linux-kernel - Re: [RFC PATCH 12/12] rcu: Nocb (de)activate through sysfs

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Message-ID: <20200923154716.GP29330@paulmck-ThinkPad-P72>
Date:   Wed, 23 Sep 2020 08:47:16 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Josh Triplett <josh@...htriplett.org>
Subject: Re: [RFC PATCH 12/12] rcu: Nocb (de)activate through sysfs

On Wed, Sep 23, 2020 at 05:27:46PM +0200, Frederic Weisbecker wrote:
> On Mon, Sep 21, 2020 at 05:26:29PM -0700, Paul E. McKenney wrote:
> > On Mon, Sep 21, 2020 at 02:43:51PM +0200, Frederic Weisbecker wrote:
> > > Not for merge.
> > > 
> > > Make nocb toggable for a given CPU using:
> > > 	/sys/devices/system/cpu/cpu*/hotplug/nocb
> > > 
> > > This is only intended for those who want to test this patchset. The real
> > > interfaces will be cpuset/isolation and rcutorture.
> > 
> > Excellent choice for testing in the near term!
> > 
> > How does rcutorture fare with this series if an additional kthread toggles
> > offloading on and off continually?
> 
> So yeah that would be the plan: having something that randomly toggles
> offloading from the RCU tests themselves. I'm not quite familiar with
> rcutorture internals yet though.

If you supply a function that selects a CPU and does the toggle, I
can quickly and easily wire it into rcutorture.  I of course have no
objection to your learning to do this yourself, but the offer stands.

> > All questions and concerns aside, excellent progress and nice work!!!
> 
> Thanks! We are slowly making progress :)

Better than quickly failing to make progress, to be sure!  ;-)

								Thanx, Paul