/*
* Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "gc_implementation/shared/collectorCounters.hpp"
#include "gc_implementation/shared/parGCAllocBuffer.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/blockOffsetTable.inline.hpp"
#include "memory/generation.inline.hpp"
#include "memory/generationSpec.hpp"
#include "memory/space.hpp"
#include "memory/tenuredGeneration.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/java.hpp"
TenuredGeneration::TenuredGeneration(ReservedSpace rs,
size_t initial_byte_size, int level,
GenRemSet* remset) :
OneContigSpaceCardGeneration(rs, initial_byte_size,
MinHeapDeltaBytes, level, remset, NULL)
{
HeapWord* bottom = (HeapWord*) _virtual_space.low();
HeapWord* end = (HeapWord*) _virtual_space.high();
_the_space = new TenuredSpace(_bts, MemRegion(bottom, end));
_the_space->reset_saved_mark();
_shrink_factor = 0;
_capacity_at_prologue = 0;
_gc_stats = new GCStats();
// initialize performance counters
const char* gen_name = "old";
// Generation Counters -- generation 1, 1 subspace
_gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space);
_gc_counters = new CollectorCounters("MSC", 1);
_space_counters = new CSpaceCounters(gen_name, 0,
_virtual_space.reserved_size(),
_the_space, _gen_counters);
#ifndef SERIALGC
if (UseParNewGC && ParallelGCThreads > 0) {
typedef ParGCAllocBufferWithBOT* ParGCAllocBufferWithBOTPtr;
_alloc_buffers = NEW_C_HEAP_ARRAY(ParGCAllocBufferWithBOTPtr,
ParallelGCThreads, mtGC);
if (_alloc_buffers == NULL)
vm_exit_during_initialization("Could not allocate alloc_buffers");
for (uint i = 0; i < ParallelGCThreads; i++) {
_alloc_buffers[i] =
new ParGCAllocBufferWithBOT(OldPLABSize, _bts);
if (_alloc_buffers[i] == NULL)
vm_exit_during_initialization("Could not allocate alloc_buffers");
}
} else {
_alloc_buffers = NULL;
}
#endif // SERIALGC
}
const char* TenuredGeneration::name() const {
return "tenured generation";
}
void TenuredGeneration::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,
spec()->init_size());
assert(used_after_gc <= minimum_desired_capacity, "sanity check");
if (PrintGC && Verbose) {
const size_t free_after_gc = free();
const double free_percentage = ((double)free_after_gc) / capacity_after_gc;
gclog_or_tty->print_cr("TenuredGeneration::compute_new_size: ");
gclog_or_tty->print_cr(" "
" minimum_free_percentage: %6.2f"
" maximum_used_percentage: %6.2f",
minimum_free_percentage,
maximum_used_percentage);
gclog_or_tty->print_cr(" "
" 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);
gclog_or_tty->print_cr(" "
" 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
}
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" 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,
spec()->init_size());
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" "
" maximum_free_percentage: %6.2f"
" minimum_used_percentage: %6.2f",
maximum_free_percentage,
minimum_used_percentage);
gclog_or_tty->print_cr(" "
" _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;
// We don't want 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;
assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
if (current_shrink_factor == 0) {
_shrink_factor = 10;
} else {
_shrink_factor = MIN2(current_shrink_factor * 4, (size_t) 100);
}
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" "
" shrinking:"
" initSize: %.1fK"
" maximum_desired_capacity: %.1fK",
spec()->init_size() / (double) K,
maximum_desired_capacity / (double) K);
gclog_or_tty->print_cr(" "
" shrink_bytes: %.1fK"
" current_shrink_factor: %d"
" new shrink factor: %d"
" _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");
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(" "
" 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);
}
assert(used() == used_after_gc && used_after_gc <= capacity(),
"sanity check");
}
void TenuredGeneration::gc_prologue(bool full) {
_capacity_at_prologue = capacity();
_used_at_prologue = used();
if (VerifyBeforeGC) {
verify_alloc_buffers_clean();
}
}
void TenuredGeneration::gc_epilogue(bool full) {
if (VerifyAfterGC) {
verify_alloc_buffers_clean();
}
OneContigSpaceCardGeneration::gc_epilogue(full);
}
bool TenuredGeneration::should_collect(bool full,
size_t size,
bool is_tlab) {
// This should be one big conditional or (||), but I want to be able to tell
// why it returns what it returns (without re-evaluating the conditionals
// in case they aren't idempotent), so I'm doing it this way.
// DeMorgan says it's okay.
bool result = false;
if (!result && full) {
result = true;
if (PrintGC && Verbose) {
gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
" full");
}
}
if (!result && should_allocate(size, is_tlab)) {
result = true;
if (PrintGC && Verbose) {
gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
" should_allocate(" SIZE_FORMAT ")",
size);
}
}
// If we don't have very much free space.
// XXX: 10000 should be a percentage of the capacity!!!
if (!result && free() < 10000) {
result = true;
if (PrintGC && Verbose) {
gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
" free(): " SIZE_FORMAT,
free());
}
}
// If we had to expand to accomodate promotions from younger generations
if (!result && _capacity_at_prologue < capacity()) {
result = true;
if (PrintGC && Verbose) {
gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
"_capacity_at_prologue: " SIZE_FORMAT " < capacity(): " SIZE_FORMAT,
_capacity_at_prologue, capacity());
}
}
return result;
}
void TenuredGeneration::collect(bool full,
bool clear_all_soft_refs,
size_t size,
bool is_tlab) {
retire_alloc_buffers_before_full_gc();
OneContigSpaceCardGeneration::collect(full, clear_all_soft_refs,
size, is_tlab);
}
void TenuredGeneration::update_gc_stats(int current_level,
bool full) {
// If the next lower level(s) has been collected, gather any statistics
// that are of interest at this point.
if (!full && (current_level + 1) == level()) {
// Calculate size of data promoted from the younger generations
// before doing the collection.
size_t used_before_gc = used();
// If the younger gen collections were skipped, then the
// number of promoted bytes will be 0 and adding it to the
// average will incorrectly lessen the average. It is, however,
// also possible that no promotion was needed.
if (used_before_gc >= _used_at_prologue) {
size_t promoted_in_bytes = used_before_gc - _used_at_prologue;
gc_stats()->avg_promoted()->sample(promoted_in_bytes);
}
}
}
void TenuredGeneration::update_counters() {
if (UsePerfData) {
_space_counters->update_all();
_gen_counters->update_all();
}
}
#ifndef SERIALGC
oop TenuredGeneration::par_promote(int thread_num,
oop old, markOop m, size_t word_sz) {
ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
HeapWord* obj_ptr = buf->allocate(word_sz);
bool is_lab = true;
if (obj_ptr == NULL) {
#ifndef PRODUCT
if (Universe::heap()->promotion_should_fail()) {
return NULL;
}
#endif // #ifndef PRODUCT
// Slow path:
if (word_sz * 100 < ParallelGCBufferWastePct * buf->word_sz()) {
// Is small enough; abandon this buffer and start a new one.
size_t buf_size = buf->word_sz();
HeapWord* buf_space =
TenuredGeneration::par_allocate(buf_size, false);
if (buf_space == NULL) {
buf_space = expand_and_allocate(buf_size, false, true /* parallel*/);
}
if (buf_space != NULL) {
buf->retire(false, false);
buf->set_buf(buf_space);
obj_ptr = buf->allocate(word_sz);
assert(obj_ptr != NULL, "Buffer was definitely big enough...");
}
};
// Otherwise, buffer allocation failed; try allocating object
// individually.
if (obj_ptr == NULL) {
obj_ptr = TenuredGeneration::par_allocate(word_sz, false);
if (obj_ptr == NULL) {
obj_ptr = expand_and_allocate(word_sz, false, true /* parallel */);
}
}
if (obj_ptr == NULL) return NULL;
}
assert(obj_ptr != NULL, "program logic");
Copy::aligned_disjoint_words((HeapWord*)old, obj_ptr, word_sz);
oop obj = oop(obj_ptr);
// Restore the mark word copied above.
obj->set_mark(m);
return obj;
}
void TenuredGeneration::par_promote_alloc_undo(int thread_num,
HeapWord* obj,
size_t word_sz) {
ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
if (buf->contains(obj)) {
guarantee(buf->contains(obj + word_sz - 1),
"should contain whole object");
buf->undo_allocation(obj, word_sz);
} else {
CollectedHeap::fill_with_object(obj, word_sz);
}
}
void TenuredGeneration::par_promote_alloc_done(int thread_num) {
ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
buf->retire(true, ParallelGCRetainPLAB);
}
void TenuredGeneration::retire_alloc_buffers_before_full_gc() {
if (UseParNewGC) {
for (uint i = 0; i < ParallelGCThreads; i++) {
_alloc_buffers[i]->retire(true /*end_of_gc*/, false /*retain*/);
}
}
}
// Verify that any retained parallel allocation buffers do not
// intersect with dirty cards.
void TenuredGeneration::verify_alloc_buffers_clean() {
if (UseParNewGC) {
for (uint i = 0; i < ParallelGCThreads; i++) {
_rs->verify_aligned_region_empty(_alloc_buffers[i]->range());
}
}
}
#else // SERIALGC
void TenuredGeneration::retire_alloc_buffers_before_full_gc() {}
void TenuredGeneration::verify_alloc_buffers_clean() {}
#endif // SERIALGC
bool TenuredGeneration::promotion_attempt_is_safe(size_t max_promotion_in_bytes) const {
size_t available = max_contiguous_available();
size_t av_promo = (size_t)gc_stats()->avg_promoted()->padded_average();
bool res = (available >= av_promo) || (available >= max_promotion_in_bytes);
if (PrintGC && Verbose) {
gclog_or_tty->print_cr(
"Tenured: promo attempt is%s safe: available("SIZE_FORMAT") %s av_promo("SIZE_FORMAT"),"
"max_promo("SIZE_FORMAT")",
res? "":" not", available, res? ">=":"<",
av_promo, max_promotion_in_bytes);
}
return res;
}