On Wed, 2009-10-14 at 16:17 -0400, David Warden wrote:
To date, the only problem we have experienced is a seemingly random
but significant slowdown in Squirrelmail's loading of the messages in
a user's Inbox. Each time, I have been able to fix the problem by
deleting the user's dovecot.index, dovecot.index.cache and
dovecot.index.log files in the user's INDEX directory for their
dovecot Inbox.
First thing to try next time: Does it help if you only delete dovecot.index.cache file? How large is the cache file? And take a copy of the dovecot.index* files before doing that, I can then ask a few more questions about them.
I tried having users experiencing this problem log in to a test
Squirrelmail box with mail_debug on, but I didn't see anything out of
the ordinary and they report the same slowness on the test server. I
don't see anything but normal login/logout IMAP lines in the
production dovecot logs.
mail_debug doesn't really help with performance debugging.
My first idea when I get
another one of these is to do a telnet IMAP session to Dovecot on one
of the Squirrelmail boxes and see if I can get it to slow down when
retrieving messages from the Inbox.
That sounds like a good idea to try. And use the exact same IMAP commands as Squirrelmail to do it. strace -tt output of of the slow imap process could also show something interesting.