truffle: src/share/vm/gc_implementation/parNew/parGCAllocBuffer.cpp comparison

comparison src/share/vm/gc_implementation/parNew/parGCAllocBuffer.cpp @ 0:a61af66fc99e jdk7-b24

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author	duke
date	Sat, 01 Dec 2007 00:00:00 +0000
parents
children	ba764ed4b6f2

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--1:000000000000
+:a61af66fc99e
+/*
+* Copyright 2001-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+* CA 95054 USA or visit www.sun.com if you need additional information or
+* have any questions.
+*
+*/
+# include "incls/_precompiled.incl"
+# include "incls/_parGCAllocBuffer.cpp.incl"
+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!");
+}
+const size_t ParGCAllocBuffer::FillerHeaderSize =
+align_object_size(arrayOopDesc::header_size(T_INT));
+// 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.
+const size_t ParGCAllocBuffer::AlignmentReserve =
+oopDesc::header_size() > MinObjAlignment ? FillerHeaderSize : 0;
+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");
+SharedHeap::fill_region_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) {
+SharedHeap::fill_region_with_object(MemRegion(_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) {
+SharedHeap::fill_region_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");
+SharedHeap::fill_region_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->address_for_index(first_card_index + 1);
+// 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.");
+MemRegion chunk_portion(chunk_boundary, _hard_end);
+_bt.BlockOffsetArray::alloc_block(chunk_portion.start(),
+chunk_portion.end());
+SharedHeap::fill_region_with_object(chunk_portion);
+_hard_end = chunk_portion.start();
+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");
+}

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comparison src/share/vm/gc_implementation/parNew/parGCAllocBuffer.cpp @ 0:a61af66fc99e jdk7-b24