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.
CPU and memory usage are ok.
What is producing this context switching storms?
It is a box with 16GB RAM and 4 XEON processors running RedHat Enterprise Linux AS.