It's funny how people think they're disabling swapping just because they don't have a swap file. Where do you think mmap()-ed file pages go? Your machine can still reclaim resident file-backed pages (either by discarding them if they're clear or writing them to their backing file if dirty) and reload them later. That's.... swap.

Instead of achieving responsiveness by disabling swap entirely (which is silly, because everyone has some very cold pages that don't deserve to be stuck in memory), people should mlockall essential processes, adjust the kernel's VM swap propensity, and so on.

Also, I wish we'd just do away with the separation between the anonymous-memory and file-backed memory subsystems entirely. The only special about MAP_ANONYMOUS should be that its backing file is the swap file.