1 /* 2 * Copyright (c) 2001, 2013, 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 // Flush the stats supporting ergonomic sizing of PLAB's 56 // Should not be called directly 57 void flush_stats(PLABStats* stats); 58 59 public: 60 // Initializes the buffer to be empty, but with the given "word_sz". 61 // Must get initialized with "set_buf" for an allocation to succeed. 62 ParGCAllocBuffer(size_t word_sz); 63 64 static const size_t min_size() { 65 return ThreadLocalAllocBuffer::min_size(); 66 } 67 68 static const size_t max_size() { 69 return ThreadLocalAllocBuffer::max_size(); 70 } 71 72 // If an allocation of the given "word_sz" can be satisfied within the 73 // buffer, do the allocation, returning a pointer to the start of the 74 // allocated block. If the allocation request cannot be satisfied, 75 // return NULL. 76 HeapWord* allocate(size_t word_sz) { 77 HeapWord* res = _top; 78 if (pointer_delta(_end, _top) >= word_sz) { 79 _top = _top + word_sz; 80 return res; 81 } else { 82 return NULL; 83 } 84 } 85 86 // Undo the last allocation in the buffer, which is required to be of the 87 // "obj" of the given "word_sz". 88 void undo_allocation(HeapWord* obj, size_t word_sz) { 89 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo"); 90 assert(pointer_delta(_top, obj) == word_sz, "Bad undo"); 91 _top = obj; 92 } 93 94 // The total (word) size of the buffer, including both allocated and 95 // unallocated space. 96 size_t word_sz() { return _word_sz; } 97 98 // Should only be done if we are about to reset with a new buffer of the 99 // given size. 100 void set_word_size(size_t new_word_sz) { 101 assert(new_word_sz > AlignmentReserve, "Too small"); 102 _word_sz = new_word_sz; 103 } 104 105 // The number of words of unallocated space remaining in the buffer. 106 size_t words_remaining() { 107 assert(_end >= _top, "Negative buffer"); 108 return pointer_delta(_end, _top, HeapWordSize); 109 } 110 111 bool contains(void* addr) { 112 return (void*)_bottom <= addr && addr < (void*)_hard_end; 113 } 114 115 // Sets the space of the buffer to be [buf, space+word_sz()). 116 void set_buf(HeapWord* buf) { 117 _bottom = buf; 118 _top = _bottom; 119 _hard_end = _bottom + word_sz(); 120 _end = _hard_end - AlignmentReserve; 121 assert(_end >= _top, "Negative buffer"); 122 // In support of ergonomic sizing 123 _allocated += word_sz(); 124 } 125 126 // Flush the stats supporting ergonomic sizing of PLAB's 127 // and retire the current buffer. 128 void flush_stats_and_retire(PLABStats* stats, bool end_of_gc, bool retain) { 129 // We flush the stats first in order to get a reading of 130 // unused space in the last buffer. 131 if (ResizePLAB) { 132 flush_stats(stats); 133 134 // Since we have flushed the stats we need to clear 135 // the _allocated and _wasted fields. Not doing so 136 // will artifically inflate the values in the stats 137 // to which we add them. 138 // The next time we flush these values, we will add 139 // what we have just flushed in addition to the size 140 // of the buffers allocated between now and then. 141 _allocated = 0; 142 _wasted = 0; 143 } 144 // Retire the last allocation buffer. 145 retire(end_of_gc, retain); 146 } 147 148 // Force future allocations to fail and queries for contains() 149 // to return false 150 void invalidate() { 151 assert(!_retained, "Shouldn't retain an invalidated buffer."); 152 _end = _hard_end; 153 _wasted += pointer_delta(_end, _top); // unused space 154 _top = _end; // force future allocations to fail 155 _bottom = _end; // force future contains() queries to return false 156 } 157 158 // Fills in the unallocated portion of the buffer with a garbage object. 159 // If "end_of_gc" is TRUE, is after the last use in the GC. IF "retain" 160 // is true, attempt to re-use the unused portion in the next GC. 161 void retire(bool end_of_gc, bool retain); 162 163 void print() PRODUCT_RETURN; 164 }; 165 166 // PLAB stats book-keeping 167 class PLABStats VALUE_OBJ_CLASS_SPEC { 168 size_t _allocated; // total allocated 169 size_t _wasted; // of which wasted (internal fragmentation) 170 size_t _unused; // Unused in last buffer 171 size_t _used; // derived = allocated - wasted - unused 172 size_t _desired_plab_sz;// output of filter (below), suitably trimmed and quantized 173 AdaptiveWeightedAverage 174 _filter; // integrator with decay 175 176 public: 177 PLABStats(size_t desired_plab_sz_, unsigned wt) : 178 _allocated(0), 179 _wasted(0), 180 _unused(0), 181 _used(0), 182 _desired_plab_sz(desired_plab_sz_), 183 _filter(wt) 184 { } 185 186 static const size_t min_size() { 187 return ParGCAllocBuffer::min_size(); 188 } 189 190 static const size_t max_size() { 191 return ParGCAllocBuffer::max_size(); 192 } 193 194 size_t desired_plab_sz() { 195 return _desired_plab_sz; 196 } 197 198 void adjust_desired_plab_sz(uint no_of_gc_workers); 199 // filter computation, latches output to 200 // _desired_plab_sz, clears sensor accumulators 201 202 void add_allocated(size_t v) { 203 Atomic::add_ptr(v, &_allocated); 204 } 205 206 void add_unused(size_t v) { 207 Atomic::add_ptr(v, &_unused); 208 } 209 210 void add_wasted(size_t v) { 211 Atomic::add_ptr(v, &_wasted); 212 } 213 }; 214 215 class ParGCAllocBufferWithBOT: public ParGCAllocBuffer { 216 BlockOffsetArrayContigSpace _bt; 217 BlockOffsetSharedArray* _bsa; 218 HeapWord* _true_end; // end of the whole ParGCAllocBuffer 219 220 static const size_t ChunkSizeInWords; 221 static const size_t ChunkSizeInBytes; 222 HeapWord* allocate_slow(size_t word_sz); 223 224 void fill_region_with_block(MemRegion mr, bool contig); 225 226 public: 227 ParGCAllocBufferWithBOT(size_t word_sz, BlockOffsetSharedArray* bsa); 228 229 HeapWord* allocate(size_t word_sz) { 230 HeapWord* res = ParGCAllocBuffer::allocate(word_sz); 231 if (res != NULL) { 232 _bt.alloc_block(res, word_sz); 233 } else { 234 res = allocate_slow(word_sz); 235 } 236 return res; 237 } 238 239 void undo_allocation(HeapWord* obj, size_t word_sz); 240 241 void set_buf(HeapWord* buf_start) { 242 ParGCAllocBuffer::set_buf(buf_start); 243 _true_end = _hard_end; 244 _bt.set_region(MemRegion(buf_start, word_sz())); 245 _bt.initialize_threshold(); 246 } 247 248 void retire(bool end_of_gc, bool retain); 249 250 MemRegion range() { 251 return MemRegion(_top, _true_end); 252 } 253 }; 254 255 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP