jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/shared/parGCAllocBuffer.cpp@f90c822e73f8 (annotated)

src/share/vm/gc_implementation/shared/parGCAllocBuffer.cpp@f90c822e73f8 (annotated)

src/share/vm/gc_implementation/shared/parGCAllocBuffer.cpp

Wed, 27 Apr 2016 01:25:04 +0800

author: aoqi
date: Wed, 27 Apr 2016 01:25:04 +0800
changeset 0: f90c822e73f8
child 6876: 710a3c8b516e
permissions: -rw-r--r--

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http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/
changeset: 6782:28b50d07f6f8
tag: jdk8u25-b17

 /*
  * 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");
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/shared/parGCAllocBuffer.cpp@f90c822e73f8 (annotated)

src/share/vm/gc_implementation/shared/parGCAllocBuffer.cpp