Date: Mon, 28 Aug 2017 12:09:57 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Chris Metcalf <cmetcalf@mellanox.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Luiz Capitulino <lcapitulino@redhat.com>,
        Christoph Lameter <cl@linux.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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On Wed, Aug 23, 2017 at 03:51:11AM +0200, Frederic Weisbecker wrote:
> We want to centralize the isolation features on the housekeeping
> subsystem and scheduler isolation is a significant part of it.
> 
> 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.
> 
> OTOH such a reimplementation that doesn't shortcut scheduler internals
> makes a better candidate for an interface extension to cpuset.

Not sure we can do this. It'll break users that rely on the no
scheduling thing, that's a well documented part of isolcpus.