* Peter Zijlstra ([email protected]) wrote:
> Would have been nice if you'd CC'ed me :-/
>
Sorry
> On Sat, 2007-07-14 at 14:42 -0400, Mathieu Desnoyers wrote:
>
> > @@ -4891,10 +4948,42 @@ static int migration_thread(void *data)
> > list_del_init(head->next);
> >
> > spin_unlock(&rq->lock);
> > - __migrate_task(req->task, cpu, req->dest_cpu);
> > + migrated = __migrate_task(req->task, cpu, req->dest_cpu);
> > local_irq_enable();
> > -
> > - complete(&req->done);
> > + if (!migrated) {
> > + /*
> > + * If the process has not been migrated, let it run
> > + * until it reaches a migration_check() so it can
> > + * wake us up.
> > + */
> > + spin_lock_irq(&rq->lock);
> > + head = &rq->migration_queue;
> > + list_add(&req->list, head);
> > + if (req->task->se.on_rq
> > + || !task_migrate_count(req->task)) {
> > + /*
> > + * The process is on the runqueue, it could
> > + * exit its critical section at any moment,
> > + * don't race with it and retry actively.
> > + * Also, if the thread is not on the runqueue
> > + * and has a zero migration count
> > + * (__migrate_task failed because cpus allowed
> > + * changed), just retry.
> > + */
> > + spin_unlock_irq(&rq->lock);
> > + continue;
> > + }
> > + set_tsk_thread_flag(req->task, TIF_NEED_MIGRATE);
> > + set_current_state(TASK_INTERRUPTIBLE);
> > + spin_unlock_irq(&rq->lock);
> > + /*
> > + * Wait for the process currently in its critical
> > + * section.
> > + */
> > + wake_up_process(req->task);
> > + schedule();
> > + } else
> > + complete(&req->done);
> > }
> > __set_current_state(TASK_RUNNING);
> > return 0;
>
> I'm not really liking this, this way we hold up all other migration
> requests.
>
True. You approach of delayed migration helps on this.
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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