/**
* Run a scheduler thread until termination.
*/
static void run(scheduler_t* sched)
{
pony_actor_t* actor = pop_global(sched);
while(true)
{
if(actor == NULL)
{
// We had an empty queue and no rescheduled actor.
actor = steal(sched, NULL);
if(actor == NULL)
{
// Termination.
assert(pop(sched) == NULL);
return;
}
}
// Run the current actor and get the next actor.
bool reschedule = ponyint_actor_run(&sched->ctx, actor, SCHED_BATCH);
pony_actor_t* next = pop_global(sched);
if(reschedule)
{
if(next != NULL)
{
// If we have a next actor, we go on the back of the queue. Otherwise,
// we continue to run this actor.
push(sched, actor);
actor = next;
} else if(ponyint_is_cycle(actor)) {
// If all we have is the cycle detector, try to steal something else to
// run as well.
next = steal(sched, actor);
if(next == NULL)
{
// Termination.
return;
}
// Push the cycle detector and run the actor we stole.
if(actor != next)
{
push(sched, actor);
actor = next;
}
}
} else {
// We aren't rescheduling, so run the next actor. This may be NULL if our
// queue was empty.
actor = next;
}
}
}
/**
* Use mpmcqs to allow stealing directly from a victim, without waiting for a
* response.
*/
static pony_actor_t* steal(scheduler_t* sched, pony_actor_t* prev)
{
send_msg(0, SCHED_BLOCK, 0);
uint64_t tsc = ponyint_cpu_tick();
pony_actor_t* actor;
while(true)
{
scheduler_t* victim = choose_victim(sched);
if(victim == NULL)
actor = (pony_actor_t*)ponyint_mpmcq_pop(&inject);
else
actor = pop_global(victim);
if(actor != NULL)
{
DTRACE3(WORK_STEAL_SUCCESSFUL, (uintptr_t)sched, (uintptr_t)victim, (uintptr_t)actor);
break;
}
uint64_t tsc2 = ponyint_cpu_tick();
if(quiescent(sched, tsc, tsc2))
{
DTRACE2(WORK_STEAL_FAILURE, (uintptr_t)sched, (uintptr_t)victim);
return NULL;
}
// If we have been passed an actor (implicitly, the cycle detector), and
// enough time has elapsed without stealing or quiescing, return the actor
// we were passed (allowing the cycle detector to run).
if((prev != NULL) && ((tsc2 - tsc) > 10000000000))
{
actor = prev;
break;
}
}
send_msg(0, SCHED_UNBLOCK, 0);
return actor;
}
/**
* Use mpmcqs to allow stealing directly from a victim, without waiting for a
* response.
*/
static pony_actor_t* steal(scheduler_t* sched, pony_actor_t* prev)
{
send_msg(0, SCHED_BLOCK, 0);
uint64_t tsc = ponyint_cpu_tick();
pony_actor_t* actor;
while(true)
{
scheduler_t* victim = choose_victim(sched);
if(victim == NULL)
victim = sched;
actor = pop_global(victim);
if(actor != NULL)
break;
uint64_t tsc2 = ponyint_cpu_tick();
if(quiescent(sched, tsc, tsc2))
return NULL;
// If we have been passed an actor (implicitly, the cycle detector), and
// enough time has elapsed without stealing or quiescing, return the actor
// we were passed (allowing the cycle detector to run).
if((prev != NULL) && ((tsc2 - tsc) > 10000000000))
{
actor = prev;
break;
}
}
send_msg(0, SCHED_UNBLOCK, 0);
return actor;
}
