linux-kernel - Re: [PATCH 4/6] sched: make schedstats helpers independent of fair sched class

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Date:   Tue, 1 Dec 2020 12:46:14 +0000
From:   Mel Gorman <mgorman@...e.de>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, bristot@...hat.com,
        qianjun.kernel@...il.com, linux-kernel@...r.kernel.org,
        linux-rt-users@...r.kernel.org
Subject: Re: [PATCH 4/6] sched: make schedstats helpers independent of fair
 sched class

On Tue, Dec 01, 2020 at 07:54:14PM +0800, Yafang Shao wrote:
> The original prototype of the schedstats helpers are
> 
> update_stats_wait_*(struct cfs_rq *cfs_rq, struct sched_entity *se)
> 
> The cfs_rq in these helpers is used to get the rq_clock, and the se is
> used to get the struct sched_statistics and the struct task_struct. In
> order to make these helpers available by all sched classes, we can pass
> the rq, sched_statistics and task_struct directly.
> 
> Then the new helpers are
> 
> update_stats_wait_*(struct rq *rq, struct task_struct *p,
> 		    struct sched_statistics *stats)
> 
> which are independent of fair sched class.
> 
> To avoid vmlinux growing too large or introducing ovehead when
> !schedstat_enabled(), some new helpers after schedstat_enabled() are also
> introduced, Suggested by Mel. These helpers are in sched/stats.c,
> 
> __update_stats_wait_*(struct rq *rq, struct task_struct *p,
> 		      struct sched_statistics *stats)
> 
> Cc: Mel Gorman <mgorman@...e.de>
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>

Think it's ok, it's mostly code shuffling. I'd have been happier if
there was evidence showing a before/after comparison of the sched stats
for something simple like "perf bench sched pipe" and a clear statement
of no functional change as well as a comparison of the vmlinux files but
I think it's ok so;

Acked-by: Mel Gorman <mgorman@...e.de>

I didn't look at the rt.c parts

-- 
Mel Gorman
SUSE Labs