linux-kernel - Re: [PATCH v7 1/2] sched/deadline: Add support for SD_PREFER_SIBLING on find_later

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Date:   Fri, 18 Aug 2017 00:21:46 -0700
From:   "Joel Fernandes (Google)" <joel.opensrc@...il.com>
To:     Byungchul Park <byungchul.park@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        juri.lelli@...il.com, rostedt@...dmis.org, kernel-team@....com,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [PATCH v7 1/2] sched/deadline: Add support for SD_PREFER_SIBLING
 on find_later_rq()

Hi Byungchul,

On Thu, Aug 17, 2017 at 11:05 PM, Byungchul Park <byungchul.park@....com> wrote:
> It would be better to avoid pushing tasks to other cpu within
> a SD_PREFER_SIBLING domain, instead, get more chances to check other
> siblings.
>
> Signed-off-by: Byungchul Park <byungchul.park@....com>
> ---
>  kernel/sched/deadline.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 52 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 0223694..8f69a37 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1319,12 +1319,35 @@ static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu
>
>  static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
>
> +/*
> + * Find the first cpu in: mask & sd & ~prefer
> + */
> +static int find_cpu(const struct cpumask *mask,
> +                   const struct sched_domain *sd,
> +                   const struct sched_domain *prefer)
> +{
> +       const struct cpumask *sds = sched_domain_span(sd);
> +       const struct cpumask *ps  = prefer ? sched_domain_span(prefer) : NULL;
> +       int cpu = -1;
> +
> +       while ((cpu = cpumask_next(cpu, mask)) < nr_cpu_ids) {

This can be simplified to for_each_cpu(cpu, mask) ?


thanks,

-Joel