[dev] I/O hammering (was: imp folder prefix)

[Anil Madhavapeddy]

Egan wrote:
>
> IMP repeats this agonizing cycle for each remaining
> message.  Just to build the message list.  Arrrgghhhh!!!!

That was an excellent trace - thanks for taking the trouble to do that!

Hrm, so Outlook does just a single sequence fetch for the entire range
of messages, whereas we do individual ones.  I can see why this hits UW
harder - since all the messages are bundled in mbox format, it would be
more efficient for it to do this in one go; in Courier-IMAP's case, the
individual maildir files would have to be opened anyway.

This needs pondering ... looking at mailbox.php, we currently do several
imap_header() calls - however, this can't be replaced with
imap_headers() since it isn't granular enough (doesn't allow the
selection of a range of headers to return, only all of them).  Also, we
imap_fetchstructure() to determine what icon to put in beside the
message.

Anil