jdk-sandbox: comparison hotspot/src/share/vm/utilities/taskqueue.inline.hpp

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+/*
+* Copyright (c) 2015, 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.
+*
+*/
+#ifndef SHARE_VM_UTILITIES_TASKQUEUE_INLINE_HPP
+#define SHARE_VM_UTILITIES_TASKQUEUE_INLINE_HPP
+#include "memory/allocation.inline.hpp"
+#include "oops/oop.inline.hpp"
+#include "utilities/debug.hpp"
+#include "utilities/taskqueue.hpp"
+#include "utilities/stack.inline.hpp"
+#include "runtime/atomic.inline.hpp"
+#include "runtime/orderAccess.inline.hpp"
+template <class T, MEMFLAGS F>
+inline GenericTaskQueueSet<T, F>::GenericTaskQueueSet(int n) : _n(n) {
+typedef T* GenericTaskQueuePtr;
+_queues = NEW_C_HEAP_ARRAY(GenericTaskQueuePtr, n, F);
+for (int i = 0; i < n; i++) {
+_queues[i] = NULL;
+}
+}
+template<class E, MEMFLAGS F, unsigned int N>
+inline void GenericTaskQueue<E, F, N>::initialize() {
+_elems = _array_allocator.allocate(N);
+}
+template<class E, MEMFLAGS F, unsigned int N>
+inline GenericTaskQueue<E, F, N>::~GenericTaskQueue() {
+FREE_C_HEAP_ARRAY(E, _elems);
+}
+template<class E, MEMFLAGS F, unsigned int N>
+bool GenericTaskQueue<E, F, N>::push_slow(E t, uint dirty_n_elems) {
+if (dirty_n_elems == N - 1) {
+// Actually means 0, so do the push.
+uint localBot = _bottom;
+// g++ complains if the volatile result of the assignment is
+// unused, so we cast the volatile away.  We cannot cast directly
+// to void, because gcc treats that as not using the result of the
+// assignment.  However, casting to E& means that we trigger an
+// unused-value warning.  So, we cast the E& to void.
+(void)const_cast<E&>(_elems[localBot] = t);
+OrderAccess::release_store(&_bottom, increment_index(localBot));
+TASKQUEUE_STATS_ONLY(stats.record_push());
+return true;
+}
+return false;
+}
+template<class E, MEMFLAGS F, unsigned int N> inline bool
+GenericTaskQueue<E, F, N>::push(E t) {
+uint localBot = _bottom;
+assert(localBot < N, "_bottom out of range.");
+idx_t top = _age.top();
+uint dirty_n_elems = dirty_size(localBot, top);
+assert(dirty_n_elems < N, "n_elems out of range.");
+if (dirty_n_elems < max_elems()) {
+// g++ complains if the volatile result of the assignment is
+// unused, so we cast the volatile away.  We cannot cast directly
+// to void, because gcc treats that as not using the result of the
+// assignment.  However, casting to E& means that we trigger an
+// unused-value warning.  So, we cast the E& to void.
+(void) const_cast<E&>(_elems[localBot] = t);
+OrderAccess::release_store(&_bottom, increment_index(localBot));
+TASKQUEUE_STATS_ONLY(stats.record_push());
+return true;
+} else {
+return push_slow(t, dirty_n_elems);
+}
+}
+template <class E, MEMFLAGS F, unsigned int N>
+inline bool OverflowTaskQueue<E, F, N>::push(E t)
+{
+if (!taskqueue_t::push(t)) {
+overflow_stack()->push(t);
+TASKQUEUE_STATS_ONLY(stats.record_overflow(overflow_stack()->size()));
+}
+return true;
+}
+// pop_local_slow() is done by the owning thread and is trying to
+// get the last task in the queue.  It will compete with pop_global()
+// that will be used by other threads.  The tag age is incremented
+// whenever the queue goes empty which it will do here if this thread
+// gets the last task or in pop_global() if the queue wraps (top == 0
+// and pop_global() succeeds, see pop_global()).
+template<class E, MEMFLAGS F, unsigned int N>
+bool GenericTaskQueue<E, F, N>::pop_local_slow(uint localBot, Age oldAge) {
+// This queue was observed to contain exactly one element; either this
+// thread will claim it, or a competing "pop_global".  In either case,
+// the queue will be logically empty afterwards.  Create a new Age value
+// that represents the empty queue for the given value of "_bottom".  (We
+// must also increment "tag" because of the case where "bottom == 1",
+// "top == 0".  A pop_global could read the queue element in that case,
+// then have the owner thread do a pop followed by another push.  Without
+// the incrementing of "tag", the pop_global's CAS could succeed,
+// allowing it to believe it has claimed the stale element.)
+Age newAge((idx_t)localBot, oldAge.tag() + 1);
+// Perhaps a competing pop_global has already incremented "top", in which
+// case it wins the element.
+if (localBot == oldAge.top()) {
+// No competing pop_global has yet incremented "top"; we'll try to
+// install new_age, thus claiming the element.
+Age tempAge = _age.cmpxchg(newAge, oldAge);
+if (tempAge == oldAge) {
+// We win.
+assert(dirty_size(localBot, _age.top()) != N - 1, "sanity");
+TASKQUEUE_STATS_ONLY(stats.record_pop_slow());
+return true;
+}
+}
+// We lose; a completing pop_global gets the element.  But the queue is empty
+// and top is greater than bottom.  Fix this representation of the empty queue
+// to become the canonical one.
+_age.set(newAge);
+assert(dirty_size(localBot, _age.top()) != N - 1, "sanity");
+return false;
+}
+template<class E, MEMFLAGS F, unsigned int N> inline bool
+GenericTaskQueue<E, F, N>::pop_local(volatile E& t) {
+uint localBot = _bottom;
+// This value cannot be N-1.  That can only occur as a result of
+// the assignment to bottom in this method.  If it does, this method
+// resets the size to 0 before the next call (which is sequential,
+// since this is pop_local.)
+uint dirty_n_elems = dirty_size(localBot, _age.top());
+assert(dirty_n_elems != N - 1, "Shouldn't be possible...");
+if (dirty_n_elems == 0) return false;
+localBot = decrement_index(localBot);
+_bottom = localBot;
+// This is necessary to prevent any read below from being reordered
+// before the store just above.
+OrderAccess::fence();
+// g++ complains if the volatile result of the assignment is
+// unused, so we cast the volatile away.  We cannot cast directly
+// to void, because gcc treats that as not using the result of the
+// assignment.  However, casting to E& means that we trigger an
+// unused-value warning.  So, we cast the E& to void.
+(void) const_cast<E&>(t = _elems[localBot]);
+// This is a second read of "age"; the "size()" above is the first.
+// If there's still at least one element in the queue, based on the
+// "_bottom" and "age" we've read, then there can be no interference with
+// a "pop_global" operation, and we're done.
+idx_t tp = _age.top();    // XXX
+if (size(localBot, tp) > 0) {
+assert(dirty_size(localBot, tp) != N - 1, "sanity");
+TASKQUEUE_STATS_ONLY(stats.record_pop());
+return true;
+} else {
+// Otherwise, the queue contained exactly one element; we take the slow
+// path.
+return pop_local_slow(localBot, _age.get());
+}
+}
+template <class E, MEMFLAGS F, unsigned int N>
+bool OverflowTaskQueue<E, F, N>::pop_overflow(E& t)
+{
+if (overflow_empty()) return false;
+t = overflow_stack()->pop();
+return true;
+}
+template<class E, MEMFLAGS F, unsigned int N>
+bool GenericTaskQueue<E, F, N>::pop_global(volatile E& t) {
+Age oldAge = _age.get();
+// Architectures with weak memory model require a barrier here
+// to guarantee that bottom is not older than age,
+// which is crucial for the correctness of the algorithm.
+#if !(defined SPARC || defined IA32 || defined AMD64)
+OrderAccess::fence();
+#endif
+uint localBot = OrderAccess::load_acquire((volatile juint*)&_bottom);
+uint n_elems = size(localBot, oldAge.top());
+if (n_elems == 0) {
+return false;
+}
+// g++ complains if the volatile result of the assignment is
+// unused, so we cast the volatile away.  We cannot cast directly
+// to void, because gcc treats that as not using the result of the
+// assignment.  However, casting to E& means that we trigger an
+// unused-value warning.  So, we cast the E& to void.
+(void) const_cast<E&>(t = _elems[oldAge.top()]);
+Age newAge(oldAge);
+newAge.increment();
+Age resAge = _age.cmpxchg(newAge, oldAge);
+// Note that using "_bottom" here might fail, since a pop_local might
+// have decremented it.
+assert(dirty_size(localBot, newAge.top()) != N - 1, "sanity");
+return resAge == oldAge;
+}
+template<class T, MEMFLAGS F> bool
+GenericTaskQueueSet<T, F>::steal_best_of_2(uint queue_num, int* seed, E& t) {
+if (_n > 2) {
+uint k1 = queue_num;
+while (k1 == queue_num) k1 = TaskQueueSetSuper::randomParkAndMiller(seed) % _n;
+uint k2 = queue_num;
+while (k2 == queue_num || k2 == k1) k2 = TaskQueueSetSuper::randomParkAndMiller(seed) % _n;
+// Sample both and try the larger.
+uint sz1 = _queues[k1]->size();
+uint sz2 = _queues[k2]->size();
+if (sz2 > sz1) return _queues[k2]->pop_global(t);
+else return _queues[k1]->pop_global(t);
+} else if (_n == 2) {
+// Just try the other one.
+uint k = (queue_num + 1) % 2;
+return _queues[k]->pop_global(t);
+} else {
+assert(_n == 1, "can't be zero.");
+return false;
+}
+}
+template<class T, MEMFLAGS F> bool
+GenericTaskQueueSet<T, F>::steal(uint queue_num, int* seed, E& t) {
+for (uint i = 0; i < 2 * _n; i++) {
+if (steal_best_of_2(queue_num, seed, t)) {
+TASKQUEUE_STATS_ONLY(queue(queue_num)->stats.record_steal(true));
+return true;
+}
+}
+TASKQUEUE_STATS_ONLY(queue(queue_num)->stats.record_steal(false));
+return false;
+}
+template <unsigned int N, MEMFLAGS F>
+inline typename TaskQueueSuper<N, F>::Age TaskQueueSuper<N, F>::Age::cmpxchg(const Age new_age, const Age old_age) volatile {
+return (size_t) Atomic::cmpxchg_ptr((intptr_t)new_age._data,
+(volatile intptr_t *)&_data,
+(intptr_t)old_age._data);
+}
+template<class E, MEMFLAGS F, unsigned int N>
+inline void GenericTaskQueue<E, F, N>::oops_do(OopClosure* f) {
+// tty->print_cr("START OopTaskQueue::oops_do");
+uint iters = size();
+uint index = _bottom;
+for (uint i = 0; i < iters; ++i) {
+index = decrement_index(index);
+// tty->print_cr("  doing entry %d," INTPTR_T " -> " INTPTR_T,
+//            index, &_elems[index], _elems[index]);
+E* t = (E*)&_elems[index];      // cast away volatility
+oop* p = (oop*)t;
+assert((*t)->is_oop_or_null(), err_msg("Expected an oop or NULL at " PTR_FORMAT, p2i(*t)));
+f->do_oop(p);
+}
+// tty->print_cr("END OopTaskQueue::oops_do");
+}
+#endif // SHARE_VM_UTILITIES_TASKQUEUE_INLINE_HPP