1 /* 2 * Copyright (c) 2014, 2015, 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.inline.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 #include "runtime/atomic.inline.hpp" 35 36 bool G1StringDedup::_enabled = false; 37 38 void G1StringDedup::initialize() { 39 assert(UseG1GC, "String deduplication only available with G1"); 40 if (UseStringDeduplication) { 41 _enabled = true; 42 G1StringDedupQueue::create(); 43 G1StringDedupTable::create(); 44 G1StringDedupThread::create(); 45 } 46 } 47 48 void G1StringDedup::stop() { 49 assert(is_enabled(), "String deduplication not enabled"); 50 G1StringDedupThread::stop(); 51 } 52 53 bool G1StringDedup::is_candidate_from_mark(oop obj) { 54 if (java_lang_String::is_instance_inlined(obj)) { 55 bool from_young = G1CollectedHeap::heap()->heap_region_containing_raw(obj)->is_young(); 56 if (from_young && obj->age() < StringDeduplicationAgeThreshold) { 57 // Candidate found. String is being evacuated from young to old but has not 58 // reached the deduplication age threshold, i.e. has not previously been a 59 // candidate during its life in the young generation. 60 return true; 61 } 62 } 63 64 // Not a candidate 65 return false; 66 } 67 68 void G1StringDedup::enqueue_from_mark(oop java_string) { 69 assert(is_enabled(), "String deduplication not enabled"); 70 if (is_candidate_from_mark(java_string)) { 71 G1StringDedupQueue::push(0 /* worker_id */, java_string); 72 } 73 } 74 75 bool G1StringDedup::is_candidate_from_evacuation(bool from_young, bool to_young, oop obj) { 76 if (from_young && java_lang_String::is_instance_inlined(obj)) { 77 if (to_young && obj->age() == StringDeduplicationAgeThreshold) { 78 // Candidate found. String is being evacuated from young to young and just 79 // reached the deduplication age threshold. 80 return true; 81 } 82 if (!to_young && obj->age() < StringDeduplicationAgeThreshold) { 83 // Candidate found. String is being evacuated from young to old but has not 84 // reached the deduplication age threshold, i.e. has not previously been a 85 // candidate during its life in the young generation. 86 return true; 87 } 88 } 89 90 // Not a candidate 91 return false; 92 } 93 94 void G1StringDedup::enqueue_from_evacuation(bool from_young, bool to_young, uint worker_id, oop java_string) { 95 assert(is_enabled(), "String deduplication not enabled"); 96 if (is_candidate_from_evacuation(from_young, to_young, java_string)) { 97 G1StringDedupQueue::push(worker_id, java_string); 98 } 99 } 100 101 void G1StringDedup::deduplicate(oop java_string) { 102 assert(is_enabled(), "String deduplication not enabled"); 103 G1StringDedupStat dummy; // Statistics from this path is never used 104 G1StringDedupTable::deduplicate(java_string, dummy); 105 } 106 107 void G1StringDedup::oops_do(OopClosure* keep_alive) { 108 assert(is_enabled(), "String deduplication not enabled"); 109 unlink_or_oops_do(NULL, keep_alive, true /* allow_resize_and_rehash */); 110 } 111 112 void G1StringDedup::unlink(BoolObjectClosure* is_alive) { 113 assert(is_enabled(), "String deduplication not enabled"); 114 // Don't allow a potential resize or rehash during unlink, as the unlink 115 // operation itself might remove enough entries to invalidate such a decision. 116 unlink_or_oops_do(is_alive, NULL, false /* allow_resize_and_rehash */); 117 } 118 119 // 120 // Task for parallel unlink_or_oops_do() operation on the deduplication queue 121 // and table. 122 // 123 class G1StringDedupUnlinkOrOopsDoTask : public AbstractGangTask { 124 private: 125 G1StringDedupUnlinkOrOopsDoClosure _cl; 126 G1GCPhaseTimes* _phase_times; 127 128 public: 129 G1StringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive, 130 OopClosure* keep_alive, 131 bool allow_resize_and_rehash, 132 G1GCPhaseTimes* phase_times) : 133 AbstractGangTask("G1StringDedupUnlinkOrOopsDoTask"), 134 _cl(is_alive, keep_alive, allow_resize_and_rehash), _phase_times(phase_times) { } 135 136 virtual void work(uint worker_id) { 137 { 138 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id); 139 G1StringDedupQueue::unlink_or_oops_do(&_cl); 140 } 141 { 142 G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id); 143 G1StringDedupTable::unlink_or_oops_do(&_cl, worker_id); 144 } 145 } 146 }; 147 148 void G1StringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive, 149 OopClosure* keep_alive, 150 bool allow_resize_and_rehash, 151 G1GCPhaseTimes* phase_times) { 152 assert(is_enabled(), "String deduplication not enabled"); 153 154 G1StringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash, phase_times); 155 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 156 g1h->set_par_threads(); 157 g1h->workers()->run_task(&task); 158 g1h->set_par_threads(0); 159 } 160 161 void G1StringDedup::threads_do(ThreadClosure* tc) { 162 assert(is_enabled(), "String deduplication not enabled"); 163 tc->do_thread(G1StringDedupThread::thread()); 164 } 165 166 void G1StringDedup::print_worker_threads_on(outputStream* st) { 167 assert(is_enabled(), "String deduplication not enabled"); 168 G1StringDedupThread::thread()->print_on(st); 169 st->cr(); 170 } 171 172 void G1StringDedup::verify() { 173 assert(is_enabled(), "String deduplication not enabled"); 174 G1StringDedupQueue::verify(); 175 G1StringDedupTable::verify(); 176 } 177 178 G1StringDedupUnlinkOrOopsDoClosure::G1StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive, 179 OopClosure* keep_alive, 180 bool allow_resize_and_rehash) : 181 _is_alive(is_alive), 182 _keep_alive(keep_alive), 183 _resized_table(NULL), 184 _rehashed_table(NULL), 185 _next_queue(0), 186 _next_bucket(0) { 187 if (allow_resize_and_rehash) { 188 // If both resize and rehash is needed, only do resize. Rehash of 189 // the table will eventually happen if the situation persists. 190 _resized_table = G1StringDedupTable::prepare_resize(); 191 if (!is_resizing()) { 192 _rehashed_table = G1StringDedupTable::prepare_rehash(); 193 } 194 } 195 } 196 197 G1StringDedupUnlinkOrOopsDoClosure::~G1StringDedupUnlinkOrOopsDoClosure() { 198 assert(!is_resizing() || !is_rehashing(), "Can not both resize and rehash"); 199 if (is_resizing()) { 200 G1StringDedupTable::finish_resize(_resized_table); 201 } else if (is_rehashing()) { 202 G1StringDedupTable::finish_rehash(_rehashed_table); 203 } 204 } 205 206 // Atomically claims the next available queue for exclusive access by 207 // the current thread. Returns the queue number of the claimed queue. 208 size_t G1StringDedupUnlinkOrOopsDoClosure::claim_queue() { 209 return (size_t)Atomic::add_ptr(1, &_next_queue) - 1; 210 } 211 212 // Atomically claims the next available table partition for exclusive 213 // access by the current thread. Returns the table bucket number where 214 // the claimed partition starts. 215 size_t G1StringDedupUnlinkOrOopsDoClosure::claim_table_partition(size_t partition_size) { 216 return (size_t)Atomic::add_ptr(partition_size, &_next_bucket) - partition_size; 217 }