linux-kernel - Re: [PATCH] timers/nohz: introduce nohz_full

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Message-ID: <2161b8c0-b08c-7bf7-4c99-3bb89ca44ad8@linutronix.de>
Date:   Wed, 10 May 2023 11:03:07 +0200 (CEST)
From:   Anna-Maria Behnsen <anna-maria@...utronix.de>
To:     Andrea Righi <andrea.righi@...onical.com>
cc:     Steven Rostedt <rostedt@...dmis.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Salvatore Bonaccorso <carnil@...ian.org>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH] timers/nohz: introduce nohz_full_aggressive

On Sun, 7 May 2023, Andrea Righi wrote:

> On Sun, May 07, 2023 at 10:08:52AM -0400, Steven Rostedt wrote:
> > 
> > [ Added Anna-Maria who is doing some timer work as well ]
> > 
> > On Sun,  7 May 2023 11:07:00 +0200
> > Andrea Righi <andrea.righi@...onical.com> wrote:
> > 
> > Now, I think what is really happening here is that you are somewhat
> > simulating the results that Anna-Maria has indirectly. That is, you
> > just prevent an idle CPU from waking up to handle interrupts when not
> > needed.
> > 
> > Anna-Maria,
> > 
> > Do you have some patches that Andrea could test with?
> > 
> > Thanks,
> > 
> > -- Steve
> 
> Thanks for looking at this (and I'm happy to help Anna-Maria with any
> test).

I posted v6 of the queue - but forgot to add you to cc list. Here is the
current version:

  https://lore.kernel.org/lkml/20230510072817.116056-1-anna-maria@linutronix.de/

I have to mention, that there is still the issue with the fair scheduler
which wakes up the CPU where the process_timeout() timer was enqueued,
because it assumes that context is still cache hot.

Thanks,

	Anna-Maria