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

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Message-ID: <49247462.4030101@qualcomm.com>
Date:	Wed, 19 Nov 2008 12:17:38 -0800
From:	Max Krasnyansky <maxk@...lcomm.com>
To:	Dimitri Sivanich <sivanich@....com>
CC:	Gregory Haskins <ghaskins@...ell.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



Dimitri Sivanich wrote:
> On Wed, Nov 19, 2008 at 11:49:36AM -0800, Max Krasnyansky wrote:
>> I think the idea is that we want to make balancer a noop on those processors.
> 
> Ultimately, making the balancer a noop on processors with load balancing turned off would be the best solution.
Yes. I forgot to point out that if we do change cpusets to generate sched
domain per cpu we want to make sure that balancer is still a noop just like it
is today with the null sched domain.

>> 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 ?
> 
> It doesn't make sense to me that they'd have a root domain attached that spans more of the the system than that cpu.
I think 'root' in this case is a bit of a misnomer. What I meant is that each
non-balanced cpu would be in a separate sched domain.

Max
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