1 /*

     2  * Copyright (c) 2001, 2015, 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 "gc_implementation/shared/gcUtil.hpp"

    29 #include "memory/allocation.hpp"

    30 #include "runtime/atomic.hpp"

    31 #include "utilities/globalDefinitions.hpp"

    32 

    33 // Forward declarations.

    34 class PLABStats;

    35 

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

    37 class ParGCAllocBuffer: public CHeapObj<mtGC> {

    38 protected:

    39   char      head[32];

    40   size_t    _word_sz;          // In HeapWord units

    41   HeapWord* _bottom;

    42   HeapWord* _top;

    43   HeapWord* _end;           // Last allocatable address + 1

    44   HeapWord* _hard_end;      // _end + AlignmentReserve

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

    46   size_t    _allocated;     // in HeapWord units

    47   size_t    _wasted;        // in HeapWord units

    48   char      tail[32];

    49   static size_t AlignmentReserve;

    50 

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

    52   // to return false. Returns the amount of unused space in this PLAB.

    53   size_t invalidate() {

    54     _end    = _hard_end;

    55     size_t remaining = pointer_delta(_end, _top);  // Calculate remaining space.

    56     _top    = _end;      // Force future allocations to fail.

    57     _bottom = _end;      // Force future contains() queries to return false.

    58     return remaining;

    59   }

    60 

    61   // Fill in remaining space with a dummy object and invalidate the PLAB. Returns

    62   // the amount of remaining space.

    63   size_t retire_internal();

    64 

    65 public:

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

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

    68   ParGCAllocBuffer(size_t word_sz);

    69   virtual ~ParGCAllocBuffer() {}

    70 

    71   // Minimum PLAB size.

    72   static size_t min_size();

    73   // Maximum PLAB size.

    74   static size_t max_size();

    75 

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

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

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

    79   // return NULL.

    80   HeapWord* allocate(size_t word_sz) {

    81     HeapWord* res = _top;

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

    83       _top = _top + word_sz;

    84       return res;

    85     } else {

    86       return NULL;

    87     }

    88   }

    89 

    90   // Allocate the object aligned to "alignment_in_bytes".

    91   HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes);

    92 

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

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

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

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

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

    98     _top = obj;

    99   }

   100 

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

   102   // unallocated space.

   103   size_t word_sz() { return _word_sz; }

   104 

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

   106   // given size.

   107   void set_word_size(size_t new_word_sz) {

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

   109     _word_sz = new_word_sz;

   110   }

   111 

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

   113   size_t words_remaining() {

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

   115     return pointer_delta(_end, _top, HeapWordSize);

   116   }

   117 

   118   bool contains(void* addr) {

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

   120   }

   121 

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

   123   virtual void set_buf(HeapWord* buf) {

   124     _bottom   = buf;

   125     _top      = _bottom;

   126     _hard_end = _bottom + word_sz();

   127     _end      = _hard_end - AlignmentReserve;

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

   129     // In support of ergonomic sizing

   130     _allocated += word_sz();

   131   }

   132 

   133   // Flush allocation statistics into the given PLABStats supporting ergonomic

   134   // sizing of PLAB's and retire the current buffer. To be called at the end of

   135   // GC.

   136   void flush_and_retire_stats(PLABStats* stats);

   137 

   138   // Fills in the unallocated portion of the buffer with a garbage object and updates

   139   // statistics. To be called during GC.

   140   virtual void retire();

   141 

   142   void print() PRODUCT_RETURN;

   143 };

   144 

   145 // PLAB book-keeping.

   146 class PLABStats VALUE_OBJ_CLASS_SPEC {

   147   size_t _allocated;      // Total allocated

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

   149   size_t _unused;         // Unused in last buffer

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

   151   AdaptiveWeightedAverage

   152          _filter;         // Integrator with decay

   153 

   154   void reset() {

   155     _allocated = 0;

   156     _wasted    = 0;

   157     _unused    = 0;

   158   }

   159  public:

   160   PLABStats(size_t desired_plab_sz_, unsigned wt) :

   161     _allocated(0),

   162     _wasted(0),

   163     _unused(0),

   164     _desired_plab_sz(desired_plab_sz_),

   165     _filter(wt)

   166   { }

   167 

   168   static const size_t min_size() {

   169     return ParGCAllocBuffer::min_size();

   170   }

   171 

   172   static const size_t max_size() {

   173     return ParGCAllocBuffer::max_size();

   174   }

   175 

   176   size_t desired_plab_sz() {

   177     return _desired_plab_sz;

   178   }

   179 

   180   // Updates the current desired PLAB size. Computes the new desired PLAB size,

   181   // updates _desired_plab_sz and clears sensor accumulators.

   182   void adjust_desired_plab_sz(uint no_of_gc_workers);

   183 

   184   void add_allocated(size_t v) {

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

   186   }

   187 

   188   void add_unused(size_t v) {

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

   190   }

   191 

   192   void add_wasted(size_t v) {

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

   194   }

   195 };

   196 

   197 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP