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Re: dbt2 performance regresses from 9.1.6 to 9.2.1

From: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
To: Dong Ye <yed(at)vmware(dot)com>
Cc: Claudio Freire <klaussfreire(at)gmail(dot)com>, Ants Aasma <ants(at)cybertec(dot)at>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: dbt2 performance regresses from 9.1.6 to 9.2.1
Date: 2012-11-07 11:43:09
Message-ID: 509A494D.10607@vmware.com (view raw or flat)
Thread:
Lists: pgsql-performance
On 05.11.2012 16:32, Claudio Freire wrote:
> On Sun, Nov 4, 2012 at 7:23 PM, Dong Ye<yed(at)vmware(dot)com>  wrote:
>>> You are using prepared statements, this makes me think that this
>>> regression might be due to support for parameter specific plans for
>>> prepared statements. [1] Can you run the test on both versions without
>>> prepared statements and see if the regressions remains.
>>
>> Without prepare statement, we got 48837.33 avg notpm with 9.1.6 and 43264.54 avg notpm with 9.2.1.
>> notps over time shows the slowdown of 9.2.1 is evident during the entire course of the run.
>> Their profiles are posted on http://pgsql.privatepaste.com/b770f72967 (9.1.6) and http://pgsql.privatepaste.com/6fa8b7f174 (9.2.1).
>
> You know... it does look as if 9.2.1 is generating a lot more pressure
> into the memory allocator (AllocSetAlloc notably higher).

Did you check the access plans of the queries? 9.2 planner might choose 
a slightly worse plan. Or perhaps index-only scans are hurting 
performance with the DBT-2 queries.

- Heikki


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