On Thu, 2011-07-07 at 12:13 +0100, Adrian Schreyer wrote: > I randomly get latency/performance problems even with very simple > queries, for example fetching a row by primary key from a small table. > Since I could not trace it back to specific queries, I decided to give > LatencyTOP (http://www.latencytop.org/) a go. Soon after running a > couple of queries, I saw this in latencytop whilst a query was hanging > in postgres: > > Cause Maximum Percentage > Writing a page to disk 19283.9 msec 99.7 What IO scheduler and filesystem are you using? I think that CFQ has some problems for database workloads. It would be easy to test: just switch to deadline and/or noop for a while and see if the problem persists. Also, I have heard of a few strange things with ext4, but they have probably fixed those issues and it would be much harder for you to test. But it might be worth searching for issues/bugs with your particular version of the filesystem. Regards, Jeff Davis -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
