> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Bill Moran > Sent: Friday, October 10, 2003 12:42 PM > To: Hervé Piedvache > Cc: Postgresql Performance > Subject: Re: [PERFORM] One or more processor ? > > > Hervé Piedvache wrote: > > Hi, > > > > A simple question about PostgreSQL ... I have a Pentium Xeon > Quadri processors > > ... > > If I do a SQL request ... does PostgreSQL use one or more processor ? > > PostgreSQL uses one processor per connection. If you have 4 simultaneous > connections, you'll use all four processors (assuming your > operating system > is properly designed/configured). > > > And if it use only one ... why ? > > Could you explain me this ;o) > > The answer to that is beyond my knowledge, but I have a few guesses: > 1) Doing so is more complicated than you think.
You need to be able to paralellize the algorithm. Even so, a 99% paralelizable algorithm over 2 cpus is only 50% faster than 1 cpu. So choose your poison: 2 processes @100% in 1tu or 1 process at 150% at .66tu (tu=time unit). This ofcourse is over simplification. I don't think 99% is reasonable in query processing (though it can depend on the query) so I expect the 2 connection method to be better, unless you only ever have 1 connection. ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
