Re: Re: Increasing work_mem and shared_buffers on Postgres 9.2 significantly slows down queries - Mailing list pgsql-performance

From Petr Praus
Subject Re: Re: Increasing work_mem and shared_buffers on Postgres 9.2 significantly slows down queries
Date
Msg-id CACezXZ-NBmEd-Ur8TKvi2fhJkLAC=7w4y93ZPPzoFa1rZH+nmg@mail.gmail.com
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In response to Re: Re: Increasing work_mem and shared_buffers on Postgres 9.2 significantly slows down queries  ("Gunnar \"Nick\" Bluth" <gunnar.bluth@pro-open.de>)
List pgsql-performance
On 3 November 2012 12:09, Gunnar "Nick" Bluth <gunnar.bluth@pro-open.de> wrote:
Am 03.11.2012 16:20, schrieb Petr Praus:

Your CPUs are indeed pretty oldschool. FSB based, IIRC, not NUMA. A process migration would be even more expensive there.


Ok, I've actually looked these up now... at the time these were current, I was in the lucky situation to only deal with Opterons. And actually, with these CPUs it is pretty possible that Scott Marlowe's hint (check vm.zone_reclaim_mode) was pointing in the right direction. Did you check that?

I did check that, it's zero. I responded to his message, but my messages to the mailing list are getting delayed by ~24 hours because somebody has to always bless them.
 


Yes, same behaviour. I let the shared_buffers be the default (which is 8MB). With work_mem 1MB the query runs fast, with 96MB it runs slow (same times as before). It really seems that the culprit is work_mem.


Well, I'm pretty sure that having more work_mem is a good thing (tm) normally ;-)

Well, that's what I always thought too! :-) 
 
-- 
Gunnar "Nick" Bluth
RHCE/SCLA

Mobil   +49 172 8853339
Email: gunnar.bluth@pro-open.de
__________________________________________________________________________
In 1984 mainstream users were choosing VMS over UNIX.  Ten years later
they are choosing Windows over UNIX.  What part of that message aren't you
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