ulimit shows no effect

[Michael Kreilmeier <lists@kreilmeier.at>]

Hi,

I'm running a debian sarge server with a few Zope-instances. A known 
issue with Zope is, that it is very RAM demanding. Anyways, what I want 
to do is to limit the physical memory my Zope processes can use. Some 
people are doing this with DJB's daemontools. If possible, I'd like 
*not* to use daemontools. I thought ulimit could do the same thing for 
me - seems that I was wrong or I'm doing something wrong.

I tried to set a memory limit in
/etc/security/limit.conf:
zope              hard    rss             65536

I tried to set a memory limit in
/etc/profile:
ulimit -m 65536

I tried to set ulimit in the Zope startup script:
#!/bin/sh
ulimit -m 65536
exec "/path/to/runzope"

All the above setups should, at least to my understanding, set a limit 
of 64 MB. I didn't get any positive results when running a test below.

Test:
* start zope
* watch memory usage with top
* make zope use much memory, i.e. up-/download a large file
* watch the process bypass the memory limit with top


What am I doing wrong. It's probably obvious, but I'm somehow stuck.

Thanks,
Michael