Re: [PATCH] sched: next buddy hint on sleep and preempt path
From: Venkatesh Pallipadi
Date: Wed Mar 02 2011 - 14:12:10 EST
On Tue, Mar 1, 2011 at 10:47 PM, Mike Galbraith <efault@xxxxxx> wrote:
> On Tue, 2011-03-01 at 21:43 -0800, Paul Turner wrote:
>> On Tue, Mar 1, 2011 at 3:33 PM, Venkatesh Pallipadi <venki@xxxxxxxxxx> wrote:
>
>> > for_each_sched_entity(se) {
>> > cfs_rq = cfs_rq_of(se);
>> > dequeue_entity(cfs_rq, se, flags);
>> >
>> > /* Don't dequeue parent if it has other entities besides us */
>> > - if (cfs_rq->load.weight)
>> > + if (cfs_rq->load.weight) {
>> > + /*
>> > + * Bias pick_next to pick a task from this cfs_rq, as
>> > + * p is sleeping when it is within its sched_slice.
>> > + */
>> > + if (task_flags & DEQUEUE_SLEEP && se->parent)
>> > + set_next_buddy(se->parent);
>>
>> re-using the last_buddy would seem like a more natural fit here; also
>> doesn't have a clobber race with a wakeup
>
> Hm, that would break last_buddy no? A preempted task won't get the CPU
> back after light preempting thread deactivates. (it's disabled atm
> unless heavily overloaded anyway, but..)
>
> This wants a tweak either way though.
>
> static inline struct task_struct *task_of(struct sched_entity *se)
> {
> #ifdef CONFIG_SCHED_DEBUG
> WARN_ON_ONCE(!entity_is_task(se));
> #endif
> return container_of(se, struct task_struct, se);
> }
>
> static void set_next_buddy(struct sched_entity *se)
> {
> if (likely(task_of(se)->policy != SCHED_IDLE)) {
> for_each_sched_entity(se)
> cfs_rq_of(se)->next = se;
> }
> }
>
Yes. Thanks for pointing this out. Will handle this in patch-respin.
Thanks,
Venki
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/