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 "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  27 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  28 #include "gc_implementation/g1/g1StringDedup.hpp"
  29 #include "gc_implementation/g1/g1StringDedupQueue.hpp"
  30 #include "gc_implementation/g1/g1StringDedupStat.hpp"
  31 #include "gc_implementation/g1/g1StringDedupTable.hpp"
  32 #include "gc_implementation/g1/g1StringDedupThread.hpp"
  33 
  34 bool G1StringDedup::_enabled = false;
  35 
  36 void G1StringDedup::initialize() {
  37   assert(UseG1GC, "String deduplication only available with G1");
  38   if (UseStringDeduplication) {
  39     _enabled = true;
  40     G1StringDedupQueue::create();
  41     G1StringDedupTable::create();
  42     G1StringDedupThread::create();
  43   }
  44 }
  45 
  46 bool G1StringDedup::is_candidate_from_mark(oop obj) {
  47   if (java_lang_String::is_instance(obj)) {
  48     bool from_young = G1CollectedHeap::heap()->heap_region_containing_raw(obj)->is_young();
  49     if (from_young && obj->age() < StringDeduplicationAgeThreshold) {
  50       // Candidate found. String is being evacuated from young to old but has not
  51       // reached the deduplication age threshold, i.e. has not previously been a
  52       // candidate during its life in the young generation.
  53       return true;
  54     }
  55   }
  56 
  57   // Not a candidate
  58   return false;
  59 }
  60 
  61 void G1StringDedup::enqueue_from_mark(oop java_string) {
  62   assert(is_enabled(), "String deduplication not enabled");
  63   if (is_candidate_from_mark(java_string)) {
  64     G1StringDedupQueue::push(0 /* worker_id */, java_string);
  65   }
  66 }
  67 
  68 bool G1StringDedup::is_candidate_from_evacuation(bool from_young, bool to_young, oop obj) {
  69   if (from_young && java_lang_String::is_instance(obj)) {
  70     if (to_young && obj->age() == StringDeduplicationAgeThreshold) {
  71       // Candidate found. String is being evacuated from young to young and just
  72       // reached the deduplication age threshold.
  73       return true;
  74     }
  75     if (!to_young && obj->age() < StringDeduplicationAgeThreshold) {
  76       // Candidate found. String is being evacuated from young to old but has not
  77       // reached the deduplication age threshold, i.e. has not previously been a
  78       // candidate during its life in the young generation.
  79       return true;
  80     }
  81   }
  82 
  83   // Not a candidate
  84   return false;
  85 }
  86 
  87 void G1StringDedup::enqueue_from_evacuation(bool from_young, bool to_young, uint worker_id, oop java_string) {
  88   assert(is_enabled(), "String deduplication not enabled");
  89   if (is_candidate_from_evacuation(from_young, to_young, java_string)) {
  90     G1StringDedupQueue::push(worker_id, java_string);
  91   }
  92 }
  93 
  94 void G1StringDedup::deduplicate(oop java_string) {
  95   assert(is_enabled(), "String deduplication not enabled");
  96   G1StringDedupStat dummy; // Statistics from this path is never used
  97   G1StringDedupTable::deduplicate(java_string, dummy);
  98 }
  99 
 100 void G1StringDedup::oops_do(OopClosure* keep_alive) {
 101   assert(is_enabled(), "String deduplication not enabled");
 102   unlink_or_oops_do(NULL, keep_alive);
 103 }
 104 
 105 void G1StringDedup::unlink(BoolObjectClosure* is_alive) {
 106   assert(is_enabled(), "String deduplication not enabled");
 107   // Don't allow a potential resize or rehash during unlink, as the unlink
 108   // operation itself might remove enough entries to invalidate such a decision.
 109   unlink_or_oops_do(is_alive, NULL, false /* allow_resize_and_rehash */);
 110 }
 111 
 112 //
 113 // Task for parallel unlink_or_oops_do() operation on the deduplication queue
 114 // and table.
 115 //
 116 class G1StringDedupUnlinkOrOopsDoTask : public AbstractGangTask {
 117 private:
 118   G1StringDedupUnlinkOrOopsDoClosure _cl;
 119 
 120 public:
 121   G1StringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive,
 122                                   OopClosure* keep_alive,
 123                                   bool allow_resize_and_rehash) :
 124     AbstractGangTask("G1StringDedupUnlinkOrOopsDoTask"),
 125     _cl(is_alive, keep_alive, allow_resize_and_rehash) {
 126   }
 127 
 128   virtual void work(uint worker_id) {
 129     double queue_fixup_start = os::elapsedTime();
 130     G1StringDedupQueue::unlink_or_oops_do(&_cl);
 131 
 132     double table_fixup_start = os::elapsedTime();
 133     G1StringDedupTable::unlink_or_oops_do(&_cl, worker_id);
 134 
 135     double queue_fixup_time_ms = (table_fixup_start - queue_fixup_start) * 1000.0;
 136     double table_fixup_time_ms = (os::elapsedTime() - table_fixup_start) * 1000.0;
 137     G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
 138     g1p->phase_times()->record_string_dedup_queue_fixup_worker_time(worker_id, queue_fixup_time_ms);
 139     g1p->phase_times()->record_string_dedup_table_fixup_worker_time(worker_id, table_fixup_time_ms);
 140   }
 141 };
 142 
 143 void G1StringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* keep_alive, bool allow_resize_and_rehash) {
 144   assert(is_enabled(), "String deduplication not enabled");
 145   G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
 146   g1p->phase_times()->note_string_dedup_fixup_start();
 147   double fixup_start = os::elapsedTime();
 148 
 149   G1StringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash);
 150   if (G1CollectedHeap::use_parallel_gc_threads()) {
 151     G1CollectedHeap* g1h = G1CollectedHeap::heap();
 152     g1h->set_par_threads();
 153     g1h->workers()->run_task(&task);
 154     g1h->set_par_threads(0);
 155   } else {
 156     task.work(0);
 157   }
 158 
 159   double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
 160   g1p->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
 161   g1p->phase_times()->note_string_dedup_fixup_end();
 162 }
 163 
 164 void G1StringDedup::threads_do(ThreadClosure* tc) {
 165   assert(is_enabled(), "String deduplication not enabled");
 166   tc->do_thread(G1StringDedupThread::thread());
 167 }
 168 
 169 void G1StringDedup::print_worker_threads_on(outputStream* st) {
 170   assert(is_enabled(), "String deduplication not enabled");
 171   G1StringDedupThread::thread()->print_on(st);
 172   st->cr();
 173 }
 174 
 175 void G1StringDedup::verify() {
 176   assert(is_enabled(), "String deduplication not enabled");
 177   G1StringDedupQueue::verify();
 178   G1StringDedupTable::verify();
 179 }
 180 
 181 G1StringDedupUnlinkOrOopsDoClosure::G1StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive,
 182                                                                        OopClosure* keep_alive,
 183                                                                        bool allow_resize_and_rehash) :
 184   _is_alive(is_alive),
 185   _keep_alive(keep_alive),
 186   _resized_table(NULL),
 187   _rehashed_table(NULL),
 188   _next_queue(0),
 189   _next_bucket(0) {
 190   if (allow_resize_and_rehash) {
 191     // If both resize and rehash is needed, only do resize. Rehash of
 192     // the table will eventually happen if the situation persists.
 193     _resized_table = G1StringDedupTable::prepare_resize();
 194     if (!is_resizing()) {
 195       _rehashed_table = G1StringDedupTable::prepare_rehash();
 196     }
 197   }
 198 }
 199 
 200 G1StringDedupUnlinkOrOopsDoClosure::~G1StringDedupUnlinkOrOopsDoClosure() {
 201   assert(!is_resizing() || !is_rehashing(), "Can not both resize and rehash");
 202   if (is_resizing()) {
 203     G1StringDedupTable::finish_resize(_resized_table);
 204   } else if (is_rehashing()) {
 205     G1StringDedupTable::finish_rehash(_rehashed_table);
 206   }
 207 }