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SubjectRe: [PATCH 05/16] sched: SCHED_DEADLINE policy implementation.
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On Fri, 2012-04-06 at 09:14 +0200, Juri Lelli wrote:
> +static
> +int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se)
> +{
> + int dmiss = dl_time_before(dl_se->deadline, rq->clock);
> + int rorun = dl_se->runtime <= 0;
>+
> + if (!rorun && !dmiss)
> + return 0;
> +
> + /*
> + * If we are beyond our current deadline and we are still
> + * executing, then we have already used some of the runtime of
> + * the next instance. Thus, if we do not account that, we are
> + * stealing bandwidth from the system at each deadline miss!
> + */
> + if (dmiss) {
> + dl_se->runtime = rorun ? dl_se->runtime : 0;
> + dl_se->runtime -= rq->clock - dl_se->deadline;
> + }

So ideally this can't happen, but since we already leak time from the
system through means of hardirq / kstop / context-switch-overhead /
clock-jitter etc.. we avoid the error accumulating?

> +
> + return 1;
> +}




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