linux-kernel - Re: [PATCH v6 1/2] sched/numa: introduce per-cgroup NUMA locality info

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Date:   Fri, 3 Jan 2020 16:14:49 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     王贇 <yun.wang@...ux.alibaba.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH v6 1/2] sched/numa: introduce per-cgroup NUMA locality
 info

Hi.

On Fri, Dec 13, 2019 at 09:47:36AM +0800, 王贇 <yun.wang@...ux.alibaba.com> wrote:
> By monitoring the increments, we will be able to locate the per-cgroup
> workload which NUMA Balancing can't helpwith (usually caused by wrong
> CPU and memory node bindings), then we got chance to fix that in time.
I just wonder do the data based on increments match with those you
obtained previously?

> +static inline void
> +update_task_locality(struct task_struct *p, int pnid, int cnid, int pages)
> +{
> +	if (!static_branch_unlikely(&sched_numa_locality))
> +		return;
> +
> +	/*
> +	 * pnid != cnid --> remote idx 0
> +	 * pnid == cnid --> local idx 1
> +	 */
> +	p->numa_page_access[!!(pnid == cnid)] += pages;
If the per-task information isn't used anywhere, why not accumulate
directly into task's cfs_rq->{local,remote}_page_access?

> @@ -4298,6 +4359,7 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
>  	 */
>  	update_load_avg(cfs_rq, curr, UPDATE_TG);
>  	update_cfs_group(curr);
> +	update_group_locality(cfs_rq);
With the per-NUMA node time tracked separately, isn't it unnecessary
doing group updates inside entity_tick? 


Regards,
Michal