| /* |
| * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "precompiled.hpp" |
| #include "gc/shared/taskqueue.hpp" |
| #include "oops/oop.inline.hpp" |
| #include "logging/log.hpp" |
| #include "runtime/atomic.hpp" |
| #include "runtime/os.hpp" |
| #include "runtime/thread.inline.hpp" |
| #include "utilities/debug.hpp" |
| #include "utilities/stack.inline.hpp" |
| |
| #ifdef TRACESPINNING |
| uint ParallelTaskTerminator::_total_yields = 0; |
| uint ParallelTaskTerminator::_total_spins = 0; |
| uint ParallelTaskTerminator::_total_peeks = 0; |
| #endif |
| |
| #if TASKQUEUE_STATS |
| const char * const TaskQueueStats::_names[last_stat_id] = { |
| "qpush", "qpop", "qpop-s", "qattempt", "qsteal", "opush", "omax" |
| }; |
| |
| TaskQueueStats & TaskQueueStats::operator +=(const TaskQueueStats & addend) |
| { |
| for (unsigned int i = 0; i < last_stat_id; ++i) { |
| _stats[i] += addend._stats[i]; |
| } |
| return *this; |
| } |
| |
| void TaskQueueStats::print_header(unsigned int line, outputStream* const stream, |
| unsigned int width) |
| { |
| // Use a width w: 1 <= w <= max_width |
| const unsigned int max_width = 40; |
| const unsigned int w = MAX2(MIN2(width, max_width), 1U); |
| |
| if (line == 0) { // spaces equal in width to the header |
| const unsigned int hdr_width = w * last_stat_id + last_stat_id - 1; |
| stream->print("%*s", hdr_width, " "); |
| } else if (line == 1) { // labels |
| stream->print("%*s", w, _names[0]); |
| for (unsigned int i = 1; i < last_stat_id; ++i) { |
| stream->print(" %*s", w, _names[i]); |
| } |
| } else if (line == 2) { // dashed lines |
| char dashes[max_width + 1]; |
| memset(dashes, '-', w); |
| dashes[w] = '\0'; |
| stream->print("%s", dashes); |
| for (unsigned int i = 1; i < last_stat_id; ++i) { |
| stream->print(" %s", dashes); |
| } |
| } |
| } |
| |
| void TaskQueueStats::print(outputStream* stream, unsigned int width) const |
| { |
| #define FMT SIZE_FORMAT_W(*) |
| stream->print(FMT, width, _stats[0]); |
| for (unsigned int i = 1; i < last_stat_id; ++i) { |
| stream->print(" " FMT, width, _stats[i]); |
| } |
| #undef FMT |
| } |
| |
| #ifdef ASSERT |
| // Invariants which should hold after a TaskQueue has been emptied and is |
| // quiescent; they do not hold at arbitrary times. |
| void TaskQueueStats::verify() const |
| { |
| assert(get(push) == get(pop) + get(steal), |
| "push=" SIZE_FORMAT " pop=" SIZE_FORMAT " steal=" SIZE_FORMAT, |
| get(push), get(pop), get(steal)); |
| assert(get(pop_slow) <= get(pop), |
| "pop_slow=" SIZE_FORMAT " pop=" SIZE_FORMAT, |
| get(pop_slow), get(pop)); |
| assert(get(steal) <= get(steal_attempt), |
| "steal=" SIZE_FORMAT " steal_attempt=" SIZE_FORMAT, |
| get(steal), get(steal_attempt)); |
| assert(get(overflow) == 0 || get(push) != 0, |
| "overflow=" SIZE_FORMAT " push=" SIZE_FORMAT, |
| get(overflow), get(push)); |
| assert(get(overflow_max_len) == 0 || get(overflow) != 0, |
| "overflow_max_len=" SIZE_FORMAT " overflow=" SIZE_FORMAT, |
| get(overflow_max_len), get(overflow)); |
| } |
| #endif // ASSERT |
| #endif // TASKQUEUE_STATS |
| |
| int TaskQueueSetSuper::randomParkAndMiller(int *seed0) { |
| const int a = 16807; |
| const int m = 2147483647; |
| const int q = 127773; /* m div a */ |
| const int r = 2836; /* m mod a */ |
| assert(sizeof(int) == 4, "I think this relies on that"); |
| int seed = *seed0; |
| int hi = seed / q; |
| int lo = seed % q; |
| int test = a * lo - r * hi; |
| if (test > 0) |
| seed = test; |
| else |
| seed = test + m; |
| *seed0 = seed; |
| return seed; |
| } |
| |
| ParallelTaskTerminator:: |
| ParallelTaskTerminator(uint n_threads, TaskQueueSetSuper* queue_set) : |
| _n_threads(n_threads), |
| _queue_set(queue_set), |
| _offered_termination(0) {} |
| |
| bool ParallelTaskTerminator::peek_in_queue_set() { |
| return _queue_set->peek(); |
| } |
| |
| void ParallelTaskTerminator::yield() { |
| assert(_offered_termination <= _n_threads, "Invariant"); |
| os::naked_yield(); |
| } |
| |
| void ParallelTaskTerminator::sleep(uint millis) { |
| assert(_offered_termination <= _n_threads, "Invariant"); |
| os::sleep(Thread::current(), millis, false); |
| } |
| |
| bool |
| ParallelTaskTerminator::offer_termination(TerminatorTerminator* terminator) { |
| assert(_n_threads > 0, "Initialization is incorrect"); |
| assert(_offered_termination < _n_threads, "Invariant"); |
| Atomic::inc((int *)&_offered_termination); |
| |
| uint yield_count = 0; |
| // Number of hard spin loops done since last yield |
| uint hard_spin_count = 0; |
| // Number of iterations in the hard spin loop. |
| uint hard_spin_limit = WorkStealingHardSpins; |
| |
| // If WorkStealingSpinToYieldRatio is 0, no hard spinning is done. |
| // If it is greater than 0, then start with a small number |
| // of spins and increase number with each turn at spinning until |
| // the count of hard spins exceeds WorkStealingSpinToYieldRatio. |
| // Then do a yield() call and start spinning afresh. |
| if (WorkStealingSpinToYieldRatio > 0) { |
| hard_spin_limit = WorkStealingHardSpins >> WorkStealingSpinToYieldRatio; |
| hard_spin_limit = MAX2(hard_spin_limit, 1U); |
| } |
| // Remember the initial spin limit. |
| uint hard_spin_start = hard_spin_limit; |
| |
| // Loop waiting for all threads to offer termination or |
| // more work. |
| while (true) { |
| assert(_offered_termination <= _n_threads, "Invariant"); |
| // Are all threads offering termination? |
| if (_offered_termination == _n_threads) { |
| return true; |
| } else { |
| // Look for more work. |
| // Periodically sleep() instead of yield() to give threads |
| // waiting on the cores the chance to grab this code |
| if (yield_count <= WorkStealingYieldsBeforeSleep) { |
| // Do a yield or hardspin. For purposes of deciding whether |
| // to sleep, count this as a yield. |
| yield_count++; |
| |
| // Periodically call yield() instead spinning |
| // After WorkStealingSpinToYieldRatio spins, do a yield() call |
| // and reset the counts and starting limit. |
| if (hard_spin_count > WorkStealingSpinToYieldRatio) { |
| yield(); |
| hard_spin_count = 0; |
| hard_spin_limit = hard_spin_start; |
| #ifdef TRACESPINNING |
| _total_yields++; |
| #endif |
| } else { |
| // Hard spin this time |
| // Increase the hard spinning period but only up to a limit. |
| hard_spin_limit = MIN2(2*hard_spin_limit, |
| (uint) WorkStealingHardSpins); |
| for (uint j = 0; j < hard_spin_limit; j++) { |
| SpinPause(); |
| } |
| hard_spin_count++; |
| #ifdef TRACESPINNING |
| _total_spins++; |
| #endif |
| } |
| } else { |
| log_develop_trace(gc, task)("ParallelTaskTerminator::offer_termination() thread " PTR_FORMAT " sleeps after %u yields", |
| p2i(Thread::current()), yield_count); |
| yield_count = 0; |
| // A sleep will cause this processor to seek work on another processor's |
| // runqueue, if it has nothing else to run (as opposed to the yield |
| // which may only move the thread to the end of the this processor's |
| // runqueue). |
| sleep(WorkStealingSleepMillis); |
| } |
| |
| #ifdef TRACESPINNING |
| _total_peeks++; |
| #endif |
| if (peek_in_queue_set() || |
| (terminator != NULL && terminator->should_exit_termination())) { |
| Atomic::dec((int *)&_offered_termination); |
| assert(_offered_termination < _n_threads, "Invariant"); |
| return false; |
| } |
| } |
| } |
| } |
| |
| #ifdef TRACESPINNING |
| void ParallelTaskTerminator::print_termination_counts() { |
| log_trace(gc, task)("ParallelTaskTerminator Total yields: %u" |
| " Total spins: %u Total peeks: %u", |
| total_yields(), |
| total_spins(), |
| total_peeks()); |
| } |
| #endif |
| |
| void ParallelTaskTerminator::reset_for_reuse() { |
| if (_offered_termination != 0) { |
| assert(_offered_termination == _n_threads, |
| "Terminator may still be in use"); |
| _offered_termination = 0; |
| } |
| } |
| |
| #ifdef ASSERT |
| bool ObjArrayTask::is_valid() const { |
| return _obj != NULL && _obj->is_objArray() && _index >= 0 && |
| _index < objArrayOop(_obj)->length(); |
| } |
| #endif // ASSERT |
| |
| void ParallelTaskTerminator::reset_for_reuse(uint n_threads) { |
| reset_for_reuse(); |
| _n_threads = n_threads; |
| } |