When trying to monitor IT Services (click monitoring -> IT Services), the page just hangs, and eventually dies with the error message in the summary in apache logs. Increasing memory to 7GB for PHP "solves" the problem, but eats up 2,4GB memory and is slow as molasses.

I've managed to capture a debug of a successful load of the page : http://www.linuxgeekz.net/IT-Services-fai.-with-huge-memory-usage.html.bz2
(It'll expand to a 169MB html file with 2,2 million keys )

My environment has 710 / 20 / 43 devices monitored, 30895 / 163681 / 54 items, and 1862 / 1019 [15 / 0 / 1847 triggers.
At the moment only 88 nvps and the servers are under otherwise very low load.

Before I started increasing PHP memory limits, this was the most common error in apache:
PHP Fatal error: Allowed memory size of 2147483648 bytes exhausted (tried to allocate 71 bytes) in /srv/www/htdocs/include/func.inc.php on line 1350, referer: http://zabbix.itmng.no/dashboard.php?ddreset=1&sid=413c78b1fd1c2a0dss