so much clock interrupts?!

Kris Kennaway kris at
Fri Nov 25 00:21:52 GMT 2005

On Fri, Nov 25, 2005 at 01:08:42AM +0100, Wojciech Puchar wrote:
> >>That's why I have kern.hz="100" in my /boot/loader.conf .
> >
> >Have you been able to measure a performance benefit from reducing it?
> >Have you shown that reducing it does not cause your performance to
> >*drop*?  It was increased for a actually increases
> >performance on some workloads.
> >
> no i'm just asking.
> does hz=1000 means that if i run >1 CPU-bound process per processor it's 
> switched 1000 times per second between them? or just 1000 times per second 
> system call is issued that does many system duties, but switches processes 
> with different frequency?

It's used to drive timers and periodic events, including scheduling.
Keep in mind that modern computers are roughly 10 times faster than
they were a few years ago.  Something that runs every 1/100 of a
second is actually waiting for 10 times as many CPU cycles as it was
on the older machine, which means that it may be working
proportionally less efficiently on the new machine.

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