linux-kernel - Re: [RFC] sched: make update_cpu_load

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Date:	Wed, 9 Sep 2015 16:31:31 +0900
From:	Byungchul Park <byungchul.park@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] sched: make update_cpu_load_active care more than one tick

On Wed, Sep 09, 2015 at 09:02:40AM +0200, Peter Zijlstra wrote:
> On Thu, Aug 13, 2015 at 06:35:24PM +0900, byungchul.park@....com wrote:
> > From: Byungchul Park <byungchul.park@....com>
> > 
> > i found do_timer accounts other than one tick, so i made
> > update_cpu_load_active care that.
> > 
> > is it intended because of its overhead?
> 
> I think the idea was that the NO_HZ bits would deal with the other
> cases.

in the case of NO_HZ (including FULL NO_HZ), NO problem. it would be dealt
by update_idle_cpu_load() or update_cpu_load_nohz() in this case.

however, we expect that update_cpu_load_active() is called every tick, but
it is not true. that's why i suggested this. actually it did not happen
a stop tick routine when i found that update_cpu_load_active() was called
with interval which is several ticks, furthermore, more than 10 ticks.
i checked this with debugger.

is there anything i missed?

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