linux-kernel - Re: [RFC PATCH] sched/fair: Optionally restrict SMT scheduling ("restrict

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Date:   Fri, 02 Feb 2018 18:18:45 +0100
From:   Mike Galbraith <efault@....de>
To:     Sergio Lopez <slp@...rega.org>, linux-kernel@...r.kernel.org
Cc:     mingo@...hat.com, peterz@...radead.org
Subject: Re: [RFC PATCH] sched/fair: Optionally restrict SMT scheduling
 ("restrict_smt")

On Fri, 2018-02-02 at 16:14 +0100, Sergio Lopez wrote:
> On Thu, 2018-02-01 at 15:37 +0100, Mike Galbraith wrote:
> > On Thu, 2018-02-01 at 13:37 +0100, Sergio Lopez wrote:
> > > Compared against "isolcpus", "restrict_smt" presents the following
> > > advantages:
> > >  - Doesn't require prior knowledge of the CPU topology, making it
> > > more friendly to both end users and automation tools.
> > >  - Load balancing is still active for tasks pinned to multiple
> > > secondary SMT threads.
> > 
> > This says that everybody and everything in the box is way smarter
> > than the admin.
> 
> If that's an argument in favor of manual pinning and isolation, I have
> to disagree with you. That's an unnecessary burden put on the shoulders
> of the admin.

Give the admin job to one of those users you mentioned who knows which
threads are "secondary" threads, he/she won't be burdened at all.

	-Mike