1 /* 2 * Copyright (c) 2001, 2017, 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 #include "precompiled.hpp" 26 #include "gc/shared/collectedHeap.hpp" 27 #include "gc/shared/plab.inline.hpp" 28 #include "gc/shared/threadLocalAllocBuffer.hpp" 29 #include "logging/log.hpp" 30 #include "oops/arrayOop.hpp" 31 #include "oops/oop.inline.hpp" 32 33 size_t PLAB::min_size() { 34 // Make sure that we return something that is larger than AlignmentReserve 35 return align_object_size(MAX2(MinTLABSize / HeapWordSize, (uintx)oopDesc::header_size())) + AlignmentReserve; 36 } 37 38 size_t PLAB::max_size() { 39 return ThreadLocalAllocBuffer::max_size(); 40 } 41 42 PLAB::PLAB(size_t desired_plab_sz_, size_t min_align_reserve) : 43 _word_sz(desired_plab_sz_), _bottom(NULL), _top(NULL), 44 _end(NULL), _hard_end(NULL), _allocated(0), _wasted(0), _undo_wasted(0) 45 { 46 // ArrayOopDesc::header_size depends on command line initialization. 47 AlignmentReserve = oopDesc::header_size() > MinObjAlignment ? 48 align_object_size(MAX2<size_t>(arrayOopDesc::header_size(T_INT), min_align_reserve)) : 49 0; 50 assert(min_size() > AlignmentReserve, 51 "Minimum PLAB size " SIZE_FORMAT " must be larger than alignment reserve " SIZE_FORMAT " " 52 "to be able to contain objects", min_size(), AlignmentReserve); 53 } 54 55 // If the minimum object size is greater than MinObjAlignment, we can 56 // end up with a shard at the end of the buffer that's smaller than 57 // the smallest object. We can't allow that because the buffer must 58 // look like it's full of objects when we retire it, so we make 59 // sure we have enough space for a filler int array object. 60 size_t PLAB::AlignmentReserve; 61 62 void PLAB::flush_and_retire_stats(PLABStats* stats) { 63 // Retire the last allocation buffer. 64 size_t unused = retire_internal(); 65 66 // Now flush the statistics. 67 stats->add_allocated(_allocated); 68 stats->add_wasted(_wasted); 69 stats->add_undo_wasted(_undo_wasted); 70 stats->add_unused(unused); 71 72 // Since we have flushed the stats we need to clear the _allocated and _wasted 73 // fields in case somebody retains an instance of this over GCs. Not doing so 74 // will artifically inflate the values in the statistics. 75 _allocated = 0; 76 _wasted = 0; 77 _undo_wasted = 0; 78 } 79 80 void PLAB::retire() { 81 _wasted += retire_internal(); 82 } 83 84 size_t PLAB::retire_internal() { 85 size_t result = 0; 86 if (_top < _hard_end) { 87 CollectedHeap::fill_with_object(_top, _hard_end); 88 result += invalidate(); 89 } 90 return result; 91 } 92 93 void PLAB::add_undo_waste(HeapWord* obj, size_t word_sz) { 94 CollectedHeap::fill_with_object(obj, word_sz); 95 _undo_wasted += word_sz; 96 } 97 98 void PLAB::undo_last_allocation(HeapWord* obj, size_t word_sz) { 99 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo"); 100 assert(pointer_delta(_top, obj) == word_sz, "Bad undo"); 101 _top = obj; 102 } 103 104 void PLAB::undo_allocation(HeapWord* obj, size_t word_sz) { 105 // Is the alloc in the current alloc buffer? 106 if (contains(obj)) { 107 assert(contains(obj + word_sz - 1), 108 "should contain whole object"); 109 undo_last_allocation(obj, word_sz); 110 } else { 111 add_undo_waste(obj, word_sz); 112 } 113 } 114 115 void PLABStats::log_plab_allocation() { 116 log_debug(gc, plab)("%s PLAB allocation: " 117 "allocated: " SIZE_FORMAT "B, " 118 "wasted: " SIZE_FORMAT "B, " 119 "unused: " SIZE_FORMAT "B, " 120 "used: " SIZE_FORMAT "B, " 121 "undo waste: " SIZE_FORMAT "B, ", 122 _description, 123 _allocated * HeapWordSize, 124 _wasted * HeapWordSize, 125 _unused * HeapWordSize, 126 used() * HeapWordSize, 127 _undo_wasted * HeapWordSize); 128 } 129 130 void PLABStats::log_sizing(size_t calculated_words, size_t net_desired_words) { 131 log_debug(gc, plab)("%s sizing: " 132 "calculated: " SIZE_FORMAT "B, " 133 "actual: " SIZE_FORMAT "B", 134 _description, 135 calculated_words * HeapWordSize, 136 net_desired_words * HeapWordSize); 137 } 138 139 // Calculates plab size for current number of gc worker threads. 140 size_t PLABStats::desired_plab_sz(uint no_of_gc_workers) { 141 return align_object_size(MIN2(MAX2(min_size(), _desired_net_plab_sz / no_of_gc_workers), max_size())); 142 } 143 144 // Compute desired plab size for one gc worker thread and latch result for later 145 // use. This should be called once at the end of parallel 146 // scavenge; it clears the sensor accumulators. 147 void PLABStats::adjust_desired_plab_sz() { 148 log_plab_allocation(); 149 150 if (!ResizePLAB) { 151 // Clear accumulators for next round. 152 reset(); 153 return; 154 } 155 156 assert(is_object_aligned(max_size()) && min_size() <= max_size(), 157 "PLAB clipping computation may be incorrect"); 158 159 assert(_allocated != 0 || _unused == 0, 160 "Inconsistency in PLAB stats: " 161 "_allocated: " SIZE_FORMAT ", " 162 "_wasted: " SIZE_FORMAT ", " 163 "_unused: " SIZE_FORMAT ", " 164 "_undo_wasted: " SIZE_FORMAT, 165 _allocated, _wasted, _unused, _undo_wasted); 166 167 size_t plab_sz = compute_desired_plab_sz(); 168 // Take historical weighted average 169 _filter.sample(plab_sz); 170 _desired_net_plab_sz = MAX2(min_size(), (size_t)_filter.average()); 171 172 log_sizing(plab_sz, _desired_net_plab_sz); 173 // Clear accumulators for next round 174 reset(); 175 } 176 177 size_t PLABStats::compute_desired_plab_sz() { 178 size_t allocated = MAX2(_allocated, size_t(1)); 179 double wasted_frac = (double)_unused / (double)allocated; 180 size_t target_refills = (size_t)((wasted_frac * TargetSurvivorRatio) / TargetPLABWastePct); 181 if (target_refills == 0) { 182 target_refills = 1; 183 } 184 size_t used = allocated - _wasted - _unused; 185 // Assumed to have 1 gc worker thread 186 size_t recent_plab_sz = used / target_refills; 187 return recent_plab_sz; 188 }