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/shenandoah/shenandoahHeap.inline.hpp"
27 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
28 #include "logging/log.hpp"
29 #include "logging/logStream.hpp"
30
31 void ShenandoahObjToScanQueueSet::clear() {
32 uint size = GenericTaskQueueSet<ShenandoahObjToScanQueue, mtGC>::size();
33 for (uint index = 0; index < size; index ++) {
34 ShenandoahObjToScanQueue* q = queue(index);
35 assert(q != NULL, "Sanity");
36 q->clear();
37 }
38 }
39
40 bool ShenandoahObjToScanQueueSet::is_empty() {
41 uint size = GenericTaskQueueSet<ShenandoahObjToScanQueue, mtGC>::size();
42 for (uint index = 0; index < size; index ++) {
43 ShenandoahObjToScanQueue* q = queue(index);
44 assert(q != NULL, "Sanity");
45 if (!q->is_empty()) {
46 return false;
47 }
48 }
49 return true;
50 }
51
52 bool ShenandoahTaskTerminator::offer_termination(ShenandoahTerminatorTerminator* terminator) {
53 assert(_n_threads > 0, "Initialization is incorrect");
54 assert(_offered_termination < _n_threads, "Invariant");
55 assert(_blocker != NULL, "Invariant");
56
57 // single worker, done
58 if (_n_threads == 1) {
59 return true;
60 }
61
62 _blocker->lock_without_safepoint_check();
63 // all arrived, done
64 if (++ _offered_termination == _n_threads) {
65 _blocker->notify_all();
66 _blocker->unlock();
67 return true;
68 }
69
70 Thread* the_thread = Thread::current();
71 while (true) {
72 if (_spin_master == NULL) {
73 _spin_master = the_thread;
74
75 _blocker->unlock();
76
77 if (do_spin_master_work(terminator)) {
78 assert(_offered_termination == _n_threads, "termination condition");
79 return true;
80 } else {
81 _blocker->lock_without_safepoint_check();
82 }
83 } else {
84 _blocker->wait(true, WorkStealingSleepMillis);
85
86 if (_offered_termination == _n_threads) {
87 _blocker->unlock();
88 return true;
89 }
90 }
91
92 if (peek_in_queue_set() || (terminator != NULL && terminator->should_exit_termination())) {
93 _offered_termination --;
94 _blocker->unlock();
95 return false;
96 }
97 }
98 }
99
100 #if TASKQUEUE_STATS
101 void ShenandoahObjToScanQueueSet::print_taskqueue_stats_hdr(outputStream* const st) {
102 st->print_raw_cr("GC Task Stats");
103 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
104 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
105 }
106
107 void ShenandoahObjToScanQueueSet::print_taskqueue_stats() const {
108 if (!log_develop_is_enabled(Trace, gc, task, stats)) {
109 return;
110 }
111 Log(gc, task, stats) log;
112 ResourceMark rm;
113 LogStream ls(log.trace());
114 outputStream* st = &ls;
115 print_taskqueue_stats_hdr(st);
116
117 ShenandoahObjToScanQueueSet* queues = const_cast<ShenandoahObjToScanQueueSet*>(this);
118 TaskQueueStats totals;
119 const uint n = size();
120 for (uint i = 0; i < n; ++i) {
121 st->print(UINT32_FORMAT_W(3), i);
122 queues->queue(i)->stats.print(st);
123 st->cr();
124 totals += queues->queue(i)->stats;
125 }
126 st->print("tot "); totals.print(st); st->cr();
127 DEBUG_ONLY(totals.verify());
128
129 }
130
131 void ShenandoahObjToScanQueueSet::reset_taskqueue_stats() {
132 const uint n = size();
133 for (uint i = 0; i < n; ++i) {
134 queue(i)->stats.reset();
135 }
136 }
137 #endif // TASKQUEUE_STATS
138
139 bool ShenandoahTaskTerminator::do_spin_master_work(ShenandoahTerminatorTerminator* terminator) {
140 uint yield_count = 0;
141 // Number of hard spin loops done since last yield
142 uint hard_spin_count = 0;
143 // Number of iterations in the hard spin loop.
144 uint hard_spin_limit = WorkStealingHardSpins;
145
146 // If WorkStealingSpinToYieldRatio is 0, no hard spinning is done.
147 // If it is greater than 0, then start with a small number
148 // of spins and increase number with each turn at spinning until
149 // the count of hard spins exceeds WorkStealingSpinToYieldRatio.
150 // Then do a yield() call and start spinning afresh.
151 if (WorkStealingSpinToYieldRatio > 0) {
152 hard_spin_limit = WorkStealingHardSpins >> WorkStealingSpinToYieldRatio;
153 hard_spin_limit = MAX2(hard_spin_limit, 1U);
154 }
155 // Remember the initial spin limit.
156 uint hard_spin_start = hard_spin_limit;
157
158 // Loop waiting for all threads to offer termination or
159 // more work.
160 while (true) {
161 // Look for more work.
162 // Periodically sleep() instead of yield() to give threads
163 // waiting on the cores the chance to grab this code
164 if (yield_count <= WorkStealingYieldsBeforeSleep) {
165 // Do a yield or hardspin. For purposes of deciding whether
166 // to sleep, count this as a yield.
167 yield_count++;
168
169 // Periodically call yield() instead spinning
170 // After WorkStealingSpinToYieldRatio spins, do a yield() call
171 // and reset the counts and starting limit.
172 if (hard_spin_count > WorkStealingSpinToYieldRatio) {
173 yield();
174 hard_spin_count = 0;
175 hard_spin_limit = hard_spin_start;
176 #ifdef TRACESPINNING
177 _total_yields++;
178 #endif
179 } else {
180 // Hard spin this time
181 // Increase the hard spinning period but only up to a limit.
182 hard_spin_limit = MIN2(2*hard_spin_limit,
183 (uint) WorkStealingHardSpins);
184 for (uint j = 0; j < hard_spin_limit; j++) {
185 SpinPause();
186 }
187 hard_spin_count++;
188 #ifdef TRACESPINNING
189 _total_spins++;
190 #endif
191 }
192 } else {
193 log_develop_trace(gc, task)("ShenanddoahTaskTerminator::do_spin_master_work() thread " PTR_FORMAT " sleeps after %u yields",
194 p2i(Thread::current()), yield_count);
195 yield_count = 0;
196
197 MonitorLockerEx locker(_blocker, Mutex::_no_safepoint_check_flag); // no safepoint check
198 _spin_master = NULL;
199 locker.wait(Mutex::_no_safepoint_check_flag, WorkStealingSleepMillis);
200 if (_spin_master == NULL) {
201 _spin_master = Thread::current();
202 } else {
203 return false;
204 }
205 }
206
207 #ifdef TRACESPINNING
208 _total_peeks++;
209 #endif
210 size_t tasks = tasks_in_queue_set();
211 if (tasks > 0 || (terminator != NULL && terminator->should_exit_termination())) {
212 MonitorLockerEx locker(_blocker, Mutex::_no_safepoint_check_flag); // no safepoint check
213
214 if (tasks >= _offered_termination - 1) {
215 locker.notify_all();
216 } else {
217 for (; tasks > 1; tasks --) {
218 locker.notify();
219 }
220 }
221 _spin_master = NULL;
222 return false;
223 } else if (_offered_termination == _n_threads) {
224 return true;
225 }
226 }
227 }