linux-kernel - Re: [PATCH v3 2/2] sched: consider missed ticks when updating global cpu load

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Message-ID: <20151013070436.GO3604@twins.programming.kicks-ass.net>
Date:	Tue, 13 Oct 2015 09:04:36 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Byungchul Park <byungchul.park@....com>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: Re: [PATCH v3 2/2] sched: consider missed ticks when updating global
 cpu load

On Mon, Oct 12, 2015 at 07:45:35PM +0200, Frederic Weisbecker wrote:
> > I think it will take more than a single patch to rework all of
> > update_process_times(). And we should also ask Thomas for his opinion,
> > but I think we want:
> > 
> > 	- make update_process_times() take a nr_ticks argument
> > 	  - fixup everything below it
> > 
> > 	- fix tick_nohz_handler to not ignore the hrtimer_forward()
> > 	  return value and pass it into
> > 	  tick_sched_handle()/update_process_times().
> > 
> > 	  (assuming this is the right oneshot tick part, tick-common
> > 	  seems to be about periodic timers which aren't used much ?!)
> 
> this_nohz_handler() is the low res nohz handler. tick_sched_handle()
> is the high res one (I should rename these). I think we should rather
> find out the pending updates from update_process_times() itself and pass
> it to scheduler_tick() which is the one interested in it.

tick_nohz_handler() calls tick_sched_handler() ?!

And tick_nohz_handler() actually computes the number of ticks -- which
we then happily ignore.

Why compute it again a few functions down?
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