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 "utilities/globalDefinitions.hpp" 31 32 // Forward declarations. 33 class PLABStats; 34 35 // A per-thread allocation buffer used during GC. 36 class PLAB: public CHeapObj<mtGC> { 37 protected: 38 char head[32]; 39 size_t _word_sz; // In HeapWord units 40 HeapWord* _bottom; 41 HeapWord* _top; 42 HeapWord* _end; // Last allocatable address + 1 43 HeapWord* _hard_end; // _end + AlignmentReserve 44 // In support of ergonomic sizing of PLAB's 45 size_t _allocated; // in HeapWord units 46 size_t _wasted; // in HeapWord units 47 size_t _undo_wasted; 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 void add_undo_waste(HeapWord* obj, size_t word_sz); 66 67 // Undo the last allocation in the buffer, which is required to be of the 68 // "obj" of the given "word_sz". 69 void undo_last_allocation(HeapWord* obj, size_t word_sz); 70 71 public: 72 // Initializes the buffer to be empty, but with the given "word_sz". 73 // Must get initialized with "set_buf" for an allocation to succeed. 74 PLAB(size_t word_sz); 75 virtual ~PLAB() {} 76 77 static size_t size_required_for_allocation(size_t word_size) { return word_size + AlignmentReserve; } 78 79 // Minimum PLAB size. 80 static size_t min_size(); 81 // Maximum PLAB size. 82 static size_t max_size(); 83 84 // If an allocation of the given "word_sz" can be satisfied within the 85 // buffer, do the allocation, returning a pointer to the start of the 86 // allocated block. If the allocation request cannot be satisfied, 87 // return NULL. 88 HeapWord* allocate(size_t word_sz) { 89 HeapWord* res = _top; 90 if (pointer_delta(_end, _top) >= word_sz) { 91 _top = _top + word_sz; 92 return res; 93 } else { 94 return NULL; 95 } 96 } 97 98 // Allocate the object aligned to "alignment_in_bytes". 99 inline HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes); 100 101 // Undo any allocation in the buffer, which is required to be of the 102 // "obj" of the given "word_sz". 103 void undo_allocation(HeapWord* obj, size_t word_sz); 104 105 // The total (word) size of the buffer, including both allocated and 106 // unallocated space. 107 size_t word_sz() { return _word_sz; } 108 109 size_t waste() { return _wasted; } 110 size_t undo_waste() { return _undo_wasted; } 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, size_t new_word_sz) { 124 assert(new_word_sz > AlignmentReserve, "Too small"); 125 _word_sz = new_word_sz; 126 127 _bottom = buf; 128 _top = _bottom; 129 _hard_end = _bottom + word_sz(); 130 _end = _hard_end - AlignmentReserve; 131 assert(_end >= _top, "Negative buffer"); 132 // In support of ergonomic sizing 133 _allocated += word_sz(); 134 } 135 136 // Flush allocation statistics into the given PLABStats supporting ergonomic 137 // sizing of PLAB's and retire the current buffer. To be called at the end of 138 // GC. 139 virtual void flush_and_retire_stats(PLABStats* stats); 140 141 // Fills in the unallocated portion of the buffer with a garbage object and updates 142 // statistics. To be called during GC. 143 virtual void retire(); 144 }; 145 146 // PLAB book-keeping. 147 class PLABStats : public CHeapObj<mtGC> { 148 protected: 149 size_t _allocated; // Total allocated 150 size_t _wasted; // of which wasted (internal fragmentation) 151 size_t _undo_wasted; // of which wasted on undo (is not used for calculation of PLAB size) 152 size_t _unused; // Unused in last buffer 153 size_t _desired_net_plab_sz;// Output of filter (below), suitably trimmed and quantized 154 AdaptiveWeightedAverage 155 _filter; // Integrator with decay 156 157 virtual void reset() { 158 _allocated = 0; 159 _wasted = 0; 160 _undo_wasted = 0; 161 _unused = 0; 162 } 163 public: 164 PLABStats(size_t desired_net_plab_sz_, unsigned wt) : 165 _allocated(0), 166 _wasted(0), 167 _undo_wasted(0), 168 _unused(0), 169 _desired_net_plab_sz(desired_net_plab_sz_), 170 _filter(wt) 171 { } 172 173 virtual ~PLABStats() { } 174 175 static const size_t min_size() { 176 return PLAB::min_size(); 177 } 178 179 static const size_t max_size() { 180 return PLAB::max_size(); 181 } 182 183 // Calculates plab size for current number of gc worker threads. 184 size_t desired_plab_sz(uint no_of_gc_workers); 185 186 // Updates the current desired PLAB size. Computes the new desired PLAB size with one gc worker thread, 187 // updates _desired_plab_sz and clears sensor accumulators. 188 virtual void adjust_desired_plab_sz(); 189 190 inline void add_allocated(size_t v); 191 192 inline void add_unused(size_t v); 193 194 inline void add_wasted(size_t v); 195 196 inline void add_undo_wasted(size_t v); 197 }; 198 199 #endif // SHARE_VM_GC_SHARED_PLAB_HPP