Date: Fri, 15 Jun 2007 13:29:36 -0400 (EDT)
From: Greg Smith <gsmith@gregsmith.com>
To: pgsql-hackers@postgresql.org
Subject: Re: Performance Monitoring
In-Reply-To: <BAY104-W14579231F227BCEBB31D7DCD1E0@phx.gbl>
Message-ID: <Pine.GSO.4.64.0706151318480.5871@westnet.com>
References: <BAY104-W14579231F227BCEBB31D7DCD1E0@phx.gbl>
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On Fri, 15 Jun 2007, Umar Farooq wrote:

> Surprisingly, no matter what type of query I execute, when I use strace 
> to monitor the system calls generated they turn out to be the same for 
> ALL sorts of queries.

How are you calling strace?  The master postgres progress forks off new 
processes for each of the clients, you need to make sure you include stats 
from all of them as well to get anything.

I normally use

strace -c -f -p [main postgres process]

which is helpful to collecte basic info, but even that's not quite right; 
you don't get the work done by the other proceses (logger, writer, stats 
collector).  To get everything, you need to start some process that you 
attach strace to like this, then have that process start the server.

I haven't found strace to be a great tool for this type of work.  You 
might take at look at systemtap instead ( 
http://sourceware.org/systemtap/wiki ) which is a bit immature but is 
going the right direction.

I will now bow my head and wait for someone to suggest you move to an OS 
that supports dtrace.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD