linux-kernel - Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on housekeeping

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Message-ID: <alpine.DEB.2.20.1708230954240.23600@nuc-kabylake>
Date:   Wed, 23 Aug 2017 09:55:51 -0500 (CDT)
From:   Christopher Lameter <cl@...ux.com>
To:     Frederic Weisbecker <fweisbec@...il.com>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Luiz Capitulino <lcapitulino@...hat.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>, Mike Galbraith <efault@....de>,
        Rik van Riel <riel@...hat.com>,
        Wanpeng Li <kernellwp@...il.com>
Subject: Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on
 housekeeping

On Wed, 23 Aug 2017, Frederic Weisbecker wrote:

> While at it, this is a proposition for a reimplementation of isolcpus=
> that doesn't involve  scheduler domain isolation. Therefore this
> brings a behaviour change: all user tasks inherit init/1 affinity which
> avoid the isolcpus= range. But if a task later overrides its affinity
> which turns out to intersect an isolated CPU, load balancing may occur
> on it.

I think that change is good maybe even a bugfix. I had some people be very
surprised when they set affinities to multiple cpus and the processeds
kept sticking to one cpu because of isolcpus.