1 /*

     2  * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP

    26 #define SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP

    27 

    28 #include "memory/allocation.hpp"

    29 #include "memory/blockOffsetTable.hpp"

    30 #include "memory/threadLocalAllocBuffer.hpp"

    31 #include "utilities/globalDefinitions.hpp"

    32 

    33 // Forward decl.

    34 

    35 class PLABStats;

    36 

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

    38 class ParGCAllocBuffer: public CHeapObj<mtGC> {

    39 protected:

    40   char head[32];

    41   size_t _word_sz;          // in HeapWord units

    42   HeapWord* _bottom;

    43   HeapWord* _top;

    44   HeapWord* _end;       // last allocatable address + 1

    45   HeapWord* _hard_end;  // _end + AlignmentReserve

    46   bool      _retained;  // whether we hold a _retained_filler

    47   MemRegion _retained_filler;

    48   // In support of ergonomic sizing of PLAB's

    49   size_t    _allocated;     // in HeapWord units

    50   size_t    _wasted;        // in HeapWord units

    51   char tail[32];

    52   static size_t FillerHeaderSize;

    53   static size_t AlignmentReserve;

    54 

    55 public:

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

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

    58   ParGCAllocBuffer(size_t word_sz);

    59 

    60   static const size_t min_size() {

    61     return ThreadLocalAllocBuffer::min_size();

    62   }

    63 

    64   static const size_t max_size() {

    65     return ThreadLocalAllocBuffer::max_size();

    66   }

    67 

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

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

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

    71   // return NULL.

    72   HeapWord* allocate(size_t word_sz) {

    73     HeapWord* res = _top;

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

    75       _top = _top + word_sz;

    76       return res;

    77     } else {

    78       return NULL;

    79     }

    80   }

    81 

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

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

    84   void undo_allocation(HeapWord* obj, size_t word_sz) {

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

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

    87     _top = obj;

    88   }

    89 

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

    91   // unallocted space.

    92   size_t word_sz() { return _word_sz; }

    93 

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

    95   // given size.

    96   void set_word_size(size_t new_word_sz) {

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

    98     _word_sz = new_word_sz;

    99   }

   100 

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

   102   size_t words_remaining() {

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

   104     return pointer_delta(_end, _top, HeapWordSize);

   105   }

   106 

   107   bool contains(void* addr) {

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

   109   }

   110 

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

   112   void set_buf(HeapWord* buf) {

   113     _bottom   = buf;

   114     _top      = _bottom;

   115     _hard_end = _bottom + word_sz();

   116     _end      = _hard_end - AlignmentReserve;

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

   118     // In support of ergonomic sizing

   119     _allocated += word_sz();

   120   }

   121 

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

   123   void flush_stats(PLABStats* stats);

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

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

   126     // unused space in the last buffer.

   127     if (ResizePLAB) {

   128       flush_stats(stats);

   129     }

   130     // Retire the last allocation buffer.

   131     retire(true, retain);

   132   }

   133 

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

   135   // to return false

   136   void invalidate() {

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

   138     _end    = _hard_end;

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

   140     _top    = _end;      // force future allocations to fail

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

   142   }

   143 

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

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

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

   147   void retire(bool end_of_gc, bool retain);

   148 

   149   void print() PRODUCT_RETURN;

   150 };

   151 

   152 // PLAB stats book-keeping

   153 class PLABStats VALUE_OBJ_CLASS_SPEC {

   154   size_t _allocated;      // total allocated

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

   156   size_t _unused;         // Unused in last buffer

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

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

   159   AdaptiveWeightedAverage

   160          _filter;         // integrator with decay

   161 

   162  public:

   163   PLABStats(size_t desired_plab_sz_, unsigned wt) :

   164     _allocated(0),

   165     _wasted(0),

   166     _unused(0),

   167     _used(0),

   168     _desired_plab_sz(desired_plab_sz_),

   169     _filter(wt)

   170   {

   171     size_t min_sz = min_size();

   172     size_t max_sz = max_size();

   173     size_t aligned_min_sz = align_object_size(min_sz);

   174     size_t aligned_max_sz = align_object_size(max_sz);

   175     assert(min_sz <= aligned_min_sz && max_sz >= aligned_max_sz &&

   176            min_sz <= max_sz,

   177            "PLAB clipping computation in adjust_desired_plab_sz()"

   178            " may be incorrect");

   179   }

   180 

   181   static const size_t min_size() {

   182     return ParGCAllocBuffer::min_size();

   183   }

   184 

   185   static const size_t max_size() {

   186     return ParGCAllocBuffer::max_size();

   187   }

   188 

   189   size_t desired_plab_sz() {

   190     return _desired_plab_sz;

   191   }

   192 

   193   void adjust_desired_plab_sz(); // filter computation, latches output to

   194                                  // _desired_plab_sz, clears sensor accumulators

   195 

   196   void add_allocated(size_t v) {

   197     Atomic::add_ptr(v, &_allocated);

   198   }

   199 

   200   void add_unused(size_t v) {

   201     Atomic::add_ptr(v, &_unused);

   202   }

   203 

   204   void add_wasted(size_t v) {

   205     Atomic::add_ptr(v, &_wasted);

   206   }

   207 };

   208 

   209 class ParGCAllocBufferWithBOT: public ParGCAllocBuffer {

   210   BlockOffsetArrayContigSpace _bt;

   211   BlockOffsetSharedArray*     _bsa;

   212   HeapWord*                   _true_end;  // end of the whole ParGCAllocBuffer

   213 

   214   static const size_t ChunkSizeInWords;

   215   static const size_t ChunkSizeInBytes;

   216   HeapWord* allocate_slow(size_t word_sz);

   217 

   218   void fill_region_with_block(MemRegion mr, bool contig);

   219 

   220 public:

   221   ParGCAllocBufferWithBOT(size_t word_sz, BlockOffsetSharedArray* bsa);

   222 

   223   HeapWord* allocate(size_t word_sz) {

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

   225     if (res != NULL) {

   226       _bt.alloc_block(res, word_sz);

   227     } else {

   228       res = allocate_slow(word_sz);

   229     }

   230     return res;

   231   }

   232 

   233   void undo_allocation(HeapWord* obj, size_t word_sz);

   234 

   235   void set_buf(HeapWord* buf_start) {

   236     ParGCAllocBuffer::set_buf(buf_start);

   237     _true_end = _hard_end;

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

   239     _bt.initialize_threshold();

   240   }

   241 

   242   void retire(bool end_of_gc, bool retain);

   243 

   244   MemRegion range() {

   245     return MemRegion(_top, _true_end);

   246   }

   247 };

   248 

   249 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP