taskqueue.hpp revision 1879
0N/A/*
1834N/A * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
0N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
0N/A *
0N/A * This code is free software; you can redistribute it and/or modify it
0N/A * under the terms of the GNU General Public License version 2 only, as
0N/A * published by the Free Software Foundation.
0N/A *
0N/A * This code is distributed in the hope that it will be useful, but WITHOUT
0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
0N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
0N/A * version 2 for more details (a copy is included in the LICENSE file that
0N/A * accompanied this code).
0N/A *
0N/A * You should have received a copy of the GNU General Public License version
0N/A * 2 along with this work; if not, write to the Free Software Foundation,
0N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
0N/A *
1472N/A * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1472N/A * or visit www.oracle.com if you need additional information or have any
1472N/A * questions.
0N/A *
0N/A */
0N/A
1879N/A#ifndef SHARE_VM_UTILITIES_TASKQUEUE_HPP
1879N/A#define SHARE_VM_UTILITIES_TASKQUEUE_HPP
1879N/A
1879N/A#include "memory/allocation.hpp"
1879N/A#include "memory/allocation.inline.hpp"
1879N/A#include "runtime/mutex.hpp"
1879N/A#include "utilities/stack.hpp"
1879N/A#ifdef TARGET_OS_ARCH_linux_x86
1879N/A# include "orderAccess_linux_x86.inline.hpp"
1879N/A#endif
1879N/A#ifdef TARGET_OS_ARCH_linux_sparc
1879N/A# include "orderAccess_linux_sparc.inline.hpp"
0N/A#endif
0N/A#ifdef TARGET_OS_ARCH_linux_zero
0N/A# include "orderAccess_linux_zero.inline.hpp"
0N/A#endif
0N/A#ifdef TARGET_OS_ARCH_solaris_x86
0N/A# include "orderAccess_solaris_x86.inline.hpp"
0N/A#endif
0N/A#ifdef TARGET_OS_ARCH_solaris_sparc
0N/A# include "orderAccess_solaris_sparc.inline.hpp"
0N/A#endif
0N/A#ifdef TARGET_OS_ARCH_windows_x86
0N/A# include "orderAccess_windows_x86.inline.hpp"
0N/A#endif
0N/A
0N/A// Simple TaskQueue stats that are collected by default in debug builds.
0N/A
0N/A#if !defined(TASKQUEUE_STATS) && defined(ASSERT)
0N/A#define TASKQUEUE_STATS 1
0N/A#elif !defined(TASKQUEUE_STATS)
0N/A#define TASKQUEUE_STATS 0
0N/A#endif
0N/A
0N/A#if TASKQUEUE_STATS
0N/A#define TASKQUEUE_STATS_ONLY(code) code
0N/A#else
2664N/A#define TASKQUEUE_STATS_ONLY(code)
2664N/A#endif // TASKQUEUE_STATS
2664N/A
2664N/A#if TASKQUEUE_STATS
2664N/Aclass TaskQueueStats {
0N/Apublic:
0N/A enum StatId {
0N/A push, // number of taskqueue pushes
0N/A pop, // number of taskqueue pops
1968N/A pop_slow, // subset of taskqueue pops that were done slow-path
0N/A steal_attempt, // number of taskqueue steal attempts
0N/A steal, // number of taskqueue steals
675N/A overflow, // number of overflow pushes
0N/A overflow_max_len, // max length of overflow stack
1968N/A last_stat_id
1968N/A };
1968N/A
1968N/Apublic:
1968N/A inline TaskQueueStats() { reset(); }
1968N/A
1968N/A inline void record_push() { ++_stats[push]; }
1968N/A inline void record_pop() { ++_stats[pop]; }
1968N/A inline void record_pop_slow() { record_pop(); ++_stats[pop_slow]; }
1968N/A inline void record_steal(bool success);
113N/A inline void record_overflow(size_t new_length);
642N/A
642N/A TaskQueueStats & operator +=(const TaskQueueStats & addend);
642N/A
113N/A inline size_t get(StatId id) const { return _stats[id]; }
0N/A inline const size_t* get() const { return _stats; }
0N/A
0N/A inline void reset();
675N/A
0N/A // Print the specified line of the header (does not include a line separator).
0N/A static void print_header(unsigned int line, outputStream* const stream = tty,
0N/A unsigned int width = 10);
0N/A // Print the statistics (does not include a line separator).
675N/A void print(outputStream* const stream = tty, unsigned int width = 10) const;
0N/A
1968N/A DEBUG_ONLY(void verify() const;)
1834N/A
1834N/Aprivate:
1367N/A size_t _stats[last_stat_id];
1367N/A static const char * const _names[last_stat_id];
1367N/A};
1367N/A
1367N/Avoid TaskQueueStats::record_steal(bool success) {
1367N/A ++_stats[steal_attempt];
1367N/A if (success) ++_stats[steal];
1367N/A}
1367N/A
1367N/Avoid TaskQueueStats::record_overflow(size_t new_len) {
1367N/A ++_stats[overflow];
0N/A if (new_len > _stats[overflow_max_len]) _stats[overflow_max_len] = new_len;
0N/A}
0N/A
0N/Avoid TaskQueueStats::reset() {
643N/A memset(_stats, 0, sizeof(_stats));
643N/A}
643N/A#endif // TASKQUEUE_STATS
675N/A
643N/Atemplate <unsigned int N>
2664N/Aclass TaskQueueSuper: public CHeapObj {
2664N/Aprotected:
2664N/A // Internal type for indexing the queue; also used for the tag.
2664N/A typedef NOT_LP64(uint16_t) LP64_ONLY(uint32_t) idx_t;
2664N/A
2664N/A // The first free element after the last one pushed (mod N).
2664N/A volatile uint _bottom;
2664N/A
2664N/A enum { MOD_N_MASK = N - 1 };
2664N/A
2664N/A class Age {
2664N/A public:
2664N/A Age(size_t data = 0) { _data = data; }
643N/A Age(const Age& age) { _data = age._data; }
643N/A Age(idx_t top, idx_t tag) { _fields._top = top; _fields._tag = tag; }
1650N/A
2664N/A Age get() const volatile { return _data; }
2664N/A void set(Age age) volatile { _data = age._data; }
2664N/A
2664N/A idx_t top() const volatile { return _fields._top; }
2664N/A idx_t tag() const volatile { return _fields._tag; }
1650N/A
1650N/A // Increment top; if it wraps, increment tag also.
1650N/A void increment() {
1650N/A _fields._top = increment_index(_fields._top);
0N/A if (_fields._top == 0) ++_fields._tag;
2664N/A }
2664N/A
643N/A Age cmpxchg(const Age new_age, const Age old_age) volatile {
2664N/A return (size_t) Atomic::cmpxchg_ptr((intptr_t)new_age._data,
2664N/A (volatile intptr_t *)&_data,
2664N/A (intptr_t)old_age._data);
2664N/A }
2664N/A
2664N/A bool operator ==(const Age& other) const { return _data == other._data; }
2664N/A
2664N/A private:
2664N/A struct fields {
641N/A idx_t _top;
641N/A idx_t _tag;
0N/A };
0N/A union {
0N/A size_t _data;
0N/A fields _fields;
0N/A };
2629N/A };
2629N/A
2629N/A volatile Age _age;
2629N/A
2629N/A // These both operate mod N.
2629N/A static uint increment_index(uint ind) {
2629N/A return (ind + 1) & MOD_N_MASK;
2629N/A }
2629N/A static uint decrement_index(uint ind) {
2629N/A return (ind - 1) & MOD_N_MASK;
2629N/A }
2629N/A
0N/A // Returns a number in the range [0..N). If the result is "N-1", it should be
0N/A // interpreted as 0.
0N/A uint dirty_size(uint bot, uint top) const {
0N/A return (bot - top) & MOD_N_MASK;
0N/A }
0N/A
0N/A // Returns the size corresponding to the given "bot" and "top".
0N/A uint size(uint bot, uint top) const {
0N/A uint sz = dirty_size(bot, top);
0N/A // Has the queue "wrapped", so that bottom is less than top? There's a
0N/A // complicated special case here. A pair of threads could perform pop_local
0N/A // and pop_global operations concurrently, starting from a state in which
0N/A // _bottom == _top+1. The pop_local could succeed in decrementing _bottom,
0N/A // and the pop_global in incrementing _top (in which case the pop_global
0N/A // will be awarded the contested queue element.) The resulting state must
0N/A // be interpreted as an empty queue. (We only need to worry about one such
0N/A // event: only the queue owner performs pop_local's, and several concurrent
0N/A // threads attempting to perform the pop_global will all perform the same
0N/A // CAS, and only one can succeed.) Any stealing thread that reads after
0N/A // either the increment or decrement will see an empty queue, and will not
0N/A // join the competitors. The "sz == -1 || sz == N-1" state will not be
0N/A // modified by concurrent queues, so the owner thread can reset the state to
0N/A // _bottom == top so subsequent pushes will be performed normally.
0N/A return (sz == N - 1) ? 0 : sz;
0N/A }
0N/A
0N/Apublic:
0N/A TaskQueueSuper() : _bottom(0), _age() {}
0N/A
0N/A // Return true if the TaskQueue contains/does not contain any tasks.
0N/A bool peek() const { return _bottom != _age.top(); }
0N/A bool is_empty() const { return size() == 0; }
0N/A
0N/A // Return an estimate of the number of elements in the queue.
0N/A // The "careful" version admits the possibility of pop_local/pop_global
0N/A // races.
0N/A uint size() const {
0N/A return size(_bottom, _age.top());
0N/A }
0N/A
0N/A uint dirty_size() const {
0N/A return dirty_size(_bottom, _age.top());
1968N/A }
1968N/A
1968N/A void set_empty() {
0N/A _bottom = 0;
0N/A _age.set(0);
0N/A }
1968N/A
0N/A // Maximum number of elements allowed in the queue. This is two less
0N/A // than the actual queue size, for somewhat complicated reasons.
1968N/A uint max_elems() const { return N - 2; }
0N/A
1968N/A // Total size of queue.
0N/A static const uint total_size() { return N; }
0N/A
0N/A TASKQUEUE_STATS_ONLY(TaskQueueStats stats;)
0N/A};
0N/A
0N/Atemplate<class E, unsigned int N = TASKQUEUE_SIZE>
0N/Aclass GenericTaskQueue: public TaskQueueSuper<N> {
0N/Aprotected:
0N/A typedef typename TaskQueueSuper<N>::Age Age;
0N/A typedef typename TaskQueueSuper<N>::idx_t idx_t;
0N/A
0N/A using TaskQueueSuper<N>::_bottom;
0N/A using TaskQueueSuper<N>::_age;
0N/A using TaskQueueSuper<N>::increment_index;
0N/A using TaskQueueSuper<N>::decrement_index;
0N/A using TaskQueueSuper<N>::dirty_size;
0N/A
0N/Apublic:
10N/A using TaskQueueSuper<N>::max_elems;
10N/A using TaskQueueSuper<N>::size;
10N/A TASKQUEUE_STATS_ONLY(using TaskQueueSuper<N>::stats;)
1968N/A
10N/Aprivate:
10N/A // Slow paths for push, pop_local. (pop_global has no fast path.)
10N/A bool push_slow(E t, uint dirty_n_elems);
10N/A bool pop_local_slow(uint localBot, Age oldAge);
10N/A
10N/Apublic:
typedef E element_type;
// Initializes the queue to empty.
GenericTaskQueue();
void initialize();
// Push the task "t" on the queue. Returns "false" iff the queue is full.
inline bool push(E t);
// Attempts to claim a task from the "local" end of the queue (the most
// recently pushed). If successful, returns true and sets t to the task;
// otherwise, returns false (the queue is empty).
inline bool pop_local(E& t);
// Like pop_local(), but uses the "global" end of the queue (the least
// recently pushed).
bool pop_global(E& t);
// Delete any resource associated with the queue.
~GenericTaskQueue();
// apply the closure to all elements in the task queue
void oops_do(OopClosure* f);
private:
// Element array.
volatile E* _elems;
};
template<class E, unsigned int N>
GenericTaskQueue<E, N>::GenericTaskQueue() {
assert(sizeof(Age) == sizeof(size_t), "Depends on this.");
}
template<class E, unsigned int N>
void GenericTaskQueue<E, N>::initialize() {
_elems = NEW_C_HEAP_ARRAY(E, N);
}
template<class E, unsigned int N>
void GenericTaskQueue<E, 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(), "Not an oop or null");
f->do_oop(p);
}
// tty->print_cr("END OopTaskQueue::oops_do");
}
template<class E, unsigned int N>
bool GenericTaskQueue<E, 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.
const_cast<E&>(_elems[localBot] = t);
OrderAccess::release_store(&_bottom, increment_index(localBot));
TASKQUEUE_STATS_ONLY(stats.record_push());
return true;
}
return false;
}
// 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, unsigned int N>
bool GenericTaskQueue<E, 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, unsigned int N>
bool GenericTaskQueue<E, N>::pop_global(E& t) {
Age oldAge = _age.get();
uint localBot = _bottom;
uint n_elems = size(localBot, oldAge.top());
if (n_elems == 0) {
return false;
}
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 E, unsigned int N>
GenericTaskQueue<E, N>::~GenericTaskQueue() {
FREE_C_HEAP_ARRAY(E, _elems);
}
// OverflowTaskQueue is a TaskQueue that also includes an overflow stack for
// elements that do not fit in the TaskQueue.
//
// This class hides two methods from super classes:
//
// push() - push onto the task queue or, if that fails, onto the overflow stack
// is_empty() - return true if both the TaskQueue and overflow stack are empty
//
// Note that size() is not hidden--it returns the number of elements in the
// TaskQueue, and does not include the size of the overflow stack. This
// simplifies replacement of GenericTaskQueues with OverflowTaskQueues.
template<class E, unsigned int N = TASKQUEUE_SIZE>
class OverflowTaskQueue: public GenericTaskQueue<E, N>
{
public:
typedef Stack<E> overflow_t;
typedef GenericTaskQueue<E, N> taskqueue_t;
TASKQUEUE_STATS_ONLY(using taskqueue_t::stats;)
// Push task t onto the queue or onto the overflow stack. Return true.
inline bool push(E t);
// Attempt to pop from the overflow stack; return true if anything was popped.
inline bool pop_overflow(E& t);
inline overflow_t* overflow_stack() { return &_overflow_stack; }
inline bool taskqueue_empty() const { return taskqueue_t::is_empty(); }
inline bool overflow_empty() const { return _overflow_stack.is_empty(); }
inline bool is_empty() const {
return taskqueue_empty() && overflow_empty();
}
private:
overflow_t _overflow_stack;
};
template <class E, unsigned int N>
bool OverflowTaskQueue<E, N>::push(E t)
{
if (!taskqueue_t::push(t)) {
overflow_stack()->push(t);
TASKQUEUE_STATS_ONLY(stats.record_overflow(overflow_stack()->size()));
}
return true;
}
template <class E, unsigned int N>
bool OverflowTaskQueue<E, N>::pop_overflow(E& t)
{
if (overflow_empty()) return false;
t = overflow_stack()->pop();
return true;
}
class TaskQueueSetSuper: public CHeapObj {
protected:
static int randomParkAndMiller(int* seed0);
public:
// Returns "true" if some TaskQueue in the set contains a task.
virtual bool peek() = 0;
};
template<class T>
class GenericTaskQueueSet: public TaskQueueSetSuper {
private:
uint _n;
T** _queues;
public:
typedef typename T::element_type E;
GenericTaskQueueSet(int n) : _n(n) {
typedef T* GenericTaskQueuePtr;
_queues = NEW_C_HEAP_ARRAY(GenericTaskQueuePtr, n);
for (int i = 0; i < n; i++) {
_queues[i] = NULL;
}
}
bool steal_1_random(uint queue_num, int* seed, E& t);
bool steal_best_of_2(uint queue_num, int* seed, E& t);
bool steal_best_of_all(uint queue_num, int* seed, E& t);
void register_queue(uint i, T* q);
T* queue(uint n);
// The thread with queue number "queue_num" (and whose random number seed is
// at "seed") is trying to steal a task from some other queue. (It may try
// several queues, according to some configuration parameter.) If some steal
// succeeds, returns "true" and sets "t" to the stolen task, otherwise returns
// false.
bool steal(uint queue_num, int* seed, E& t);
bool peek();
};
template<class T> void
GenericTaskQueueSet<T>::register_queue(uint i, T* q) {
assert(i < _n, "index out of range.");
_queues[i] = q;
}
template<class T> T*
GenericTaskQueueSet<T>::queue(uint i) {
return _queues[i];
}
template<class T> bool
GenericTaskQueueSet<T>::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<class T> bool
GenericTaskQueueSet<T>::steal_best_of_all(uint queue_num, int* seed, E& t) {
if (_n > 2) {
int best_k;
uint best_sz = 0;
for (uint k = 0; k < _n; k++) {
if (k == queue_num) continue;
uint sz = _queues[k]->size();
if (sz > best_sz) {
best_sz = sz;
best_k = k;
}
}
return best_sz > 0 && _queues[best_k]->pop_global(t);
} else if (_n == 2) {
// Just try the other one.
int k = (queue_num + 1) % 2;
return _queues[k]->pop_global(t);
} else {
assert(_n == 1, "can't be zero.");
return false;
}
}
template<class T> bool
GenericTaskQueueSet<T>::steal_1_random(uint queue_num, int* seed, E& t) {
if (_n > 2) {
uint k = queue_num;
while (k == queue_num) k = randomParkAndMiller(seed) % _n;
return _queues[2]->pop_global(t);
} else if (_n == 2) {
// Just try the other one.
int k = (queue_num + 1) % 2;
return _queues[k]->pop_global(t);
} else {
assert(_n == 1, "can't be zero.");
return false;
}
}
template<class T> bool
GenericTaskQueueSet<T>::steal_best_of_2(uint queue_num, int* seed, E& t) {
if (_n > 2) {
uint k1 = queue_num;
while (k1 == queue_num) k1 = randomParkAndMiller(seed) % _n;
uint k2 = queue_num;
while (k2 == queue_num || k2 == k1) k2 = 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>
bool GenericTaskQueueSet<T>::peek() {
// Try all the queues.
for (uint j = 0; j < _n; j++) {
if (_queues[j]->peek())
return true;
}
return false;
}
// When to terminate from the termination protocol.
class TerminatorTerminator: public CHeapObj {
public:
virtual bool should_exit_termination() = 0;
};
// A class to aid in the termination of a set of parallel tasks using
// TaskQueueSet's for work stealing.
#undef TRACESPINNING
class ParallelTaskTerminator: public StackObj {
private:
int _n_threads;
TaskQueueSetSuper* _queue_set;
int _offered_termination;
#ifdef TRACESPINNING
static uint _total_yields;
static uint _total_spins;
static uint _total_peeks;
#endif
bool peek_in_queue_set();
protected:
virtual void yield();
void sleep(uint millis);
public:
// "n_threads" is the number of threads to be terminated. "queue_set" is a
// queue sets of work queues of other threads.
ParallelTaskTerminator(int n_threads, TaskQueueSetSuper* queue_set);
// The current thread has no work, and is ready to terminate if everyone
// else is. If returns "true", all threads are terminated. If returns
// "false", available work has been observed in one of the task queues,
// so the global task is not complete.
bool offer_termination() {
return offer_termination(NULL);
}
// As above, but it also terminates if the should_exit_termination()
// method of the terminator parameter returns true. If terminator is
// NULL, then it is ignored.
bool offer_termination(TerminatorTerminator* terminator);
// Reset the terminator, so that it may be reused again.
// The caller is responsible for ensuring that this is done
// in an MT-safe manner, once the previous round of use of
// the terminator is finished.
void reset_for_reuse();
// Same as above but the number of parallel threads is set to the
// given number.
void reset_for_reuse(int n_threads);
#ifdef TRACESPINNING
static uint total_yields() { return _total_yields; }
static uint total_spins() { return _total_spins; }
static uint total_peeks() { return _total_peeks; }
static void print_termination_counts();
#endif
};
template<class E, unsigned int N> inline bool
GenericTaskQueue<E, N>::push(E t) {
uint localBot = _bottom;
assert((localBot >= 0) && (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.
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, unsigned int N> inline bool
GenericTaskQueue<E, N>::pop_local(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();
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());
}
}
typedef GenericTaskQueue<oop> OopTaskQueue;
typedef GenericTaskQueueSet<OopTaskQueue> OopTaskQueueSet;
#ifdef _MSC_VER
#pragma warning(push)
// warning C4522: multiple assignment operators specified
#pragma warning(disable:4522)
#endif
// This is a container class for either an oop* or a narrowOop*.
// Both are pushed onto a task queue and the consumer will test is_narrow()
// to determine which should be processed.
class StarTask {
void* _holder; // either union oop* or narrowOop*
enum { COMPRESSED_OOP_MASK = 1 };
public:
StarTask(narrowOop* p) {
assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!");
_holder = (void *)((uintptr_t)p | COMPRESSED_OOP_MASK);
}
StarTask(oop* p) {
assert(((uintptr_t)p & COMPRESSED_OOP_MASK) == 0, "Information loss!");
_holder = (void*)p;
}
StarTask() { _holder = NULL; }
operator oop*() { return (oop*)_holder; }
operator narrowOop*() {
return (narrowOop*)((uintptr_t)_holder & ~COMPRESSED_OOP_MASK);
}
StarTask& operator=(const StarTask& t) {
_holder = t._holder;
return *this;
}
volatile StarTask& operator=(const volatile StarTask& t) volatile {
_holder = t._holder;
return *this;
}
bool is_narrow() const {
return (((uintptr_t)_holder & COMPRESSED_OOP_MASK) != 0);
}
};
class ObjArrayTask
{
public:
ObjArrayTask(oop o = NULL, int idx = 0): _obj(o), _index(idx) { }
ObjArrayTask(oop o, size_t idx): _obj(o), _index(int(idx)) {
assert(idx <= size_t(max_jint), "too big");
}
ObjArrayTask(const ObjArrayTask& t): _obj(t._obj), _index(t._index) { }
ObjArrayTask& operator =(const ObjArrayTask& t) {
_obj = t._obj;
_index = t._index;
return *this;
}
volatile ObjArrayTask&
operator =(const volatile ObjArrayTask& t) volatile {
_obj = t._obj;
_index = t._index;
return *this;
}
inline oop obj() const { return _obj; }
inline int index() const { return _index; }
DEBUG_ONLY(bool is_valid() const); // Tasks to be pushed/popped must be valid.
private:
oop _obj;
int _index;
};
#ifdef _MSC_VER
#pragma warning(pop)
#endif
typedef OverflowTaskQueue<StarTask> OopStarTaskQueue;
typedef GenericTaskQueueSet<OopStarTaskQueue> OopStarTaskQueueSet;
typedef OverflowTaskQueue<size_t> RegionTaskQueue;
typedef GenericTaskQueueSet<RegionTaskQueue> RegionTaskQueueSet;
#endif // SHARE_VM_UTILITIES_TASKQUEUE_HPP