> Any idea how to improve the performance?
Hmmm, I guess we'll need more info about resource usage (CPU, I/O, locks)
used when the commit happens. Run these two commands
$ iostat -x 1
$ vmstat 1
and then execute the commit. See what's causing problems. Is the drive
utilization close to 100%? You've problems with disks (I'd bet this is the
cause). Etc.
There's a very nice chapter about this in Greg's book.
BTW what filesystem are you using? Ext3, ext4, reiserfs, xfs? I do
remember there were some problems with sync, that some filesystems are
unable to sync individual files and always sync everything (which is going
to suck if you want to sync just the WAL).
regards
Tomas