Tue, 04 Aug 2009 16:00:17 -0700
6819077: G1: first GC thread coming late into the GC.
Summary: The first worker thread is delayed when entering the GC because it clears the card count table that is used in identifying hot cards. Replace the card count table with a dynamically sized evicting hash table that includes an epoch based counter.
Reviewed-by: iveresov, tonyp
ysr@777 | 1 | /* |
xdono@1014 | 2 | * Copyright 2001-2009 Sun Microsystems, Inc. All Rights Reserved. |
ysr@777 | 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
ysr@777 | 4 | * |
ysr@777 | 5 | * This code is free software; you can redistribute it and/or modify it |
ysr@777 | 6 | * under the terms of the GNU General Public License version 2 only, as |
ysr@777 | 7 | * published by the Free Software Foundation. |
ysr@777 | 8 | * |
ysr@777 | 9 | * This code is distributed in the hope that it will be useful, but WITHOUT |
ysr@777 | 10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
ysr@777 | 11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
ysr@777 | 12 | * version 2 for more details (a copy is included in the LICENSE file that |
ysr@777 | 13 | * accompanied this code). |
ysr@777 | 14 | * |
ysr@777 | 15 | * You should have received a copy of the GNU General Public License version |
ysr@777 | 16 | * 2 along with this work; if not, write to the Free Software Foundation, |
ysr@777 | 17 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
ysr@777 | 18 | * |
ysr@777 | 19 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
ysr@777 | 20 | * CA 95054 USA or visit www.sun.com if you need additional information or |
ysr@777 | 21 | * have any questions. |
ysr@777 | 22 | * |
ysr@777 | 23 | */ |
ysr@777 | 24 | |
ysr@777 | 25 | // Forward decl |
ysr@777 | 26 | class ConcurrentG1RefineThread; |
ysr@777 | 27 | class G1RemSet; |
ysr@777 | 28 | |
apetrusenko@984 | 29 | class ConcurrentG1Refine: public CHeapObj { |
iveresov@1229 | 30 | ConcurrentG1RefineThread** _threads; |
iveresov@1229 | 31 | int _n_threads; |
johnc@1325 | 32 | |
ysr@777 | 33 | // The cache for card refinement. |
johnc@1325 | 34 | bool _use_cache; |
johnc@1325 | 35 | bool _def_use_cache; |
ysr@777 | 36 | |
johnc@1325 | 37 | size_t _n_periods; // Used as clearing epoch |
johnc@1325 | 38 | |
johnc@1325 | 39 | // An evicting cache of the number of times each card |
johnc@1325 | 40 | // is accessed. Reduces, but does not eliminate, the amount |
johnc@1325 | 41 | // of duplicated processing of dirty cards. |
johnc@1325 | 42 | |
johnc@1325 | 43 | enum SomePrivateConstants { |
johnc@1325 | 44 | epoch_bits = 32, |
johnc@1325 | 45 | card_num_shift = epoch_bits, |
johnc@1325 | 46 | epoch_mask = AllBits, |
johnc@1325 | 47 | card_num_mask = AllBits, |
johnc@1325 | 48 | |
johnc@1325 | 49 | // The initial cache size is approximately this fraction |
johnc@1325 | 50 | // of a maximal cache (i.e. the size needed for all cards |
johnc@1325 | 51 | // in the heap) |
johnc@1325 | 52 | InitialCacheFraction = 512 |
johnc@1325 | 53 | }; |
johnc@1325 | 54 | |
johnc@1325 | 55 | const static julong card_num_mask_in_place = |
johnc@1325 | 56 | (julong) card_num_mask << card_num_shift; |
johnc@1325 | 57 | |
johnc@1325 | 58 | typedef struct { |
johnc@1325 | 59 | julong _value; // | card_num | epoch | |
johnc@1325 | 60 | } CardEpochCacheEntry; |
johnc@1325 | 61 | |
johnc@1325 | 62 | julong make_epoch_entry(unsigned int card_num, unsigned int epoch) { |
johnc@1325 | 63 | assert(0 <= card_num && card_num < _max_n_card_counts, "Bounds"); |
johnc@1325 | 64 | assert(0 <= epoch && epoch <= _n_periods, "must be"); |
johnc@1325 | 65 | |
johnc@1325 | 66 | return ((julong) card_num << card_num_shift) | epoch; |
johnc@1325 | 67 | } |
johnc@1325 | 68 | |
johnc@1325 | 69 | unsigned int extract_epoch(julong v) { |
johnc@1325 | 70 | return (v & epoch_mask); |
johnc@1325 | 71 | } |
johnc@1325 | 72 | |
johnc@1325 | 73 | unsigned int extract_card_num(julong v) { |
johnc@1325 | 74 | return (v & card_num_mask_in_place) >> card_num_shift; |
johnc@1325 | 75 | } |
johnc@1325 | 76 | |
johnc@1325 | 77 | typedef struct { |
johnc@1325 | 78 | unsigned char _count; |
johnc@1325 | 79 | unsigned char _evict_count; |
johnc@1325 | 80 | } CardCountCacheEntry; |
johnc@1325 | 81 | |
johnc@1325 | 82 | CardCountCacheEntry* _card_counts; |
johnc@1325 | 83 | CardEpochCacheEntry* _card_epochs; |
johnc@1325 | 84 | |
johnc@1325 | 85 | // The current number of buckets in the card count cache |
johnc@1325 | 86 | unsigned _n_card_counts; |
johnc@1325 | 87 | |
johnc@1325 | 88 | // The max number of buckets required for the number of |
johnc@1325 | 89 | // cards for the entire reserved heap |
johnc@1325 | 90 | unsigned _max_n_card_counts; |
johnc@1325 | 91 | |
johnc@1325 | 92 | // Possible sizes of the cache: odd primes that roughly double in size. |
johnc@1325 | 93 | // (See jvmtiTagMap.cpp). |
johnc@1325 | 94 | static int _cc_cache_sizes[]; |
johnc@1325 | 95 | |
johnc@1325 | 96 | // The index in _cc_cache_sizes corresponding to the size of |
johnc@1325 | 97 | // _card_counts. |
johnc@1325 | 98 | int _cache_size_index; |
johnc@1325 | 99 | |
johnc@1325 | 100 | bool _expand_card_counts; |
johnc@1325 | 101 | |
johnc@1325 | 102 | const jbyte* _ct_bot; |
johnc@1324 | 103 | |
johnc@1324 | 104 | jbyte** _hot_cache; |
johnc@1324 | 105 | int _hot_cache_size; |
johnc@1324 | 106 | int _n_hot; |
johnc@1324 | 107 | int _hot_cache_idx; |
johnc@1324 | 108 | |
johnc@1324 | 109 | int _hot_cache_par_chunk_size; |
johnc@1324 | 110 | volatile int _hot_cache_par_claimed_idx; |
ysr@777 | 111 | |
johnc@1325 | 112 | // Needed to workaround 6817995 |
johnc@1325 | 113 | CardTableModRefBS* _ct_bs; |
johnc@1325 | 114 | G1CollectedHeap* _g1h; |
johnc@1325 | 115 | |
johnc@1325 | 116 | // Expands the array that holds the card counts to the next size up |
johnc@1325 | 117 | void expand_card_count_cache(); |
johnc@1325 | 118 | |
johnc@1325 | 119 | // hash a given key (index of card_ptr) with the specified size |
johnc@1325 | 120 | static unsigned int hash(size_t key, int size) { |
johnc@1325 | 121 | return (unsigned int) key % size; |
johnc@1325 | 122 | } |
johnc@1325 | 123 | |
johnc@1325 | 124 | // hash a given key (index of card_ptr) |
johnc@1325 | 125 | unsigned int hash(size_t key) { |
johnc@1325 | 126 | return hash(key, _n_card_counts); |
johnc@1325 | 127 | } |
johnc@1325 | 128 | |
johnc@1325 | 129 | unsigned ptr_2_card_num(jbyte* card_ptr) { |
johnc@1325 | 130 | return (unsigned) (card_ptr - _ct_bot); |
johnc@1325 | 131 | } |
johnc@1325 | 132 | |
johnc@1325 | 133 | jbyte* card_num_2_ptr(unsigned card_num) { |
johnc@1325 | 134 | return (jbyte*) (_ct_bot + card_num); |
johnc@1325 | 135 | } |
johnc@1325 | 136 | |
ysr@777 | 137 | // Returns the count of this card after incrementing it. |
johnc@1325 | 138 | jbyte* add_card_count(jbyte* card_ptr, int* count, bool* defer); |
ysr@777 | 139 | |
johnc@1325 | 140 | // Returns true if this card is in a young region |
johnc@1325 | 141 | bool is_young_card(jbyte* card_ptr); |
johnc@1325 | 142 | |
ysr@777 | 143 | public: |
ysr@777 | 144 | ConcurrentG1Refine(); |
ysr@777 | 145 | ~ConcurrentG1Refine(); |
ysr@777 | 146 | |
ysr@777 | 147 | void init(); // Accomplish some initialization that has to wait. |
iveresov@1229 | 148 | void stop(); |
ysr@777 | 149 | |
iveresov@1229 | 150 | // Iterate over the conc refine threads |
iveresov@1229 | 151 | void threads_do(ThreadClosure *tc); |
ysr@777 | 152 | |
ysr@777 | 153 | // If this is the first entry for the slot, writes into the cache and |
ysr@777 | 154 | // returns NULL. If it causes an eviction, returns the evicted pointer. |
ysr@777 | 155 | // Otherwise, its a cache hit, and returns NULL. |
johnc@1325 | 156 | jbyte* cache_insert(jbyte* card_ptr, bool* defer); |
ysr@777 | 157 | |
ysr@777 | 158 | // Process the cached entries. |
ysr@777 | 159 | void clean_up_cache(int worker_i, G1RemSet* g1rs); |
ysr@777 | 160 | |
johnc@1324 | 161 | // Set up for parallel processing of the cards in the hot cache |
johnc@1324 | 162 | void clear_hot_cache_claimed_index() { |
johnc@1324 | 163 | _hot_cache_par_claimed_idx = 0; |
johnc@1324 | 164 | } |
johnc@1324 | 165 | |
ysr@777 | 166 | // Discard entries in the hot cache. |
ysr@777 | 167 | void clear_hot_cache() { |
ysr@777 | 168 | _hot_cache_idx = 0; _n_hot = 0; |
ysr@777 | 169 | } |
ysr@777 | 170 | |
ysr@777 | 171 | bool hot_cache_is_empty() { return _n_hot == 0; } |
ysr@777 | 172 | |
ysr@777 | 173 | bool use_cache() { return _use_cache; } |
ysr@777 | 174 | void set_use_cache(bool b) { |
ysr@777 | 175 | if (b) _use_cache = _def_use_cache; |
ysr@777 | 176 | else _use_cache = false; |
ysr@777 | 177 | } |
ysr@777 | 178 | |
ysr@777 | 179 | void clear_and_record_card_counts(); |
iveresov@1230 | 180 | |
iveresov@1230 | 181 | static size_t thread_num(); |
ysr@777 | 182 | }; |