linux-kernel - Re: [GIT PULL] isolation: 1Hz residual tick offloading v3

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Message-ID: <20180116225333.GB32665@lerouge>
Date:   Tue, 16 Jan 2018 23:53:45 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Mike Galbraith <efault@....de>
Cc:     Luiz Capitulino <lcapitulino@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Christoph Lameter <cl@...ux.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Rik van Riel <riel@...hat.com>
Subject: Re: [GIT PULL] isolation: 1Hz residual tick offloading v3

On Tue, Jan 16, 2018 at 06:58:18PM +0100, Mike Galbraith wrote:
> On Tue, 2018-01-16 at 16:41 +0100, Frederic Weisbecker wrote:
> > On Fri, Jan 12, 2018 at 02:18:13PM -0500, Luiz Capitulino wrote:
> > 
> > > Why are extending isolcpus= given that it's a deprecated interface?
> > > Some people have already moved away from isolcpus= now, but with this
> > > new feature they will be forced back to using it.
> > 
> > I tried to remove isolcpus or at least change the way it works so that its
> > effects are reversible (ie: affine the init task instead of isolating domains)
> > but that got nacked due to the behaviour's expectations for userspace.
> 
> So we paint ourselves into a static corner forever more, despite every
> bit of this being all about "properties of sets of cpus", ie precisely
> what cpusets was born to do.  That's sad, dynamic wasn't that far away.

Hence why we need to propagate "isolcpus=" to cpusets.