1 /*
2 * Copyright (c) 2016, 2019, Red Hat, Inc. All rights reserved.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24 #include "precompiled.hpp"
25
26 #include "gc_implementation/shenandoah/shenandoahHeap.inline.hpp"
27 #include "gc_implementation/shenandoah/shenandoahLogging.hpp"
28 #include "gc_implementation/shenandoah/shenandoahTaskqueue.inline.hpp"
29
30 void ShenandoahObjToScanQueueSet::clear() {
31 uint size = GenericTaskQueueSet<ShenandoahObjToScanQueue, mtGC>::size();
32 for (uint index = 0; index < size; index ++) {
33 ShenandoahObjToScanQueue* q = queue(index);
34 assert(q != NULL, "Sanity");
35 q->clear();
36 }
37 }
38
39 bool ShenandoahObjToScanQueueSet::is_empty() {
40 uint size = GenericTaskQueueSet<ShenandoahObjToScanQueue, mtGC>::size();
41 for (uint index = 0; index < size; index ++) {
42 ShenandoahObjToScanQueue* q = queue(index);
43 assert(q != NULL, "Sanity");
44 if (!q->is_empty()) {
45 return false;
46 }
47 }
48 return true;
49 }
50
51 bool ShenandoahTaskTerminator::offer_termination(ShenandoahTerminatorTerminator* terminator) {
52 assert(_n_threads > 0, "Initialization is incorrect");
53 assert(_offered_termination < _n_threads, "Invariant");
54 assert(_blocker != NULL, "Invariant");
55
56 // single worker, done
57 if (_n_threads == 1) {
58 return true;
59 }
60
61 _blocker->lock_without_safepoint_check();
62 // all arrived, done
63 if (++ _offered_termination == _n_threads) {
64 _blocker->notify_all();
65 _blocker->unlock();
66 return true;
67 }
68
69 Thread* the_thread = Thread::current();
70 while (true) {
71 if (_spin_master == NULL) {
72 _spin_master = the_thread;
73
74 _blocker->unlock();
75
76 if (do_spin_master_work(terminator)) {
77 assert(_offered_termination == _n_threads, "termination condition");
78 return true;
79 } else {
80 _blocker->lock_without_safepoint_check();
81 }
82 } else {
83 _blocker->wait(true, WorkStealingSleepMillis);
84
85 if (_offered_termination == _n_threads) {
86 _blocker->unlock();
87 return true;
88 }
89 }
90
91 if (peek_in_queue_set() || (terminator != NULL && terminator->should_exit_termination())) {
92 _offered_termination --;
93 _blocker->unlock();
94 return false;
95 }
96 }
97 }
98
99 #if TASKQUEUE_STATS
100 void ShenandoahObjToScanQueueSet::print_taskqueue_stats_hdr(outputStream* const st) {
101 st->print_raw_cr("GC Task Stats");
102 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
103 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
104 }
105
106 void ShenandoahObjToScanQueueSet::print_taskqueue_stats() {
107 if (! ShenandoahLogTrace) {
108 return;
109 }
110 ResourceMark rm;
111 outputStream* st = gclog_or_tty;
112 print_taskqueue_stats_hdr(st);
113
114 TaskQueueStats totals;
115 const uint n = size();
116 for (uint i = 0; i < n; ++i) {
117 st->print(UINT32_FORMAT_W(3), i);
118 queue(i)->stats.print(st);
119 st->cr();
120 totals += queue(i)->stats;
121 }
122 st->print("tot "); totals.print(st); st->cr();
123 DEBUG_ONLY(totals.verify());
124 }
125
126 void ShenandoahObjToScanQueueSet::reset_taskqueue_stats() {
127 const uint n = size();
128 for (uint i = 0; i < n; ++i) {
129 queue(i)->stats.reset();
130 }
131 }
132 #endif // TASKQUEUE_STATS
133
134 bool ShenandoahTaskTerminator::do_spin_master_work(ShenandoahTerminatorTerminator* terminator) {
135 uint yield_count = 0;
136 // Number of hard spin loops done since last yield
137 uint hard_spin_count = 0;
138 // Number of iterations in the hard spin loop.
139 uint hard_spin_limit = WorkStealingHardSpins;
140
141 // If WorkStealingSpinToYieldRatio is 0, no hard spinning is done.
142 // If it is greater than 0, then start with a small number
143 // of spins and increase number with each turn at spinning until
144 // the count of hard spins exceeds WorkStealingSpinToYieldRatio.
145 // Then do a yield() call and start spinning afresh.
146 if (WorkStealingSpinToYieldRatio > 0) {
147 hard_spin_limit = WorkStealingHardSpins >> WorkStealingSpinToYieldRatio;
148 hard_spin_limit = MAX2(hard_spin_limit, 1U);
149 }
150 // Remember the initial spin limit.
151 uint hard_spin_start = hard_spin_limit;
152
153 // Loop waiting for all threads to offer termination or
154 // more work.
155 while (true) {
156 // Look for more work.
157 // Periodically sleep() instead of yield() to give threads
158 // waiting on the cores the chance to grab this code
159 if (yield_count <= WorkStealingYieldsBeforeSleep) {
160 // Do a yield or hardspin. For purposes of deciding whether
161 // to sleep, count this as a yield.
162 yield_count++;
163
164 // Periodically call yield() instead spinning
165 // After WorkStealingSpinToYieldRatio spins, do a yield() call
166 // and reset the counts and starting limit.
167 if (hard_spin_count > WorkStealingSpinToYieldRatio) {
168 yield();
169 hard_spin_count = 0;
170 hard_spin_limit = hard_spin_start;
171 #ifdef TRACESPINNING
172 _total_yields++;
173 #endif
174 } else {
175 // Hard spin this time
176 // Increase the hard spinning period but only up to a limit.
177 hard_spin_limit = MIN2(2*hard_spin_limit,
178 (uint) WorkStealingHardSpins);
179 for (uint j = 0; j < hard_spin_limit; j++) {
180 SpinPause();
181 }
182 hard_spin_count++;
183 #ifdef TRACESPINNING
184 _total_spins++;
185 #endif
186 }
187 } else {
188 log_develop_trace(gc, task)("ShenanddoahTaskTerminator::do_spin_master_work() thread " PTR_FORMAT " sleeps after %u yields",
189 p2i(Thread::current()), yield_count);
190 yield_count = 0;
191
192 MonitorLockerEx locker(_blocker, Mutex::_no_safepoint_check_flag); // no safepoint check
193 _spin_master = NULL;
194 locker.wait(Mutex::_no_safepoint_check_flag, WorkStealingSleepMillis);
195 if (_spin_master == NULL) {
196 _spin_master = Thread::current();
197 } else {
198 return false;
199 }
200 }
201
202 #ifdef TRACESPINNING
203 _total_peeks++;
204 #endif
205 size_t tasks = tasks_in_queue_set();
206 if (tasks > 0 || (terminator != NULL && terminator->should_exit_termination())) {
207 MonitorLockerEx locker(_blocker, Mutex::_no_safepoint_check_flag); // no safepoint check
208
209 if ((int) tasks >= _offered_termination - 1) {
210 locker.notify_all();
211 } else {
212 for (; tasks > 1; tasks --) {
213 locker.notify();
214 }
215 }
216 _spin_master = NULL;
217 return false;
218 } else if (_offered_termination == _n_threads) {
219 return true;
220 }
221 }
222 }
223
224 bool ShenandoahTerminatorTerminator::should_exit_termination() {
225 return _heap->cancelled_gc();
226 }
227