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 #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_) : 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 ? align_object_size(arrayOopDesc::header_size(T_INT)) : 0; 48 assert(min_size() > AlignmentReserve, 49 "Minimum PLAB size " SIZE_FORMAT " must be larger than alignment reserve " SIZE_FORMAT " " 50 "to be able to contain objects", min_size(), AlignmentReserve); 51 } 52 53 // If the minimum object size is greater than MinObjAlignment, we can 54 // end up with a shard at the end of the buffer that's smaller than 55 // the smallest object. We can't allow that because the buffer must 56 // look like it's full of objects when we retire it, so we make 57 // sure we have enough space for a filler int array object. 58 size_t PLAB::AlignmentReserve; 59 60 void PLAB::flush_and_retire_stats(PLABStats* stats) { 61 // Retire the last allocation buffer. 62 size_t unused = retire_internal(); 63 64 // Now flush the statistics. 65 stats->add_allocated(_allocated); 66 stats->add_wasted(_wasted); 67 stats->add_undo_wasted(_undo_wasted); 68 stats->add_unused(unused); 69 70 // Since we have flushed the stats we need to clear the _allocated and _wasted 71 // fields in case somebody retains an instance of this over GCs. Not doing so 72 // will artifically inflate the values in the statistics. 73 _allocated = 0; 74 _wasted = 0; 75 _undo_wasted = 0; 76 } 77 78 void PLAB::retire() { 79 _wasted += retire_internal(); 80 } 81 82 size_t PLAB::retire_internal() { 83 size_t result = 0; 84 if (_top < _hard_end) { 85 CollectedHeap::fill_with_object(_top, _hard_end); 86 result += invalidate(); 87 } 88 return result; 89 } 90 91 void PLAB::add_undo_waste(HeapWord* obj, size_t word_sz) { 92 CollectedHeap::fill_with_object(obj, word_sz); 93 _undo_wasted += word_sz; 94 } 95 96 void PLAB::undo_last_allocation(HeapWord* obj, size_t word_sz) { 97 assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo"); 98 assert(pointer_delta(_top, obj) == word_sz, "Bad undo"); 99 _top = obj; 100 } 101 102 void PLAB::undo_allocation(HeapWord* obj, size_t word_sz) { 103 // Is the alloc in the current alloc buffer? 104 if (contains(obj)) { 105 assert(contains(obj + word_sz - 1), 106 "should contain whole object"); 107 undo_last_allocation(obj, word_sz); 108 } else { 109 add_undo_waste(obj, word_sz); 110 } 111 } 112 113 // Calculates plab size for current number of gc worker threads. 114 size_t PLABStats::desired_plab_sz(uint no_of_gc_workers) { 115 return MAX2(min_size(), (size_t)align_object_size(_desired_net_plab_sz / no_of_gc_workers)); 116 } 117 118 // Compute desired plab size for one gc worker thread and latch result for later 119 // use. This should be called once at the end of parallel 120 // scavenge; it clears the sensor accumulators. 121 void PLABStats::adjust_desired_plab_sz() { 122 assert(ResizePLAB, "Not set"); 123 124 assert(is_object_aligned(max_size()) && min_size() <= max_size(), 125 "PLAB clipping computation may be incorrect"); 126 127 if (_allocated == 0) { 128 assert(_unused == 0, 129 "Inconsistency in PLAB stats: " 130 "_allocated: " SIZE_FORMAT ", " 131 "_wasted: " SIZE_FORMAT ", " 132 "_unused: " SIZE_FORMAT ", " 133 "_undo_wasted: " SIZE_FORMAT, 134 _allocated, _wasted, _unused, _undo_wasted); 135 136 _allocated = 1; 137 } 138 double wasted_frac = (double)_unused / (double)_allocated; 139 size_t target_refills = (size_t)((wasted_frac * TargetSurvivorRatio) / TargetPLABWastePct); 140 if (target_refills == 0) { 141 target_refills = 1; 142 } 143 size_t used = _allocated - _wasted - _unused; 144 // Assumed to have 1 gc worker thread 145 size_t recent_plab_sz = used / target_refills; 146 // Take historical weighted average 147 _filter.sample(recent_plab_sz); 148 // Clip from above and below, and align to object boundary 149 size_t new_plab_sz = MAX2(min_size(), (size_t)_filter.average()); 150 new_plab_sz = MIN2(max_size(), new_plab_sz); 151 new_plab_sz = align_object_size(new_plab_sz); 152 // Latch the result 153 log_trace(gc, plab)("Plab_size = " SIZE_FORMAT " desired_net_plab_sz = " SIZE_FORMAT ") ", recent_plab_sz, new_plab_sz); 154 _desired_net_plab_sz = new_plab_sz; 155 156 reset(); 157 }