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

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Message-Id: <CEA7D572-2506-496A-B09D-4172D6070E02@linux.alibaba.com>
Date:   Thu, 12 Aug 2021 20:18:24 +0800
From:   changhuaixin <changhuaixin@...ux.alibaba.com>
To:     Huaixin Chang <changhuaixin@...ux.alibaba.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, anderson@...unc.edu,
        baruah@...tl.edu, Benjamin Segall <bsegall@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        dtcccc@...ux.alibaba.com, Juri Lelli <juri.lelli@...hat.com>,
        khlebnikov@...dex-team.ru,
        open list <linux-kernel@...r.kernel.org>,
        luca.abeni@...tannapisa.it, Mel Gorman <mgorman@...e.de>,
        Ingo Molnar <mingo@...hat.com>, Odin Ugedal <odin@...d.al>,
        Odin Ugedal <odin@...dal.com>, pauld@...head.com,
        Paul Turner <pjt@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Shanpei Chen <shanpeic@...ux.alibaba.com>,
        Tejun Heo <tj@...nel.org>, tommaso.cucinotta@...tannapisa.it,
        Vincent Guittot <vincent.guittot@...aro.org>,
        xiyou.wangcong@...il.com
Subject: Re: [PATCH 1/2] sched/fair: Add cfs bandwidth burst statistics

Ping.

The statistics code is further simplified than the one discussed before. Mind having a look at it?

> On Jul 30, 2021, at 3:09 PM, Huaixin Chang <changhuaixin@...ux.alibaba.com> 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>
> ---
> 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);
> +
> 	return 0;
> }
> #endif /* CONFIG_CFS_BANDWIDTH */
> @@ -10184,16 +10187,20 @@ 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;
> +		u64 throttled_usec, burst_usec;
> 
> 		throttled_usec = cfs_b->throttled_time;
> 		do_div(throttled_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_usec %llu\n"
> +			   "nr_bursts %d\n"
> +			   "burst_usec %llu\n",
> 			   cfs_b->nr_periods, cfs_b->nr_throttled,
> -			   throttled_usec);
> +			   throttled_usec, cfs_b->nr_burst, burst_usec);
> 	}
> #endif
> 	return 0;
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 44c452072a1b..464371f364f1 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4655,11 +4655,20 @@ static inline u64 sched_cfs_bandwidth_slice(void)
>  */
> void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
> {
> +	s64 runtime;
> +
> 	if (unlikely(cfs_b->quota == RUNTIME_INF))
> 		return;
> 
> 	cfs_b->runtime += cfs_b->quota;
> +	runtime = cfs_b->runtime_snap - cfs_b->runtime;
> +	if (runtime > 0) {
> +		cfs_b->burst_time += runtime;
> +		cfs_b->nr_burst++;
> +	}
> +
> 	cfs_b->runtime = min(cfs_b->runtime, cfs_b->quota + cfs_b->burst);
> +	cfs_b->runtime_snap = cfs_b->runtime;
> }
> 
> static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 14a41a243f7b..80e4322727b4 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -367,6 +367,7 @@ struct cfs_bandwidth {
> 	u64			quota;
> 	u64			runtime;
> 	u64			burst;
> +	u64			runtime_snap;
> 	s64			hierarchical_quota;
> 
> 	u8			idle;
> @@ -379,7 +380,9 @@ struct cfs_bandwidth {
> 	/* Statistics: */
> 	int			nr_periods;
> 	int			nr_throttled;
> +	int			nr_burst;
> 	u64			throttled_time;
> +	u64			burst_time;
> #endif
> };
> 
> -- 
> 2.14.4.44.g2045bb6
> 
>