1 /* 2 * Copyright (c) 2001, 2014, 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 "runtime/thread.inline.hpp" 29 #include "utilities/debug.hpp" 30 #include "utilities/stack.inline.hpp" 31 #include "utilities/taskqueue.hpp" 32 33 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 34 35 #ifdef TRACESPINNING 36 uint ParallelTaskTerminator::_total_yields = 0; 37 uint ParallelTaskTerminator::_total_spins = 0; 38 uint ParallelTaskTerminator::_total_peeks = 0; 39 #endif 40 41 #if TASKQUEUE_STATS 42 const char * const TaskQueueStats::_names[last_stat_id] = { 43 "qpush", "qpop", "qpop-s", "qattempt", "qsteal", "opush", "omax" 44 }; 45 46 TaskQueueStats & TaskQueueStats::operator +=(const TaskQueueStats & addend) 47 { 48 for (unsigned int i = 0; i < last_stat_id; ++i) { 49 _stats[i] += addend._stats[i]; 50 } 51 return *this; 52 } 53 54 void TaskQueueStats::print_header(unsigned int line, outputStream* const stream, 55 unsigned int width) 56 { 57 // Use a width w: 1 <= w <= max_width 58 const unsigned int max_width = 40; 59 const unsigned int w = MAX2(MIN2(width, max_width), 1U); 60 61 if (line == 0) { // spaces equal in width to the header 62 const unsigned int hdr_width = w * last_stat_id + last_stat_id - 1; 63 stream->print("%*s", hdr_width, " "); 64 } else if (line == 1) { // labels 65 stream->print("%*s", w, _names[0]); 66 for (unsigned int i = 1; i < last_stat_id; ++i) { 67 stream->print(" %*s", w, _names[i]); 68 } 69 } else if (line == 2) { // dashed lines 70 char dashes[max_width + 1]; 71 memset(dashes, '-', w); 72 dashes[w] = '\0'; 73 stream->print("%s", dashes); 74 for (unsigned int i = 1; i < last_stat_id; ++i) { 75 stream->print(" %s", dashes); 76 } 77 } 78 } 79 80 void TaskQueueStats::print(outputStream* stream, unsigned int width) const 81 { 82 #define FMT SIZE_FORMAT_W(*) 83 stream->print(FMT, width, _stats[0]); 84 for (unsigned int i = 1; i < last_stat_id; ++i) { 85 stream->print(" " FMT, width, _stats[i]); 86 } 87 #undef FMT 88 } 89 90 #ifdef ASSERT 91 // Invariants which should hold after a TaskQueue has been emptied and is 92 // quiescent; they do not hold at arbitrary times. 93 void TaskQueueStats::verify() const 94 { 95 assert(get(push) == get(pop) + get(steal), 96 err_msg("push=" SIZE_FORMAT " pop=" SIZE_FORMAT " steal=" SIZE_FORMAT, 97 get(push), get(pop), get(steal))); 98 assert(get(pop_slow) <= get(pop), 99 err_msg("pop_slow=" SIZE_FORMAT " pop=" SIZE_FORMAT, 100 get(pop_slow), get(pop))); 101 assert(get(steal) <= get(steal_attempt), 102 err_msg("steal=" SIZE_FORMAT " steal_attempt=" SIZE_FORMAT, 103 get(steal), get(steal_attempt))); 104 assert(get(overflow) == 0 || get(push) != 0, 105 err_msg("overflow=" SIZE_FORMAT " push=" SIZE_FORMAT, 106 get(overflow), get(push))); 107 assert(get(overflow_max_len) == 0 || get(overflow) != 0, 108 err_msg("overflow_max_len=" SIZE_FORMAT " overflow=" SIZE_FORMAT, 109 get(overflow_max_len), get(overflow))); 110 } 111 #endif // ASSERT 112 #endif // TASKQUEUE_STATS 113 114 int TaskQueueSetSuper::randomParkAndMiller(int *seed0) { 115 const int a = 16807; 116 const int m = 2147483647; 117 const int q = 127773; /* m div a */ 118 const int r = 2836; /* m mod a */ 119 assert(sizeof(int) == 4, "I think this relies on that"); 120 int seed = *seed0; 121 int hi = seed / q; 122 int lo = seed % q; 123 int test = a * lo - r * hi; 124 if (test > 0) 125 seed = test; 126 else 127 seed = test + m; 128 *seed0 = seed; 129 return seed; 130 } 131 132 ParallelTaskTerminator:: 133 ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set) : 134 _n_threads(n_threads), 135 _queue_set(queue_set), 136 _offered_termination(0) {} 137 138 bool ParallelTaskTerminator::peek_in_queue_set() { 139 return _queue_set->peek(); 140 } 141 142 void ParallelTaskTerminator::yield() { 143 assert(_offered_termination <= _n_threads, "Invariant"); 144 os::yield(); 145 } 146 147 void ParallelTaskTerminator::sleep(uint millis) { 148 assert(_offered_termination <= _n_threads, "Invariant"); 149 os::sleep(Thread::current(), millis, false); 150 } 151 152 bool 153 ParallelTaskTerminator::offer_termination(TerminatorTerminator* terminator) { 154 assert(_n_threads > 0, "Initialization is incorrect"); 155 assert(_offered_termination < _n_threads, "Invariant"); 156 Atomic::inc(&_offered_termination); 157 158 uint yield_count = 0; 159 // Number of hard spin loops done since last yield 160 uint hard_spin_count = 0; 161 // Number of iterations in the hard spin loop. 162 uint hard_spin_limit = WorkStealingHardSpins; 163 164 // If WorkStealingSpinToYieldRatio is 0, no hard spinning is done. 165 // If it is greater than 0, then start with a small number 166 // of spins and increase number with each turn at spinning until 167 // the count of hard spins exceeds WorkStealingSpinToYieldRatio. 168 // Then do a yield() call and start spinning afresh. 169 if (WorkStealingSpinToYieldRatio > 0) { 170 hard_spin_limit = WorkStealingHardSpins >> WorkStealingSpinToYieldRatio; 171 hard_spin_limit = MAX2(hard_spin_limit, 1U); 172 } 173 // Remember the initial spin limit. 174 uint hard_spin_start = hard_spin_limit; 175 176 // Loop waiting for all threads to offer termination or 177 // more work. 178 while (true) { 179 assert(_offered_termination <= _n_threads, "Invariant"); 180 // Are all threads offering termination? 181 if (_offered_termination == _n_threads) { 182 return true; 183 } else { 184 // Look for more work. 185 // Periodically sleep() instead of yield() to give threads 186 // waiting on the cores the chance to grab this code 187 if (yield_count <= WorkStealingYieldsBeforeSleep) { 188 // Do a yield or hardspin. For purposes of deciding whether 189 // to sleep, count this as a yield. 190 yield_count++; 191 192 // Periodically call yield() instead spinning 193 // After WorkStealingSpinToYieldRatio spins, do a yield() call 194 // and reset the counts and starting limit. 195 if (hard_spin_count > WorkStealingSpinToYieldRatio) { 196 yield(); 197 hard_spin_count = 0; 198 hard_spin_limit = hard_spin_start; 199 #ifdef TRACESPINNING 200 _total_yields++; 201 #endif 202 } else { 203 // Hard spin this time 204 // Increase the hard spinning period but only up to a limit. 205 hard_spin_limit = MIN2(2*hard_spin_limit, 206 (uint) WorkStealingHardSpins); 207 for (uint j = 0; j < hard_spin_limit; j++) { 208 SpinPause(); 209 } 210 hard_spin_count++; 211 #ifdef TRACESPINNING 212 _total_spins++; 213 #endif 214 } 215 } else { 216 if (PrintGCDetails && Verbose) { 217 gclog_or_tty->print_cr("ParallelTaskTerminator::offer_termination() " 218 "thread %d sleeps after %d yields", 219 Thread::current(), yield_count); 220 } 221 yield_count = 0; 222 // A sleep will cause this processor to seek work on another processor's 223 // runqueue, if it has nothing else to run (as opposed to the yield 224 // which may only move the thread to the end of the this processor's 225 // runqueue). 226 sleep(WorkStealingSleepMillis); 227 } 228 229 #ifdef TRACESPINNING 230 _total_peeks++; 231 #endif 232 if ((peek_in_queue_set() && (terminator == NULL || ! terminator->should_force_termination())) || 233 (terminator != NULL && terminator->should_exit_termination())) { 234 Atomic::dec(&_offered_termination); 235 assert(_offered_termination < _n_threads, "Invariant"); 236 return false; 237 } 238 } 239 } 240 } 241 242 #ifdef TRACESPINNING 243 void ParallelTaskTerminator::print_termination_counts() { 244 gclog_or_tty->print_cr("ParallelTaskTerminator Total yields: " UINT32_FORMAT 245 " Total spins: " UINT32_FORMAT " Total peeks: " UINT32_FORMAT, 246 total_yields(), 247 total_spins(), 248 total_peeks()); 249 } 250 #endif 251 252 void ParallelTaskTerminator::reset_for_reuse() { 253 if (_offered_termination != 0) { 254 assert(_offered_termination == _n_threads, 255 "Terminator may still be in use"); 256 _offered_termination = 0; 257 } 258 } 259 260 #ifdef ASSERT 261 bool ObjArrayTask::is_valid() const { 262 return _obj != NULL && _obj->is_objArray() && _index > 0 && 263 _index < objArrayOop(_obj)->length(); 264 } 265 #endif // ASSERT 266 267 void ParallelTaskTerminator::reset_for_reuse(int n_threads) { 268 reset_for_reuse(); 269 _n_threads = n_threads; 270 }