lkml.org 
[lkml]   [2015]   [Apr]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: load average always more then 1 on idle system with dyntick (just after boot)
On Tue, Apr 14, 2015 at 11:54:24AM +0200, Peter Zijlstra wrote:
> On Tue, Mar 31, 2015 at 10:52:48PM +0300, Azat Khuzhin wrote:
> > Hi all,
> >
> > On one of machines [SUPERMICRO], after installing fresh kernel
> > (v4.0-rc5-25-g90a5a89), I noticed that loadavg always greater then 1.
> >
> > I do a lot of digging and finally have more information on this issue:
> > CONFIG_NO_HZ_IDLE=y # loadavg always > 1
> > CONFIG_HZ_PERIODIC=y # loadavg < 1
> >
> > After this I tried to disable "nohz" at boot, to determine whether it is
> > statically added code under #ifdef during compilation or not, so I added
> > "nohz=off" to cmdline, and it helps!
> >
> > Also if you enable preemption loadavg is also < 1:
> > CONFIG_PREEMPT_VOLUNTARY=y
>
> So you need CONFIG_PREEMPT=n and CONFIG_NO_HZ_IDLE=y for this to happen?

Yep, CONFIG_PREEMPT_NONE=y and CONFIG_NO_HZ_IDLE=y

> That's somewhat odd (and uncommon I think, most everybody has at least
> VOLUNTARY enabled these days).

This is not a big problem for me, I could enable VOLUNTARY, but I don't
think that it will be useful for my workload. But I could be wrong.

> I'll try to look over the code to see if I can find a preempt relation,
> weird that.

Thanks!


\
 
 \ /
  Last update: 2015-04-14 12:41    [W:0.063 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site