Re: [RFC][PATCH] cpuidle: avoid singing capacitors

From: Pierre Ossman
Date: Sat Mar 01 2008 - 07:32:33 EST


On Fri, 29 Feb 2008 16:44:07 -0500
lsorense@xxxxxxxxxxxxxxxxxxx (Lennart Sorensen) wrote:

> On Fri, Feb 29, 2008 at 07:38:12PM +0100, Pierre Ossman wrote:
> > +/*
> > + * The minimum number of ticks needed to not oscillate faster than
> > + * 500 Hz.
> > + */
> > +#define MIN_DEEP_INTERVAL (HZ / 500)
>
> What happens here if HZ < 500? Or does the fact that you have less than
> 500HZ jiffies automatically imply that you can't go to sleep more than
> the jiffy rate times per second?

A low HZ will still go to sleep very often (provided NO_HZ is in effect). But a HZ < 500 makes that number up there turn to zero. But the check further down makes sure that at least 1 tick passes. So that means it will not enter C3 more often than min(HZ, 500) Hz. Another reason to stop using jiffies.

--
-- 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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