Re: dynamic-hz

Pavel Machek
2004-12-13T11:23:16Z

Hi!

> > > The performance benefit, if any, is often lost in noise during
> > > benchmarks and when there, is less than 1%. So I was wondering if you
> > > had some specific advantage in mind for this patch? Is there some
> > > arch-specific advantage? I can certainly envision disadvantages to lower Hz.
> >
> > There are apparently some laptops which exhibit appreciable latency between
> > the start of ACPI sleep and actually consuming less power. The 1ms wakeup
> > frequency will shorten battery life on these machines significantly. (I
> > forget the exact numbers - Len will know).
>
> Is there any recommended lower bound setting?
> Would there be a point in recommending lower settings for desktops
> running only text consoles opposed to X desktops?

I tried defining HZ to 10 once, and there are some #if arrays in the
kernel that prevented me from doing that.

Some drivers do timeouts based on jiffies; having HZ=1 may turn 20msec
timeout into 1sec, that could hurt a lot in the error case...

Pavel
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