linux-kernel - Re: [PATCH 2/2] sched: add throttled time stat for throttled children

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Date:   Tue, 23 May 2023 11:44:53 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Josh Don <joshdon@...gle.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>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org,
        Xiangling Kong <xiangling@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 2/2] sched: add throttled time stat for throttled children

Hello,

(cc'ing Johannes)

On Wed, May 17, 2023 at 06:34:14PM -0700, Josh Don wrote:
> We currently export the total throttled time for cgroups that are given
> a bandwidth limit. This patch extends this accounting to also account
> the total time that each children cgroup has been throttled.
> 
> This is useful to understand the degree to which children have been
> affected by the throttling control. Children which are not runnable
> during the entire throttled period, for example, will not show any
> self-throttling time during this period.
...
> @@ -11204,20 +11217,24 @@ static int cpu_extra_stat_show(struct seq_file *sf,
>  	{
>  		struct task_group *tg = css_tg(css);
>  		struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
> -		u64 throttled_usec, burst_usec;
> +		u64 throttled_usec, burst_usec, throttled_self_usec;
>  
>  		throttled_usec = cfs_b->throttled_time;
>  		do_div(throttled_usec, NSEC_PER_USEC);
> +		throttled_self_usec = throttled_time_self(tg);
> +		do_div(throttled_self_usec, NSEC_PER_USEC);
>  		burst_usec = cfs_b->burst_time;
>  		do_div(burst_usec, NSEC_PER_USEC);
>  
>  		seq_printf(sf, "nr_periods %d\n"
>  			   "nr_throttled %d\n"
>  			   "throttled_usec %llu\n"
> +			   "throttled_self_usec %llu\n"

This is fine in principle but I think it'd be better to keep it consistent
with how non-hierarchical events are in memory.events.local. ie. Can we
please add cpu.stat.local instead of adding the _self key to cpu.stat?

Thanks.

-- 
tejun