lkml.org 
[lkml]   [2011]   [Jul]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: nohz: remove nohz_cpu_mask
From
Date
On Tue, 2011-07-12 at 01:30 +0800, Paul E. McKenney wrote:
> On Mon, Jul 11, 2011 at 08:47:05AM +0800, Alex,Shi wrote:
> > RCU didn't use this global variable now. Currently no user on it.
>
> Indeed. RCU's use of it turned out to be quite buggy. :-(
>
> > Since the ts->do_timer_last is not the real last periodic tick cpu in
> > most of time. I once want to compare the cpu_online_mask and
> > nohz_cpu_mask to get a real one, and than only let that cpu sleep
> > shorter, other cpu will try to sleep KTIME_MAX, that need a extra lock
> > for nohz_cpu_mask. But I checked my all platforms, from NHM-EX server to
> > laptops, all of them are waked up a few times per second. So, the
> > advantage is only in theory.
> >
> > Since no clear usage of this variable, why not remove it? That can save
> > a cache-line in all cpus and reduce atomic sync contention.
>
> Works for me!
>
> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>

Thomas, would you like to give some comments of this?

Best regards!
Alex



\
 
 \ /
  Last update: 2011-07-15 02:55    [W:0.075 / U:0.248 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site