| /* |
| * Copyright (c) 2014, 2015, 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/shared/blockOffsetTable.inline.hpp" |
| #include "gc/shared/cardGeneration.inline.hpp" |
| #include "gc/shared/gcLocker.hpp" |
| #include "gc/shared/genOopClosures.inline.hpp" |
| #include "gc/shared/genRemSet.hpp" |
| #include "gc/shared/generationSpec.hpp" |
| #include "gc/shared/space.inline.hpp" |
| #include "memory/iterator.hpp" |
| #include "memory/memRegion.hpp" |
| #include "runtime/java.hpp" |
| |
| CardGeneration::CardGeneration(ReservedSpace rs, |
| size_t initial_byte_size, |
| GenRemSet* 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()->barrier_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(); |
| |
| if (Verbose && PrintGC) { |
| size_t new_mem_size = _virtual_space.committed_size(); |
| size_t old_mem_size = new_mem_size - bytes; |
| gclog_or_tty->print_cr("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 (PrintGC && Verbose) { |
| if (success && GC_locker::is_active_and_needs_gc()) { |
| gclog_or_tty->print_cr("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) warning("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()->barrier_set()->resize_covered_region(mr); |
| |
| if (Verbose && PrintGC) { |
| size_t new_mem_size = _virtual_space.committed_size(); |
| size_t old_mem_size = new_mem_size + size; |
| gclog_or_tty->print_cr("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, |
| 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: " 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"); |
| 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); |
| } |
| } |
| |
| // 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(); |
| } |
