I've seen the answer to this in the FAQ. However, 1) I am definitely not running out of swap, and 2) "ulimit -HSd" reports that the max segment size is set to unlimited by default. I am seeing this behavior consistently on a number of boxes when they get to a little over 1GB of resident memory usage. The amount of physical RAM on the boxes ranges from 4-8GB. The boxes are all running Fedora Core 4. I haven't been able to find much documentation on how to find what the max segment size is for a given running process, i.e. whether "unlimited" really means unlimited or whether there might be a hard cap imposed elsewhere. Any pointers? Or are there any known issues with Squid using >1GB of memory?