Messages in this thread | | | From | (Eric W. Biederman) | Date | Fri, 01 Aug 2008 11:27:20 -0700 | Subject | Re: [Patch] Scale pidhash_shift/pidhash_size up based on num_possible_cpus(). |
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Robin Holt <holt@sgi.com> writes:
> On Thu, Jul 31, 2008 at 03:04:56PM -0700, Eric W. Biederman wrote: >> Robin Holt <holt@sgi.com> writes: >> >> > Like so??? >> > >> > I have not tested this yet. >> >> Looks reasonable to me. >> >> In what circumstances was the lookup in the pid hash table with >> long changes causing a performance slowdown?. We don't perform >> a lot of lookups. > > It was initially detected while profiling 'ps' on a 2048p machine that > had 13 kernel threads per cpu. We added a couple more device drivers > which added additional threads. We then started a pthread-on-process > MPI job which had 2048 ranks each with 4 threads (test-case from > customer job). There were misc other processes out there which brought > our task count up to approx 63k. Larger page size helped the problem > (went from 16k to 64k).
Large page size? Do you mean larger hash size?
What were you measuring that showed improvement with the large hash size?
Eric
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