Date: Sun, 24 Sep 2006 04:36:29 +0200
From: Voluspa <lista1@comhem.se>
To: Ingo Molnar <mingo@elte.hu>
Cc: Daniel Walker <dwalker@mvista.com>, brugolsky@telemetry-investments.com,
       pavel@suse.cz, akpm@osdl.org, tglx@linutronix.de,
       linux-kernel@vger.kernel.org
Subject: Re: hires timer patchset [was Re: 2.6.19 -mm merge plans]
Message-ID: <20060924043629.5bebc404@loke.fish.not>
In-Reply-To: <20060923202027.GA8350@elte.hu>
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	<20060923215832.03b1dac5@loke.fish.not>
	<20060923202027.GA8350@elte.hu>
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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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