Date: Wed, 23 Aug 2017 09:55:51 -0500 (CDT)
From: Christopher Lameter <cl@linux.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
cc: LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Chris Metcalf <cmetcalf@mellanox.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Luiz Capitulino <lcapitulino@redhat.com>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@kernel.org>, Mike Galbraith <efault@gmx.de>,
        Rik van Riel <riel@redhat.com>, Wanpeng Li <kernellwp@gmail.com>
Subject: Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on
 housekeeping
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References: <1503453071-952-1-git-send-email-fweisbec@gmail.com> <1503453071-952-13-git-send-email-fweisbec@gmail.com>
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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.