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.hpp" 28 #include "gc/shared/threadLocalAllocBuffer.hpp" 29 #include "oops/arrayOop.hpp" 30 #include "oops/oop.inline.hpp" 31 32 size_t PLAB::min_size() { 33 // Make sure that we return something that is larger than AlignmentReserve 34 return align_object_size(MAX2(MinTLABSize / HeapWordSize, (uintx)oopDesc::header_size())) + AlignmentReserve; 35 } 36 37 size_t PLAB::max_size() { 38 return ThreadLocalAllocBuffer::max_size(); 39 } 40 41 PLAB::PLAB(size_t desired_plab_sz_) : 42 _word_sz(desired_plab_sz_), _bottom(NULL), _top(NULL), 43 _end(NULL), _hard_end(NULL), _allocated(0), _wasted(0), _undo_wasted(0) 44 { 45 // ArrayOopDesc::header_size depends on command line initialization. 46 AlignmentReserve = oopDesc::header_size() > MinObjAlignment ? align_object_size(arrayOopDesc::header_size(T_INT)) : 0; 47 assert(min_size() > AlignmentReserve, 48 err_msg("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 CollectedHeap::fill_with_object(_top, _hard_end); 85 result += invalidate(); 86 } 87 return result; 88 } 89 90 void PLAB::add_undo_waste(HeapWord* obj, size_t word_sz) { 91 CollectedHeap::fill_with_object(obj, word_sz); 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 // Compute desired plab size and latch result for later 113 // use. This should be called once at the end of parallel 114 // scavenge; it clears the sensor accumulators. 115 void PLABStats::adjust_desired_plab_sz(uint no_of_gc_workers) { 116 assert(ResizePLAB, "Not set"); 117 118 assert(is_object_aligned(max_size()) && min_size() <= max_size(), 119 "PLAB clipping computation may be incorrect"); 120 121 if (_allocated == 0) { 122 assert(_unused == 0, 123 err_msg("Inconsistency in PLAB stats: " 124 "_allocated: "SIZE_FORMAT", " 125 "_wasted: "SIZE_FORMAT", " 126 "_unused: "SIZE_FORMAT", " 127 "_undo_wasted: "SIZE_FORMAT, 128 _allocated, _wasted, _unused, _undo_wasted)); 129 130 _allocated = 1; 131 } 132 double wasted_frac = (double)_unused / (double)_allocated; 133 size_t target_refills = (size_t)((wasted_frac * TargetSurvivorRatio) / TargetPLABWastePct); 134 if (target_refills == 0) { 135 target_refills = 1; 136 } 137 size_t used = _allocated - _wasted - _unused; 138 size_t recent_plab_sz = used / (target_refills * no_of_gc_workers); 139 // Take historical weighted average 140 _filter.sample(recent_plab_sz); 141 // Clip from above and below, and align to object boundary 142 size_t new_plab_sz = MAX2(min_size(), (size_t)_filter.average()); 143 new_plab_sz = MIN2(max_size(), new_plab_sz); 144 new_plab_sz = align_object_size(new_plab_sz); 145 // Latch the result 146 if (PrintPLAB) { 147 gclog_or_tty->print(" (plab_sz = " SIZE_FORMAT" desired_plab_sz = " SIZE_FORMAT") ", recent_plab_sz, new_plab_sz); 148 } 149 _desired_plab_sz = new_plab_sz; 150 151 reset(); 152 } 153 154 #ifndef PRODUCT 155 void PLAB::print() { 156 gclog_or_tty->print_cr("PLAB: _bottom: " PTR_FORMAT " _top: " PTR_FORMAT 157 " _end: " PTR_FORMAT " _hard_end: " PTR_FORMAT ")", 158 p2i(_bottom), p2i(_top), p2i(_end), p2i(_hard_end)); 159 } 160 #endif // !PRODUCT