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 }
--- EOF ---