On Mon, Feb 13, 2006 at 11:22:26AM +1100, grant beattie wrote:
the only side effect of using this feature is that you need to leave it turned on, even after users have POP'd into their mailbox because if you turn it off and are using an X-UIDL format such as the default, Dovecot knows that it can generate it on the fly and does so, even if the X-UIDL for a given message is present in the index.
the upshot of this is that every (new) message in a mailbox is read on each pop3 connection, looking for an X-UIDL header (that won't be there), resulting in higher disk IO than necessary.
I need to hack on the code to always use the X-UIDL from the index if present, then turn off pop3_reuse_xuidl and eliminate a bunch of disk IO.
That optimisation may be unnecessary: the common case is going to be that new messages will be read, indexed, downloaded in one go. It'll all be in buffer cache for that time so I wouldn't expect any additional I/O on a sane OS; just more syscalls by Dovecot to get the data.
In particular, no extra disk seek (which is what kills us). Although I confess I'm thinking mostly of maildirs here.
/k
-- Josh "Koshua" Goodall "as modern as tomorrow afternoon" joshua@roughtrade.net - FW109