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
