Performance regressions on 6.11

The issue is that certain operations are much slower on kernel 6.11, since the start of the merge window. 6.10 exhibits none of these issues.

Most commonly, simply repeatedly switching focus (and therefore, cursor) between different monitors on sway is enough to cause clients on either monitor to drop 8 frames or so. libwayland itself warns that the system is too slow.

perf top shows that delay_halt() has higher activity than before 6.11 while repeatedly switching focus.

New windows also open slower, and some games have new large lag spikes.

The best setup to replicate would be to use sway, use two monitors, run mpv on both with a 60fps (or higher) framerate video, and switch focus back and forth quickly.

My guess is that certain uploads or downloads block for longer, causing clients to lag behind.