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
