linux-kernel - Re: [PATCH] sched: arch_reinit_sched_domains() must destroy domains to force rebuild

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Message-ID: <20080906172316.GK4856@elte.hu>
Date:	Sat, 6 Sep 2008 19:23:16 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Max Krasnyansky <maxk@...lcomm.com>
Cc:	linux-kernel@...r.kernel.org, svaidy@...ux.vnet.ibm.com,
	peterz@...radead.org
Subject: Re: [PATCH] sched: arch_reinit_sched_domains() must destroy
	domains to force rebuild


* Max Krasnyansky <maxk@...lcomm.com> wrote:

> What I realized recently is that calling rebuild_sched_domains() in
> arch_reinit_sched_domains() by itself is not enough when cpusets are enabled.
> partition_sched_domains() code is trying to avoid unnecessary domain rebuilds
> and will not actually rebuild anything if new domain masks match the old ones.
> 
> What this means is that doing
>      echo 1 > /sys/devices/system/cpu/sched_mc_power_savings
> on a system with cpusets enabled will not take affect untill something changes
> in the cpuset setup (ie new sets created or deleted).
> 
> This patch fixes restore correct behaviour where domains must be rebuilt in
> order to enable MC powersaving flags.
> 
> Test on quad-core Core2 box with both CONFIG_CPUSETS and !CONFIG_CPUSETS.
> Also tested on dual-core Core2 laptop. Lockdep is happy and things are working
> as expected.
> 
> Ingo, please apply.

applied to tip/sched/cpuset, thanks Max.

> btw We also need to push my other cpuset patch into mainline.  [...]

will push it once this has been tested some more.

	Ingo
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