Message-ID: <441963F4.1010607@aeccom.com>
Date: Thu, 16 Mar 2006 14:11:16 +0100
From: Sven Geisler <sgeisler@aeccom.com>
Organization: AEC/communications GmbH
User-Agent: Thunderbird 1.5 (Windows/20051201)
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To: Guillaume Smet <guillaume.smet@gmail.com>
Cc: Richard Huxton <dev@archonet.com>,
	pgsql-performance@postgresql.org
Subject: Re: PostgreSQL and Xeon MP
References: <1d4e0c10603160245n55128e86t35431a339afcf8cc@mail.gmail.com>	
	<44194A4B.3020106@archonet.com>
	<1d4e0c10603160428s1a3c1f4cocbe8489634524387@mail.gmail.com>
In-Reply-To: <1d4e0c10603160428s1a3c1f4cocbe8489634524387@mail.gmail.com>
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Hi Guillaume,

I had a similar issue last summer. Could you please provide details 
about your XEON MP server and some statistics (context-switches/load/CPU 
usage)?

I tried different servers (x86) with different results. I saw a 
difference between XEON MP w/ and w/o EMT64. The memory bandwidth makes 
also a difference.

What version of XEON MP does your server have?
Which type of RAM does you server have?
Do you use Hyperthreading?

You should provide details from the XEON DP?

Regards
Sven.

Guillaume Smet schrieb:
> Richard,
> 
>> You should be seeing context-switching jump dramatically if it's the
>> "classic" multi-Xeon problem. There's a point at which it seems to just
>> escalate without a corresponding jump in activity.
> 
> No we don't have this problem of very high context switching in our
> case even when the database is very slow. When I mean very slow, we
> have pages which loads in a few seconds in the normal case (load
> between 3 and 4) which takes several minutes (up to 5-10 minutes) to
> be generated in the worst case (load at 4 but really bad
> performances).
> If I take a look on our cpu load graph, in one year, the cpu load was
> never higher than 5 even in the worst cases...
> 
>> I checked with Tom last week. Thread starts below:
>>    http://archives.postgresql.org/pgsql-hackers/2006-02/msg01118.php
>>
>> He's of the opinion that 8.1.3 will be an improvement.
> 
> Thanks for pointing me this thread, I searched in -performance not in
> -hackers as the original thread was in -performance. We planned a
> migration to 8.1.3 so we'll see what happen with this version.
> 
> Do you plan to test it before next tuesday? If so, I'm interested in
> your results. I'll post our results here as soon as we complete the
> upgrade.
> 
> --
> Guillaume
> 
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Sven Geisler <sgeisler@aeccom.com> Tel +49.30.5362.1627 Fax .1638
Senior Developer,    AEC/communications GmbH    Berlin,   Germany