[imp] upgrade from IMP3 -> IMP4 : serious performance hit

[Chris J. Alexander]

We upgraded our Horde/IMP/Turba installation from the Horde 2 / IMP 3 tree to 
the latest version this weekend (Horde 3.0.4 / IMP 4.0.3 / Turba 2.0.2).  We are 
running behing a Foundry load balancer on two Sun Fire v280s, Solaris 9, Apache 
2.0.54, PHP 4.3.11.  One of the two 280Rs also functions as a mySQL 4.1.2 DB 
server strictly for the Horde implementation.  Each box has 2 900 MHz and 4 GB 
RAM - they aren't small by any means.

Before, these two boxes barely ever broke a sweat.  After the upgrade, during 
business hours, these boxes are falling over regularly with load averages into 
the 30's.  The only thing that changed was the version of horde/imp; under lite 
load the two boxes are fine, but as soon as any kind of load is applied, smoke 
appears.  It's CPU smoke, too, not memory or network as best I can tell.

I've already done almost everything within the performance document to try to 
alleviate the problem:

*) We were running Zend Performance Suite 4.0.2; one of the two boxes was 
upgraded to Zend Platform 1.1.2 this morning but this has not helped.
*) PHP is compiled with inline optimization.
*) Mcrypt is installed and used
*) Keep Alives are turned on
*) up-imaproxy-1.2.2 is installed and used by both servers.
*) The Apache SSL cache is in shared memory
*) Output compression is enabled in Apache.
*) session_gc.probability is 1.

Sessions are kept within the MySQL database, which is also running a lot hotter 
than it did under the old Horde.

Is this just a symptom that I need much much larger hardware to run the new 
version of Horde for my installation?  My higher ups are screaming at me every 
hour to do something about it; I don't want to downrev if I can help it, but I 
may not have a choice since I can't produce new hardware that fast.

Help?
Thanks
CJA
--
Chris J. Alexander
Information Technology Division
404-727-8333 / FAX 404-727-0817