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Re: Low CPU Usage

From: Bill Moran <wmoran(at)collaborativefusion(dot)com>
To: brauagustin-susc(at)yahoo(dot)com(dot)ar
Cc: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Low CPU Usage
Date: 2007-09-21 18:33:54
Message-ID: 20070921143354.3d35cbff.wmoran@collaborativefusion.com (view raw or flat)
Thread:
Lists: pgsql-performance
In response to brauagustin-susc(at)yahoo(dot)com(dot)ar:

> > That's not what it looks like based on the EXPLAIN ANALYZE output.
> > It looks like run time dropped from two seconds to half a second.
>  
> > It seems as though you either have a network delay delivering the results,
> > or your application is slow to read them.
> 
> > Exactly how are you arriving at those timings you're reporting to us?
>  
> I have noticed this in a daly process I run which involves normally 45 minutes and with the new server takes 1:40.
> 
> Some days ago I began to do some tests with no success, then I opened PgAdmin with this simply query to read 2 big tables and then compare disk access.
> SELECT *
> FROM fact_ven_renta fvr, dim_producto_std_producto dpp
> WHERE
>   fvr.producto_std_producto_sk = dpp.producto_sk
>  
> fact_ven_renta has 136316 rows
> dim_producto_std_producto has 3669 rows

Run the tests from psql on the same server.  As Kevin pointed out, the
_server_ is faster, but it appears as if the connection between PGadmin
and this new server is slower somehow.

Are you sure of your speed/duplex settings on the network side?  That's
the most common cause of this kind of thing in my experience.  Try doing
a raw FTP transfer between the client and server and see if you get the
speed you should.

> 
> 
> 
> I have made all possible combinations pgadmin (running in the same server each query, in the old one, in the new one), without difference  and I only retrieve the first 100 records (I didn't count the network time in any case).
> But the weird thing is running the query in the new server the are many disk access and cpu usage. And with other applications in the same server are a lot of disks access.



-- 
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran(at)collaborativefusion(dot)com
Phone: 412-422-3463x4023

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Subject: Re: Searching for the cause of a bad plan
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