linux-kernel - Re: [PATCH v2 04/13] sched: Introduce SD_ASYM_CPUCAPACITY sched

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Message-ID: <20160711095523.GL30909@twins.programming.kicks-ass.net>
Date:	Mon, 11 Jul 2016 11:55:23 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Morten Rasmussen <morten.rasmussen@....com>
Cc:	mingo@...hat.com, dietmar.eggemann@....com, yuyang.du@...el.com,
	vincent.guittot@...aro.org, mgalbraith@...e.de,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 04/13] sched: Introduce SD_ASYM_CPUCAPACITY
 sched_domain topology flag

On Wed, Jun 22, 2016 at 06:03:15PM +0100, Morten Rasmussen wrote:
> Add a topology flag to the sched_domain hierarchy indicating
> sched_groups at this sched_domain level having different per cpu
> capacity (e.g. big.LITTLE big-only and little-only groups) or groups in
> sibling domains with different capacity.

>                                          IOW, domains not spanning cpus
> of all available capacities up until and including the first level
> spanning cpus of all capacities available system wide.

This ^, which would be SD1 below, why? I would expect only SD2 to be
tagged, since that does indeed have asymmetric capacities.

> 
> SD 2      [  0      1      2      3]  SD_ASYM_CPUCAPACITY
> 
> SD 1      [  0      1] [   2      3]  SD_ASYM_CPUCAPACITY
>
> cpu:         0      1      2      3
> capacity:  756    756   1024   1024
>