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 #include "gc_interface/collectedHeap.hpp" 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 virtual ~ParGCAllocBuffer() {} 64 65 static const size_t min_size() { 66 // Make sure that we return something that is larger than AlignmentReserve 67 return align_object_size(MAX2(MinTLABSize / HeapWordSize, (uintx)oopDesc::header_size())) + AlignmentReserve; 68 } 69 70 static const size_t max_size() { 71 return ThreadLocalAllocBuffer::max_size(); 72 } 73 74 // If an allocation of the given "word_sz" can be satisfied within the 75 // buffer, do the allocation, returning a pointer to the start of the 76 // allocated block. If the allocation request cannot be satisfied, 77 // return NULL. 78 HeapWord* allocate(size_t word_sz) { 79 HeapWord* res = _top; 80 if (pointer_delta(_end, _top) >= word_sz) { 81 _top = _top + word_sz; 82 return res; 83 } else { 84 return NULL; 85 } 86 } 87 88 // Allocate the object aligned to "alignment_in_bytes". 89 HeapWord* allocate_aligned(size_t word_sz, unsigned short alignment_in_bytes); 90 91 // Undo the last allocation in the buffer, which is required to be of the 92 // "obj" of the given "word_sz". 93 void undo_allocation(HeapWord* obj, size_t word_sz) { 94 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo"); 95 assert(pointer_delta(_top, obj) == word_sz, "Bad undo"); 96 _top = obj; 97 } 98 99 // The total (word) size of the buffer, including both allocated and 100 // unallocated space. 101 size_t word_sz() { return _word_sz; } 102 103 // Should only be done if we are about to reset with a new buffer of the 104 // given size. 105 void set_word_size(size_t new_word_sz) { 106 assert(new_word_sz > AlignmentReserve, "Too small"); 107 _word_sz = new_word_sz; 108 } 109 110 // The number of words of unallocated space remaining in the buffer. 111 size_t words_remaining() { 112 assert(_end >= _top, "Negative buffer"); 113 return pointer_delta(_end, _top, HeapWordSize); 114 } 115 116 bool contains(void* addr) { 117 return (void*)_bottom <= addr && addr < (void*)_hard_end; 118 } 119 120 // Sets the space of the buffer to be [buf, space+word_sz()). 121 virtual void set_buf(HeapWord* buf) { 122 _bottom = buf; 123 _top = _bottom; 124 _hard_end = _bottom + word_sz(); 125 _end = _hard_end - AlignmentReserve; 126 assert(_end >= _top, "Negative buffer"); 127 // In support of ergonomic sizing 128 _allocated += word_sz(); 129 } 130 131 // Flush the stats supporting ergonomic sizing of PLAB's 132 // and retire the current buffer. 133 void flush_stats_and_retire(PLABStats* stats, bool end_of_gc, bool retain) { 134 // We flush the stats first in order to get a reading of 135 // unused space in the last buffer. 136 if (ResizePLAB) { 137 flush_stats(stats); 138 139 // Since we have flushed the stats we need to clear 140 // the _allocated and _wasted fields. Not doing so 141 // will artifically inflate the values in the stats 142 // to which we add them. 143 // The next time we flush these values, we will add 144 // what we have just flushed in addition to the size 145 // of the buffers allocated between now and then. 146 _allocated = 0; 147 _wasted = 0; 148 } 149 // Retire the last allocation buffer. 150 retire(end_of_gc, retain); 151 } 152 153 // Force future allocations to fail and queries for contains() 154 // to return false 155 void invalidate() { 156 assert(!_retained, "Shouldn't retain an invalidated buffer."); 157 _end = _hard_end; 158 _wasted += pointer_delta(_end, _top); // unused space 159 _top = _end; // force future allocations to fail 160 _bottom = _end; // force future contains() queries to return false 161 } 162 163 // Fills in the unallocated portion of the buffer with a garbage object. 164 // If "end_of_gc" is TRUE, is after the last use in the GC. IF "retain" 165 // is true, attempt to re-use the unused portion in the next GC. 166 virtual void retire(bool end_of_gc, bool retain); 167 168 void print() PRODUCT_RETURN; 169 }; 170 171 // PLAB stats book-keeping 172 class PLABStats VALUE_OBJ_CLASS_SPEC { 173 size_t _allocated; // total allocated 174 size_t _wasted; // of which wasted (internal fragmentation) 175 size_t _unused; // Unused in last buffer 176 size_t _used; // derived = allocated - wasted - unused 177 size_t _desired_plab_sz;// output of filter (below), suitably trimmed and quantized 178 AdaptiveWeightedAverage 179 _filter; // integrator with decay 180 181 public: 182 PLABStats(size_t desired_plab_sz_, unsigned wt) : 183 _allocated(0), 184 _wasted(0), 185 _unused(0), 186 _used(0), 187 _desired_plab_sz(desired_plab_sz_), 188 _filter(wt) 189 { } 190 191 static const size_t min_size() { 192 return ParGCAllocBuffer::min_size(); 193 } 194 195 static const size_t max_size() { 196 return ParGCAllocBuffer::max_size(); 197 } 198 199 size_t desired_plab_sz() { 200 return _desired_plab_sz; 201 } 202 203 void adjust_desired_plab_sz(uint no_of_gc_workers); 204 // filter computation, latches output to 205 // _desired_plab_sz, clears sensor accumulators 206 207 void add_allocated(size_t v) { 208 Atomic::add_ptr(v, &_allocated); 209 } 210 211 void add_unused(size_t v) { 212 Atomic::add_ptr(v, &_unused); 213 } 214 215 void add_wasted(size_t v) { 216 Atomic::add_ptr(v, &_wasted); 217 } 218 }; 219 220 #endif // SHARE_VM_GC_IMPLEMENTATION_PARNEW_PARGCALLOCBUFFER_HPP