Re: Why HZ on i386 is 100 ?

John Alvord
2002-04-22T17:20:51Z

On Sun, 21 Apr 2002, Pavel Machek wrote:

> Hi!
>
> > Davide> i still have pieces of paper on my desk about tests done on
> > Davide> my dual piii where by hacking HZ to 1000 the kernel build
> > Davide> time went from an average of 2min:30sec to an average
> > Davide> 2min:43sec. that is pretty close to 10%
> >
> > The last time I measured timer tick overhead on ia64 it was well below
> > 1% of overhead. I don't really like using kernel builds as a
> > benchmark, because there are far too many variables for the results to
> > have any long-term or cross-platform value. But since it's popular, I
> > did measure it quickly on a relatively slow (old) Itanium box: with
> > 100Hz, the kernel compile was about 0.6% faster than with 1024Hz
> > (2.4.18 UP kernel).
>
> .5% still looks like a lot to me. Good compiler optimization is .5% on
> average...
>
> And think what it does with old 386sx.. Maybe time for those "tick on demand"
> patches?

Doesn't IBM have a tickless patch.. useful when demonstrating 10,000
virtual linux machines on a single system.

john alvord