linux-kernel - Re: Interrupt latency on some 945GM platforms

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Message-Id: <201009141109.41596.anarsoul@gmail.com>
Date:	Tue, 14 Sep 2010 11:09:36 +0300
From:	Vasily Khoruzhick <anarsoul@...il.com>
To:	Venkatesh Pallipadi <venki@...gle.com>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	intel-gfx@...ts.freedesktop.org,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: Interrupt latency on some 945GM platforms

В сообщении от 14 of September 2010 03:55:32 автор Venkatesh Pallipadi 
написал:

> Whats the clockevent in this case ("Tick Device" section of
> /proc/timer_list). clocksource= option only changes the clocksource used
> to maintain
> timeofday. But, timer interrupt (clockevent) source will not change.
> Wondering how just the clocksource change is making the diff here..
> 
> Also, if clocksource tsc has a higher rating than HPET. The reason
> HPET is getting used as clocksource in the first place seems to be due
> to TSC is not a dependable clocksource on this platform (may be it
> stops in C3). So, I am not sure forcing it to tsc will be a good
> thing. May be clocksource=acpi_pm is a better thing to try.
> 
> Thanks,
> Venki

I investigated it a bit and found out that single nohz=off option helps. Just 
changing clocksource doesn't help, but it works smoothly with any clocksource 
with nohz=off. So, it seems that something wrong with intel driver while 
system is in tickless mode. 

Regards
Vasily

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