[horde] Performance problems with Horde 4

[Montagutelli Xavier]

We face serious performance problems with Horde 4.

Our "old" setup with Horde 3 runs on a Xeon server. On the same  
hardware, H4 is unusable. The new system is under Debian squeeze, with  
as many native packages as possible. I have tried both apache2 prefork  
+ mod_php5 vs. apache2 worker + php5 fast CGI. MySQL (unix sockets)  
and memcache are running on the same server. CSS and JS caching is  
enabled.

One or two minutes after launching apache2, we have "MaxClient"  
processes (when using prefork, fixed at 300), the four CPUs stays at  
100% (mainly user time), the load average increases. H4 sometimes  
becomes unresponsive, with strange error messages ("no handler for  
/imp", CSS not delivered, etc.).

Having decreased the PHP parameter max_execution_time (10 s) helps a  
little bit. MaxRequestsPerChild doesn't change anything. We have tried  
the apc accelerator. Memcache consumes few memory (~120 MB) despite  
using the "-m 1024" switch to increase its upper limit.

It looks like PHP is "eating" all the CPU given to it. Something must  
be wrong in my setup ?? Do someone use H4 with more than 200  
simultaneous users on the same server ? Do you use Debian or another  
distro ?

I know it's a bit vague, but I don't understand how to handle this  
problem. Any help wanted ...

-- 
Xavier Montagutelli
SERVICE COMMUN INFORMATIQUE
123  Avenue   ALBERT THOMAS
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