linux-kernel - Re: [PATCH 07/16] sched: Make SD_BALANCE

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Message-ID: <20160601201817.GF28447@twins.programming.kicks-ass.net>
Date:	Wed, 1 Jun 2016 22:18:17 +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 07/16] sched: Make SD_BALANCE_WAKE a topology flag

On Mon, May 23, 2016 at 11:58:49AM +0100, Morten Rasmussen wrote:
> For systems with the SD_ASYM_CPUCAPACITY flag set on higher level in the
> sched_domain hierarchy we need a way to enable wake-up balancing for the
> lower levels as well as we may want to balance tasks that don't fit the
> capacity of the previous cpu.
> 
> We have the option of introducing a new topology flag to express this
> requirement, or let the existing SD_BALANCE_WAKE flag be set by the
> architecture as a topology flag. The former means introducing yet
> another flag, the latter breaks the current meaning of topology flags.
> None of the options are really desirable.

So why can't you couple this to ASYM_CAPACITY? If that's set anywhere,
add BALANCE_WAKE as appropriate?