/*
* Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
#include "precompiled.hpp"
#include "gc/shared/blockOffsetTable.inline.hpp"
#include "gc/shared/cardGeneration.inline.hpp"
#include "gc/shared/cardTableRS.hpp"
#include "gc/shared/gcLocker.hpp"
#include "gc/shared/genCollectedHeap.hpp"
#include "gc/shared/genOopClosures.inline.hpp"
#include "gc/shared/generationSpec.hpp"
#include "gc/shared/space.inline.hpp"
#include "memory/iterator.hpp"
#include "memory/memRegion.hpp"
#include "logging/log.hpp"
#include "runtime/java.hpp"
CardGeneration::CardGeneration(ReservedSpace rs,
size_t initial_byte_size,
CardTableRS* remset) :
Generation(rs, initial_byte_size), _rs(remset),
_shrink_factor(0), _min_heap_delta_bytes(), _capacity_at_prologue(),
_used_at_prologue()
{
HeapWord* start = (HeapWord*)rs.base();
size_t reserved_byte_size = rs.size();
assert((uintptr_t(start) & 3) == 0, "bad alignment");
assert((reserved_byte_size & 3) == 0, "bad alignment");
MemRegion reserved_mr(start, heap_word_size(reserved_byte_size));
_bts = new BlockOffsetSharedArray(reserved_mr,
heap_word_size(initial_byte_size));
MemRegion committed_mr(start, heap_word_size(initial_byte_size));
_rs->resize_covered_region(committed_mr);
if (_bts == NULL) {
vm_exit_during_initialization("Could not allocate a BlockOffsetArray");
}
// Verify that the start and end of this generation is the start of a card.
// If this wasn't true, a single card could span more than on generation,
// which would cause problems when we commit/uncommit memory, and when we
// clear and dirty cards.
guarantee(_rs->is_aligned(reserved_mr.start()), "generation must be card aligned");
if (reserved_mr.end() != GenCollectedHeap::heap()->reserved_region().end()) {
// Don't check at the very end of the heap as we'll assert that we're probing off
// the end if we try.
guarantee(_rs->is_aligned(reserved_mr.end()), "generation must be card aligned");
}
_min_heap_delta_bytes = MinHeapDeltaBytes;
_capacity_at_prologue = initial_byte_size;
_used_at_prologue = 0;
}
bool CardGeneration::grow_by(size_t bytes) {
assert_correct_size_change_locking();
bool result = _virtual_space.expand_by(bytes);
if (result) {
size_t new_word_size =
heap_word_size(_virtual_space.committed_size());
MemRegion mr(space()->bottom(), new_word_size);
// Expand card table
GenCollectedHeap::heap()->rem_set()->resize_covered_region(mr);
// Expand shared block offset array
_bts->resize(new_word_size);
// Fix for bug #4668531
if (ZapUnusedHeapArea) {
MemRegion mangle_region(space()->end(),
(HeapWord*)_virtual_space.high());
SpaceMangler::mangle_region(mangle_region);
}
// Expand space -- also expands space's BOT
// (which uses (part of) shared array above)
space()->set_end((HeapWord*)_virtual_space.high());
// update the space and generation capacity counters
update_counters();
size_t new_mem_size = _virtual_space.committed_size();
size_t old_mem_size = new_mem_size - bytes;
log_trace(gc, heap)("Expanding %s from " SIZE_FORMAT "K by " SIZE_FORMAT "K to " SIZE_FORMAT "K",
name(), old_mem_size/K, bytes/K, new_mem_size/K);
}
return result;
}
bool CardGeneration::expand(size_t bytes, size_t expand_bytes) {
assert_locked_or_safepoint(Heap_lock);
if (bytes == 0) {
return true; // That's what grow_by(0) would return
}
size_t aligned_bytes = ReservedSpace::page_align_size_up(bytes);
if (aligned_bytes == 0){
// The alignment caused the number of bytes to wrap. An expand_by(0) will
// return true with the implication that an expansion was done when it
// was not. A call to expand implies a best effort to expand by "bytes"
// but not a guarantee. Align down to give a best effort. This is likely
// the most that the generation can expand since it has some capacity to
// start with.
aligned_bytes = ReservedSpace::page_align_size_down(bytes);
}
size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
bool success = false;
if (aligned_expand_bytes > aligned_bytes) {
success = grow_by(aligned_expand_bytes);
}
if (!success) {
success = grow_by(aligned_bytes);
}
if (!success) {
success = grow_to_reserved();
}
if (success && GCLocker::is_active_and_needs_gc()) {
log_trace(gc, heap)("Garbage collection disabled, expanded heap instead");
}
return success;
}
bool CardGeneration::grow_to_reserved() {
assert_correct_size_change_locking();
bool success = true;
const size_t remaining_bytes = _virtual_space.uncommitted_size();
if (remaining_bytes > 0) {
success = grow_by(remaining_bytes);
DEBUG_ONLY(if (!success) log_warning(gc)("grow to reserved failed");)
}
return success;
}
void CardGeneration::shrink(size_t bytes) {
assert_correct_size_change_locking();
size_t size = ReservedSpace::page_align_size_down(bytes);
if (size == 0) {
return;
}
// Shrink committed space
_virtual_space.shrink_by(size);
// Shrink space; this also shrinks the space's BOT
space()->set_end((HeapWord*) _virtual_space.high());
size_t new_word_size = heap_word_size(space()->capacity());
// Shrink the shared block offset array
_bts->resize(new_word_size);
MemRegion mr(space()->bottom(), new_word_size);
// Shrink the card table
GenCollectedHeap::heap()->rem_set()->resize_covered_region(mr);
size_t new_mem_size = _virtual_space.committed_size();
size_t old_mem_size = new_mem_size + size;
log_trace(gc, heap)("Shrinking %s from " SIZE_FORMAT "K to " SIZE_FORMAT "K",
name(), old_mem_size/K, new_mem_size/K);
}
// No young generation references, clear this generation's cards.
void CardGeneration::clear_remembered_set() {
_rs->clear(reserved());
}
// Objects in this generation may have moved, invalidate this
// generation's cards.
void CardGeneration::invalidate_remembered_set() {
_rs->invalidate(used_region());
}
void CardGeneration::compute_new_size() {
assert(_shrink_factor <= 100, "invalid shrink factor");
size_t current_shrink_factor = _shrink_factor;
_shrink_factor = 0;
// We don't have floating point command-line arguments
// Note: argument processing ensures that MinHeapFreeRatio < 100.
const double minimum_free_percentage = MinHeapFreeRatio / 100.0;
const double maximum_used_percentage = 1.0 - minimum_free_percentage;
// Compute some numbers about the state of the heap.
const size_t used_after_gc = used();
const size_t capacity_after_gc = capacity();
const double min_tmp = used_after_gc / maximum_used_percentage;
size_t minimum_desired_capacity = (size_t)MIN2(min_tmp, double(max_uintx));
// Don't shrink less than the initial generation size
minimum_desired_capacity = MAX2(minimum_desired_capacity, initial_size());
assert(used_after_gc <= minimum_desired_capacity, "sanity check");
const size_t free_after_gc = free();
const double free_percentage = ((double)free_after_gc) / capacity_after_gc;
log_trace(gc, heap)("TenuredGeneration::compute_new_size:");
log_trace(gc, heap)(" minimum_free_percentage: %6.2f maximum_used_percentage: %6.2f",
minimum_free_percentage,
maximum_used_percentage);
log_trace(gc, heap)(" free_after_gc : %6.1fK used_after_gc : %6.1fK capacity_after_gc : %6.1fK",
free_after_gc / (double) K,
used_after_gc / (double) K,
capacity_after_gc / (double) K);
log_trace(gc, heap)(" free_percentage: %6.2f", free_percentage);
if (capacity_after_gc < minimum_desired_capacity) {
// If we have less free space than we want then expand
size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
// Don't expand unless it's significant
if (expand_bytes >= _min_heap_delta_bytes) {
expand(expand_bytes, 0); // safe if expansion fails
}
log_trace(gc, heap)(" expanding: minimum_desired_capacity: %6.1fK expand_bytes: %6.1fK _min_heap_delta_bytes: %6.1fK",
minimum_desired_capacity / (double) K,
expand_bytes / (double) K,
_min_heap_delta_bytes / (double) K);
return;
}
// No expansion, now see if we want to shrink
size_t shrink_bytes = 0;
// We would never want to shrink more than this
size_t max_shrink_bytes = capacity_after_gc - minimum_desired_capacity;
if (MaxHeapFreeRatio < 100) {
const double maximum_free_percentage = MaxHeapFreeRatio / 100.0;
const double minimum_used_percentage = 1.0 - maximum_free_percentage;
const double max_tmp = used_after_gc / minimum_used_percentage;
size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(max_uintx));
maximum_desired_capacity = MAX2(maximum_desired_capacity, initial_size());
log_trace(gc, heap)(" maximum_free_percentage: %6.2f minimum_used_percentage: %6.2f",
maximum_free_percentage, minimum_used_percentage);
log_trace(gc, heap)(" _capacity_at_prologue: %6.1fK minimum_desired_capacity: %6.1fK maximum_desired_capacity: %6.1fK",
_capacity_at_prologue / (double) K,
minimum_desired_capacity / (double) K,
maximum_desired_capacity / (double) K);
assert(minimum_desired_capacity <= maximum_desired_capacity,
"sanity check");
if (capacity_after_gc > maximum_desired_capacity) {
// Capacity too large, compute shrinking size
shrink_bytes = capacity_after_gc - maximum_desired_capacity;
if (ShrinkHeapInSteps) {
// If ShrinkHeapInSteps is true (the default),
// we don't want to shrink all the way back to initSize if people call
// System.gc(), because some programs do that between "phases" and then
// we'd just have to grow the heap up again for the next phase. So we
// damp the shrinking: 0% on the first call, 10% on the second call, 40%
// on the third call, and 100% by the fourth call. But if we recompute
// size without shrinking, it goes back to 0%.
shrink_bytes = shrink_bytes / 100 * current_shrink_factor;
if (current_shrink_factor == 0) {
_shrink_factor = 10;
} else {
_shrink_factor = MIN2(current_shrink_factor * 4, (size_t) 100);
}
}
assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
log_trace(gc, heap)(" shrinking: initSize: %.1fK maximum_desired_capacity: %.1fK",
initial_size() / (double) K, maximum_desired_capacity / (double) K);
log_trace(gc, heap)(" shrink_bytes: %.1fK current_shrink_factor: " SIZE_FORMAT " new shrink factor: " SIZE_FORMAT " _min_heap_delta_bytes: %.1fK",
shrink_bytes / (double) K,
current_shrink_factor,
_shrink_factor,
_min_heap_delta_bytes / (double) K);
}
}
if (capacity_after_gc > _capacity_at_prologue) {
// We might have expanded for promotions, in which case we might want to
// take back that expansion if there's room after GC. That keeps us from
// stretching the heap with promotions when there's plenty of room.
size_t expansion_for_promotion = capacity_after_gc - _capacity_at_prologue;
expansion_for_promotion = MIN2(expansion_for_promotion, max_shrink_bytes);
// We have two shrinking computations, take the largest
shrink_bytes = MAX2(shrink_bytes, expansion_for_promotion);
assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
log_trace(gc, heap)(" aggressive shrinking: _capacity_at_prologue: %.1fK capacity_after_gc: %.1fK expansion_for_promotion: %.1fK shrink_bytes: %.1fK",
capacity_after_gc / (double) K,
_capacity_at_prologue / (double) K,
expansion_for_promotion / (double) K,
shrink_bytes / (double) K);
}
// Don't shrink unless it's significant
if (shrink_bytes >= _min_heap_delta_bytes) {
shrink(shrink_bytes);
}
}
// Currently nothing to do.
void CardGeneration::prepare_for_verify() {}
void CardGeneration::space_iterate(SpaceClosure* blk,
bool usedOnly) {
blk->do_space(space());
}
void CardGeneration::younger_refs_iterate(OopsInGenClosure* blk, uint n_threads) {
blk->set_generation(this);
younger_refs_in_space_iterate(space(), blk, n_threads);
blk->reset_generation();
}