[usefulcat]

I do a lot of dev work on a machine that has 12 cores and 96 GB of RAM and I currently have swappiness set to 85.

96 GB would be plenty of memory for what I need to do--mostly I benefit from lots of filesystem caching. BUT--there's another user of this system and he does most of his work using Matlab. For the stuff he's doing, Matlab routinely sucks down 10s of gigabytes of memory. And it may stay that way for days at a time.

Without swapping, Matlab will happily sit on all that memory indefinitely, whether it's doing anything or not. Meanwhile, everything I do takes ages because of the paltry amount of memory left for FS caching.

With swapping, I can get some of that memory back for FS cache when Matlab isn't being used, and it makes a huge difference.