| /* |
| * Copyright (c) 2015, 2022, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "precompiled.hpp" |
| #include "gc/g1/g1EvacStats.hpp" |
| #include "gc/shared/gcId.hpp" |
| #include "gc/shared/gc_globals.hpp" |
| #include "logging/log.hpp" |
| #include "memory/allocation.inline.hpp" |
| #include "runtime/globals.hpp" |
| |
| void G1EvacStats::log_plab_allocation() { |
| log_debug(gc, plab)("%s PLAB allocation: " |
| "allocated: %zuB, " |
| "wasted: %zuB, " |
| "unused: %zuB, " |
| "used: %zuB, " |
| "undo waste: %zuB, ", |
| _description, |
| _allocated * HeapWordSize, |
| _wasted * HeapWordSize, |
| _unused * HeapWordSize, |
| used() * HeapWordSize, |
| _undo_wasted * HeapWordSize); |
| log_debug(gc, plab)("%s other allocation: " |
| "region end waste: %zuB, " |
| "regions filled: %u, " |
| "num plab filled: %zu, " |
| "direct allocated: %zuB, " |
| "num direct allocated: %zu, " |
| "failure used: %zuB, " |
| "failure wasted: %zuB", |
| _description, |
| _region_end_waste * HeapWordSize, |
| _regions_filled, |
| _num_plab_filled, |
| _direct_allocated * HeapWordSize, |
| _num_direct_allocated, |
| _failure_used * HeapWordSize, |
| _failure_waste * HeapWordSize); |
| } |
| |
| void G1EvacStats::log_sizing(size_t calculated_words, size_t net_desired_words) { |
| log_debug(gc, plab)("%s sizing: " |
| "calculated: %zuB, " |
| "actual: %zuB", |
| _description, |
| calculated_words * HeapWordSize, |
| net_desired_words * HeapWordSize); |
| } |
| |
| size_t G1EvacStats::compute_desired_plab_size() const { |
| // The size of the PLAB caps the amount of space that can be wasted at the |
| // end of the collection. In the worst case the last PLAB could be completely |
| // empty. |
| // This allows us to calculate the new PLAB size to achieve the |
| // TargetPLABWastePct given the latest memory usage and that the last buffer |
| // will be G1LastPLABAverageOccupancy full. |
| // |
| // E.g. assume that if in the current GC 100 words were allocated and a |
| // TargetPLABWastePct of 10 had been set. |
| // |
| // So we could waste up to 10 words to meet that percentage. Given that we |
| // also assume that that buffer is typically half-full (G1LastPLABAverageOccupancy), |
| // the new desired PLAB size is set to 20 words. |
| // |
| // (This also implies that we expect G1LastPLABAverageOccupancy/TargetPLABWastePct |
| // number of refills during allocation). |
| // |
| // The amount of allocation performed should be independent of the number of |
| // threads, so should the maximum waste we can spend in total. So if |
| // we used n threads to allocate, each of them can spend maximum waste/n words in |
| // a first rough approximation. The number of threads only comes into play later |
| // when actually retrieving the actual desired PLAB size. |
| // |
| // After calculating this optimal PLAB size the algorithm applies the usual |
| // exponential decaying average over this value to guess the next PLAB size. |
| // |
| // We account region end waste fully to PLAB allocation (in the calculation of |
| // what we consider as "used_for_waste_calculation" below). This is not |
| // completely fair, but is a conservative assumption because PLABs may be sized |
| // flexibly while we cannot adjust inline allocations. |
| // Allocation during GC will try to minimize region end waste so this impact |
| // should be minimal. |
| // |
| // We need to cover overflow when calculating the amount of space actually used |
| // by objects in PLABs when subtracting the region end waste. |
| // Region end waste may be higher than actual allocation. This may occur if many |
| // threads do not allocate anything but a few rather large objects. In this |
| // degenerate case the PLAB size would simply quickly tend to minimum PLAB size, |
| // which is an okay reaction. |
| size_t const used_for_waste_calculation = used() > _region_end_waste ? used() - _region_end_waste : 0; |
| |
| size_t const total_waste_allowed = used_for_waste_calculation * TargetPLABWastePct; |
| return (size_t)((double)total_waste_allowed / G1LastPLABAverageOccupancy); |
| } |
| |
| G1EvacStats::G1EvacStats(const char* description, size_t default_per_thread_plab_size, unsigned wt) : |
| PLABStats(description), |
| _default_plab_size(default_per_thread_plab_size), |
| _desired_net_plab_size(default_per_thread_plab_size * ParallelGCThreads), |
| _net_plab_size_filter(wt), |
| _region_end_waste(0), |
| _regions_filled(0), |
| _num_plab_filled(0), |
| _direct_allocated(0), |
| _num_direct_allocated(0), |
| _failure_used(0), |
| _failure_waste(0) { |
| } |
| |
| // Calculates plab size for current number of gc worker threads. |
| size_t G1EvacStats::desired_plab_size(uint no_of_gc_workers) const { |
| if (!ResizePLAB) { |
| return _default_plab_size; |
| } |
| return align_object_size(clamp(_desired_net_plab_size / no_of_gc_workers, min_size(), max_size())); |
| } |
| |
| void G1EvacStats::adjust_desired_plab_size() { |
| log_plab_allocation(); |
| |
| if (ResizePLAB) { |
| assert(is_object_aligned(max_size()) && min_size() <= max_size(), |
| "PLAB clipping computation may be incorrect"); |
| |
| assert(_allocated != 0 || _unused == 0, |
| "Inconsistency in PLAB stats: " |
| "_allocated: %zu, " |
| "_wasted: %zu, " |
| "_unused: %zu, " |
| "_undo_wasted: %zu", |
| _allocated, _wasted, _unused, _undo_wasted); |
| |
| size_t plab_size = compute_desired_plab_size(); |
| // Take historical weighted average |
| _net_plab_size_filter.sample(plab_size); |
| _desired_net_plab_size = MAX2(min_size(), (size_t)_net_plab_size_filter.average()); |
| |
| log_sizing(plab_size, _desired_net_plab_size); |
| } |
| // Clear accumulators for next round |
| reset(); |
| } |
