1 /*
2 * Copyright (c) 2001, 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 "oops/oop.inline.hpp"
27 #include "runtime/atomic.inline.hpp"
28 #include "runtime/os.hpp"
29 #include "runtime/thread.inline.hpp"
30 #include "utilities/debug.hpp"
31 #include "utilities/stack.inline.hpp"
32 #include "utilities/taskqueue.hpp"
33
34 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
35
36 #ifdef TRACESPINNING
37 uint ParallelTaskTerminator::_total_yields = 0;
38 uint ParallelTaskTerminator::_total_spins = 0;
39 uint ParallelTaskTerminator::_total_peeks = 0;
40 #endif
41
42 #if TASKQUEUE_STATS
43 const char * const TaskQueueStats::_names[last_stat_id] = {
44 "qpush", "qpop", "qpop-s", "qattempt", "qsteal", "opush", "omax"
45 };
46
47 TaskQueueStats & TaskQueueStats::operator +=(const TaskQueueStats & addend)
48 {
49 for (unsigned int i = 0; i < last_stat_id; ++i) {
50 _stats[i] += addend._stats[i];
51 }
52 return *this;
53 }
54
55 void TaskQueueStats::print_header(unsigned int line, outputStream* const stream,
56 unsigned int width)
57 {
58 // Use a width w: 1 <= w <= max_width
59 const unsigned int max_width = 40;
60 const unsigned int w = MAX2(MIN2(width, max_width), 1U);
61
62 if (line == 0) { // spaces equal in width to the header
63 const unsigned int hdr_width = w * last_stat_id + last_stat_id - 1;
64 stream->print("%*s", hdr_width, " ");
65 } else if (line == 1) { // labels
66 stream->print("%*s", w, _names[0]);
67 for (unsigned int i = 1; i < last_stat_id; ++i) {
68 stream->print(" %*s", w, _names[i]);
69 }
70 } else if (line == 2) { // dashed lines
71 char dashes[max_width + 1];
72 memset(dashes, '-', w);
73 dashes[w] = '\0';
74 stream->print("%s", dashes);
75 for (unsigned int i = 1; i < last_stat_id; ++i) {
76 stream->print(" %s", dashes);
77 }
78 }
79 }
80
81 void TaskQueueStats::print(outputStream* stream, unsigned int width) const
82 {
83 #define FMT SIZE_FORMAT_W(*)
84 stream->print(FMT, width, _stats[0]);
85 for (unsigned int i = 1; i < last_stat_id; ++i) {
86 stream->print(" " FMT, width, _stats[i]);
87 }
88 #undef FMT
89 }
90
91 #ifdef ASSERT
92 // Invariants which should hold after a TaskQueue has been emptied and is
93 // quiescent; they do not hold at arbitrary times.
94 void TaskQueueStats::verify() const
95 {
96 assert(get(push) == get(pop) + get(steal),
97 err_msg("push=" SIZE_FORMAT " pop=" SIZE_FORMAT " steal=" SIZE_FORMAT,
98 get(push), get(pop), get(steal)));
99 assert(get(pop_slow) <= get(pop),
100 err_msg("pop_slow=" SIZE_FORMAT " pop=" SIZE_FORMAT,
101 get(pop_slow), get(pop)));
102 assert(get(steal) <= get(steal_attempt),
103 err_msg("steal=" SIZE_FORMAT " steal_attempt=" SIZE_FORMAT,
104 get(steal), get(steal_attempt)));
105 assert(get(overflow) == 0 || get(push) != 0,
106 err_msg("overflow=" SIZE_FORMAT " push=" SIZE_FORMAT,
107 get(overflow), get(push)));
108 assert(get(overflow_max_len) == 0 || get(overflow) != 0,
109 err_msg("overflow_max_len=" SIZE_FORMAT " overflow=" SIZE_FORMAT,
110 get(overflow_max_len), get(overflow)));
111 }
112 #endif // ASSERT
113 #endif // TASKQUEUE_STATS
114
115 int TaskQueueSetSuper::randomParkAndMiller(int *seed0) {
116 const int a = 16807;
117 const int m = 2147483647;
118 const int q = 127773; /* m div a */
119 const int r = 2836; /* m mod a */
120 assert(sizeof(int) == 4, "I think this relies on that");
121 int seed = *seed0;
122 int hi = seed / q;
123 int lo = seed % q;
124 int test = a * lo - r * hi;
125 if (test > 0)
126 seed = test;
127 else
128 seed = test + m;
129 *seed0 = seed;
130 return seed;
131 }
132
133 ParallelTaskTerminator::
134 ParallelTaskTerminator(uint n_threads, TaskQueueSetSuper* queue_set) :
135 _n_threads(n_threads),
136 _queue_set(queue_set),
137 _offered_termination(0) {}
138
139 bool ParallelTaskTerminator::peek_in_queue_set() {
140 return _queue_set->peek();
141 }
142
143 void ParallelTaskTerminator::yield() {
144 assert(_offered_termination <= _n_threads, "Invariant");
145 os::naked_yield();
146 }
147
148 void ParallelTaskTerminator::sleep(uint millis) {
149 assert(_offered_termination <= _n_threads, "Invariant");
150 os::sleep(Thread::current(), millis, false);
151 }
152
153 bool
154 ParallelTaskTerminator::offer_termination(TerminatorTerminator* terminator) {
155 assert(_n_threads > 0, "Initialization is incorrect");
156 assert(_offered_termination < _n_threads, "Invariant");
157 Atomic::inc((int *)&_offered_termination);
158
159 uint yield_count = 0;
160 // Number of hard spin loops done since last yield
161 uint hard_spin_count = 0;
162 // Number of iterations in the hard spin loop.
163 uint hard_spin_limit = WorkStealingHardSpins;
164
165 // If WorkStealingSpinToYieldRatio is 0, no hard spinning is done.
166 // If it is greater than 0, then start with a small number
167 // of spins and increase number with each turn at spinning until
168 // the count of hard spins exceeds WorkStealingSpinToYieldRatio.
169 // Then do a yield() call and start spinning afresh.
170 if (WorkStealingSpinToYieldRatio > 0) {
171 hard_spin_limit = WorkStealingHardSpins >> WorkStealingSpinToYieldRatio;
172 hard_spin_limit = MAX2(hard_spin_limit, 1U);
173 }
174 // Remember the initial spin limit.
175 uint hard_spin_start = hard_spin_limit;
176
177 // Loop waiting for all threads to offer termination or
178 // more work.
179 while (true) {
180 assert(_offered_termination <= _n_threads, "Invariant");
181 // Are all threads offering termination?
182 if (_offered_termination == _n_threads) {
183 return true;
184 } else {
185 // Look for more work.
186 // Periodically sleep() instead of yield() to give threads
187 // waiting on the cores the chance to grab this code
188 if (yield_count <= WorkStealingYieldsBeforeSleep) {
189 // Do a yield or hardspin. For purposes of deciding whether
190 // to sleep, count this as a yield.
191 yield_count++;
192
193 // Periodically call yield() instead spinning
194 // After WorkStealingSpinToYieldRatio spins, do a yield() call
195 // and reset the counts and starting limit.
196 if (hard_spin_count > WorkStealingSpinToYieldRatio) {
197 yield();
198 hard_spin_count = 0;
199 hard_spin_limit = hard_spin_start;
200 #ifdef TRACESPINNING
201 _total_yields++;
202 #endif
203 } else {
204 // Hard spin this time
205 // Increase the hard spinning period but only up to a limit.
206 hard_spin_limit = MIN2(2*hard_spin_limit,
207 (uint) WorkStealingHardSpins);
208 for (uint j = 0; j < hard_spin_limit; j++) {
209 SpinPause();
210 }
211 hard_spin_count++;
212 #ifdef TRACESPINNING
213 _total_spins++;
214 #endif
215 }
216 } else {
217 if (PrintGCDetails && Verbose) {
218 gclog_or_tty->print_cr("ParallelTaskTerminator::offer_termination() "
219 "thread %d sleeps after %d yields",
220 Thread::current(), yield_count);
221 }
222 yield_count = 0;
223 // A sleep will cause this processor to seek work on another processor's
224 // runqueue, if it has nothing else to run (as opposed to the yield
225 // which may only move the thread to the end of the this processor's
226 // runqueue).
227 sleep(WorkStealingSleepMillis);
228 }
229
230 #ifdef TRACESPINNING
231 _total_peeks++;
232 #endif
233 if (peek_in_queue_set() ||
234 (terminator != NULL && terminator->should_exit_termination())) {
235 Atomic::dec((int *)&_offered_termination);
236 assert(_offered_termination < _n_threads, "Invariant");
237 return false;
238 }
239 }
240 }
241 }
242
243 #ifdef TRACESPINNING
244 void ParallelTaskTerminator::print_termination_counts() {
245 gclog_or_tty->print_cr("ParallelTaskTerminator Total yields: %u"
246 " Total spins: %u Total peeks: %u",
247 total_yields(),
248 total_spins(),
249 total_peeks());
250 }
251 #endif
252
253 void ParallelTaskTerminator::reset_for_reuse() {
254 if (_offered_termination != 0) {
255 assert(_offered_termination == _n_threads,
256 "Terminator may still be in use");
257 _offered_termination = 0;
258 }
259 }
260
261 #ifdef ASSERT
262 bool ObjArrayTask::is_valid() const {
263 return _obj != NULL && _obj->is_objArray() && _index > 0 &&
264 _index < objArrayOop(_obj)->length();
265 }
266 #endif // ASSERT
267
268 void ParallelTaskTerminator::reset_for_reuse(uint n_threads) {
269 reset_for_reuse();
270 _n_threads = n_threads;
271 }