linux-kernel - Re: hires timer patchset [was Re: 2.6.19 -mm merge plans]

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Date:	Sun, 24 Sep 2006 04:36:29 +0200
From:	Voluspa <lista1@...hem.se>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Daniel Walker <dwalker@...sta.com>,
	brugolsky@...emetry-investments.com, pavel@...e.cz, akpm@...l.org,
	tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: hires timer patchset [was Re: 2.6.19 -mm merge plans]

On Sat, 23 Sep 2006 22:20:27 +0200 Ingo Molnar wrote:
> 
> * Voluspa wrote:
> 
> > WARNING: "monotonic_clock" [drivers/char/hangcheck-timer.ko]
> > undefined!
> 
> turn off the CONFIG_HANGCHECK_TIMER option.
> 
> > WARNING: "hrtimer_stop_sched_tick" [drivers/acpi/processor.ko]
> > undefined! WARNING:
> > "hrtimer_restart_sched_tick" [drivers/acpi/processor.ko] undefined!
> 
> add these two lins to the end of kernel/hrtimer.c:
> 
> EXPORT_SYMBOL_GPL(hrtimer_stop_sched_tick);
> EXPORT_SYMBOL_GPL(hrtimer_restart_sched_tick);

My mind was clouded close to bedtime. I now remember the fix that
was published already at 2.6.17 time, from Steven Rostedt:

http://marc.theaimsgroup.com/?l=linux-kernel&m=115124086410874&w=2

Well, result is that NO_HZ indeed is the culprit for this CPU
issue. /proc/interrupts showed the timer to be stuck on an initial 3044
triggers after boot, while NMI: counted up almost as fast as LOC: (if
that tells any tale). Observing "top -d 1" for awhile revealed SYS
bursting (almost regularly alternating) between 50% and 100% CPU each 2
to 3 seconds. In between it was 0. USER also had the same pattern, but
with much longer duration. Perhaps 10 seconds from one show to the next.

I've gotten the broken out hrt-dyntick1 patches so will be able to
experiment on my own - slowly, on spare time.

I am of course available for any thoughts or trials you can come up
with in the meantime.

Mvh
Mats Johannesson
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