kern.hz="100" stops high-pitched whine

Chuck Swiger cswiger at
Sun Jul 1 13:46:26 UTC 2007

cpghost wrote:
> Are there any reasons NOT changing kern.hz from the
> default 1000 back to 100? With my typical mix of
> desktop apps (EPIA) and networking / server (Soekris),
> everything seems to be running just as smoothly with
> 100 Hz than with 1000 Hz (testing now for two weeks
> without problems). Even playing videos with mplayer
> on the EPIA doesn't look different in any way.
> Is it okay to stay with 100 Hz with this type of
> low-speed CPU/boards? Or are there some compelling
> reasons not to?

Actually, many Unix systems ran with HZ=100 until a few years ago, about when 
Gb ethernet and CPUs became common.  A slower machine like the EPIA boxes do 
quite well with HZ=100/200/250 or so...HZ=1000 is better if you have a fast 
box running lots of concurrent processes, and/or are proxying or routing 
network traffic where the difference between 10 ms and 1ms of latency adds up 
and/or effects other systems.


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