However in order to actually notice it you must have other programs
running that uses close to 100% CPU *AT LEAST AT THE SAME OR HIGHER
PRIORITY*. To test this, just running a couple of shells/script with
while [true;] won't slow you down until you aggressively renice the
shells/script.
THus: Setting it higher *may* improve your latency if you've other CPU
intensive task going. Setting it lower will only be a boon if you have
so many active processes that the kernel spend more than negligible time
scheduling, thus you spend fewer cycles scheduling per sec. I don't know
that *so many* is with a 1 GHz CPU is but it's very likely to be > 10.
The O(1) scheduler in progress will push that even higher.
TJ
On Tue, 2002-04-16 at 12:01, Olaf Fraczyk wrote:
> On 2002.04.16 12:29 Liam Girdwood wrote:
> > On Tue, 2002-04-16 at 09:18, BALBIR SINGH wrote:
> > > I remember seeing somewhere unix system VII used to have HZ set to
> > 60
> > > for the machines built in the 70's. I wonder if todays pentium iiis
> > and ivs
> > > should still use HZ of 100, though their internal clock is in GHz.
> > >
> > > I think somethings in the kernel may be tuned for the value of HZ,
> > these
> > > things would be arch specific.
> > >
> > > Increasing the HZ on your system should change the scheduling
> > behaviour,
> > > it could lead to more aggresive scheduling and could affect the
> > > behaviour of the VM subsystem if scheduling happens more frequently.
> > I am
> > > just guessing, I do not know.
> > >
> >
> > I remember reading that a higher HZ value will make your machine more
> > responsive, but will also mean that each running process will have a
> > smaller CPU time slice and that the kernel will spend more CPU time
> > scheduling at the expense of processes.
> >
> Has anyone measured this?
> This shouldn't be a big problem, because some architectures use value
> 1024, eg. Alpha, ia-64.
> And todays Intel/AMD 32-bit processors are as fast as Alpha was 1-2
> years ago.
>
> Regards,
>
> Olaf
>
>
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-- _________________________________________________________________________Terje Eggestad mailto:terje.eggestad@scali.no Scali Scalable Linux Systems http://www.scali.com
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