Date: Fri, 29 Sep 2017 16:26:10 +0100
From: Morten Rasmussen <morten.rasmussen@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, tj@kernel.org,
        josef@toxicpanda.com, torvalds@linux-foundation.org,
        vincent.guittot@linaro.org, efault@gmx.de, pjt@google.com, clm@fb.com,
        dietmar.eggemann@arm.com, bsegall@google.com, yuyang.du@intel.com
Subject: Re: [PATCH -v2 04/18] sched/fair: Remove se->load.weight from
 se->avg.load_sum
Message-ID: <20170929152607.GC16286@e105550-lin.cambridge.arm.com>
References: <20170901132059.342024223@infradead.org>
 <20170901132748.190668510@infradead.org>
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On Fri, Sep 01, 2017 at 03:21:03PM +0200, Peter Zijlstra wrote:
> +/*
> + * sched_entity:
> + *
> + *   load_sum := runnable_sum
> + *   load_avg = se_weight(se) * runnable_avg
> + *
> + * cfq_rs:

I think this should be "cfs_rq" instead.

> + *
> + *   load_sum = \Sum se_weight(se) * se->avg.load_sum
> + *   load_avg = \Sum se->avg.load_avg
> + */

I find it a bit confusing that load_sum and load_avg have different
definitions, but I guess I will discover why dropping weight from
se->avg.load_sum helps a bit later. We can't do the same for cfs_rq as
it is a \Sum of sums where we add/remove contributions when tasks
migrate.

Have we defined the relation between runnable_sum and runnable_avg in a
comment somewhere already? Otherwise it might be helpful to add. It is
in the code of course :-)