"Anjan Dave" <adave@vantage.com> writes:
> None of the locks are in state false actually.
In that case you don't have a locking problem.
> I don't have iostat on that machine, but vmstat shows a lot of writes to
> the drives, and the runnable processes are more than 1:
I get the impression that you are just saturating the write bandwidth of
your disk :-(
It's fairly likely that this happens during checkpoints. Look to see if
the postmaster has a child that shows itself as a checkpointer in "ps"
when the saturation is occurring. You might be able to improve matters
by altering the checkpoint frequency parameters (though beware that
either too small or too large will likely make matters even worse).
regards, tom lane