Ejemplo n.º 1
0
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;
}
Ejemplo n.º 2
0
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;
}
Ejemplo n.º 3
0
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;
}
Ejemplo n.º 4
0
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;
}
Ejemplo n.º 5
0
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);
  }
}
Ejemplo n.º 6
0
void StealTask::do_it(GCTaskManager* manager, uint which) {
  assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");

  PSPromotionManager* pm =
    PSPromotionManager::gc_thread_promotion_manager(which);
  pm->drain_stacks(true);
  guarantee(pm->stacks_empty(),
            "stacks should be empty at this point");

  int random_seed = 17;
  while(true) {
    StarTask p;
    if (PSPromotionManager::steal_depth(which, &random_seed, p)) {
      TASKQUEUE_STATS_ONLY(pm->record_steal(p));
      pm->process_popped_location_depth(p);
      pm->drain_stacks_depth(true);
    } else {
      if (terminator()->offer_termination()) {
        break;
      }
    }
  }
  guarantee(pm->stacks_empty(), "stacks should be empty at this point");
}
Ejemplo n.º 7
0
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());
  }
}