Specifically, the weak spot is in "maple tree," a new data structure system for VMAs introduced in Linux kernel 6.1 that replaced the "red-black trees" and relied on the read-copy-update (RCU) mechanism.
Maple Tree also recently caused intermittent failures in some of my CPU-intensive tasks, in such an obscure way that I only found out by dumb luck that it was a kernel bug. I expect it will be great eventually, but it's feeling pretty rough at the moment. I'm thinking this code should have had more testing and maturing before going mainline.