Got as much as 30% when launching apps a lot. This causes memory pressure and the bug happens.
Known as "kswapd bug" and affects many devices, as it isn't even Android or ARM specific. Same can happen on a regular PC.
Here's the fix. Believe the original's from CM. you can search web for "contention_wait_kswapd" to see where it applies.
While the kernel provided there works (running on my phone always, latest revision), I'm not providing binaries.