decreasing #define HZ in the linux kernel for CPU/memory bound apps ?

Josip Loncaric josip at icase.edu
Tue Apr 16 15:58:40 EDT 2002


Greg Lindahl wrote:
> 
> As for "what HZ would be a good value?", Alpha has always used 1000,
> and it isn't a significant performance hit. But x86 started life on
> much slower machines, and now we're stuck with 100, unless you want to
> rebuild ALL your packages.
> 
> I suspect IA64 uses 100 for compatibility reasons. I wonder how the
> x86 emulator on AlphaLinux got around this... hm...

A minor correction: HZ=1024 on Alphas and on ia64 (elsewhere HZ=100).

HZ=1024 helps, e.g. it prevents certain kinds of timer-resolved TCP
stalls in kernel 2.2 on Alphas.  However, recompiling user programs
which were built with HZ=100 would be a pain... and one might uncover
new problems with the i386 hardware which has not been tested much with
HZ=1024.

Sincerely,
Josip

-- 
Dr. Josip Loncaric, Research Fellow               mailto:josip at icase.edu
ICASE, Mail Stop 132C           PGP key at http://www.icase.edu./~josip/
NASA Langley Research Center             mailto:j.loncaric at larc.nasa.gov
Hampton, VA 23681-2199, USA    Tel. +1 757 864-2192  Fax +1 757 864-6134
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