Re: PostgreSQL and Xeon MP

On Thu, Mar 16, 2006 at 11:45:12AM +0100, Guillaume Smet wrote:
> Hello,
>
> We are experiencing performances problem with a quad Xeon MP and
> PostgreSQL 7.4 for a year now. Our context switch rate is not so high
> but the load of the server is blocked to 4 even on very high load and
> we have 60% cpu idle even in this case. Our database fits in RAM and
> we don't have any IO problem. I saw this post from Tom Lane
> http://archives.postgresql.org/pgsql-performance/2004-04/msg00249.php
> and several other references to problem with Xeon MP and I suspect our
> problems are related to this.
> We tried to put our production load on a dual standard Xeon on monday
> and it performs far better with the same configuration parameters.
>
> I know that work has been done by Tom for PostgreSQL 8.1 on
> multiprocessor support but I didn't find any information on if it
> solves the problem with Xeon MP or not.
>
> My question is should we expect a resolution of our problem by
> switching to 8.1 or will we still have problems and should we consider
> a hardware change? We will try to upgrade next tuesday so we will have
> the real answer soon but if anyone has any experience or information
> on this, he will be very welcome.
>
> Thanks for your help.
>
> --
> Guillaume
>

Guillaume,

We had a similar problem with poor performance on a Xeon DP and
PostgreSQL 7.4.x. 8.0 came out in time for preliminary testing but
it did not solve the problem and our production systems went live
using a different database product. We are currently testing against
8.1.x and the seemingly bizarre lack of performance is gone. I would
suspect that a quad-processor box would have the same issue. I would
definitely recommend giving 8.1 a try.

Ken