Hi, I have not seen the iowaits numbers and yes, it is a xeon, four processors. With the 7.4 version the problem did not exist but I think Tom Lane cleared why this behavior with 8.0 and 8.1 versions in http://archives.postgresql.org/pgsql-performance/2006-11/msg00050.php Reimer > -----Mensagem original----- > De: Josh Berkus [mailto:josh@xxxxxxxxxxxx] > Enviada em: terça-feira, 7 de novembro de 2006 15:42 > Para: pgsql-performance@xxxxxxxxxxxxxx; carlos.reimer@xxxxxxxxxxxxx > Assunto: Re: [PERFORM] Context switching > > > Carlos, > > > We've migrated one of our servers from pg 7.4 to 8.1 and from times to > > times (4 hours) the server start doing a lot of context > switching and all > > transactions become very slow. > > > > The average context switching for this server as vmstat shows > is 1 but when > > the problem occurs it goes to 250000. > > Context Switching is a symptom rather than a cause. What's most likely > happening is that you have a combined heavy-CPU and heavy-IO > workload, so you > have bursts of CPU activity stalled by iowaits. > > Can you check the rate of iowaits during the "storm" periods? > > Also, is this Xeon? And are you saying that you *didn't* have > this issue > under 7.4? > > -- > Josh Berkus > PostgreSQL @ Sun > San Francisco > >
