Decibel! <decibel@xxxxxxxxxxx> writes: > Interesting. I'm guessing that ext3 has to sync out the entire journal > up to the point in time that fsync() is called, regardless of what > files/information the journal contains. Fortunately I think it's common > knowledge to mount PostgreSQL filesystems with data=3Dwriteback, which > hopefully eliminates much of that bottleneck... but if you don't do > noatime you're probably still spewing a lot out to the drive. FWIW, I tried to test the above by running Pavel's script on an ext3 partition mounted noatime,data=writeback. This didn't seem to make any difference --- still very large deviations in the time to do a TRUNCATE. However the problem seems harder to reproduce now than it was three weeks ago. In the meantime I installed a 2.6.22-based kernel instead of the 2.6.20 one that Fedora was using before; I wonder whether the kernel guys tweaked something related ... regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
