1/*
2 * Copyright (c) 2014, 2017, 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/g1/g1CollectedHeap.inline.hpp"
28#include "gc/g1/g1GCPhaseTimes.hpp"
29#include "gc/g1/g1StringDedup.hpp"
30#include "gc/g1/g1StringDedupQueue.hpp"
31#include "gc/g1/g1StringDedupStat.hpp"
32#include "gc/g1/g1StringDedupTable.hpp"
33#include "gc/g1/g1StringDedupThread.hpp"
34#include "runtime/atomic.hpp"
35
36bool G1StringDedup::_enabled = false;
37
38void 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
48void G1StringDedup::stop() {
49  assert(is_enabled(), "String deduplication not enabled");
50  G1StringDedupThread::thread()->stop();
51}
52
53bool 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(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
68void 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
75bool 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
94void 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
101void 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
107void 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
112void G1StringDedup::parallel_unlink(G1StringDedupUnlinkOrOopsDoClosure* unlink, uint worker_id) {
113  assert(is_enabled(), "String deduplication not enabled");
114  G1StringDedupQueue::unlink_or_oops_do(unlink);
115  G1StringDedupTable::unlink_or_oops_do(unlink, worker_id);
116}
117
118//
119// Task for parallel unlink_or_oops_do() operation on the deduplication queue
120// and table.
121//
122class G1StringDedupUnlinkOrOopsDoTask : public AbstractGangTask {
123private:
124  G1StringDedupUnlinkOrOopsDoClosure _cl;
125  G1GCPhaseTimes* _phase_times;
126
127public:
128  G1StringDedupUnlinkOrOopsDoTask(BoolObjectClosure* is_alive,
129                                  OopClosure* keep_alive,
130                                  bool allow_resize_and_rehash,
131                                  G1GCPhaseTimes* phase_times) :
132    AbstractGangTask("G1StringDedupUnlinkOrOopsDoTask"),
133    _cl(is_alive, keep_alive, allow_resize_and_rehash), _phase_times(phase_times) { }
134
135  virtual void work(uint worker_id) {
136    {
137      G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
138      G1StringDedupQueue::unlink_or_oops_do(&_cl);
139    }
140    {
141      G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
142      G1StringDedupTable::unlink_or_oops_do(&_cl, worker_id);
143    }
144  }
145};
146
147void G1StringDedup::unlink_or_oops_do(BoolObjectClosure* is_alive,
148                                      OopClosure* keep_alive,
149                                      bool allow_resize_and_rehash,
150                                      G1GCPhaseTimes* phase_times) {
151  assert(is_enabled(), "String deduplication not enabled");
152
153  G1StringDedupUnlinkOrOopsDoTask task(is_alive, keep_alive, allow_resize_and_rehash, phase_times);
154  G1CollectedHeap* g1h = G1CollectedHeap::heap();
155  g1h->workers()->run_task(&task);
156}
157
158void G1StringDedup::threads_do(ThreadClosure* tc) {
159  assert(is_enabled(), "String deduplication not enabled");
160  tc->do_thread(G1StringDedupThread::thread());
161}
162
163void G1StringDedup::print_worker_threads_on(outputStream* st) {
164  assert(is_enabled(), "String deduplication not enabled");
165  G1StringDedupThread::thread()->print_on(st);
166  st->cr();
167}
168
169void G1StringDedup::verify() {
170  assert(is_enabled(), "String deduplication not enabled");
171  G1StringDedupQueue::verify();
172  G1StringDedupTable::verify();
173}
174
175G1StringDedupUnlinkOrOopsDoClosure::G1StringDedupUnlinkOrOopsDoClosure(BoolObjectClosure* is_alive,
176                                                                       OopClosure* keep_alive,
177                                                                       bool allow_resize_and_rehash) :
178  _is_alive(is_alive),
179  _keep_alive(keep_alive),
180  _resized_table(NULL),
181  _rehashed_table(NULL),
182  _next_queue(0),
183  _next_bucket(0) {
184  if (allow_resize_and_rehash) {
185    // If both resize and rehash is needed, only do resize. Rehash of
186    // the table will eventually happen if the situation persists.
187    _resized_table = G1StringDedupTable::prepare_resize();
188    if (!is_resizing()) {
189      _rehashed_table = G1StringDedupTable::prepare_rehash();
190    }
191  }
192}
193
194G1StringDedupUnlinkOrOopsDoClosure::~G1StringDedupUnlinkOrOopsDoClosure() {
195  assert(!is_resizing() || !is_rehashing(), "Can not both resize and rehash");
196  if (is_resizing()) {
197    G1StringDedupTable::finish_resize(_resized_table);
198  } else if (is_rehashing()) {
199    G1StringDedupTable::finish_rehash(_rehashed_table);
200  }
201}
202
203// Atomically claims the next available queue for exclusive access by
204// the current thread. Returns the queue number of the claimed queue.
205size_t G1StringDedupUnlinkOrOopsDoClosure::claim_queue() {
206  return (size_t)Atomic::add_ptr(1, &_next_queue) - 1;
207}
208
209// Atomically claims the next available table partition for exclusive
210// access by the current thread. Returns the table bucket number where
211// the claimed partition starts.
212size_t G1StringDedupUnlinkOrOopsDoClosure::claim_table_partition(size_t partition_size) {
213  return (size_t)Atomic::add_ptr(partition_size, &_next_bucket) - partition_size;
214}
215