Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt.

Nish Aravamudan
2005-05-17T23:50:16Z

On 5/17/05, Lee Revell <rlrevell@joe-job.com> wrote:
> On Mon, 2005-05-16 at 17:55 -0700, christoph wrote:
> >
> > Runtime? That seems to be a bad idea. It would be better to rewrite
> > the timer subsystem to be able to work tickless.
> >
>
> I agree 100%, I think it's especially crazy to allow selecting 100, 250,
> 500, etc, whether at runtime or compile time. Might as well just go
> tickless.
>
> How do you expect application developers to handle not being able to
> count on the resolution of nanosleep()? Currently they can at least
> assume 10ms on 2.4, 1ms on 2.6. Seems to me that if you are no longer
> guaranteed to be able to sleep 5ms on 2.6, you would just have to
> busywait. Is it me, or does that way lie madness?

>From my meager understanding of sys_nanosleep() in 2.6 -- we'd round
up currently, If you request a microsecond of sleep, we'll sleep for a
jiffy + 1 (or 2, maybe). I am not sure we want a syscall that allows
busy-waiting, but I'm not certain. If you're interesting, my patch
(just posted again to LKML) tries to divorce HZ and soft-timers
somewhat.

-Nish