We're running a WordPress multisite instance on two Rackspace Cloud servers, one web and one database, with 30 or so sites currently. I've put Nginx in front for static assets and Apache handles all dynamic requests. I've also configured Memcached for the database and APC op code caching for PHP. W3 Total Cache is enabled by default across all of the sites we have.
It's wicked fast with one issue: Apache processes regularly weigh in between 80 and 120 MB. The web server has 2 GB of memory, meaning I get 15 or so processes until things go on the fritz. The processes obviously shouldn't be that large but I'm perplexed as to why they are.
What's a good strategy for identifying what's going on?
Thanks in advance!
Update 10/2/10: For those wondering, the resolution of the memory issue problem was disabling PHP xdebug (was inadvertently enabled on configuration and caused random memory usage spikes).