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 "precompiled.hpp"
26 #include "oops/oop.inline.hpp"
27 #include "runtime/os.hpp"
28 #include "utilities/debug.hpp"
29 #include "utilities/stack.inline.hpp"
30 #include "utilities/taskqueue.hpp"
31 #ifdef TARGET_OS_FAMILY_linux
32 # include "thread_linux.inline.hpp"
33 #endif
34 #ifdef TARGET_OS_FAMILY_solaris
35 # include "thread_solaris.inline.hpp"
36 #endif
37 #ifdef TARGET_OS_FAMILY_windows
38 # include "thread_windows.inline.hpp"
39 #endif
40
41 #ifdef TRACESPINNING
42 uint ParallelTaskTerminator::_total_yields = 0;
43 uint ParallelTaskTerminator::_total_spins = 0;
44 uint ParallelTaskTerminator::_total_peeks = 0;
45 #endif
46
47 #if TASKQUEUE_STATS
48 const char * const TaskQueueStats::_names[last_stat_id] = {
49 "qpush", "qpop", "qpop-s", "qattempt", "qsteal", "opush", "omax"
50 };
51
52 TaskQueueStats & TaskQueueStats::operator +=(const TaskQueueStats & addend)
53 {
54 for (unsigned int i = 0; i < last_stat_id; ++i) {
55 _stats[i] += addend._stats[i];
56 }
57 return *this;
58 }
59
60 void TaskQueueStats::print_header(unsigned int line, outputStream* const stream,
61 unsigned int width)
62 {
63 // Use a width w: 1 <= w <= max_width
64 const unsigned int max_width = 40;
65 const unsigned int w = MAX2(MIN2(width, max_width), 1U);
66
67 if (line == 0) { // spaces equal in width to the header
68 const unsigned int hdr_width = w * last_stat_id + last_stat_id - 1;
69 stream->print("%*s", hdr_width, " ");
70 } else if (line == 1) { // labels
71 stream->print("%*s", w, _names[0]);
72 for (unsigned int i = 1; i < last_stat_id; ++i) {
73 stream->print(" %*s", w, _names[i]);
74 }
75 } else if (line == 2) { // dashed lines
76 char dashes[max_width + 1];
77 memset(dashes, '-', w);
78 dashes[w] = '\0';
79 stream->print("%s", dashes);
80 for (unsigned int i = 1; i < last_stat_id; ++i) {
81 stream->print(" %s", dashes);
82 }
83 }
84 }
85
86 void TaskQueueStats::print(outputStream* stream, unsigned int width) const
87 {
88 #define FMT SIZE_FORMAT_W(*)
89 stream->print(FMT, width, _stats[0]);
90 for (unsigned int i = 1; i < last_stat_id; ++i) {
91 stream->print(" " FMT, width, _stats[i]);
92 }
93 #undef FMT
94 }
95
96 #ifdef ASSERT
97 // Invariants which should hold after a TaskQueue has been emptied and is
98 // quiescent; they do not hold at arbitrary times.
99 void TaskQueueStats::verify() const
100 {
101 assert(get(push) == get(pop) + get(steal),
102 err_msg("push=" SIZE_FORMAT " pop=" SIZE_FORMAT " steal=" SIZE_FORMAT,
103 get(push), get(pop), get(steal)));
104 assert(get(pop_slow) <= get(pop),
105 err_msg("pop_slow=" SIZE_FORMAT " pop=" SIZE_FORMAT,
106 get(pop_slow), get(pop)));
107 assert(get(steal) <= get(steal_attempt),
108 err_msg("steal=" SIZE_FORMAT " steal_attempt=" SIZE_FORMAT,
109 get(steal), get(steal_attempt)));
110 assert(get(overflow) == 0 || get(push) != 0,
111 err_msg("overflow=" SIZE_FORMAT " push=" SIZE_FORMAT,
112 get(overflow), get(push)));
113 assert(get(overflow_max_len) == 0 || get(overflow) != 0,
114 err_msg("overflow_max_len=" SIZE_FORMAT " overflow=" SIZE_FORMAT,
115 get(overflow_max_len), get(overflow)));
116 }
117 #endif // ASSERT
118 #endif // TASKQUEUE_STATS
119
120 int TaskQueueSetSuper::randomParkAndMiller(int *seed0) {
121 const int a = 16807;
122 const int m = 2147483647;
123 const int q = 127773; /* m div a */
124 const int r = 2836; /* m mod a */
125 assert(sizeof(int) == 4, "I think this relies on that");
126 int seed = *seed0;
127 int hi = seed / q;
128 int lo = seed % q;
129 int test = a * lo - r * hi;
130 if (test > 0)
131 seed = test;
132 else
133 seed = test + m;
134 *seed0 = seed;
135 return seed;
136 }
137
138 ParallelTaskTerminator::
139 ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set) :
140 _n_threads(n_threads),
141 _queue_set(queue_set),
142 _offered_termination(0) {}
143
144 bool ParallelTaskTerminator::peek_in_queue_set() {
145 return _queue_set->peek();
146 }
147
148 void ParallelTaskTerminator::yield() {
149 assert(_offered_termination <= _n_threads, "Invariant");
150 os::yield();
151 }
152
153 void ParallelTaskTerminator::sleep(uint millis) {
154 assert(_offered_termination <= _n_threads, "Invariant");
155 os::sleep(Thread::current(), millis, false);
156 }
157
158 bool
159 ParallelTaskTerminator::offer_termination(TerminatorTerminator* terminator) {
160 assert(_n_threads > 0, "Initialization is incorrect");
161 assert(_offered_termination < _n_threads, "Invariant");
162 Atomic::inc(&_offered_termination);
163
164 uint yield_count = 0;
165 // Number of hard spin loops done since last yield
166 uint hard_spin_count = 0;
167 // Number of iterations in the hard spin loop.
168 uint hard_spin_limit = WorkStealingHardSpins;
169
170 // If WorkStealingSpinToYieldRatio is 0, no hard spinning is done.
171 // If it is greater than 0, then start with a small number
172 // of spins and increase number with each turn at spinning until
173 // the count of hard spins exceeds WorkStealingSpinToYieldRatio.
174 // Then do a yield() call and start spinning afresh.
175 if (WorkStealingSpinToYieldRatio > 0) {
176 hard_spin_limit = WorkStealingHardSpins >> WorkStealingSpinToYieldRatio;
177 hard_spin_limit = MAX2(hard_spin_limit, 1U);
178 }
179 // Remember the initial spin limit.
180 uint hard_spin_start = hard_spin_limit;
181
182 // Loop waiting for all threads to offer termination or
183 // more work.
184 while (true) {
185 assert(_offered_termination <= _n_threads, "Invariant");
186 // Are all threads offering termination?
187 if (_offered_termination == _n_threads) {
188 return true;
189 } else {
190 // Look for more work.
191 // Periodically sleep() instead of yield() to give threads
192 // waiting on the cores the chance to grab this code
193 if (yield_count <= WorkStealingYieldsBeforeSleep) {
194 // Do a yield or hardspin. For purposes of deciding whether
195 // to sleep, count this as a yield.
196 yield_count++;
197
198 // Periodically call yield() instead spinning
199 // After WorkStealingSpinToYieldRatio spins, do a yield() call
200 // and reset the counts and starting limit.
201 if (hard_spin_count > WorkStealingSpinToYieldRatio) {
202 yield();
203 hard_spin_count = 0;
204 hard_spin_limit = hard_spin_start;
205 #ifdef TRACESPINNING
206 _total_yields++;
207 #endif
208 } else {
209 // Hard spin this time
210 // Increase the hard spinning period but only up to a limit.
211 hard_spin_limit = MIN2(2*hard_spin_limit,
212 (uint) WorkStealingHardSpins);
213 for (uint j = 0; j < hard_spin_limit; j++) {
214 SpinPause();
215 }
216 hard_spin_count++;
217 #ifdef TRACESPINNING
218 _total_spins++;
219 #endif
220 }
221 } else {
222 if (PrintGCDetails && Verbose) {
223 gclog_or_tty->print_cr("ParallelTaskTerminator::offer_termination() "
224 "thread %d sleeps after %d yields",
225 Thread::current(), yield_count);
226 }
227 yield_count = 0;
228 // A sleep will cause this processor to seek work on another processor's
229 // runqueue, if it has nothing else to run (as opposed to the yield
230 // which may only move the thread to the end of the this processor's
231 // runqueue).
232 sleep(WorkStealingSleepMillis);
233 }
234
235 #ifdef TRACESPINNING
236 _total_peeks++;
237 #endif
238 if (peek_in_queue_set() ||
239 (terminator != NULL && terminator->should_exit_termination())) {
240 Atomic::dec(&_offered_termination);
241 assert(_offered_termination < _n_threads, "Invariant");
242 return false;
243 }
244 }
245 }
246 }
247
248 #ifdef TRACESPINNING
249 void ParallelTaskTerminator::print_termination_counts() {
250 gclog_or_tty->print_cr("ParallelTaskTerminator Total yields: %lld "
251 "Total spins: %lld Total peeks: %lld",
252 total_yields(),
253 total_spins(),
254 total_peeks());
255 }
256 #endif
257
258 void ParallelTaskTerminator::reset_for_reuse() {
259 if (_offered_termination != 0) {
260 assert(_offered_termination == _n_threads,
261 "Terminator may still be in use");
262 _offered_termination = 0;
263 }
264 }
265
266 #ifdef ASSERT
267 bool ObjArrayTask::is_valid() const {
268 return _obj != NULL && _obj->is_objArray() && _index > 0 &&
269 _index < objArrayOop(_obj)->length();
270 }
271 #endif // ASSERT
272
273 void ParallelTaskTerminator::reset_for_reuse(int n_threads) {
274 reset_for_reuse();
275 _n_threads = n_threads;
276 }
277