Thu, 07 Aug 2014 22:28:53 +0200
8054341: Remove some obsolete code in G1CollectedHeap class
Summary: Remove dead code.
Reviewed-by: stefank, brutisso
aoqi@0 | 1 | /* |
aoqi@0 | 2 | * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. |
aoqi@0 | 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
aoqi@0 | 4 | * |
aoqi@0 | 5 | * This code is free software; you can redistribute it and/or modify it |
aoqi@0 | 6 | * under the terms of the GNU General Public License version 2 only, as |
aoqi@0 | 7 | * published by the Free Software Foundation. |
aoqi@0 | 8 | * |
aoqi@0 | 9 | * This code is distributed in the hope that it will be useful, but WITHOUT |
aoqi@0 | 10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
aoqi@0 | 11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
aoqi@0 | 12 | * version 2 for more details (a copy is included in the LICENSE file that |
aoqi@0 | 13 | * accompanied this code). |
aoqi@0 | 14 | * |
aoqi@0 | 15 | * You should have received a copy of the GNU General Public License version |
aoqi@0 | 16 | * 2 along with this work; if not, write to the Free Software Foundation, |
aoqi@0 | 17 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
aoqi@0 | 18 | * |
aoqi@0 | 19 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
aoqi@0 | 20 | * or visit www.oracle.com if you need additional information or have any |
aoqi@0 | 21 | * questions. |
aoqi@0 | 22 | * |
aoqi@0 | 23 | */ |
aoqi@0 | 24 | |
aoqi@0 | 25 | #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1STRINGDEDUPTABLE_HPP |
aoqi@0 | 26 | #define SHARE_VM_GC_IMPLEMENTATION_G1_G1STRINGDEDUPTABLE_HPP |
aoqi@0 | 27 | |
aoqi@0 | 28 | #include "gc_implementation/g1/g1StringDedupStat.hpp" |
aoqi@0 | 29 | #include "runtime/mutexLocker.hpp" |
aoqi@0 | 30 | |
aoqi@0 | 31 | class G1StringDedupEntryCache; |
aoqi@0 | 32 | |
aoqi@0 | 33 | // |
aoqi@0 | 34 | // Table entry in the deduplication hashtable. Points weakly to the |
aoqi@0 | 35 | // character array. Can be chained in a linked list in case of hash |
aoqi@0 | 36 | // collisions or when placed in a freelist in the entry cache. |
aoqi@0 | 37 | // |
aoqi@0 | 38 | class G1StringDedupEntry : public CHeapObj<mtGC> { |
aoqi@0 | 39 | private: |
aoqi@0 | 40 | G1StringDedupEntry* _next; |
aoqi@0 | 41 | unsigned int _hash; |
aoqi@0 | 42 | typeArrayOop _obj; |
aoqi@0 | 43 | |
aoqi@0 | 44 | public: |
aoqi@0 | 45 | G1StringDedupEntry() : |
aoqi@0 | 46 | _next(NULL), |
aoqi@0 | 47 | _hash(0), |
aoqi@0 | 48 | _obj(NULL) { |
aoqi@0 | 49 | } |
aoqi@0 | 50 | |
aoqi@0 | 51 | G1StringDedupEntry* next() { |
aoqi@0 | 52 | return _next; |
aoqi@0 | 53 | } |
aoqi@0 | 54 | |
aoqi@0 | 55 | G1StringDedupEntry** next_addr() { |
aoqi@0 | 56 | return &_next; |
aoqi@0 | 57 | } |
aoqi@0 | 58 | |
aoqi@0 | 59 | void set_next(G1StringDedupEntry* next) { |
aoqi@0 | 60 | _next = next; |
aoqi@0 | 61 | } |
aoqi@0 | 62 | |
aoqi@0 | 63 | unsigned int hash() { |
aoqi@0 | 64 | return _hash; |
aoqi@0 | 65 | } |
aoqi@0 | 66 | |
aoqi@0 | 67 | void set_hash(unsigned int hash) { |
aoqi@0 | 68 | _hash = hash; |
aoqi@0 | 69 | } |
aoqi@0 | 70 | |
aoqi@0 | 71 | typeArrayOop obj() { |
aoqi@0 | 72 | return _obj; |
aoqi@0 | 73 | } |
aoqi@0 | 74 | |
aoqi@0 | 75 | typeArrayOop* obj_addr() { |
aoqi@0 | 76 | return &_obj; |
aoqi@0 | 77 | } |
aoqi@0 | 78 | |
aoqi@0 | 79 | void set_obj(typeArrayOop obj) { |
aoqi@0 | 80 | _obj = obj; |
aoqi@0 | 81 | } |
aoqi@0 | 82 | }; |
aoqi@0 | 83 | |
aoqi@0 | 84 | // |
aoqi@0 | 85 | // The deduplication hashtable keeps track of all unique character arrays used |
aoqi@0 | 86 | // by String objects. Each table entry weakly points to an character array, allowing |
aoqi@0 | 87 | // otherwise unreachable character arrays to be declared dead and pruned from the |
aoqi@0 | 88 | // table. |
aoqi@0 | 89 | // |
aoqi@0 | 90 | // The table is dynamically resized to accommodate the current number of table entries. |
aoqi@0 | 91 | // The table has hash buckets with chains for hash collision. If the average chain |
aoqi@0 | 92 | // length goes above or below given thresholds the table grows or shrinks accordingly. |
aoqi@0 | 93 | // |
aoqi@0 | 94 | // The table is also dynamically rehashed (using a new hash seed) if it becomes severely |
aoqi@0 | 95 | // unbalanced, i.e., a hash chain is significantly longer than average. |
aoqi@0 | 96 | // |
aoqi@0 | 97 | // All access to the table is protected by the StringDedupTable_lock, except under |
aoqi@0 | 98 | // safepoints in which case GC workers are allowed to access a table partitions they |
aoqi@0 | 99 | // have claimed without first acquiring the lock. Note however, that this applies only |
aoqi@0 | 100 | // the table partition (i.e. a range of elements in _buckets), not other parts of the |
aoqi@0 | 101 | // table such as the _entries field, statistics counters, etc. |
aoqi@0 | 102 | // |
aoqi@0 | 103 | class G1StringDedupTable : public CHeapObj<mtGC> { |
aoqi@0 | 104 | private: |
aoqi@0 | 105 | // The currently active hashtable instance. Only modified when |
aoqi@0 | 106 | // the table is resizes or rehashed. |
aoqi@0 | 107 | static G1StringDedupTable* _table; |
aoqi@0 | 108 | |
aoqi@0 | 109 | // Cache for reuse and fast alloc/free of table entries. |
aoqi@0 | 110 | static G1StringDedupEntryCache* _entry_cache; |
aoqi@0 | 111 | |
aoqi@0 | 112 | G1StringDedupEntry** _buckets; |
aoqi@0 | 113 | size_t _size; |
aoqi@0 | 114 | uintx _entries; |
aoqi@0 | 115 | uintx _shrink_threshold; |
aoqi@0 | 116 | uintx _grow_threshold; |
aoqi@0 | 117 | bool _rehash_needed; |
aoqi@0 | 118 | |
aoqi@0 | 119 | // The hash seed also dictates which hash function to use. A |
aoqi@0 | 120 | // zero hash seed means we will use the Java compatible hash |
aoqi@0 | 121 | // function (which doesn't use a seed), and a non-zero hash |
aoqi@0 | 122 | // seed means we use the murmur3 hash function. |
aoqi@0 | 123 | jint _hash_seed; |
aoqi@0 | 124 | |
aoqi@0 | 125 | // Constants governing table resize/rehash/cache. |
aoqi@0 | 126 | static const size_t _min_size; |
aoqi@0 | 127 | static const size_t _max_size; |
aoqi@0 | 128 | static const double _grow_load_factor; |
aoqi@0 | 129 | static const double _shrink_load_factor; |
aoqi@0 | 130 | static const uintx _rehash_multiple; |
aoqi@0 | 131 | static const uintx _rehash_threshold; |
aoqi@0 | 132 | static const double _max_cache_factor; |
aoqi@0 | 133 | |
aoqi@0 | 134 | // Table statistics, only used for logging. |
aoqi@0 | 135 | static uintx _entries_added; |
aoqi@0 | 136 | static uintx _entries_removed; |
aoqi@0 | 137 | static uintx _resize_count; |
aoqi@0 | 138 | static uintx _rehash_count; |
aoqi@0 | 139 | |
aoqi@0 | 140 | G1StringDedupTable(size_t size, jint hash_seed = 0); |
aoqi@0 | 141 | ~G1StringDedupTable(); |
aoqi@0 | 142 | |
aoqi@0 | 143 | // Returns the hash bucket at the given index. |
aoqi@0 | 144 | G1StringDedupEntry** bucket(size_t index) { |
aoqi@0 | 145 | return _buckets + index; |
aoqi@0 | 146 | } |
aoqi@0 | 147 | |
aoqi@0 | 148 | // Returns the hash bucket index for the given hash code. |
aoqi@0 | 149 | size_t hash_to_index(unsigned int hash) { |
aoqi@0 | 150 | return (size_t)hash & (_size - 1); |
aoqi@0 | 151 | } |
aoqi@0 | 152 | |
aoqi@0 | 153 | // Adds a new table entry to the given hash bucket. |
aoqi@0 | 154 | void add(typeArrayOop value, unsigned int hash, G1StringDedupEntry** list); |
aoqi@0 | 155 | |
aoqi@0 | 156 | // Removes the given table entry from the table. |
aoqi@0 | 157 | void remove(G1StringDedupEntry** pentry, uint worker_id); |
aoqi@0 | 158 | |
aoqi@0 | 159 | // Transfers a table entry from the current table to the destination table. |
aoqi@0 | 160 | void transfer(G1StringDedupEntry** pentry, G1StringDedupTable* dest); |
aoqi@0 | 161 | |
aoqi@0 | 162 | // Returns an existing character array in the given hash bucket, or NULL |
aoqi@0 | 163 | // if no matching character array exists. |
aoqi@0 | 164 | typeArrayOop lookup(typeArrayOop value, unsigned int hash, |
aoqi@0 | 165 | G1StringDedupEntry** list, uintx &count); |
aoqi@0 | 166 | |
aoqi@0 | 167 | // Returns an existing character array in the table, or inserts a new |
aoqi@0 | 168 | // table entry if no matching character array exists. |
aoqi@0 | 169 | typeArrayOop lookup_or_add_inner(typeArrayOop value, unsigned int hash); |
aoqi@0 | 170 | |
aoqi@0 | 171 | // Thread safe lookup or add of table entry |
aoqi@0 | 172 | static typeArrayOop lookup_or_add(typeArrayOop value, unsigned int hash) { |
aoqi@0 | 173 | // Protect the table from concurrent access. Also note that this lock |
aoqi@0 | 174 | // acts as a fence for _table, which could have been replaced by a new |
aoqi@0 | 175 | // instance if the table was resized or rehashed. |
aoqi@0 | 176 | MutexLockerEx ml(StringDedupTable_lock, Mutex::_no_safepoint_check_flag); |
aoqi@0 | 177 | return _table->lookup_or_add_inner(value, hash); |
aoqi@0 | 178 | } |
aoqi@0 | 179 | |
aoqi@0 | 180 | // Returns true if the hashtable is currently using a Java compatible |
aoqi@0 | 181 | // hash function. |
aoqi@0 | 182 | static bool use_java_hash() { |
aoqi@0 | 183 | return _table->_hash_seed == 0; |
aoqi@0 | 184 | } |
aoqi@0 | 185 | |
aoqi@0 | 186 | static bool equals(typeArrayOop value1, typeArrayOop value2); |
aoqi@0 | 187 | |
aoqi@0 | 188 | // Computes the hash code for the given character array, using the |
aoqi@0 | 189 | // currently active hash function and hash seed. |
aoqi@0 | 190 | static unsigned int hash_code(typeArrayOop value); |
aoqi@0 | 191 | |
aoqi@0 | 192 | static uintx unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, |
aoqi@0 | 193 | size_t partition_begin, |
aoqi@0 | 194 | size_t partition_end, |
aoqi@0 | 195 | uint worker_id); |
aoqi@0 | 196 | |
aoqi@0 | 197 | public: |
aoqi@0 | 198 | static void create(); |
aoqi@0 | 199 | |
aoqi@0 | 200 | // Deduplicates the given String object, or adds its backing |
aoqi@0 | 201 | // character array to the deduplication hashtable. |
aoqi@0 | 202 | static void deduplicate(oop java_string, G1StringDedupStat& stat); |
aoqi@0 | 203 | |
aoqi@0 | 204 | // If a table resize is needed, returns a newly allocated empty |
aoqi@0 | 205 | // hashtable of the proper size. |
aoqi@0 | 206 | static G1StringDedupTable* prepare_resize(); |
aoqi@0 | 207 | |
aoqi@0 | 208 | // Installs a newly resized table as the currently active table |
aoqi@0 | 209 | // and deletes the previously active table. |
aoqi@0 | 210 | static void finish_resize(G1StringDedupTable* resized_table); |
aoqi@0 | 211 | |
aoqi@0 | 212 | // If a table rehash is needed, returns a newly allocated empty |
aoqi@0 | 213 | // hashtable and updates the hash seed. |
aoqi@0 | 214 | static G1StringDedupTable* prepare_rehash(); |
aoqi@0 | 215 | |
aoqi@0 | 216 | // Transfers rehashed entries from the currently active table into |
aoqi@0 | 217 | // the new table. Installs the new table as the currently active table |
aoqi@0 | 218 | // and deletes the previously active table. |
aoqi@0 | 219 | static void finish_rehash(G1StringDedupTable* rehashed_table); |
aoqi@0 | 220 | |
aoqi@0 | 221 | // If the table entry cache has grown too large, trim it down according to policy |
aoqi@0 | 222 | static void trim_entry_cache(); |
aoqi@0 | 223 | |
aoqi@0 | 224 | static void unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, uint worker_id); |
aoqi@0 | 225 | |
aoqi@0 | 226 | static void print_statistics(outputStream* st); |
aoqi@0 | 227 | static void verify(); |
aoqi@0 | 228 | }; |
aoqi@0 | 229 | |
aoqi@0 | 230 | #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1STRINGDEDUPTABLE_HPP |