Re: [PATCH] sched: activate SCHED BATCH expired

Nick Piggin
2006-03-17T13:26:22Z

Con Kolivas wrote:

>
> Ok here's a patch that does exactly that. Without an "inline" hint, gcc 4.1.0
> chooses not to inline this function. I can't say I have a strong opinion
> about whether it should be inlined or not (93 bytes larger inlined), so I've
> decided not to given the current trend.
>

Sigh, sacrifice for the common case! :P

> Index: linux-2.6.16-rc6-mm1/kernel/sched.c
> ===================================================================
> --- linux-2.6.16-rc6-mm1.orig/kernel/sched.c 2006-03-13 20:12:15.000000000 +1100
> +++ linux-2.6.16-rc6-mm1/kernel/sched.c 2006-03-17 23:08:12.000000000 +1100
> @@ -737,9 +737,12 @@ static inline void dec_nr_running(task_t
> /*
> * __activate_task - move a task to the runqueue.
> */
> -static inline void __activate_task(task_t *p, runqueue_t *rq)
> +static void __activate_task(task_t *p, runqueue_t *rq)
> {
> - enqueue_task(p, rq->active);
> + if (batch_task(p))
> + enqueue_task(p, rq->expired);
> + else
> + enqueue_task(p, rq->active);
> inc_nr_running(p, rq);
> }
>

I prefer:

prio_array_t *target = rq->active;
if (batch_task(p))
target = rq->expired;
enqueue_task(p, target);

Because gcc can use things like predicated instructions for it.
But perhaps it is smart enough these days to recognise this?
At least in the past I have seen it start using cmov after doing
such a conversion.

At any rate, I think it looks nicer as well. IMO, of course.

--
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com