linux-kernel - Re: [RFC PATCH] membarrier: handle nohz_full with expedited thread registration

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Date:   Tue, 17 Jan 2017 12:53:21 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Frederic Weisbecker <fweisbec@...il.com>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Josh Triplett <josh@...htriplett.org>,
        KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
        rostedt <rostedt@...dmis.org>,
        Nicholas Miell <nmiell@...cast.net>,
        Ingo Molnar <mingo@...hat.com>,
        One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
        Lai Jiangshan <laijs@...fujitsu.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        David Howells <dhowells@...hat.com>,
        bobby prani <bobby.prani@...il.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Shuah Khan <shuahkh@....samsung.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH] membarrier: handle nohz_full with expedited thread
 registration

On Tue, Jan 17, 2017 at 04:55:22AM +0100, Frederic Weisbecker wrote:

[ . . . ]

> In fact due to the complexity involved, I have to ask first if we
> really need this feature.  Typically nohz_full workloads don't want to
> be disturbed at all, so do we have real and significant usecases of CPU
> isolation workloads that want to be concerned by this membarrier so much
> that they can tolerate some random IRQ?

I believe that we need to explore the options for implementing it and
to -at- -least- have a patch ready, even if that patch doesn't go
upstream immediately.

							Thanx, Paul