1 /*
2 * Copyright (c) 2001, 2010, 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 "incls/_precompiled.incl"
26 # include "incls/_taskqueue.cpp.incl"
27
28 #ifdef TRACESPINNING
29 uint ParallelTaskTerminator::_total_yields = 0;
30 uint ParallelTaskTerminator::_total_spins = 0;
31 uint ParallelTaskTerminator::_total_peeks = 0;
32 #endif
33
34 #if TASKQUEUE_STATS
35 const char * const TaskQueueStats::_names[last_stat_id] = {
36 "qpush", "qpop", "qpop-s", "qattempt", "qsteal", "opush", "omax"
37 };
38
39 TaskQueueStats & TaskQueueStats::operator +=(const TaskQueueStats & addend)
40 {
41 for (unsigned int i = 0; i < last_stat_id; ++i) {
42 _stats[i] += addend._stats[i];
43 }
44 return *this;
45 }
46
47 void TaskQueueStats::print_header(unsigned int line, outputStream* const stream,
48 unsigned int width)
49 {
50 // Use a width w: 1 <= w <= max_width
51 const unsigned int max_width = 40;
52 const unsigned int w = MAX2(MIN2(width, max_width), 1U);
53
54 if (line == 0) { // spaces equal in width to the header
55 const unsigned int hdr_width = w * last_stat_id + last_stat_id - 1;
56 stream->print("%*s", hdr_width, " ");
57 } else if (line == 1) { // labels
58 stream->print("%*s", w, _names[0]);
59 for (unsigned int i = 1; i < last_stat_id; ++i) {
60 stream->print(" %*s", w, _names[i]);
61 }
62 } else if (line == 2) { // dashed lines
63 char dashes[max_width + 1];
64 memset(dashes, '-', w);
65 dashes[w] = '\0';
66 stream->print("%s", dashes);
67 for (unsigned int i = 1; i < last_stat_id; ++i) {
68 stream->print(" %s", dashes);
69 }
70 }
71 }
72
73 void TaskQueueStats::print(outputStream* stream, unsigned int width) const
74 {
75 #define FMT SIZE_FORMAT_W(*)
76 stream->print(FMT, width, _stats[0]);
77 for (unsigned int i = 1; i < last_stat_id; ++i) {
78 stream->print(" " FMT, width, _stats[i]);
79 }
80 #undef FMT
81 }
82
83 #ifdef ASSERT
84 // Invariants which should hold after a TaskQueue has been emptied and is
85 // quiescent; they do not hold at arbitrary times.
86 void TaskQueueStats::verify() const
87 {
88 assert(get(push) == get(pop) + get(steal),
89 err_msg("push=" SIZE_FORMAT " pop=" SIZE_FORMAT " steal=" SIZE_FORMAT,
90 get(push), get(pop), get(steal)));
91 assert(get(pop_slow) <= get(pop),
92 err_msg("pop_slow=" SIZE_FORMAT " pop=" SIZE_FORMAT,
93 get(pop_slow), get(pop)));
94 assert(get(steal) <= get(steal_attempt),
95 err_msg("steal=" SIZE_FORMAT " steal_attempt=" SIZE_FORMAT,
96 get(steal), get(steal_attempt)));
97 assert(get(overflow) == 0 || get(push) != 0,
98 err_msg("overflow=" SIZE_FORMAT " push=" SIZE_FORMAT,
99 get(overflow), get(push)));
100 assert(get(overflow_max_len) == 0 || get(overflow) != 0,
101 err_msg("overflow_max_len=" SIZE_FORMAT " overflow=" SIZE_FORMAT,
102 get(overflow_max_len), get(overflow)));
103 }
104 #endif // ASSERT
105 #endif // TASKQUEUE_STATS
106
107 int TaskQueueSetSuper::randomParkAndMiller(int *seed0) {
108 const int a = 16807;
109 const int m = 2147483647;
110 const int q = 127773; /* m div a */
111 const int r = 2836; /* m mod a */
112 assert(sizeof(int) == 4, "I think this relies on that");
113 int seed = *seed0;
114 int hi = seed / q;
115 int lo = seed % q;
116 int test = a * lo - r * hi;
117 if (test > 0)
118 seed = test;
119 else
120 seed = test + m;
121 *seed0 = seed;
122 return seed;
123 }
124
125 ParallelTaskTerminator::
126 ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set) :
127 _n_threads(n_threads),
128 _queue_set(queue_set),
129 _offered_termination(0) {}
130
131 bool ParallelTaskTerminator::peek_in_queue_set() {
132 return _queue_set->peek();
133 }
134
135 void ParallelTaskTerminator::yield() {
136 assert(_offered_termination <= _n_threads, "Invariant");
137 os::yield();
138 }
139
140 void ParallelTaskTerminator::sleep(uint millis) {
141 assert(_offered_termination <= _n_threads, "Invariant");
142 os::sleep(Thread::current(), millis, false);
143 }
144
145 bool
146 ParallelTaskTerminator::offer_termination(TerminatorTerminator* terminator) {
147 assert(_n_threads > 0, "Initialization is incorrect");
148 assert(_offered_termination < _n_threads, "Invariant");
149 Atomic::inc(&_offered_termination);
150
151 uint yield_count = 0;
152 // Number of hard spin loops done since last yield
153 uint hard_spin_count = 0;
154 // Number of iterations in the hard spin loop.
155 uint hard_spin_limit = WorkStealingHardSpins;
156
157 // If WorkStealingSpinToYieldRatio is 0, no hard spinning is done.
158 // If it is greater than 0, then start with a small number
159 // of spins and increase number with each turn at spinning until
160 // the count of hard spins exceeds WorkStealingSpinToYieldRatio.
161 // Then do a yield() call and start spinning afresh.
162 if (WorkStealingSpinToYieldRatio > 0) {
163 hard_spin_limit = WorkStealingHardSpins >> WorkStealingSpinToYieldRatio;
164 hard_spin_limit = MAX2(hard_spin_limit, 1U);
165 }
166 // Remember the initial spin limit.
167 uint hard_spin_start = hard_spin_limit;
168
169 // Loop waiting for all threads to offer termination or
170 // more work.
171 while (true) {
172 assert(_offered_termination <= _n_threads, "Invariant");
173 // Are all threads offering termination?
174 if (_offered_termination == _n_threads) {
175 return true;
176 } else {
177 // Look for more work.
178 // Periodically sleep() instead of yield() to give threads
179 // waiting on the cores the chance to grab this code
180 if (yield_count <= WorkStealingYieldsBeforeSleep) {
181 // Do a yield or hardspin. For purposes of deciding whether
182 // to sleep, count this as a yield.
183 yield_count++;
184
185 // Periodically call yield() instead spinning
186 // After WorkStealingSpinToYieldRatio spins, do a yield() call
187 // and reset the counts and starting limit.
188 if (hard_spin_count > WorkStealingSpinToYieldRatio) {
189 yield();
190 hard_spin_count = 0;
191 hard_spin_limit = hard_spin_start;
192 #ifdef TRACESPINNING
193 _total_yields++;
194 #endif
195 } else {
196 // Hard spin this time
197 // Increase the hard spinning period but only up to a limit.
198 hard_spin_limit = MIN2(2*hard_spin_limit,
199 (uint) WorkStealingHardSpins);
200 for (uint j = 0; j < hard_spin_limit; j++) {
201 SpinPause();
202 }
203 hard_spin_count++;
204 #ifdef TRACESPINNING
205 _total_spins++;
206 #endif
207 }
208 } else {
209 if (PrintGCDetails && Verbose) {
210 gclog_or_tty->print_cr("ParallelTaskTerminator::offer_termination() "
211 "thread %d sleeps after %d yields",
212 Thread::current(), yield_count);
213 }
214 yield_count = 0;
215 // A sleep will cause this processor to seek work on another processor's
216 // runqueue, if it has nothing else to run (as opposed to the yield
217 // which may only move the thread to the end of the this processor's
218 // runqueue).
219 sleep(WorkStealingSleepMillis);
220 }
221
222 #ifdef TRACESPINNING
223 _total_peeks++;
224 #endif
225 if (peek_in_queue_set() ||
226 (terminator != NULL && terminator->should_exit_termination())) {
227 Atomic::dec(&_offered_termination);
228 assert(_offered_termination < _n_threads, "Invariant");
229 return false;
230 }
231 }
232 }
233 }
234
235 #ifdef TRACESPINNING
236 void ParallelTaskTerminator::print_termination_counts() {
237 gclog_or_tty->print_cr("ParallelTaskTerminator Total yields: %lld "
238 "Total spins: %lld Total peeks: %lld",
239 total_yields(),
240 total_spins(),
241 total_peeks());
242 }
243 #endif
244
245 void ParallelTaskTerminator::reset_for_reuse() {
246 if (_offered_termination != 0) {
247 assert(_offered_termination == _n_threads,
248 "Terminator may still be in use");
249 _offered_termination = 0;
250 }
251 }
252
253 #ifdef ASSERT
254 bool ObjArrayTask::is_valid() const {
255 return _obj != NULL && _obj->is_objArray() && _index > 0 &&
256 _index < objArrayOop(_obj)->length();
257 }
258 #endif // ASSERT
259
260 void ParallelTaskTerminator::reset_for_reuse(int n_threads) {
261 reset_for_reuse();
262 _n_threads = n_threads;
263 }
264