Comment 80 for bug 855124

Sorry for the delay in follow-up:

Yes, the patch when cherry-picked into a recentish mainline kernel shows noticable improvement. Subjectively, it still feels a little "chunky" when starting up (I think the login manager and gnome 3 both seem to issue a large number of xrandr requests), but night and day compared to the previous succession of stalls.

w.r.t. bug 29536? I can't say whether it's a dupe or not. i specifically wasn't getting the periodic stalls every 10-30s. But perhaps the other reporter had something that was doing xrandr requests with that frequency whereas for me it was only during log-in.