From: ebiederm@xmission.com (Eric W. Biederman)
To: Robin Holt <holt@sgi.com>
Cc: linux-kernel@vger.kernel.org, Pavel Emelyanov <xemul@openvz.org>,
Oleg Nesterov <oleg@tv-sign.ru>,
Sukadev Bhattiprolu <sukadev@us.ibm.com>,
Paul Menage <menage@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [Patch] Scale pidhash_shift/pidhash_size up based on num_possible_cpus().
Date: Fri, 01 Aug 2008 11:27:20 -0700 [thread overview]
Message-ID: <m1proszj3r.fsf@frodo.ebiederm.org> (raw)
In-Reply-To: <20080801120455.GP9663@sgi.com> (Robin Holt's message of "Fri, 1 Aug 2008 07:04:55 -0500")
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
next prev parent reply other threads:[~2008-08-01 18:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-31 17:00 [Patch] Scale pidhash_shift/pidhash_size up based on num_possible_cpus() Robin Holt
2008-07-31 18:35 ` Eric W. Biederman
2008-07-31 19:32 ` Robin Holt
2008-07-31 19:49 ` Eric W. Biederman
2008-07-31 20:08 ` Robin Holt
2008-07-31 22:04 ` Eric W. Biederman
2008-08-01 12:04 ` Robin Holt
2008-08-01 18:27 ` Eric W. Biederman [this message]
2008-08-01 19:13 ` Robin Holt
2008-08-01 19:59 ` Eric W. Biederman
2008-08-04 13:11 ` Stephen Champion
2008-08-04 20:36 ` Eric W. Biederman
2008-08-04 23:58 ` Robin Holt
2008-08-05 0:38 ` Eric W. Biederman
2008-08-06 3:21 ` Stephen Champion
2008-08-01 18:49 ` Linus Torvalds
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