linux-kernel - Re: RT sched: cpupri_vec lock contention with def_root

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Message-ID: <49246DD0.3010509@qualcomm.com>
Date:	Wed, 19 Nov 2008 11:49:36 -0800
From:	Max Krasnyansky <maxk@...lcomm.com>
To:	Gregory Haskins <ghaskins@...ell.com>
CC:	Dimitri Sivanich <sivanich@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: RT sched: cpupri_vec lock contention with def_root_domain and
 no load balance

Gregory Haskins wrote:
> If you tried creating different cpusets and it still had them all end up
> in the def_root_domain, something is very broken indeed.  I will take a
> look.

I beleive that's the intended behaviour. We always put cpus that are not
balanced into null sched domains. This was done since day one (ie when
cpuisol= option was introduced) and cpusets just followed the same convention.

I think the idea is that we want to make balancer a noop on those processors.
We could change cpusets code to create a root sched domain for each cpu I
guess. But can we maybe scale cpupri some other way ?

Max
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