HZ and HPC

Greg Lindahl lindahl at keyresearch.com
Tue Jan 28 22:33:54 PST 2003

On Tue, Jan 28, 2003 at 08:24:28PM -0500, Jean-Christophe Ducom wrote:

> 	I dont' know if this topic has been discussed previously. I was 
> wondering how good/bad is the new value for timeslices HZ=512 for RH8.0 
> (other distributions?) and HZ=1000 for kernel2.5.

I've lived on Alphas for ages, and it seemed to work OK.

> I understand how good it is for desktop responsiveness but won't it
> be bad if two 'intensive' jobs are running causing a lot of cache
> misses at every timeslice,

Most HPC clusters only run 1 intensive process per cpu. Yes, loading
the entire cache from a cold start takes around 1 millisecond.
Fortunately, not that many jobs are sensitive to the exact cache size
-- they tend to need more or less. If less, it won't thrash. If more,
it always thrashes.

-- greg

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