the old collector set are performed by GC, generally using PLABs for both
// promotions and evacuations. The partition between which old memory is reserved for evacuation and
// which is reserved for promotion is enforced using thread-local variables that prescribe intentions for
// each PLAB's available memory.
if (have_evacuation_reserves) {
// We are rebuilding at the end of final mark, having already established evacuation budgets for this GC pass.
const size_t promoted_reserve = old_generation->get_promoted_reserve();
const size_t old_evac_reserve = old_generation->get_evacuation_reserve();
young_reserve_result = young_generation->get_evacuation_reserve();
old_reserve_result = promoted_reserve + old_evac_reserve;
assert(old_reserve_result <= old_available,
"Cannot reserve (%zu + %zu) more OLD than is available: %zu",
promoted_reserve, old_evac_reserve, old_available);
} else {
// We are rebuilding at end of GC, so we set aside budgets specified on command line (or defaults)
young_reserve_result = (young_capacity * ShenandoahEvacReserve) / 100;
// The auto-sizer has already made old-gen large enough to hold all anticipated evacuations and promotions.
// Affiliated old-gen regions are already in the OldCollector free set. Add in the relevant number of
// unaffiliated regions.
old_reserve_result = old_available;
}
// Old available regions that have less than PLAB::min_size() of available memory are not placed into the OldCollector
// free set. Because of this, old_available may not have enough memory to represent the intended reserve. Adjust
// the reserve downward to account for this possibility. This loss is part of the reason why the original budget
// was adjusted with ShenandoahOldEvacWaste and ShenandoahOldPromoWaste multipliers.
if (old_reserve_result >
_partitions.capacity_of(ShenandoahFreeSetPartitionId::OldCollector) + old_unaffiliated_regions * region_size_bytes) {
old_reserve_result =
_partitions.capacity_of(ShenandoahFreeSetPartitionId::OldCollector) + old_unaffiliated_regions * region_size_bytes;
}
if (young_reserve_result > young_unaffiliated_regions * region_size_bytes) {
young_reserve_result = young_unaffiliated_regions * region_size_bytes;
}
}
// Having placed all regions that have allocation capacity into the mutator set if they identify as is_young()
// or into the old collector set if they identify as is_old(), move some of these regions from the mutator set
// into the collector set or old collector set in order to assure that the memory available for allocations within
// the collector set is at least to_reserve and the memory available for allocations within the old collector set
// is at least to_reserve_old.
void ShenandoahFreeSet::reserve_regions(size_t to_reserve, size_t to_reserve_old, size_t &old_region_count) {
for (size_t i = _heap->num_regions(); i > 0; i--) {
size_t idx = i - 1;
ShenandoahHeapRegion* r = _heap->get_region(idx);
if (!_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, idx)) {
continue;
}
size_t ac = alloc_capacity(r);
assert (ac > 0, "Membership in free set implies has capacity");
assert (!r->is_old() || r->is_trash(), "Except for trash, mutator_is_free regions should not be affiliated OLD");
bool move_to_old_collector = _partitions.available_in(ShenandoahFreeSetPartitionId::OldCollector) < to_reserve_old;
bool move_to_collector = _partitions.available_in(ShenandoahFreeSetPartitionId::Collector) < to_reserve;
if (!move_to_collector && !move_to_old_collector) {
// We've satisfied both to_reserve and to_reserved_old
break;
}
if (move_to_old_collector) {
// We give priority to OldCollector partition because we desire to pack OldCollector regions into higher
// addresses than Collector regions. Presumably, OldCollector regions are more "stable" and less likely to
// be collected in the near future.
if (r->is_trash() || !r->is_affiliated()) {
// OLD regions that have available memory are already in the old_collector free set.
_partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
ShenandoahFreeSetPartitionId::OldCollector, ac);
log_trace(gc, free)(" Shifting region %zu from mutator_free to old_collector_free", idx);
log_trace(gc, free)(" Shifted Mutator range [%zd, %zd],"
" Old Collector range [%zd, %zd]",
_partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
_partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector));
old_region_count++;
continue;
}
}
if (move_to_collector) {
// Note: In a previous implementation, regions were only placed into the survivor space (collector_is_free) if
// they were entirely empty. This has the effect of causing new Mutator allocation to reside next to objects
// that have already survived at least one GC, mixing ephemeral with longer-lived objects in the same region.
// Any objects that have survived a GC are less likely to immediately become garbage, so a region that contains
// survivor objects is less likely to be selected for the collection set. This alternative implementation allows
// survivor regions to continue accumulating other survivor objects, and makes it more likely that ephemeral objects
// occupy regions comprised entirely of ephemeral objects. These regions are highly likely to be included in the next
// collection set, and they are easily evacuated because they have low density of live objects.
_partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
ShenandoahFreeSetPartitionId::Collector, ac);
log_trace(gc, free)(" Shifting region %zu from mutator_free to collector_free", idx);
log_trace(gc, free)(" Shifted Mutator range [%zd, %zd],"
" Collector range [%zd, %zd]",
_partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.leftmost(ShenandoahFreeSetPartitionId::Collector),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Collector));
}
}
if (LogTarget(Info, gc, free)::is_enabled()) {
size_t old_reserve = _partitions.available_in(ShenandoahFreeSetPartitionId::OldCollector);
if (old_reserve < to_reserve_old) {
log_info(gc, free)("Wanted " PROPERFMT " for old reserve, but only reserved: " PROPERFMT,
PROPERFMTARGS(to_reserve_old), PROPERFMTARGS(old_reserve));
}
size_t reserve = _partitions.available_in(ShenandoahFreeSetPartitionId::Collector);
if (reserve < to_reserve) {
log_info(gc, free)("Wanted " PROPERFMT " for young reserve, but only reserved: " PROPERFMT,
PROPERFMTARGS(to_reserve), PROPERFMTARGS(reserve));
}
}
}
void ShenandoahFreeSet::establish_old_collector_alloc_bias() {
ShenandoahHeap* heap = ShenandoahHeap::heap();
shenandoah_assert_heaplocked();
idx_t left_idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
idx_t right_idx = _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector);
idx_t middle = (left_idx + right_idx) / 2;
size_t available_in_first_half = 0;
size_t available_in_second_half = 0;
for (idx_t index = left_idx; index < middle; index++) {
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
ShenandoahHeapRegion* r = heap->get_region((size_t) index);
available_in_first_half += r->free();
}
}
for (idx_t index = middle; index <= right_idx; index++) {
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
ShenandoahHeapRegion* r = heap->get_region(index);
available_in_second_half += r->free();
}
}
// We desire to first consume the sparsely distributed regions in order that the remaining regions are densely packed.
// Densely packing regions reduces the effort to search for a region that has sufficient memory to satisfy a new allocation
// request. Regions become sparsely distributed following a Full GC, which tends to slide all regions to the front of the
// heap rather than allowing survivor regions to remain at the high end of the heap where we intend for them to congregate.
_partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::OldCollector,
(available_in_second_half > available_in_first_half));
}
void ShenandoahFreeSet::log_status_under_lock() {
// Must not be heap locked, it acquires heap lock only when log is enabled
shenandoah_assert_not_heaplocked();
if (LogTarget(Info, gc, free)::is_enabled()
DEBUG_ONLY(|| LogTarget(Debug, gc, free)::is_enabled())) {
ShenandoahHeapLocker locker(_heap->lock());
log_status();
}
}
void ShenandoahFreeSet::log_status() {
shenandoah_assert_heaplocked();
#ifdef ASSERT
// Dump of the FreeSet details is only enabled if assertions are enabled
LogTarget(Debug, gc, free) debug_free;
if (debug_free.is_enabled()) {
#define BUFFER_SIZE 80
LogStream ls(debug_free);
char buffer[BUFFER_SIZE];
for (uint i = 0; i < BUFFER_SIZE; i++) {
buffer[i] = '\0';
}
ls.cr();
ls.print_cr("Mutator free range [%zd..%zd] allocating from %s",
_partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
_partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Mutator)? "left to right": "right to left");
ls.print_cr("Collector free range [%zd..%zd] allocating from %s",
_partitions.leftmost(ShenandoahFreeSetPartitionId::Collector),
_partitions.rightmost(ShenandoahFreeSetPartitionId::Collector),
_partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Collector)? "left to right": "right to left");
ls.print_cr("Old collector free range [%zd..%zd] allocates from %s",
_partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
_partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector),
_partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::OldCollector)? "left to right": "right to left");
ls.cr();
ls.print_cr("FreeSet map legend:");
ls.print_cr(" M/m:mutator, C/c:collector O/o:old_collector (Empty/Occupied)");
ls.print_cr(" H/h:humongous, X/x:no alloc capacity, ~/_:retired (Old/Young)");
for (uint i = 0; i < _heap->num_regions(); i++) {
ShenandoahHeapRegion *r = _heap->get_region(i);
uint idx = i % 64;
if ((i != 0) && (idx == 0)) {
ls.print_cr(" %6u: %s", i-64, buffer);
}
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, i)) {
size_t capacity = alloc_capacity(r);
assert(!r->is_old() || r->is_trash(), "Old regions except trash regions should not be in mutator_free set");
buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'M' : 'm';
} else if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Collector, i)) {
size_t capacity = alloc_capacity(r);
assert(!r->is_old() || r->is_trash(), "Old regions except trash regions should not be in collector_free set");
buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'C' : 'c';
} else if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, i)) {
size_t capacity = alloc_capacity(r);
buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'O' : 'o';
} else if (r->is_humongous()) {
buffer[idx] = (r->is_old() ? 'H' : 'h');
} else if (alloc_capacity(r) == 0) {
buffer[idx] = (r->is_old() ? 'X' : 'x');
} else {
buffer[idx] = (r->is_old() ? '~' : '_');
}
}
uint remnant = _heap->num_regions() % 64;
if (remnant > 0) {
buffer[remnant] = '\0';
} else {
remnant = 64;
}
ls.print_cr(" %6u: %s", (uint) (_heap->num_regions() - remnant), buffer);
}
#endif
LogTarget(Info, gc, free) lt;
if (lt.is_enabled()) {
ResourceMark rm;
LogStream ls(lt);
{
idx_t last_idx = 0;
size_t max = 0;
size_t max_contig = 0;
size_t empty_contig = 0;
size_t total_used = 0;
size_t total_free = 0;
size_t total_free_ext = 0;
for (idx_t idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator);
idx <= _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator); idx++) {
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, idx)) {
ShenandoahHeapRegion *r = _heap->get_region(idx);
size_t free = alloc_capacity(r);
max = MAX2(max, free);
if (r->is_empty()) {
total_free_ext += free;
if (last_idx + 1 == idx) {
empty_contig++;
} else {
empty_contig = 1;
}
} else {
empty_contig = 0;
}
total_used += r->used();
total_free += free;
max_contig = MAX2(max_contig, empty_contig);
last_idx = idx;
}
}
size_t max_humongous = max_contig * ShenandoahHeapRegion::region_size_bytes();
size_t free = capacity() - used();
// Since certain regions that belonged to the Mutator free partition at the time of most recent rebuild may have been
// retired, the sum of used and capacities within regions that are still in the Mutator free partition may not match
// my internally tracked values of used() and free().
assert(free == total_free, "Free memory should match");
ls.print("Free: %zu%s, Max: %zu%s regular, %zu%s humongous, ",
byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
byte_size_in_proper_unit(max), proper_unit_for_byte_size(max),
byte_size_in_proper_unit(max_humongous), proper_unit_for_byte_size(max_humongous)
);
ls.print("Frag: ");
size_t frag_ext;
if (total_free_ext > 0) {
frag_ext = 100 - (100 * max_humongous / total_free_ext);
} else {
frag_ext = 0;
}
ls.print("%zu%% external, ", frag_ext);
size_t frag_int;
if (_partitions.count(ShenandoahFreeSetPartitionId::Mutator) > 0) {
frag_int = (100 * (total_used / _partitions.count(ShenandoahFreeSetPartitionId::Mutator))
/ ShenandoahHeapRegion::region_size_bytes());
} else {
frag_int = 0;
}
ls.print("%zu%% internal; ", frag_int);
ls.print("Used: %zu%s, Mutator Free: %zu",
byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used),
_partitions.count(ShenandoahFreeSetPartitionId::Mutator));
}
{
size_t max = 0;
size_t total_free = 0;
size_t total_used = 0;
for (idx_t idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::Collector);
idx <= _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector); idx++) {
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Collector, idx)) {
ShenandoahHeapRegion *r = _heap->get_region(idx);
size_t free = alloc_capacity(r);
max = MAX2(max, free);
total_free += free;
total_used += r->used();
}
}
ls.print(" Collector Reserve: %zu%s, Max: %zu%s; Used: %zu%s",
byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
byte_size_in_proper_unit(max), proper_unit_for_byte_size(max),
byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used));
}
if (_heap->mode()->is_generational()) {
size_t max = 0;
size_t total_free = 0;
size_t total_used = 0;
for (idx_t idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
idx <= _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector); idx++) {
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, idx)) {
ShenandoahHeapRegion *r = _heap->get_region(idx);
size_t free = alloc_capacity(r);
max = MAX2(max, free);
total_free += free;
total_used += r->used();
}
}
ls.print_cr(" Old Collector Reserve: %zu%s, Max: %zu%s; Used: %zu%s",
byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
byte_size_in_proper_unit(max), proper_unit_for_byte_size(max),
byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used));
}
}
}
HeapWord* ShenandoahFreeSet::allocate(ShenandoahAllocRequest& req, bool& in_new_region) {
shenandoah_assert_heaplocked();
if (ShenandoahHeapRegion::requires_humongous(req.size())) {
switch (req.type()) {
case ShenandoahAllocRequest::_alloc_shared:
case ShenandoahAllocRequest::_alloc_shared_gc:
in_new_region = true;
return allocate_contiguous(req, /* is_humongous = */ true);
case ShenandoahAllocRequest::_alloc_cds:
in_new_region = true;
return allocate_contiguous(req, /* is_humongous = */ false);
case ShenandoahAllocRequest::_alloc_plab:
case ShenandoahAllocRequest::_alloc_gclab:
case ShenandoahAllocRequest::_alloc_tlab:
in_new_region = false;
assert(false, "Trying to allocate TLAB in humongous region: %zu", req.size());
return nullptr;
default:
ShouldNotReachHere();
return nullptr;
}
} else {
return allocate_single(req, in_new_region);
}
}
void ShenandoahFreeSet::print_on(outputStream* out) const {
out->print_cr("Mutator Free Set: %zu", _partitions.count(ShenandoahFreeSetPartitionId::Mutator));
ShenandoahLeftRightIterator mutator(const_cast<ShenandoahRegionPartitions*>(&_partitions), ShenandoahFreeSetPartitionId::Mutator);
for (idx_t index = mutator.current(); mutator.has_next(); index = mutator.next()) {
_heap->get_region(index)->print_on(out);
}
out->print_cr("Collector Free Set: %zu", _partitions.count(ShenandoahFreeSetPartitionId::Collector));
ShenandoahLeftRightIterator collector(const_cast<ShenandoahRegionPartitions*>(&_partitions), ShenandoahFreeSetPartitionId::Collector);
for (idx_t index = collector.current(); collector.has_next(); index = collector.next()) {
_heap->get_region(index)->print_on(out);
}
if (_heap->mode()->is_generational()) {
out->print_cr("Old Collector Free Set: %zu", _partitions.count(ShenandoahFreeSetPartitionId::OldCollector));
for (idx_t index = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
index <= _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector); index++) {
if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
_heap->get_region(index)->print_on(out);
}
}
}
}
double ShenandoahFreeSet::internal_fragmentation() {
double squared = 0;
double linear = 0;
ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
for (idx_t index = iterator.current(); iterator.has_next(); index = iterator.next()) {
ShenandoahHeapRegion* r = _heap->get_region(index);
size_t used = r->used();
squared += used * used;
linear += used;
}
if (linear > 0) {
double s = squared / (ShenandoahHeapRegion::region_size_bytes() * linear);
return 1 - s;
} else {
return 0;
}
}
double ShenandoahFreeSet::external_fragmentation() {
idx_t last_idx = 0;
size_t max_contig = 0;
size_t empty_contig = 0;
size_t free = 0;
ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
for (idx_t index = iterator.current(); iterator.has_next(); index = iterator.next()) {
ShenandoahHeapRegion* r = _heap->get_region(index);
if (r->is_empty()) {
free += ShenandoahHeapRegion::region_size_bytes();
if (last_idx + 1 == index) {
empty_contig++;
} else {
empty_contig = 1;
}
} else {
empty_contig = 0;
}
max_contig = MAX2(max_contig, empty_contig);
last_idx = index;
}
if (free > 0) {
return 1 - (1.0 * max_contig * ShenandoahHeapRegion::region_size_bytes() / free);
} else {
return 0;
}
}