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_SHARED_PLAB_HPP

    26 #define SHARE_VM_GC_SHARED_PLAB_HPP

    27 

    28 #include "gc/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 PLAB: 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   size_t    _undo_wasted;

    49   char      tail[32];

    50   static size_t AlignmentReserve;

    51 

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

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

    54   size_t invalidate() {

    55     _end    = _hard_end;

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

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

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

    59     return remaining;

    60   }

    61 

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

    63   // the amount of remaining space.

    64   size_t retire_internal();

    65 

    66   void add_undo_waste(HeapWord* obj, size_t word_sz);

    67 

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

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

    70   void undo_last_allocation(HeapWord* obj, size_t word_sz);

    71 

    72 public:

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

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

    75   PLAB(size_t word_sz);

    76   virtual ~PLAB() {}

    77 

    78   // Minimum PLAB size.

    79   static size_t min_size();

    80   // Maximum PLAB size.

    81   static size_t max_size();

    82 

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

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

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

    86   // return NULL.

    87   HeapWord* allocate(size_t word_sz) {

    88     HeapWord* res = _top;

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

    90       _top = _top + word_sz;

    91       return res;

    92     } else {

    93       return NULL;

    94     }

    95   }

    96 

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

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

    99 

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

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

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

   103 

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

   105   // unallocated space.

   106   size_t word_sz() { return _word_sz; }

   107 

   108   size_t waste() { return _wasted; }

   109   size_t undo_waste() { return _undo_wasted; }

   110 

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

   112   // given size.

   113   void set_word_size(size_t new_word_sz) {

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

   115     _word_sz = new_word_sz;

   116   }

   117 

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

   119   size_t words_remaining() {

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

   121     return pointer_delta(_end, _top, HeapWordSize);

   122   }

   123 

   124   bool contains(void* addr) {

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

   126   }

   127 

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

   129   virtual void set_buf(HeapWord* buf) {

   130     _bottom   = buf;

   131     _top      = _bottom;

   132     _hard_end = _bottom + word_sz();

   133     _end      = _hard_end - AlignmentReserve;

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

   135     // In support of ergonomic sizing

   136     _allocated += word_sz();

   137   }

   138 

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

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

   141   // GC.

   142   virtual void flush_and_retire_stats(PLABStats* stats);

   143 

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

   145   // statistics. To be called during GC.

   146   virtual void retire();

   147 

   148   void print() PRODUCT_RETURN;

   149 };

   150 

   151 // PLAB book-keeping.

   152 class PLABStats VALUE_OBJ_CLASS_SPEC {

   153   size_t _allocated;      // Total allocated

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

   155   size_t _undo_wasted;    // of which wasted on undo (is not used for calculation of PLAB size)

   156   size_t _unused;         // Unused in last buffer

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

   158   AdaptiveWeightedAverage

   159          _filter;         // Integrator with decay

   160 

   161   void reset() {

   162     _allocated   = 0;

   163     _wasted      = 0;

   164     _undo_wasted = 0;

   165     _unused      = 0;

   166   }

   167  public:

   168   PLABStats(size_t desired_plab_sz_, unsigned wt) :

   169     _allocated(0),

   170     _wasted(0),

   171     _undo_wasted(0),

   172     _unused(0),

   173     _desired_plab_sz(desired_plab_sz_),

   174     _filter(wt)

   175   { }

   176 

   177   static const size_t min_size() {

   178     return PLAB::min_size();

   179   }

   180 

   181   static const size_t max_size() {

   182     return PLAB::max_size();

   183   }

   184 

   185   size_t desired_plab_sz() {

   186     return _desired_plab_sz;

   187   }

   188 

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

   190   // updates _desired_plab_sz and clears sensor accumulators.

   191   void adjust_desired_plab_sz(uint no_of_gc_workers);

   192 

   193   void add_allocated(size_t v) {

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

   195   }

   196 

   197   void add_unused(size_t v) {

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

   199   }

   200 

   201   void add_wasted(size_t v) {

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

   203   }

   204 

   205   void add_undo_wasted(size_t v) {

   206     Atomic::add_ptr(v, &_undo_wasted);

   207   }

   208 };

   209 

   210 #endif // SHARE_VM_GC_SHARED_PLAB_HPP