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    SubjectRe: [Patch] Scale pidhash_shift/pidhash_size up based on num_possible_cpus().
    On Fri, Aug 01, 2008 at 11:27:20AM -0700, Eric W. Biederman wrote:
    > 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?

    Oops, confusing details. That was a different problem we had been
    tracking.

    Sorry for the confusion,
    Robin


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