1 /* 2 * Copyright (c) 2001, 2018, 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, (size_t)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_) : 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 AlignmentReserve = Universe::heap()->tlab_alloc_reserve(); 47 assert(min_size() > AlignmentReserve, 48 "Minimum PLAB size " SIZE_FORMAT " must be larger than alignment reserve " SIZE_FORMAT " " 49 "to be able to contain objects", min_size(), AlignmentReserve); 50 } 51 52 // If the minimum object size is greater than MinObjAlignment, we can 53 // end up with a shard at the end of the buffer that's smaller than 54 // the smallest object. We can't allow that because the buffer must 55 // look like it's full of objects when we retire it, so we make 56 // sure we have enough space for a filler int array object. 57 size_t PLAB::AlignmentReserve; 58 59 void PLAB::flush_and_retire_stats(PLABStats* stats) { 60 // Retire the last allocation buffer. 61 size_t unused = retire_internal(); 62 63 // Now flush the statistics. 64 stats->add_allocated(_allocated); 65 stats->add_wasted(_wasted); 66 stats->add_undo_wasted(_undo_wasted); 67 stats->add_unused(unused); 68 69 // Since we have flushed the stats we need to clear the _allocated and _wasted 70 // fields in case somebody retains an instance of this over GCs. Not doing so 71 // will artifically inflate the values in the statistics. 72 _allocated = 0; 73 _wasted = 0; 74 _undo_wasted = 0; 75 } 76 77 void PLAB::retire() { 78 _wasted += retire_internal(); 79 } 80 81 size_t PLAB::retire_internal() { 82 size_t result = 0; 83 if (_top < _hard_end) { 84 Universe::heap()->fill_with_dummy_object(_top, _hard_end, true); 85 result += invalidate(); 86 } 87 return result; 88 } 89 90 void PLAB::add_undo_waste(HeapWord* obj, size_t word_sz) { 91 Universe::heap()->fill_with_dummy_object(obj, obj + word_sz, true); 92 _undo_wasted += word_sz; 93 } 94 95 void PLAB::undo_last_allocation(HeapWord* obj, size_t word_sz) { 96 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo"); 97 assert(pointer_delta(_top, obj) == word_sz, "Bad undo"); 98 _top = obj; 99 } 100 101 void PLAB::undo_allocation(HeapWord* obj, size_t word_sz) { 102 // Is the alloc in the current alloc buffer? 103 if (contains(obj)) { 104 assert(contains(obj + word_sz - 1), 105 "should contain whole object"); 106 undo_last_allocation(obj, word_sz); 107 } else { 108 add_undo_waste(obj, word_sz); 109 } 110 } 111 112 void PLABStats::log_plab_allocation() { 113 log_debug(gc, plab)("%s PLAB allocation: " 114 "allocated: " SIZE_FORMAT "B, " 115 "wasted: " SIZE_FORMAT "B, " 116 "unused: " SIZE_FORMAT "B, " 117 "used: " SIZE_FORMAT "B, " 118 "undo waste: " SIZE_FORMAT "B, ", 119 _description, 120 _allocated * HeapWordSize, 121 _wasted * HeapWordSize, 122 _unused * HeapWordSize, 123 used() * HeapWordSize, 124 _undo_wasted * HeapWordSize); 125 } 126 127 void PLABStats::log_sizing(size_t calculated_words, size_t net_desired_words) { 128 log_debug(gc, plab)("%s sizing: " 129 "calculated: " SIZE_FORMAT "B, " 130 "actual: " SIZE_FORMAT "B", 131 _description, 132 calculated_words * HeapWordSize, 133 net_desired_words * HeapWordSize); 134 } 135 136 // Calculates plab size for current number of gc worker threads. 137 size_t PLABStats::desired_plab_sz(uint no_of_gc_workers) { 138 return align_object_size(MIN2(MAX2(min_size(), _desired_net_plab_sz / no_of_gc_workers), max_size())); 139 } 140 141 // Compute desired plab size for one gc worker thread and latch result for later 142 // use. This should be called once at the end of parallel 143 // scavenge; it clears the sensor accumulators. 144 void PLABStats::adjust_desired_plab_sz() { 145 log_plab_allocation(); 146 147 if (!ResizePLAB) { 148 // Clear accumulators for next round. 149 reset(); 150 return; 151 } 152 153 assert(is_object_aligned(max_size()) && min_size() <= max_size(), 154 "PLAB clipping computation may be incorrect"); 155 156 assert(_allocated != 0 || _unused == 0, 157 "Inconsistency in PLAB stats: " 158 "_allocated: " SIZE_FORMAT ", " 159 "_wasted: " SIZE_FORMAT ", " 160 "_unused: " SIZE_FORMAT ", " 161 "_undo_wasted: " SIZE_FORMAT, 162 _allocated, _wasted, _unused, _undo_wasted); 163 164 size_t plab_sz = compute_desired_plab_sz(); 165 // Take historical weighted average 166 _filter.sample(plab_sz); 167 _desired_net_plab_sz = MAX2(min_size(), (size_t)_filter.average()); 168 169 log_sizing(plab_sz, _desired_net_plab_sz); 170 // Clear accumulators for next round 171 reset(); 172 } 173 174 size_t PLABStats::compute_desired_plab_sz() { 175 size_t allocated = MAX2(_allocated, size_t(1)); 176 double wasted_frac = (double)_unused / (double)allocated; 177 size_t target_refills = (size_t)((wasted_frac * TargetSurvivorRatio) / TargetPLABWastePct); 178 if (target_refills == 0) { 179 target_refills = 1; 180 } 181 size_t used = allocated - _wasted - _unused; 182 // Assumed to have 1 gc worker thread 183 size_t recent_plab_sz = used / target_refills; 184 return recent_plab_sz; 185 }