[Dovecot] rc14 and rc15 performance issues

[Jeff A. Earickson]

On Mon, 20 Nov 2006, Timo Sirainen wrote:

> Date: Mon, 20 Nov 2006 18:36:17 +0200
> From: Timo Sirainen <tss at iki.fi>
> Reply-To: Dovecot Mailing List <dovecot at dovecot.org>
> To: Jeff A. Earickson <jaearick at colby.edu>
> Cc: dovecot at dovecot.org
> Subject: Re: [Dovecot] rc14 and rc15 performance issues
> 
> On Mon, 2006-11-20 at 09:25 -0500, Jeff A. Earickson wrote:
>> Hi,
>>
>> I am stuck at rc13 because rc14 and rc15 have both failed to keep
>> up with imap connections on my (slow old) system.  I have the problem
>> where if a lot of people check their email at once (like at the
>> top of the hour) then my load goes way up and things slow to a
>> crawl.  My setup: Solaris 10 on an E220R, mbox format, imap and imaps
>> only.  I also use "login_process_per_connection = no".  Any suggestions?
>
> Like Marcus asked, is it I/O load or CPU load? And if CPU, what process
> is using it? What passdb and userdb do you use? If you're not sure if
> it's imap process or something else doing it, you could eg. run with
> rc15's imap and everything else with rc13, or vice versa.
>
> Anyway I don't see what could have caused anything to work slower..
>

Because of screaming users, I didn't have a lot of time at analyze
the situation.  The cpu load climbed and climbed, to 40+ (uptime number),
memory was really low, it may have been paging.  passdb is passwd-file
and userdb is passwd, nothing exotic here.

We have times like the top of the hour, and 11 AM especially, where
everybody checks their email at once.  This tends to spike the load.
With rc13, it drops back quickly.  With rc14/15 it goes up and stays
there.  Memory leak someplace?

Our IMAP server is seriously underpowered and needs to be replaced.

Jeff Earickson
Colby College