Re: [PATCH v4 1/4] sched/fair: Introduce primitives for CFS bandwidth burst

Peter Zijlstra
2021-03-16T09:56:03Z

On Tue, Mar 16, 2021 at 12:49:28PM +0800, Huaixin Chang wrote:
> @@ -8982,6 +8983,12 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
> if (quota != RUNTIME_INF && quota > max_cfs_runtime)
> return -EINVAL;
>
> + /*
> + * Bound burst to defend burst against overflow during bandwidth shift.
> + */
> + if (burst > max_cfs_runtime)
> + return -EINVAL;

Why do you allow such a large burst? I would expect something like:

if (burst > quote)
return -EINVAL;

That limits the variance in the system. Allowing super long bursts seems
to defeat the entire purpose of bandwidth control.