Jeff, > Do we know why anti-wraparound uses so many resources in the first place? > The default settings seem to be quite conservative to me, even for a > system that has only a single 5400 rpm hdd (and even more so for any real > production system that would be used for a many-GB database). > > I wonder if there is something simple but currently unknown going on which > is causing it to damage performance out of all proportion to the resources > it ought to be using.
Does anti-wraparound vacuum (AWAV) write synchronously? If so, there's a potential whole world of hurt there. Otherwise, the effect you're seeing is just blowing out various caches: the CPU cache, storage cache, and filesystem cache. While we can (and do) prevent vacuum from blowing out shared_buffers, we can't do much about the others. Also, locking while it does its work. -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers