| /* |
| * Copyright (c) 2018, 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. |
| * |
| */ |
| |
| #ifndef SHARE_VM_GC_G1_G1REGIONMARKSTATSCACHE_HPP |
| #define SHARE_VM_GC_G1_G1REGIONMARKSTATSCACHE_HPP |
| |
| #include "memory/allocation.hpp" |
| #include "utilities/debug.hpp" |
| #include "utilities/globalDefinitions.hpp" |
| #include "utilities/pair.hpp" |
| |
| // Per-Region statistics gathered during marking. |
| // |
| // This includes |
| // * the number of live words gathered during marking for the area from bottom |
| // to ntams. This is an exact measure. |
| // The code corrects later for the live data between ntams and top. |
| struct G1RegionMarkStats { |
| size_t _live_words; |
| |
| // Clear all members. |
| void clear() { |
| _live_words = 0; |
| } |
| // Clear all members after a marking overflow. Nothing to do as the live words |
| // are updated by the atomic mark. We do not remark objects after overflow. |
| void clear_during_overflow() { |
| } |
| |
| bool is_clear() const { return _live_words == 0; } |
| }; |
| |
| // Per-marking thread cache for the region mark statistics. |
| // |
| // Each cache is a larg'ish map of region-idx -> G1RegionMarkStats entries that cache |
| // currently gathered statistics; entries are evicted to the global statistics array |
| // on every collision. This minimizes synchronization overhead which would be required |
| // every time statistics change, as marking is very localized. |
| // The map entry number is a power of two to allow simple and fast hashing using |
| // logical and. |
| class G1RegionMarkStatsCache { |
| private: |
| // The array of statistics entries to evict to; the global array. |
| G1RegionMarkStats* _target; |
| // Number of entries in the eviction target. |
| uint _num_stats; |
| |
| // An entry of the statistics cache. |
| struct G1RegionMarkStatsCacheEntry { |
| uint _region_idx; |
| G1RegionMarkStats _stats; |
| |
| void clear() { |
| _region_idx = 0; |
| _stats.clear(); |
| } |
| |
| bool is_clear() const { |
| return _region_idx == 0 && _stats.is_clear(); |
| } |
| }; |
| |
| // The actual cache and its number of entries. |
| G1RegionMarkStatsCacheEntry* _cache; |
| uint _num_cache_entries; |
| |
| // Cache hits/miss counters. |
| size_t _cache_hits; |
| size_t _cache_misses; |
| |
| // Evict a given element of the statistics cache. |
| void evict(uint idx); |
| |
| size_t _num_cache_entries_mask; |
| |
| uint hash(uint idx) { |
| return idx & _num_cache_entries_mask; |
| } |
| |
| G1RegionMarkStatsCacheEntry* find_for_add(uint region_idx); |
| public: |
| G1RegionMarkStatsCache(G1RegionMarkStats* target, uint max_regions, uint num_cache_entries); |
| |
| ~G1RegionMarkStatsCache(); |
| |
| void add_live_words(uint region_idx, size_t live_words) { |
| G1RegionMarkStatsCacheEntry* const cur = find_for_add(region_idx); |
| cur->_stats._live_words += live_words; |
| } |
| |
| void reset(uint region_idx) { |
| uint const cache_idx = hash(region_idx); |
| G1RegionMarkStatsCacheEntry* cur = &_cache[cache_idx]; |
| if (cur->_region_idx == region_idx) { |
| _cache[cache_idx].clear(); |
| } |
| } |
| |
| // Evict all remaining statistics, returning cache hits and misses. |
| Pair<size_t, size_t> evict_all(); |
| |
| // Reset all cache entries to their default values. |
| void reset(); |
| |
| size_t hits() const { return _cache_hits; } |
| size_t misses() const { return _cache_misses; } |
| }; |
| |
| #endif // SHARE_VM_GC_G1_G1REGIONMARKSTATSCACHE_HPP |