[imp] Slow mailbox list from time to time

[Tornoci Laszlo]

Hi,

I have a Horde/IMP system that behaves strangely since I upgraded from 
3.1.5/4.1.5 to 3.3.4/4.3.4. I have about 400 users with 50-70 concurrent 
sessions usually. The IMAP mailstore (Cyrus) and the MTA are on separate 
boxes. The system is dual Xeon (quad core) 2GHz, 2GB RAM.

We had excellent response times before the upgrade. The problem is, we 
still have excellent response times (practically instantaneous mailbox 
lists with > 3000 mails in one folder) most of the time, BUT sometimes 
for long periods of time, I get miserable response times (30-80 sec 
waiting) for the same large mailbox to be listed. "top" show the http 
process to shoot up to 100% cpu while waiting, but nothing else 
remarkable. Restarting http or mysqld doesn't help. Logging in is not 
slow. The larger a mailbox, the worse the problem is.
After some time, response times get back to normal.

It's not the IMAP box. Using IMAP clients, direct access to the IMAP box 
shows absolutely no difference.

Access is always fine if I use the "dynamic" mode. This problem appears 
only if using the "traditional" mode.

Can't see any unusual network or process activity. There is no obvious 
correlation with the number of concurrent users either.

Any ideas, anyone?


					Yours: Laszlo