From: Dimitri Sivanich <sivanich@sgi.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] specific do_timer_cpu value for nohz off mode
Date: Wed, 15 Feb 2012 08:37:10 -0600 [thread overview]
Message-ID: <20120215143710.GA10543@sgi.com> (raw)
In-Reply-To: <alpine.LFD.2.02.1202151512420.2794@ionos>
On Wed, Feb 15, 2012 at 03:16:34PM +0100, Thomas Gleixner wrote:
> On Tue, 8 Nov 2011, Dimitri Sivanich wrote:
> >
> > Allow manual override of the tick_do_timer_cpu.
> >
> > While not necessarily harmful, doing jiffies updates on an application cpu
> > does cause some extra overhead that HPC benchmarking people notice. They
> > prefer to have OS activity isolated to certain cpus. They like reproducibility
> > of results, and having jiffies updates bouncing around introduces variability.
>
> I really wonder about this changelog. The only case where jiffies
> updates bounces around is the NOHZ case. In all other modes (periodic
> or highres) the boot cpu gets the do_timer() duty and it's never
> assigned to any other cpu.
>
> So what's the point of this exercise? Moving it away from CPU0 for
> acedemic reasons or what?
>
I wasn't specifically trying to move it away from CPU0 (having jiffies updates
on CPU0 was and would be just fine for the nohz=off case). The issue was
that the tick_do_timer_cpu could be any cpu even in the nohz=off case (maybe
something has changed that since?). After the point of assignment it is
static, but you never know which cpu it is.
next prev parent reply other threads:[~2012-02-15 14:37 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-08 19:11 [PATCH] specific do_timer_cpu value for nohz off mode Dimitri Sivanich
2011-11-23 0:08 ` Andrew Morton
2011-11-30 15:29 ` Dimitri Sivanich
2011-12-01 0:11 ` Andrew Morton
2011-12-01 0:16 ` Andrew Morton
2011-12-01 2:07 ` Dimitri Sivanich
2011-12-01 2:13 ` Andrew Morton
2011-12-01 16:37 ` Dimitri Sivanich
2011-12-01 22:56 ` Andrew Morton
2011-12-02 20:14 ` Dimitri Sivanich
2011-12-02 20:22 ` Dimitri Sivanich
2011-12-02 22:42 ` Thomas Gleixner
2011-12-01 2:06 ` Dimitri Sivanich
2011-12-01 2:12 ` Andrew Morton
2011-12-01 2:34 ` Dimitri Sivanich
2011-12-01 2:38 ` Andrew Morton
2012-01-15 13:46 ` Mike Galbraith
2012-01-15 14:04 ` Mike Galbraith
2012-01-15 14:23 ` Mike Galbraith
2012-01-25 11:27 ` Mike Galbraith
2012-02-15 14:16 ` Thomas Gleixner
2012-02-15 14:37 ` Dimitri Sivanich [this message]
2012-02-15 14:52 ` Thomas Gleixner
2012-02-15 15:34 ` Dimitri Sivanich
2012-02-15 20:36 ` Thomas Gleixner
2012-02-16 14:59 ` Dimitri Sivanich
2013-03-19 17:03 ` [PATCH][RFC] " Jiri Bohac
-- strict thread matches above, loose matches on Subject: below --
2011-08-17 16:07 [PATCH] " Dimitri Sivanich
2011-08-17 16:47 ` Thomas Gleixner
2011-08-23 19:56 ` Dimitri Sivanich
2011-09-02 8:19 ` Thomas Gleixner
2011-09-02 19:29 ` Dimitri Sivanich
2011-09-02 19:57 ` Thomas Gleixner
2011-09-02 20:39 ` Dimitri Sivanich
2011-08-03 19:57 Dimitri Sivanich
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