In Mac OS X 10.9+, Apple modified the way VRAM is allocated to *integrated* GPU chipsets. I've been trying to profile why sk only has half second long hangs every second on Mavericks, but not Mountain Lion or lower, and came upon this fact. SK needs to fix how it allocates VRAM so it doesn't thrash the paging system used, as the VRAM is now dynamically allocated instead of wired. What this means is that SK can allocate more VRAM than it could before on previous systems, but it also means that it's on-demand allocated rather than pre-allocated under the "wired" category. As a result allocation overhead on OS X is no longer free™ and if you thrash the VRAM allocations you will experience garbage collection like hiccups from within kernel_task, which is what is happening on the multiple systems I've tested. I've tested MacBooks and MacBook Pros with integrated VRAM forced and noted this only happens on Mavericks+. I clean tested java updates and various configs, even a blank HDD to start off the testing with. It's the VRAM allocation change in Mavericks+ that SK is incompatible with. I'm guessing devs at OOO might be using a mac with a dedicated card and might not be experiencing this issue, but this issue affects probably almost all of SK's Apple device based userbase.

Affected GPUs include the Intel based on-die and Nvidia based brands (Tested 9800m and the 320m) stretching from oldest to around circa 2013.

If you are experiencing hangs every couple seconds on OS X at what seems regularly spaced intervals, please note the CPU load (noted it sitting at ~50%) and memory levels (going up and down every few seconds by 50 megabytes) of kernel_task.

tl;dr Spiral Knights does not work with Mac OS X 10.9+'s VRAM allocation algorithms, needs a refactor within sk.

Also it's been an issue since mavericks was released years ago, so I bet OOO's userbase loss might have been sightly due to this.