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 /*

  * Copyright (c) 2001, 2013, 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

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP

 #include "memory/allocation.hpp"

 #include "memory/blockOffsetTable.hpp"

 #include "memory/threadLocalAllocBuffer.hpp"

 #include "utilities/globalDefinitions.hpp"

 // Forward decl.

 class PLABStats;

 // A per-thread allocation buffer used during GC.

 class ParGCAllocBuffer: public CHeapObj<mtGC> {

 protected:

   char head[32];

   size_t _word_sz;          // in HeapWord units

   HeapWord* _bottom;

   HeapWord* _top;

   HeapWord* _end;       // last allocatable address + 1

   HeapWord* _hard_end;  // _end + AlignmentReserve

   bool      _retained;  // whether we hold a _retained_filler

   MemRegion _retained_filler;

   // In support of ergonomic sizing of PLAB's

   size_t    _allocated;     // in HeapWord units

   size_t    _wasted;        // in HeapWord units

   char tail[32];

   static size_t FillerHeaderSize;

   static size_t AlignmentReserve;

   // Flush the stats supporting ergonomic sizing of PLAB's

   // Should not be called directly

   void flush_stats(PLABStats* stats);

 public:

   // Initializes the buffer to be empty, but with the given "word_sz".

   // Must get initialized with "set_buf" for an allocation to succeed.

   ParGCAllocBuffer(size_t word_sz);

   virtual ~ParGCAllocBuffer() {}

   static const size_t min_size() {

     return ThreadLocalAllocBuffer::min_size();

   }

   static const size_t max_size() {

     return ThreadLocalAllocBuffer::max_size();

   }

   // If an allocation of the given "word_sz" can be satisfied within the

   // buffer, do the allocation, returning a pointer to the start of the

   // allocated block.  If the allocation request cannot be satisfied,

   // return NULL.

   HeapWord* allocate(size_t word_sz) {

     HeapWord* res = _top;

     if (pointer_delta(_end, _top) >= word_sz) {

       _top = _top + word_sz;

       return res;

     } else {

       return NULL;

     }

   }

   // Undo the last allocation in the buffer, which is required to be of the

   // "obj" of the given "word_sz".

   void undo_allocation(HeapWord* obj, size_t word_sz) {

     assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");

     assert(pointer_delta(_top, obj)     == word_sz, "Bad undo");

     _top = obj;

   }

   // The total (word) size of the buffer, including both allocated and

   // unallocted space.

   size_t word_sz() { return _word_sz; }

   // Should only be done if we are about to reset with a new buffer of the

   // given size.

   void set_word_size(size_t new_word_sz) {

     assert(new_word_sz > AlignmentReserve, "Too small");

     _word_sz = new_word_sz;

   }

   // The number of words of unallocated space remaining in the buffer.

   size_t words_remaining() {

     assert(_end >= _top, "Negative buffer");

     return pointer_delta(_end, _top, HeapWordSize);

   }

   bool contains(void* addr) {

     return (void*)_bottom <= addr && addr < (void*)_hard_end;

   }

   // Sets the space of the buffer to be [buf, space+word_sz()).

   virtual void set_buf(HeapWord* buf) {

     _bottom   = buf;

     _top      = _bottom;

     _hard_end = _bottom + word_sz();

     _end      = _hard_end - AlignmentReserve;

     assert(_end >= _top, "Negative buffer");

     // In support of ergonomic sizing

     _allocated += word_sz();

   }

   // Flush the stats supporting ergonomic sizing of PLAB's

   // and retire the current buffer.

   void flush_stats_and_retire(PLABStats* stats, bool end_of_gc, bool retain) {

     // We flush the stats first in order to get a reading of

     // unused space in the last buffer.

     if (ResizePLAB) {

       flush_stats(stats);

       // Since we have flushed the stats we need to clear

       // the _allocated and _wasted fields. Not doing so

       // will artifically inflate the values in the stats

       // to which we add them.

       // The next time we flush these values, we will add

       // what we have just flushed in addition to the size

       // of the buffers allocated between now and then.

       _allocated = 0;

       _wasted = 0;

     }

     // Retire the last allocation buffer.

     retire(end_of_gc, retain);

   }

   // Force future allocations to fail and queries for contains()

   // to return false

   void invalidate() {

     assert(!_retained, "Shouldn't retain an invalidated buffer.");

     _end    = _hard_end;

     _wasted += pointer_delta(_end, _top);  // unused  space

     _top    = _end;      // force future allocations to fail

     _bottom = _end;      // force future contains() queries to return false

   }

   // Fills in the unallocated portion of the buffer with a garbage object.

   // If "end_of_gc" is TRUE, is after the last use in the GC.  IF "retain"

   // is true, attempt to re-use the unused portion in the next GC.

   virtual void retire(bool end_of_gc, bool retain);

   void print() PRODUCT_RETURN;

 };

 // PLAB stats book-keeping

 class PLABStats VALUE_OBJ_CLASS_SPEC {

   size_t _allocated;      // total allocated

   size_t _wasted;         // of which wasted (internal fragmentation)

   size_t _unused;         // Unused in last buffer

   size_t _used;           // derived = allocated - wasted - unused

   size_t _desired_plab_sz;// output of filter (below), suitably trimmed and quantized

   AdaptiveWeightedAverage

          _filter;         // integrator with decay

  public:

   PLABStats(size_t desired_plab_sz_, unsigned wt) :

     _allocated(0),

     _wasted(0),

     _unused(0),

     _used(0),

     _desired_plab_sz(desired_plab_sz_),

     _filter(wt)

   { }

   static const size_t min_size() {

     return ParGCAllocBuffer::min_size();

   }

   static const size_t max_size() {

     return ParGCAllocBuffer::max_size();

   }

   size_t desired_plab_sz() {

     return _desired_plab_sz;

   }

   void adjust_desired_plab_sz(uint no_of_gc_workers);

                                  // filter computation, latches output to

                                  // _desired_plab_sz, clears sensor accumulators

   void add_allocated(size_t v) {

     Atomic::add_ptr(v, &_allocated);

   }

   void add_unused(size_t v) {

     Atomic::add_ptr(v, &_unused);

   }

   void add_wasted(size_t v) {

     Atomic::add_ptr(v, &_wasted);

   }

 };

 class ParGCAllocBufferWithBOT: public ParGCAllocBuffer {

   BlockOffsetArrayContigSpace _bt;

   BlockOffsetSharedArray*     _bsa;

   HeapWord*                   _true_end;  // end of the whole ParGCAllocBuffer

   static const size_t ChunkSizeInWords;

   static const size_t ChunkSizeInBytes;

   HeapWord* allocate_slow(size_t word_sz);

   void fill_region_with_block(MemRegion mr, bool contig);

 public:

   ParGCAllocBufferWithBOT(size_t word_sz, BlockOffsetSharedArray* bsa);

   HeapWord* allocate(size_t word_sz) {

     HeapWord* res = ParGCAllocBuffer::allocate(word_sz);

     if (res != NULL) {

       _bt.alloc_block(res, word_sz);

     } else {

       res = allocate_slow(word_sz);

     }

     return res;

   }

   void undo_allocation(HeapWord* obj, size_t word_sz);

   virtual void set_buf(HeapWord* buf_start) {

     ParGCAllocBuffer::set_buf(buf_start);

     _true_end = _hard_end;

     _bt.set_region(MemRegion(buf_start, word_sz()));

     _bt.initialize_threshold();

   }

   virtual void retire(bool end_of_gc, bool retain);

   MemRegion range() {

     return MemRegion(_top, _true_end);

   }

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP