Running a PostgreSQL database and trying to understand the bottleneck in my setup. I now know there is a fdsync being issued to a database file. This one takes up to 10 seconds. The problem here is that all the other processes are entering a wait state (this is in postgres itself. The syncing process holds a latch in exclusive mode, that is needed by all others) waiting for this flush to finish. All my 128+ processes accumulate 10 seconds, throttling my throughput for a total of 1280 seconds. This is significant! There is definitely a relation with the database checkpoints that when happening consequently make the long fdsync show up.
I would like to delve in a little deeper. It could be the sheer number of pages that are being written due the fdsycn. Wonder if someone has a dtrace script snippet I could use here to understand a little better what is going on under the hood. BTW running ZFS where my intent log is on a RAID array which has 1GB of write caches. Thanks, Paul -- This message posted from opensolaris.org _______________________________________________ dtrace-discuss mailing list [email protected]
