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Re: postgreSQL performance 8.2.6 vs 8.3.3

From: david(at)lang(dot)hm
To: David Rees <drees76(at)gmail(dot)com>
Cc: Battle Mage <battlemage(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: postgreSQL performance 8.2.6 vs 8.3.3
Date: 2009-02-23 21:02:38
Message-ID: alpine.DEB.1.10.0902231300110.26625@asgard.lang.hm (view raw or flat)
Thread:
Lists: pgsql-performance
On Fri, 20 Feb 2009, David Rees wrote:

> On Fri, Feb 20, 2009 at 1:34 PM, Battle Mage <battlemage(at)gmail(dot)com> wrote:
>> The amount of tps almost doubled, which is good, but i'm worried about the
>> load.  For my application, a load increase is bad and I'd like to keep it
>> just like in 8.2.6 (a load average between 3.4 and 4.3).  What parameters
>> should I work with to decrease the resulting load average at the expense of
>> tps?
>
> Why is it bad?  High load can mean a number of things.
>
> The only way to reduce the load is to get the client to submit
> requests slower.  I don't think you'll be successful in tuning the
> database to run slower.  I think you're headed in the wrong direction.

note that on linux the loadave includes processes that are stalled waiting 
for I/O to complete. as a result loadave isn't the entire picture. you 
need to also look to see what the cpu idle time looks like.

that being said, I am generally very happy with loadave <= # cores and 
consider loadave <= 2x # cores to be acceptable

it's nowhere near perfect, but it seems to serve me well as a rule of 
thumb.

David Lang

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