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Re: Perf regression in 2.6.32 (Ubuntu 10.04 LTS)

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Domas Mituzas <midom(dot)lists(at)gmail(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Perf regression in 2.6.32 (Ubuntu 10.04 LTS)
Date: 2010-09-13 09:29:00
Message-ID: 4C8DEEDC.40105@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On 12/09/10 23:31, Domas Mituzas wrote:
> I've been playing around today a lot with sysbench, and observed that 2.6.32 kernel supplied by Ubuntu is having perf regression with PG (which does not affect MySQL), compared to 2.6.28 builds I have.
> What I observed can be seen in a paste at http://p.defau.lt/?8_GQV82Pz3_SDZbNOdP93Q (db12 is 2.6.28, db20 is 2.6.32 - 2.6.32-24-server).
>
> Machines are two socket quad-opterons 2356s.
>
> oprofile output can be seen at http://p.defau.lt/?OIR1vDFK4cze_fmBTQbV9w - system has>20% of idle cpu, which is somewhere in the top symbol :)

Can you run oprofile on the older kernel, so that we can compare and see 
where the time is spent?

Looks like over 7% of the time is spent in s_lock, which suggests some 
change in behavior in context switching or something like that, but 
let's see what the old profile looks like.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com

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