linux-kernel - Re: [PATCH v3 3/4] sched/fair: Add cfs bandwidth burst statistics

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Date:   Wed, 10 Mar 2021 14:10:56 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Huaixin Chang <changhuaixin@...ux.alibaba.com>
Cc:     bsegall@...gle.com, dietmar.eggemann@....com,
        juri.lelli@...hat.com, khlebnikov@...dex-team.ru,
        linux-kernel@...r.kernel.org, mgorman@...e.de, mingo@...hat.com,
        pauld@...head.com, pjt@...gle.com, rostedt@...dmis.org,
        shanpeic@...ux.alibaba.com, vincent.guittot@...aro.org,
        xiyou.wangcong@...il.com
Subject: Re: [PATCH v3 3/4] sched/fair: Add cfs bandwidth burst statistics

On Thu, Jan 21, 2021 at 07:04:52PM +0800, Huaixin Chang wrote:
> Introduce statistics exports for the burstable cfs bandwidth
> controller.
> 
> The following exports are included:
> 
> current_bw: current runtime in global pool
> nr_burst:   number of periods bandwidth burst occurs
> burst_time: cumulative wall-time that any cpus has
> 	    used above quota in respective periods
> 
> Signed-off-by: Huaixin Chang <changhuaixin@...ux.alibaba.com>
> Signed-off-by: Shanpei Chen <shanpeic@...ux.alibaba.com>

Consistently fail.

> ---
>  kernel/sched/core.c  |  6 ++++++
>  kernel/sched/fair.c  | 12 +++++++++++-
>  kernel/sched/sched.h |  3 +++
>  3 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index fecf0f05ef0c..80ca763ca492 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7986,6 +7986,8 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
>  		cfs_b->runtime = min(max_cfs_runtime, cfs_b->runtime);
>  	}
>  
> +	cfs_b->previous_runtime = cfs_b->runtime;
> +
>  	/* Restart the period timer (if active) to handle new period expiry: */
>  	if (runtime_enabled)
>  		start_cfs_bandwidth(cfs_b, 1);
> @@ -8234,6 +8236,10 @@ static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
>  		seq_printf(sf, "wait_sum %llu\n", ws);
>  	}
>  
> +	seq_printf(sf, "current_bw %llu\n", cfs_b->runtime);
> +	seq_printf(sf, "nr_burst %d\n", cfs_b->nr_burst);
> +	seq_printf(sf, "burst_time %llu\n", cfs_b->burst_time);
> +
>  	return 0;
>  }
>  #endif /* CONFIG_CFS_BANDWIDTH */

This is ABI; and the Changelog has no justification what so ever...