I run the mpm-itk apache2 module on my server since it’s shared between a few sites. A few rogue crawlers brought it down a few days ago and while I was checking the logs I noticed a lot more apache children processes running than I had defined. One quick look in apache2.conf and I noticed my mistake. I had configured under a different prefork module since the default config shipping with debian has no section for itk. So I added it myself:
Of course adjust values according to your resources.