--- a/hotspot/src/share/vm/gc_implementation/parNew/parGCAllocBuffer.cpp Thu Aug 23 12:27:59 2012 -0700
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,344 +0,0 @@
-/*
- * Copyright (c) 2001, 2010, 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/parNew/parGCAllocBuffer.hpp"
-#include "memory/sharedHeap.hpp"
-#include "oops/arrayOop.hpp"
-#include "oops/oop.inline.hpp"
-
-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() {
- assert(ResizePLAB, "Not set");
- if (_allocated == 0) {
- assert(_unused == 0, "Inconsistency in PLAB stats");
- _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*ParallelGCThreads);
- 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);
- if (ResizePLAB) {
- _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");
-}