Re: PostgreSQL and Xeon MP

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