On Wed, Oct 10, 2007 at 09:22:48AM -0700, mike kravetz wrote: > On Wed, Oct 10, 2007 at 10:49:35AM -0400, Gregory Haskins wrote: > > diff --git a/kernel/sched.c b/kernel/sched.c > > index 3e75c62..b7f7a96 100644 > > --- a/kernel/sched.c > > +++ b/kernel/sched.c > > @@ -1869,7 +1869,8 @@ out_activate: > > * extra locking in this particular case, because > > * we are on the current CPU.) > > */ > > - if (TASK_PREEMPTS_CURR(p, this_rq)) > > + if (TASK_PREEMPTS_CURR(p, this_rq) > > + && cpu_isset(this_cpu, p->cpus_allowed)) > > set_tsk_need_resched(this_rq->curr); > > else > > /* > > I wonder if it might better to explicitly take the rq lock and try to > put the task on this_rq in this situation? Rather than waiting for > schedule to pull it from a remote rq as part of balance_rt_tasks. > > A question that has passed through my head a few times is: When waking > a RT task is it better to: > 1) run on current CPU if possible > 2) run on CPU task previously ran on > > I think #1 may result in lower latency. But, if the task has lots of > cache warmth the lower wakeup latency may be negated by running on a > 'remote' cpu. Could we use task_hot() routine to find if the task is cache hot? If it isn't, if possible, we could run on current CPU, else, if possible, on the CPU it last ran on? -- Regards, Ankita Garg (ankita@xxxxxxxxxx) Linux Technology Center IBM India Systems & Technology Labs, Bangalore, India - To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
