Re: [PATCH 2/6] sched: rt-bandwidth accounting fix

Max Krasnyansky
2008-08-19T18:34:16Z

Peter Zijlstra wrote:
> It fixes an accounting bug where we would continue accumulating runtime
> even though the bandwidth control is disabled. This would lead to very long
> throttle periods once bandwidth control gets turned on again.
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
> kernel/sched_rt.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> Index: linux-2.6/kernel/sched_rt.c
> ===================================================================
> --- linux-2.6.orig/kernel/sched_rt.c
> +++ linux-2.6/kernel/sched_rt.c
> @@ -438,9 +438,6 @@ static int sched_rt_runtime_exceeded(str
> {
> u64 runtime = sched_rt_runtime(rt_rq);
>
> - if (runtime == RUNTIME_INF)
> - return 0;
> -
> if (rt_rq->rt_throttled)
> return rt_rq_throttled(rt_rq);
>
> @@ -491,9 +488,11 @@ static void update_curr_rt(struct rq *rq
> rt_rq = rt_rq_of_se(rt_se);
>
> spin_lock(&rt_rq->rt_runtime_lock);
> - rt_rq->rt_time += delta_exec;
> - if (sched_rt_runtime_exceeded(rt_rq))
> - resched_task(curr);
> + if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
> + rt_rq->rt_time += delta_exec;
> + if (sched_rt_runtime_exceeded(rt_rq))
> + resched_task(curr);
> + }
> spin_unlock(&rt_rq->rt_runtime_lock);
> }
> }

This will make 'disabled' case more expensive, will it not ?
I mean now we'll have to run balance_runtime() even if throttling is
disabled.

Do you guys mind if I make this stuff configurable ? ie Just like
CONFIG_RT_GROUP_SCHED we could add CONFIG_RT_BANDWIDTH_THROTTLE.

Max