linux-kernel - Re: [PATCH] sched: Fix numabalancing to work with isolated cpus

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Message-ID: <20170406104204.GI5497@dhcp22.suse.cz>
Date:   Thu, 6 Apr 2017 12:42:04 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH] sched: Fix numabalancing to work with isolated cpus

On Thu 06-04-17 12:29:57, Peter Zijlstra wrote:
> On Thu, Apr 06, 2017 at 12:13:49PM +0200, Michal Hocko wrote:
> > On Thu 06-04-17 11:23:29, Peter Zijlstra wrote:
> > > On Thu, Apr 06, 2017 at 09:34:36AM +0200, Michal Hocko wrote:
> > [...]
> > > > I would really like to see it confirmed by the scheduler maintainers and
> > > > documented properly as well. What you are claiming here is rather
> > > > surprising to my understanding of what isolcpus acutally is.
> > > 
> > > isolcpus gets you a set of fully partitioned CPUs. What's surprising
> > > about that?
> > 
> > Well, I thought that all isolated cpus simply form their own scheduling
> > domain which is isolated from the general workload on the system
> > (kthreads, softirqs etc...).
> 
> No, they all form their own 1 cpu partition.

Is this something dictated by usecases which rely on isolcpus or rather
nobody bothered to implement one scheduling domain?

-- 
Michal Hocko
SUSE Labs