If anything in the kernel is written in a language that has an extensive runtime system... Well, extensive runtime systems are pretty reliably resource hungry. And when they might suddenly need which sorts of resources tends to be unpredictable.
Vs. the kernel must keep working reliably when resources are running low.
But, today linux simply kills any process to free memory. What could prevent a gc (which also serves allocations, not only collects them back) to just do that on an emergency cycle? Destroy a record in a process array and reclaim its pages (of course without doing any allocations on the way, or by using an emergency pool). Or even just reclaim its pages and wait for it to crash on a page fault if you feel lazy.
which sorts
Dynamic languages only do memory-related ops unpredictably, or is it more than that?
Vs. the kernel must keep working reliably when resources are running low.