author | kbarrett |
Wed, 24 Feb 2016 13:18:54 -0500 | |
changeset 36354 | 28bbe66a0498 |
parent 35061 | be6025ebffea |
child 36390 | a2d991d1d628 |
permissions | -rw-r--r-- |
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/* |
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* Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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* |
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*/ |
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#include "precompiled.hpp" |
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#include "memory/allocation.inline.hpp" |
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#include "gc/g1/g1EvacStats.hpp" |
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#include "gc/shared/gcId.hpp" |
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#include "logging/log.hpp" |
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#include "trace/tracing.hpp" |
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void G1EvacStats::adjust_desired_plab_sz() { |
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if (!ResizePLAB) { |
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log_debug(gc, plab)(" (allocated = " SIZE_FORMAT " wasted = " SIZE_FORMAT " " |
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"unused = " SIZE_FORMAT " used = " SIZE_FORMAT " " |
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"undo_waste = " SIZE_FORMAT " region_end_waste = " SIZE_FORMAT " " |
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"regions filled = %u direct_allocated = " SIZE_FORMAT " " |
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"failure_used = " SIZE_FORMAT " failure_waste = " SIZE_FORMAT ") ", |
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_allocated, _wasted, _unused, used(), _undo_wasted, _region_end_waste, |
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_regions_filled, _direct_allocated, _failure_used, _failure_waste); |
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// Clear accumulators for next round. |
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reset(); |
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return; |
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} |
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assert(is_object_aligned(max_size()) && min_size() <= max_size(), |
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"PLAB clipping computation may be incorrect"); |
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if (_allocated == 0) { |
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assert((_unused == 0), |
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"Inconsistency in PLAB stats: " |
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"_allocated: " SIZE_FORMAT ", " |
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"_wasted: " SIZE_FORMAT ", " |
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"_region_end_waste: " SIZE_FORMAT ", " |
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"_unused: " SIZE_FORMAT ", " |
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"_used : " SIZE_FORMAT, |
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_allocated, _wasted, _region_end_waste, _unused, used()); |
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_allocated = 1; |
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} |
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// The size of the PLAB caps the amount of space that can be wasted at the |
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// end of the collection. In the worst case the last PLAB could be completely |
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// empty. |
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// This allows us to calculate the new PLAB size to achieve the |
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// TargetPLABWastePct given the latest memory usage and that the last buffer |
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// will be G1LastPLABAverageOccupancy full. |
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// |
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// E.g. assume that if in the current GC 100 words were allocated and a |
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// TargetPLABWastePct of 10 had been set. |
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// |
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// So we could waste up to 10 words to meet that percentage. Given that we |
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// also assume that that buffer is typically half-full, the new desired PLAB |
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// size is set to 20 words. |
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// |
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// The amount of allocation performed should be independent of the number of |
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// threads, so should the maximum waste we can spend in total. So if |
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// we used n threads to allocate, each of them can spend maximum waste/n words in |
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// a first rough approximation. The number of threads only comes into play later |
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// when actually retrieving the actual desired PLAB size. |
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// |
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// After calculating this optimal PLAB size the algorithm applies the usual |
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// exponential decaying average over this value to guess the next PLAB size. |
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// |
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// We account region end waste fully to PLAB allocation (in the calculation of |
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// what we consider as "used_for_waste_calculation" below). This is not |
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// completely fair, but is a conservative assumption because PLABs may be sized |
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// flexibly while we cannot adjust inline allocations. |
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// Allocation during GC will try to minimize region end waste so this impact |
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// should be minimal. |
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// |
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// We need to cover overflow when calculating the amount of space actually used |
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// by objects in PLABs when subtracting the region end waste. |
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// Region end waste may be higher than actual allocation. This may occur if many |
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// threads do not allocate anything but a few rather large objects. In this |
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// degenerate case the PLAB size would simply quickly tend to minimum PLAB size, |
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// which is an okay reaction. |
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size_t const used_for_waste_calculation = used() > _region_end_waste ? used() - _region_end_waste : 0; |
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size_t const total_waste_allowed = used_for_waste_calculation * TargetPLABWastePct; |
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size_t const cur_plab_sz = (size_t)((double)total_waste_allowed / G1LastPLABAverageOccupancy); |
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// Take historical weighted average |
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_filter.sample(cur_plab_sz); |
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// Clip from above and below, and align to object boundary |
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size_t plab_sz; |
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plab_sz = MAX2(min_size(), (size_t)_filter.average()); |
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plab_sz = MIN2(max_size(), plab_sz); |
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plab_sz = align_object_size(plab_sz); |
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// Latch the result |
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_desired_net_plab_sz = plab_sz; |
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log_debug(gc, plab)(" (allocated = " SIZE_FORMAT " wasted = " SIZE_FORMAT " " |
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"unused = " SIZE_FORMAT " used = " SIZE_FORMAT " " |
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"undo_waste = " SIZE_FORMAT " region_end_waste = " SIZE_FORMAT " " |
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"regions filled = %u direct_allocated = " SIZE_FORMAT " " |
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"failure_used = " SIZE_FORMAT " failure_waste = " SIZE_FORMAT ") " |
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" (plab_sz = " SIZE_FORMAT " desired_plab_sz = " SIZE_FORMAT ")", |
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_allocated, _wasted, _unused, used(), _undo_wasted, _region_end_waste, |
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_regions_filled, _direct_allocated, _failure_used, _failure_waste, |
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cur_plab_sz, plab_sz); |
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// Clear accumulators for next round. |
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reset(); |
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} |
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G1EvacStats::~G1EvacStats() { } |