linux-kernel - Re: NO_HZ: timer interrupt stuck [Re: Linux 2.6.21-rc1]

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Message-ID: <45DDC488.1080008@drzeus.cx>
Date:	Thu, 22 Feb 2007 17:27:52 +0100
From:	Pierre Ossman <drzeus-list@...eus.cx>
To:	tglx@...utronix.de
CC:	Arjan van de Ven <arjan@...radead.org>,
	Jan Engelhardt <jengelh@...ux01.gwdg.de>,
	Luca Tettamanti <kronos.it@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: NO_HZ: timer interrupt stuck [Re: Linux 2.6.21-rc1]

Thomas Gleixner wrote:
>
> Here is the reason. The local APIC stops working in C3 state and we fall
> back to the PIT in that case. Not really exciting for dynticks, but the
> only way to keep the system alive. There is a patch coming up from
> Intel, which finds out how to use HPET even if it is not enabled by the
> BIOS. This will still end up on IRQ#0, but will give way longer idle
> sleeps than the PIT.
>
>   

So then the next two questions are; is it possible to disable C3 and is
it a net power gain to get rid of the wakeups in favor of having C3.

Rgds

-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  PulseAudio, core developer          http://pulseaudio.org
  rdesktop, core developer          http://www.rdesktop.org

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