1 /* 2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/javaClasses.hpp" 27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 28 #include "gc_implementation/g1/g1GCPhaseTimes.hpp" 29 #include "gc_implementation/g1/g1StringDedup.hpp" 30 #include "gc_implementation/g1/g1StringDedupQueue.hpp" 31 #include "gc_implementation/g1/g1StringDedupStat.hpp" 32 #include "gc_implementation/g1/g1StringDedupTable.hpp" 33 #include "gc_implementation/g1/g1StringDedupThread.hpp" 34 35 bool G1StringDedup::_enabled = false; 36 37 void G1StringDedup::initialize() { 38 assert(UseG1GC, "String deduplication only available with G1"); 39 if (UseStringDeduplication) { 40 _enabled = true; 41 G1StringDedupQueue::create(); 42 G1StringDedupTable::create(); 43 G1StringDedupThread::create(); 44 } 45 } 46 47 bool G1StringDedup::is_candidate_from_mark(oop obj) { 48 if (java_lang_String::is_instance(obj)) { 49 bool from_young = G1CollectedHeap::heap()->heap_region_containing_raw(obj)->is_young(); 50 if (from_young && obj->age() < StringDeduplicationAgeThreshold) { 51 // Candidate found. String is being evacuated from young to old but has not 52 // reached the deduplication age threshold, i.e. has not previously been a 53 // candidate during its life in the young generation. 54 return true; 55 } 56 } 57 58 // Not a candidate 59 return false; 60 } 61 62 void G1StringDedup::enqueue_from_mark(oop java_string) { 63 assert(is_enabled(), "String deduplication not enabled"); 64 if (is_candidate_from_mark(java_string)) { 65 G1StringDedupQueue::push(0 /* worker_id */, java_string); 66 } 67 } 68 69 bool G1StringDedup::is_candidate_from_evacuation(bool from_young, bool to_young, oop obj) { 70 if (from_young && java_lang_String::is_instance(obj)) { 71 if (to_young && obj->age() == StringDeduplicationAgeThreshold) { 72 // Candidate found. String is being evacuated from young to young and just 73 // reached the deduplication age threshold. 74 return true; 75 } 76 if (!to_young && obj->age() < StringDeduplicationAgeThreshold) { 77 // Candidate found. String is being evacuated from young to old but has not 78 // reached the deduplication age threshold, i.e. has not previously been a 79 // candidate during its life in the young generation. 80 return true; 81 } 82 } 83 84 // Not a candidate 85 return false; 86 } 87 88 void G1StringDedup::enqueue_from_evacuation(bool from_young, bool to_young, uint worker_id, oop java_string) { 89 assert(is_enabled(), "String deduplication not enabled"); 90 if (is_candidate_from_evacuation(from_young, to_young, java_string)) { 91 G1StringDedupQueue::push(worker_id, java_string); 92 } 93 } 94 95 void G1StringDedup::deduplicate(oop java_string) { 96 assert(is_enabled(), "String deduplication not enabled"); 97 G1StringDedupStat dummy; // Statistics from this path is never used 98 G1StringDedupTable::deduplicate(java_string, dummy); 99 } 100 101 void G1StringDedup::oops_do(OopClosure* keep_alive) { 102 assert(is_enabled(), "String deduplication not enabled"); 103 unlink_or_oops_do(NULL, keep_alive); 104 } 105 106 void G1StringDedup::unlink(BoolObjectClosure* is_alive) { 107 assert(is_enabled(), "String deduplication not enabled"); 108 // Don't allow a potential resize or rehash during unlink, as the unlink 109 // operation itself might remove enough entries to invalidate such a decision. 110 unlink_or_oops_do(is_alive, NULL, false /* allow_resize_and_rehash */); 111 } 112 113 // 114 // Task for parallel unlink_or_oops_do() operation on the deduplication queue 115 // and table. 116 // 117 class G1StringDedupUnlinkOrOopsDoTask : public AbstractGangTask { 118 private: 119 G1StringDedupUnlinkOrOopsDoClosure _cl; 120 121 public: 122 G1StringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive, 123 OopClosure* keep_alive, 124 bool allow_resize_and_rehash) : 125 AbstractGangTask("G1StringDedupUnlinkOrOopsDoTask"), 126 _cl(is_alive, keep_alive, allow_resize_and_rehash) { 127 } 128 129 virtual void work(uint worker_id) { 130 double queue_fixup_start = os::elapsedTime(); 131 G1StringDedupQueue::unlink_or_oops_do(&_cl); 132 133 double table_fixup_start = os::elapsedTime(); 134 G1StringDedupTable::unlink_or_oops_do(&_cl, worker_id); 135 136 double queue_fixup_time_ms = (table_fixup_start - queue_fixup_start) * 1000.0; 137 double table_fixup_time_ms = (os::elapsedTime() - table_fixup_start) * 1000.0; 138 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy(); 139 g1p->phase_times()->record_string_dedup_queue_fixup_worker_time(worker_id, queue_fixup_time_ms); 140 g1p->phase_times()->record_string_dedup_table_fixup_worker_time(worker_id, table_fixup_time_ms); 141 } 142 }; 143 144 void G1StringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* keep_alive, bool allow_resize_and_rehash) { 145 assert(is_enabled(), "String deduplication not enabled"); 146 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy(); 147 g1p->phase_times()->note_string_dedup_fixup_start(); 148 double fixup_start = os::elapsedTime(); 149 150 G1StringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash); 151 if (G1CollectedHeap::use_parallel_gc_threads()) { 152 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 153 g1h->set_par_threads(); 154 g1h->workers()->run_task(&task); 155 g1h->set_par_threads(0); 156 } else { 157 task.work(0); 158 } 159 160 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0; 161 g1p->phase_times()->record_string_dedup_fixup_time(fixup_time_ms); 162 g1p->phase_times()->note_string_dedup_fixup_end(); 163 } 164 165 void G1StringDedup::threads_do(ThreadClosure* tc) { 166 assert(is_enabled(), "String deduplication not enabled"); 167 tc->do_thread(G1StringDedupThread::thread()); 168 } 169 170 void G1StringDedup::print_worker_threads_on(outputStream* st) { 171 assert(is_enabled(), "String deduplication not enabled"); 172 G1StringDedupThread::thread()->print_on(st); 173 st->cr(); 174 } 175 176 void G1StringDedup::verify() { 177 assert(is_enabled(), "String deduplication not enabled"); 178 G1StringDedupQueue::verify(); 179 G1StringDedupTable::verify(); 180 } 181 182 G1StringDedupUnlinkOrOopsDoClosure::G1StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive, 183 OopClosure* keep_alive, 184 bool allow_resize_and_rehash) : 185 _is_alive(is_alive), 186 _keep_alive(keep_alive), 187 _resized_table(NULL), 188 _rehashed_table(NULL), 189 _next_queue(0), 190 _next_bucket(0) { 191 if (allow_resize_and_rehash) { 192 // If both resize and rehash is needed, only do resize. Rehash of 193 // the table will eventually happen if the situation persists. 194 _resized_table = G1StringDedupTable::prepare_resize(); 195 if (!is_resizing()) { 196 _rehashed_table = G1StringDedupTable::prepare_rehash(); 197 } 198 } 199 } 200 201 G1StringDedupUnlinkOrOopsDoClosure::~G1StringDedupUnlinkOrOopsDoClosure() { 202 assert(!is_resizing() || !is_rehashing(), "Can not both resize and rehash"); 203 if (is_resizing()) { 204 G1StringDedupTable::finish_resize(_resized_table); 205 } else if (is_rehashing()) { 206 G1StringDedupTable::finish_rehash(_rehashed_table); 207 } 208 }