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 #ifdef TARGET_OS_FAMILY_bsd 41 # include "thread_bsd.inline.hpp" 42 #endif 43 44 #ifdef TRACESPINNING 45 uint ParallelTaskTerminator::_total_yields = 0; 46 uint ParallelTaskTerminator::_total_spins = 0; 47 uint ParallelTaskTerminator::_total_peeks = 0; 48 #endif 49 50 #if TASKQUEUE_STATS 51 const char * const TaskQueueStats::_names[last_stat_id] = { 52 "qpush", "qpop", "qpop-s", "qattempt", "qsteal", "opush", "omax" 53 }; 54 55 TaskQueueStats & TaskQueueStats::operator +=(const TaskQueueStats & addend) 56 { 57 for (unsigned int i = 0; i < last_stat_id; ++i) { 58 _stats[i] += addend._stats[i]; 59 } 60 return *this; 61 } 62 63 void TaskQueueStats::print_header(unsigned int line, outputStream* const stream, 64 unsigned int width) 65 { 66 // Use a width w: 1 <= w <= max_width 67 const unsigned int max_width = 40; 68 const unsigned int w = MAX2(MIN2(width, max_width), 1U); 69 70 if (line == 0) { // spaces equal in width to the header 71 const unsigned int hdr_width = w * last_stat_id + last_stat_id - 1; 72 stream->print("%*s", hdr_width, " "); 73 } else if (line == 1) { // labels 74 stream->print("%*s", w, _names[0]); 75 for (unsigned int i = 1; i < last_stat_id; ++i) { 76 stream->print(" %*s", w, _names[i]); 77 } 78 } else if (line == 2) { // dashed lines 79 char dashes[max_width + 1]; 80 memset(dashes, '-', w); 81 dashes[w] = '\0'; 82 stream->print("%s", dashes); 83 for (unsigned int i = 1; i < last_stat_id; ++i) { 84 stream->print(" %s", dashes); 85 } 86 } 87 } 88 89 void TaskQueueStats::print(outputStream* stream, unsigned int width) const 90 { 91 #define FMT SIZE_FORMAT_W(*) 92 stream->print(FMT, width, _stats[0]); 93 for (unsigned int i = 1; i < last_stat_id; ++i) { 94 stream->print(" " FMT, width, _stats[i]); 95 } 96 #undef FMT 97 } 98 99 #ifdef ASSERT 100 // Invariants which should hold after a TaskQueue has been emptied and is 101 // quiescent; they do not hold at arbitrary times. 102 void TaskQueueStats::verify() const 103 { 104 assert(get(push) == get(pop) + get(steal), 105 err_msg("push=" SIZE_FORMAT " pop=" SIZE_FORMAT " steal=" SIZE_FORMAT, 106 get(push), get(pop), get(steal))); 107 assert(get(pop_slow) <= get(pop), 108 err_msg("pop_slow=" SIZE_FORMAT " pop=" SIZE_FORMAT, 109 get(pop_slow), get(pop))); 110 assert(get(steal) <= get(steal_attempt), 111 err_msg("steal=" SIZE_FORMAT " steal_attempt=" SIZE_FORMAT, 112 get(steal), get(steal_attempt))); 113 assert(get(overflow) == 0 || get(push) != 0, 114 err_msg("overflow=" SIZE_FORMAT " push=" SIZE_FORMAT, 115 get(overflow), get(push))); 116 assert(get(overflow_max_len) == 0 || get(overflow) != 0, 117 err_msg("overflow_max_len=" SIZE_FORMAT " overflow=" SIZE_FORMAT, 118 get(overflow_max_len), get(overflow))); 119 } 120 #endif // ASSERT 121 #endif // TASKQUEUE_STATS 122 123 int TaskQueueSetSuper::randomParkAndMiller(int *seed0) { 124 const int a = 16807; 125 const int m = 2147483647; 126 const int q = 127773; /* m div a */ 127 const int r = 2836; /* m mod a */ 128 assert(sizeof(int) == 4, "I think this relies on that"); 129 int seed = *seed0; 130 int hi = seed / q; 131 int lo = seed % q; 132 int test = a * lo - r * hi; 133 if (test > 0) 134 seed = test; 135 else 136 seed = test + m; 137 *seed0 = seed; 138 return seed; 139 } 140 141 ParallelTaskTerminator:: 142 ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set) : 143 _n_threads(n_threads), 144 _queue_set(queue_set), 145 _offered_termination(0) {} 146 147 bool ParallelTaskTerminator::peek_in_queue_set() { 148 return _queue_set->peek(); 149 } 150 151 void ParallelTaskTerminator::yield() { 152 assert(_offered_termination <= _n_threads, "Invariant"); 153 os::yield(); 154 } 155 156 void ParallelTaskTerminator::sleep(uint millis) { 157 assert(_offered_termination <= _n_threads, "Invariant"); 158 os::sleep(Thread::current(), millis, false); 159 } 160 161 bool 162 ParallelTaskTerminator::offer_termination(TerminatorTerminator* terminator) { 163 assert(_n_threads > 0, "Initialization is incorrect"); 164 assert(_offered_termination < _n_threads, "Invariant"); 165 Atomic::inc(&_offered_termination); 166 167 uint yield_count = 0; 168 // Number of hard spin loops done since last yield 169 uint hard_spin_count = 0; 170 // Number of iterations in the hard spin loop. 171 uint hard_spin_limit = WorkStealingHardSpins; 172 173 // If WorkStealingSpinToYieldRatio is 0, no hard spinning is done. 174 // If it is greater than 0, then start with a small number 175 // of spins and increase number with each turn at spinning until 176 // the count of hard spins exceeds WorkStealingSpinToYieldRatio. 177 // Then do a yield() call and start spinning afresh. 178 if (WorkStealingSpinToYieldRatio > 0) { 179 hard_spin_limit = WorkStealingHardSpins >> WorkStealingSpinToYieldRatio; 180 hard_spin_limit = MAX2(hard_spin_limit, 1U); 181 } 182 // Remember the initial spin limit. 183 uint hard_spin_start = hard_spin_limit; 184 185 // Loop waiting for all threads to offer termination or 186 // more work. 187 while (true) { 188 assert(_offered_termination <= _n_threads, "Invariant"); 189 // Are all threads offering termination? 190 if (_offered_termination == _n_threads) { 191 return true; 192 } else { 193 // Look for more work. 194 // Periodically sleep() instead of yield() to give threads 195 // waiting on the cores the chance to grab this code 196 if (yield_count <= WorkStealingYieldsBeforeSleep) { 197 // Do a yield or hardspin. For purposes of deciding whether 198 // to sleep, count this as a yield. 199 yield_count++; 200 201 // Periodically call yield() instead spinning 202 // After WorkStealingSpinToYieldRatio spins, do a yield() call 203 // and reset the counts and starting limit. 204 if (hard_spin_count > WorkStealingSpinToYieldRatio) { 205 yield(); 206 hard_spin_count = 0; 207 hard_spin_limit = hard_spin_start; 208 #ifdef TRACESPINNING 209 _total_yields++; 210 #endif 211 } else { 212 // Hard spin this time 213 // Increase the hard spinning period but only up to a limit. 214 hard_spin_limit = MIN2(2*hard_spin_limit, 215 (uint) WorkStealingHardSpins); 216 for (uint j = 0; j < hard_spin_limit; j++) { 217 SpinPause(); 218 } 219 hard_spin_count++; 220 #ifdef TRACESPINNING 221 _total_spins++; 222 #endif 223 } 224 } else { 225 if (PrintGCDetails && Verbose) { 226 gclog_or_tty->print_cr("ParallelTaskTerminator::offer_termination() " 227 "thread %d sleeps after %d yields", 228 Thread::current(), yield_count); 229 } 230 yield_count = 0; 231 // A sleep will cause this processor to seek work on another processor's 232 // runqueue, if it has nothing else to run (as opposed to the yield 233 // which may only move the thread to the end of the this processor's 234 // runqueue). 235 sleep(WorkStealingSleepMillis); 236 } 237 238 #ifdef TRACESPINNING 239 _total_peeks++; 240 #endif 241 if (peek_in_queue_set() || 242 (terminator != NULL && terminator->should_exit_termination())) { 243 Atomic::dec(&_offered_termination); 244 assert(_offered_termination < _n_threads, "Invariant"); 245 return false; 246 } 247 } 248 } 249 } 250 251 #ifdef TRACESPINNING 252 void ParallelTaskTerminator::print_termination_counts() { 253 gclog_or_tty->print_cr("ParallelTaskTerminator Total yields: %lld " 254 "Total spins: %lld Total peeks: %lld", 255 total_yields(), 256 total_spins(), 257 total_peeks()); 258 } 259 #endif 260 261 void ParallelTaskTerminator::reset_for_reuse() { 262 if (_offered_termination != 0) { 263 assert(_offered_termination == _n_threads, 264 "Terminator may still be in use"); 265 _offered_termination = 0; 266 } 267 } 268 269 #ifdef ASSERT 270 bool ObjArrayTask::is_valid() const { 271 return _obj != NULL && _obj->is_objArray() && _index > 0 && 272 _index < objArrayOop(_obj)->length(); 273 } 274 #endif // ASSERT 275 276 void ParallelTaskTerminator::reset_for_reuse(int n_threads) { 277 reset_for_reuse(); 278 _n_threads = n_threads; 279 }