Re: No 100 HZ timer !

Mark Salisbury
2001-04-09T18:29:46Z

this is one of linux biggest weaknesses. the fixed interval timer is a
throwback. it should be replaced with a variable interval timer with interrupts
on demand for any system with a cpu sane/modern enough to have an on-chip
interrupting decrementer. (i.e just about any modern chip)

On Mon, 09 Apr 2001, Jeff Dike wrote:
> schwidefsky@de.ibm.com said:
> > I have a suggestion that might seem unusual at first but it is
> > important for Linux on S/390. We are facing the problem that we want
> > to start many (> 1000) Linux images on a big S/390 machine. Every
> > image has its own 100 HZ timer on every processor the images uses
> > (normally 1). On a single image system the processor use of the 100 HZ
> > timer is not a big deal but with > 1000 images you need a lot of
> > processing power just to execute the 100 HZ timers. You quickly end up
> > with 100% CPU only for the timer interrupts of otherwise idle images.
>
> This is going to be a problem for UML as well, and I was considering something
> very similar. I did a quick scan of your prose, and the description sounds
> like what I had in mind.
>
> So, count me in as a supporter of this.
>
> A small request: Since S/390 is not the only port that needs this, I'd be
> happy if it was made as generic as possible (and it may already be, I haven't
> gone through the code yet).
>
> Jeff
>
>
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