linux-kernel - Re: [PATCH 1/2] sched/fair: Add cfs bandwidth burst statistics

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Date:   Mon, 23 Aug 2021 14:32:10 -0400
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Huaixin Chang <changhuaixin@...ux.alibaba.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        anderson@...unc.edu, baruah@...tl.edu, bsegall@...gle.com,
        dietmar.eggemann@....com, dtcccc@...ux.alibaba.com,
        juri.lelli@...hat.com, khlebnikov@...dex-team.ru,
        luca.abeni@...tannapisa.it, mgorman@...e.de, mingo@...hat.com,
        odin@...d.al, odin@...dal.com, pauld@...head.com, pjt@...gle.com,
        rostedt@...dmis.org, shanpeic@...ux.alibaba.com, tj@...nel.org,
        tommaso.cucinotta@...tannapisa.it, vincent.guittot@...aro.org,
        xiyou.wangcong@...il.com
Subject: Re: [PATCH 1/2] sched/fair: Add cfs bandwidth burst statistics

On Mon, Aug 16, 2021 at 03:08:48PM +0800, Huaixin Chang wrote:
> Two new statistics are introduced to show the internal of burst feature
> and explain why burst helps or not.
> 
> nr_bursts:  number of periods bandwidth burst occurs
> burst_usec: cumulative wall-time that any cpus has
> 	    used above quota in respective periods
> 
> Co-developed-by: Shanpei Chen <shanpeic@...ux.alibaba.com>
> Signed-off-by: Shanpei Chen <shanpeic@...ux.alibaba.com>
> Co-developed-by: Tianchen Ding <dtcccc@...ux.alibaba.com>
> Signed-off-by: Tianchen Ding <dtcccc@...ux.alibaba.com>
> Signed-off-by: Huaixin Chang <changhuaixin@...ux.alibaba.com>
> Acked-by: Tejun Heo <tj@...nel.org>
> ---
>  kernel/sched/core.c  | 13 ++++++++++---
>  kernel/sched/fair.c  |  9 +++++++++
>  kernel/sched/sched.h |  3 +++
>  3 files changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 2d9ff40f4661..9a286c8a1354 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -10088,6 +10088,9 @@ static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
>  		seq_printf(sf, "wait_sum %llu\n", ws);
>  	}
>  
> +	seq_printf(sf, "nr_bursts %d\n", cfs_b->nr_burst);
> +	seq_printf(sf, "burst_usec %llu\n", cfs_b->burst_time);

burst_time is nsec, not usec.

Just "burst_time" seems the way to go for consistency with
throttled_time in the same file, though "burst_usec" nicely has units
and would have the same name between cgroup1 and 2.