Re: load average always more then 1 on idle system with dyntick (just after boot)

From: Peter Zijlstra
Date: Tue Apr 14 2015 - 05:54:47 EST

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:

So you need CONFIG_PREEMPT=n and CONFIG_NO_HZ_IDLE=y for this to happen?

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

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