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

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Message-ID: <20081119214756.GA3582@sgi.com>
Date:	Wed, 19 Nov 2008 15:47:56 -0600
From:	Dimitri Sivanich <sivanich@....com>
To:	Gregory Haskins <ghaskins@...ell.com>
Cc:	Max Krasnyansky <maxk@...lcomm.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

On Wed, Nov 19, 2008 at 04:30:08PM -0500, Gregory Haskins wrote:
> Dimitri Sivanich wrote:
> > On Wed, Nov 19, 2008 at 03:25:15PM -0500, Gregory Haskins wrote:
> >   
> >> It sounds like the problem with my code is that "null sched domain"
> >> translates into "default root-domain" which is understandably unexpected
> >> by Dimitri (and myself).  Really I intended root-domains to become
> >> associated with each exclusive/disjoint cpuset that is created.  In a
> >> way, non-balanced/isolated cpus could be modeled as an exclusive cpuset
> >> with one member, but that is somewhat beyond the scope of the
> >>     
> >
> > Actually, at one time, that is how things were setup.  Setting the
> > cpu_exclusive bit on a single cpu cpuset would isolate that cpu from
> > load balancing.
> >   
> Do you know if this was pre or post the root-domain code?  Here is a
> reference to the commit:

It was pre root-domain.  That behavior was replaced by addition of the sched_load_balance flag with the following commit (though it was actually removed even earlier):

http://git2.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=029190c515f15f512ac85de8fc686d4dbd0ae731

> 
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=57d885fea0da0e9541d7730a9e1dcf734981a173
> 
> A bisection that shows when this last worked for you would be very
> appreciated if you have the time, Dimitri.
> 
> Regards,
> -Greg
> 
> 


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