short hang when compositing is off, coffee lake
I've been seeing this since around 5.4 or 5.3, I believe, and I continue to see this with the 5.5 drm-intel-fixes tree, which is at e85ade1f50aae464ce1 as of writing.
When compositing is turned off, there is sometimes a 1 to 3 second hang, especially when using chromium. This sometimes results in plasma/kwin becoming unresponsive until I kill it all and restart it with compositing reenabled. With compositing turned on, these problems do not manifest themselves.
I believe this is a different issue than #673 (closed)
CC @ickle