If you are using Varnish version >= 2.1 and experiencing an ever increasing CPU usage up to a point where you need to restart the service to force CPU usage to drop you may want to add the “-h classic” argument to the command line.

This will revert to use the older hashing method instead of the newer “critbit” that was first introduced in version 2.1.

You can read a little bit more about it on the Yedda Dev Blog.