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_implementation/shared/parGCAllocBuffer.hpp" 27 #include "memory/threadLocalAllocBuffer.hpp" 28 #include "oops/arrayOop.hpp" 29 #include "oops/oop.inline.hpp" 30 31 const size_t ParGCAllocBuffer::min_size() { 32 // Make sure that we return something that is larger than AlignmentReserve 33 return align_object_size(MAX2(MinTLABSize / HeapWordSize, (uintx)oopDesc::header_size())) + AlignmentReserve; 34 } 35 36 const size_t ParGCAllocBuffer::max_size() { 37 return ThreadLocalAllocBuffer::max_size(); 38 } 39 40 ParGCAllocBuffer::ParGCAllocBuffer(size_t desired_plab_sz_) : 41 _word_sz(desired_plab_sz_), _bottom(NULL), _top(NULL), 42 _end(NULL), _hard_end(NULL), _allocated(0), _wasted(0) 43 { 44 assert (min_size() > AlignmentReserve, "Inconsistency!"); 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 } 48 49 // If the minimum object size is greater than MinObjAlignment, we can 50 // end up with a shard at the end of the buffer that's smaller than 51 // the smallest object. We can't allow that because the buffer must 52 // look like it's full of objects when we retire it, so we make 53 // sure we have enough space for a filler int array object. 54 size_t ParGCAllocBuffer::AlignmentReserve; 55 56 void ParGCAllocBuffer::flush_and_retire_stats(PLABStats* stats) { 57 // We want to distinguish between unused space in the last buffer and waste 58 // created otherwise. Save the amount of unused space because retire() will 59 // update the pointers we use. 60 size_t unused = pointer_delta(_end, _top); 61 62 // Retire the last allocation buffer. 63 retire(); 64 65 stats->add_allocated(_allocated); 66 // Retire() counts the unused space as wasted. So we need to remove it again 67 // before updating the statistics. 68 stats->add_wasted(_wasted - unused); 69 stats->add_unused(unused); 70 71 // Since we have flushed the stats we need to clear the _allocated and _wasted 72 // fields in case somebody retains an instance of this over GCs. Not doing so 73 // will artifically inflate the values in the statistics. 74 _allocated = 0; 75 _wasted = 0; 76 } 77 78 void ParGCAllocBuffer::retire() { 79 if (_top < _hard_end) { 80 CollectedHeap::fill_with_object(_top, _hard_end); 81 invalidate(); 82 } 83 } 84 85 // Compute desired plab size and latch result for later 86 // use. This should be called once at the end of parallel 87 // scavenge; it clears the sensor accumulators. 88 void PLABStats::adjust_desired_plab_sz(uint no_of_gc_workers) { 89 assert(ResizePLAB, "Not set"); 90 91 assert(is_object_aligned(max_size()) && min_size() <= max_size(), 92 "PLAB clipping computation may be incorrect"); 93 94 if (_allocated == 0) { 95 assert(_unused == 0, 96 err_msg("Inconsistency in PLAB stats: " 97 "_allocated: "SIZE_FORMAT", " 98 "_wasted: "SIZE_FORMAT", " 99 "_unused: "SIZE_FORMAT, 100 _allocated, _wasted, _unused)); 101 102 _allocated = 1; 103 } 104 double wasted_frac = (double)_unused / (double)_allocated; 105 size_t target_refills = (size_t)((wasted_frac * TargetSurvivorRatio) / TargetPLABWastePct); 106 if (target_refills == 0) { 107 target_refills = 1; 108 } 109 size_t used = _allocated - _wasted - _unused; 110 size_t recent_plab_sz = used / (target_refills * no_of_gc_workers); 111 // Take historical weighted average 112 _filter.sample(recent_plab_sz); 113 // Clip from above and below, and align to object boundary 114 size_t new_plab_sz = MAX2(min_size(), (size_t)_filter.average()); 115 new_plab_sz = MIN2(max_size(), new_plab_sz); 116 new_plab_sz = align_object_size(new_plab_sz); 117 // Latch the result 118 if (PrintPLAB) { 119 gclog_or_tty->print(" (plab_sz = " SIZE_FORMAT" desired_plab_sz = " SIZE_FORMAT") ", recent_plab_sz, new_plab_sz); 120 } 121 _desired_plab_sz = new_plab_sz; 122 123 reset(); 124 } 125 126 #ifndef PRODUCT 127 void ParGCAllocBuffer::print() { 128 gclog_or_tty->print_cr("parGCAllocBuffer: _bottom: " PTR_FORMAT " _top: " PTR_FORMAT 129 " _end: " PTR_FORMAT " _hard_end: " PTR_FORMAT ")", 130 p2i(_bottom), p2i(_top), p2i(_end), p2i(_hard_end)); 131 } 132 #endif // !PRODUCT