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SubjectRe: [PATCH 11/15] sched/eevdf: Better handle mixed slice length
On 2023-05-31 at 13:58:50 +0200, Peter Zijlstra wrote:
> In the case where (due to latency-nice) there are different request
> sizes in the tree, the smaller requests tend to be dominated by the
> larger. Also note how the EEVDF lag limits are based on r_max.
>
> Therefore; add a heuristic that for the mixed request size case, moves
> smaller requests to placement strategy #2 which ensures they're
> immidiately eligible and and due to their smaller (virtual) deadline
> will cause preemption.
>
> NOTE: this relies on update_entity_lag() to impose lag limits above
> a single slice.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> kernel/sched/fair.c | 30 ++++++++++++++++++++++++++++++
> kernel/sched/features.h | 1 +
> kernel/sched/sched.h | 1 +
> 3 files changed, 32 insertions(+)
>
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -642,6 +642,7 @@ avg_vruntime_add(struct cfs_rq *cfs_rq,
> s64 key = entity_key(cfs_rq, se);
>
> cfs_rq->avg_vruntime += key * weight;
> + cfs_rq->avg_slice += se->slice * weight;
> cfs_rq->avg_load += weight;
> }
>
> @@ -652,6 +653,7 @@ avg_vruntime_sub(struct cfs_rq *cfs_rq,
> s64 key = entity_key(cfs_rq, se);
>
> cfs_rq->avg_vruntime -= key * weight;
> + cfs_rq->avg_slice -= se->slice * weight;
> cfs_rq->avg_load -= weight;
> }
>
> @@ -4908,6 +4910,21 @@ static inline void update_misfit_status(
>
> #endif /* CONFIG_SMP */
>
> +static inline bool
> +entity_has_slept(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> +{
> + u64 now;
> +
> + if (!(flags & ENQUEUE_WAKEUP))
> + return false;
> +
> + if (flags & ENQUEUE_MIGRATED)
> + return true;
> +
> + now = rq_clock_task(rq_of(cfs_rq));
> + return (s64)(se->exec_start - now) >= se->slice;
> +}
A minor question, should it be now - se->exec_start ?
(se->exec_start - now) is always negetive on local wakeup?

thanks,
Chenyu

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