| /* |
| * Copyright (c) 2001, 2014, 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/parGCAllocBuffer.hpp" |
| #include "memory/sharedHeap.hpp" |
| #include "oops/arrayOop.hpp" |
| #include "oops/oop.inline.hpp" |
| |
| PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC |
| |
| ParGCAllocBuffer::ParGCAllocBuffer(size_t desired_plab_sz_) : |
| _word_sz(desired_plab_sz_), _bottom(NULL), _top(NULL), |
| _end(NULL), _hard_end(NULL), |
| _retained(false), _retained_filler(), |
| _allocated(0), _wasted(0) |
| { |
| assert (min_size() > AlignmentReserve, "Inconsistency!"); |
| // arrayOopDesc::header_size depends on command line initialization. |
| FillerHeaderSize = align_object_size(arrayOopDesc::header_size(T_INT)); |
| AlignmentReserve = oopDesc::header_size() > MinObjAlignment ? FillerHeaderSize : 0; |
| } |
| |
| size_t ParGCAllocBuffer::FillerHeaderSize; |
| |
| // If the minimum object size is greater than MinObjAlignment, we can |
| // end up with a shard at the end of the buffer that's smaller than |
| // the smallest object. We can't allow that because the buffer must |
| // look like it's full of objects when we retire it, so we make |
| // sure we have enough space for a filler int array object. |
| size_t ParGCAllocBuffer::AlignmentReserve; |
| |
| void ParGCAllocBuffer::retire(bool end_of_gc, bool retain) { |
| assert(!retain || end_of_gc, "Can only retain at GC end."); |
| if (_retained) { |
| // If the buffer had been retained shorten the previous filler object. |
| assert(_retained_filler.end() <= _top, "INVARIANT"); |
| CollectedHeap::fill_with_object(_retained_filler); |
| // Wasted space book-keeping, otherwise (normally) done in invalidate() |
| _wasted += _retained_filler.word_size(); |
| _retained = false; |
| } |
| assert(!end_of_gc || !_retained, "At this point, end_of_gc ==> !_retained."); |
| if (_top < _hard_end) { |
| CollectedHeap::fill_with_object(_top, _hard_end); |
| if (!retain) { |
| invalidate(); |
| } else { |
| // Is there wasted space we'd like to retain for the next GC? |
| if (pointer_delta(_end, _top) > FillerHeaderSize) { |
| _retained = true; |
| _retained_filler = MemRegion(_top, FillerHeaderSize); |
| _top = _top + FillerHeaderSize; |
| } else { |
| invalidate(); |
| } |
| } |
| } |
| } |
| |
| void ParGCAllocBuffer::flush_stats(PLABStats* stats) { |
| assert(ResizePLAB, "Wasted work"); |
| stats->add_allocated(_allocated); |
| stats->add_wasted(_wasted); |
| stats->add_unused(pointer_delta(_end, _top)); |
| } |
| |
| // Compute desired plab size and latch result for later |
| // use. This should be called once at the end of parallel |
| // scavenge; it clears the sensor accumulators. |
| void PLABStats::adjust_desired_plab_sz(uint no_of_gc_workers) { |
| assert(ResizePLAB, "Not set"); |
| |
| assert(is_object_aligned(max_size()) && min_size() <= max_size(), |
| "PLAB clipping computation may be incorrect"); |
| |
| if (_allocated == 0) { |
| assert(_unused == 0, |
| err_msg("Inconsistency in PLAB stats: " |
| "_allocated: "SIZE_FORMAT", " |
| "_wasted: "SIZE_FORMAT", " |
| "_unused: "SIZE_FORMAT", " |
| "_used : "SIZE_FORMAT, |
| _allocated, _wasted, _unused, _used)); |
| |
| _allocated = 1; |
| } |
| double wasted_frac = (double)_unused/(double)_allocated; |
| size_t target_refills = (size_t)((wasted_frac*TargetSurvivorRatio)/ |
| TargetPLABWastePct); |
| if (target_refills == 0) { |
| target_refills = 1; |
| } |
| _used = _allocated - _wasted - _unused; |
| size_t plab_sz = _used/(target_refills*no_of_gc_workers); |
| if (PrintPLAB) gclog_or_tty->print(" (plab_sz = %d ", plab_sz); |
| // Take historical weighted average |
| _filter.sample(plab_sz); |
| // Clip from above and below, and align to object boundary |
| plab_sz = MAX2(min_size(), (size_t)_filter.average()); |
| plab_sz = MIN2(max_size(), plab_sz); |
| plab_sz = align_object_size(plab_sz); |
| // Latch the result |
| if (PrintPLAB) gclog_or_tty->print(" desired_plab_sz = %d) ", plab_sz); |
| _desired_plab_sz = plab_sz; |
| // Now clear the accumulators for next round: |
| // note this needs to be fixed in the case where we |
| // are retaining across scavenges. FIX ME !!! XXX |
| _allocated = 0; |
| _wasted = 0; |
| _unused = 0; |
| } |
| |
| #ifndef PRODUCT |
| void ParGCAllocBuffer::print() { |
| gclog_or_tty->print("parGCAllocBuffer: _bottom: %p _top: %p _end: %p _hard_end: %p" |
| "_retained: %c _retained_filler: [%p,%p)\n", |
| _bottom, _top, _end, _hard_end, |
| "FT"[_retained], _retained_filler.start(), _retained_filler.end()); |
| } |
| #endif // !PRODUCT |
| |
| const size_t ParGCAllocBufferWithBOT::ChunkSizeInWords = |
| MIN2(CardTableModRefBS::par_chunk_heapword_alignment(), |
| ((size_t)Generation::GenGrain)/HeapWordSize); |
| const size_t ParGCAllocBufferWithBOT::ChunkSizeInBytes = |
| MIN2(CardTableModRefBS::par_chunk_heapword_alignment() * HeapWordSize, |
| (size_t)Generation::GenGrain); |
| |
| ParGCAllocBufferWithBOT::ParGCAllocBufferWithBOT(size_t word_sz, |
| BlockOffsetSharedArray* bsa) : |
| ParGCAllocBuffer(word_sz), |
| _bsa(bsa), |
| _bt(bsa, MemRegion(_bottom, _hard_end)), |
| _true_end(_hard_end) |
| {} |
| |
| // The buffer comes with its own BOT, with a shared (obviously) underlying |
| // BlockOffsetSharedArray. We manipulate this BOT in the normal way |
| // as we would for any contiguous space. However, on accasion we |
| // need to do some buffer surgery at the extremities before we |
| // start using the body of the buffer for allocations. Such surgery |
| // (as explained elsewhere) is to prevent allocation on a card that |
| // is in the process of being walked concurrently by another GC thread. |
| // When such surgery happens at a point that is far removed (to the |
| // right of the current allocation point, top), we use the "contig" |
| // parameter below to directly manipulate the shared array without |
| // modifying the _next_threshold state in the BOT. |
| void ParGCAllocBufferWithBOT::fill_region_with_block(MemRegion mr, |
| bool contig) { |
| CollectedHeap::fill_with_object(mr); |
| if (contig) { |
| _bt.alloc_block(mr.start(), mr.end()); |
| } else { |
| _bt.BlockOffsetArray::alloc_block(mr.start(), mr.end()); |
| } |
| } |
| |
| HeapWord* ParGCAllocBufferWithBOT::allocate_slow(size_t word_sz) { |
| HeapWord* res = NULL; |
| if (_true_end > _hard_end) { |
| assert((HeapWord*)align_size_down(intptr_t(_hard_end), |
| ChunkSizeInBytes) == _hard_end, |
| "or else _true_end should be equal to _hard_end"); |
| assert(_retained, "or else _true_end should be equal to _hard_end"); |
| assert(_retained_filler.end() <= _top, "INVARIANT"); |
| CollectedHeap::fill_with_object(_retained_filler); |
| if (_top < _hard_end) { |
| fill_region_with_block(MemRegion(_top, _hard_end), true); |
| } |
| HeapWord* next_hard_end = MIN2(_true_end, _hard_end + ChunkSizeInWords); |
| _retained_filler = MemRegion(_hard_end, FillerHeaderSize); |
| _bt.alloc_block(_retained_filler.start(), _retained_filler.word_size()); |
| _top = _retained_filler.end(); |
| _hard_end = next_hard_end; |
| _end = _hard_end - AlignmentReserve; |
| res = ParGCAllocBuffer::allocate(word_sz); |
| if (res != NULL) { |
| _bt.alloc_block(res, word_sz); |
| } |
| } |
| return res; |
| } |
| |
| void |
| ParGCAllocBufferWithBOT::undo_allocation(HeapWord* obj, size_t word_sz) { |
| ParGCAllocBuffer::undo_allocation(obj, word_sz); |
| // This may back us up beyond the previous threshold, so reset. |
| _bt.set_region(MemRegion(_top, _hard_end)); |
| _bt.initialize_threshold(); |
| } |
| |
| void ParGCAllocBufferWithBOT::retire(bool end_of_gc, bool retain) { |
| assert(!retain || end_of_gc, "Can only retain at GC end."); |
| if (_retained) { |
| // We're about to make the retained_filler into a block. |
| _bt.BlockOffsetArray::alloc_block(_retained_filler.start(), |
| _retained_filler.end()); |
| } |
| // Reset _hard_end to _true_end (and update _end) |
| if (retain && _hard_end != NULL) { |
| assert(_hard_end <= _true_end, "Invariant."); |
| _hard_end = _true_end; |
| _end = MAX2(_top, _hard_end - AlignmentReserve); |
| assert(_end <= _hard_end, "Invariant."); |
| } |
| _true_end = _hard_end; |
| HeapWord* pre_top = _top; |
| |
| ParGCAllocBuffer::retire(end_of_gc, retain); |
| // Now any old _retained_filler is cut back to size, the free part is |
| // filled with a filler object, and top is past the header of that |
| // object. |
| |
| if (retain && _top < _end) { |
| assert(end_of_gc && retain, "Or else retain should be false."); |
| // If the lab does not start on a card boundary, we don't want to |
| // allocate onto that card, since that might lead to concurrent |
| // allocation and card scanning, which we don't support. So we fill |
| // the first card with a garbage object. |
| size_t first_card_index = _bsa->index_for(pre_top); |
| HeapWord* first_card_start = _bsa->address_for_index(first_card_index); |
| if (first_card_start < pre_top) { |
| HeapWord* second_card_start = |
| _bsa->inc_by_region_size(first_card_start); |
| |
| // Ensure enough room to fill with the smallest block |
| second_card_start = MAX2(second_card_start, pre_top + AlignmentReserve); |
| |
| // If the end is already in the first card, don't go beyond it! |
| // Or if the remainder is too small for a filler object, gobble it up. |
| if (_hard_end < second_card_start || |
| pointer_delta(_hard_end, second_card_start) < AlignmentReserve) { |
| second_card_start = _hard_end; |
| } |
| if (pre_top < second_card_start) { |
| MemRegion first_card_suffix(pre_top, second_card_start); |
| fill_region_with_block(first_card_suffix, true); |
| } |
| pre_top = second_card_start; |
| _top = pre_top; |
| _end = MAX2(_top, _hard_end - AlignmentReserve); |
| } |
| |
| // If the lab does not end on a card boundary, we don't want to |
| // allocate onto that card, since that might lead to concurrent |
| // allocation and card scanning, which we don't support. So we fill |
| // the last card with a garbage object. |
| size_t last_card_index = _bsa->index_for(_hard_end); |
| HeapWord* last_card_start = _bsa->address_for_index(last_card_index); |
| if (last_card_start < _hard_end) { |
| |
| // Ensure enough room to fill with the smallest block |
| last_card_start = MIN2(last_card_start, _hard_end - AlignmentReserve); |
| |
| // If the top is already in the last card, don't go back beyond it! |
| // Or if the remainder is too small for a filler object, gobble it up. |
| if (_top > last_card_start || |
| pointer_delta(last_card_start, _top) < AlignmentReserve) { |
| last_card_start = _top; |
| } |
| if (last_card_start < _hard_end) { |
| MemRegion last_card_prefix(last_card_start, _hard_end); |
| fill_region_with_block(last_card_prefix, false); |
| } |
| _hard_end = last_card_start; |
| _end = MAX2(_top, _hard_end - AlignmentReserve); |
| _true_end = _hard_end; |
| assert(_end <= _hard_end, "Invariant."); |
| } |
| |
| // At this point: |
| // 1) we had a filler object from the original top to hard_end. |
| // 2) We've filled in any partial cards at the front and back. |
| if (pre_top < _hard_end) { |
| // Now we can reset the _bt to do allocation in the given area. |
| MemRegion new_filler(pre_top, _hard_end); |
| fill_region_with_block(new_filler, false); |
| _top = pre_top + ParGCAllocBuffer::FillerHeaderSize; |
| // If there's no space left, don't retain. |
| if (_top >= _end) { |
| _retained = false; |
| invalidate(); |
| return; |
| } |
| _retained_filler = MemRegion(pre_top, _top); |
| _bt.set_region(MemRegion(_top, _hard_end)); |
| _bt.initialize_threshold(); |
| assert(_bt.threshold() > _top, "initialize_threshold failed!"); |
| |
| // There may be other reasons for queries into the middle of the |
| // filler object. When such queries are done in parallel with |
| // allocation, bad things can happen, if the query involves object |
| // iteration. So we ensure that such queries do not involve object |
| // iteration, by putting another filler object on the boundaries of |
| // such queries. One such is the object spanning a parallel card |
| // chunk boundary. |
| |
| // "chunk_boundary" is the address of the first chunk boundary less |
| // than "hard_end". |
| HeapWord* chunk_boundary = |
| (HeapWord*)align_size_down(intptr_t(_hard_end-1), ChunkSizeInBytes); |
| assert(chunk_boundary < _hard_end, "Or else above did not work."); |
| assert(pointer_delta(_true_end, chunk_boundary) >= AlignmentReserve, |
| "Consequence of last card handling above."); |
| |
| if (_top <= chunk_boundary) { |
| assert(_true_end == _hard_end, "Invariant."); |
| while (_top <= chunk_boundary) { |
| assert(pointer_delta(_hard_end, chunk_boundary) >= AlignmentReserve, |
| "Consequence of last card handling above."); |
| _bt.BlockOffsetArray::alloc_block(chunk_boundary, _hard_end); |
| CollectedHeap::fill_with_object(chunk_boundary, _hard_end); |
| _hard_end = chunk_boundary; |
| chunk_boundary -= ChunkSizeInWords; |
| } |
| _end = _hard_end - AlignmentReserve; |
| assert(_top <= _end, "Invariant."); |
| // Now reset the initial filler chunk so it doesn't overlap with |
| // the one(s) inserted above. |
| MemRegion new_filler(pre_top, _hard_end); |
| fill_region_with_block(new_filler, false); |
| } |
| } else { |
| _retained = false; |
| invalidate(); |
| } |
| } else { |
| assert(!end_of_gc || |
| (!_retained && _true_end == _hard_end), "Checking."); |
| } |
| assert(_end <= _hard_end, "Invariant."); |
| assert(_top < _end || _top == _hard_end, "Invariant"); |
| } |
