Message-ID: <4419605F.9000806@archonet.com>
Date: Thu, 16 Mar 2006 12:55:59 +0000
From: Richard Huxton <dev@archonet.com>
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To: Guillaume Smet <guillaume.smet@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: PostgreSQL and Xeon MP
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	<1d4e0c10603160428s1a3c1f4cocbe8489634524387@mail.gmail.com>
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Guillaume Smet wrote:
> 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).

Very strange.

> 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.

The client has just bought an Opteron to run on, I'm afraid. I might try 
8.1 on the Xeon but it'll just be to see what happens and that won't be 
for a while.

-- 
   Richard Huxton
   Archonet Ltd