Comment 23 for bug 914773

" So while the monitor is inactive, unhandled events queue up in the compiz process. And it would appear even after the monitor wakes, the backlog of 1.5 million events is too large. So compiz appears to hang, or never catches up. "

When I become active again after a long period of inactivity, and the monitor comes out of its sleep, I always see an old frame, with the clock showing the time of a few minutes after I have left (so probably when the the monitor goes into sleep).

Then either compiz hangs and I need to switch to a vc to force KILL it, or I'll get new frames after a few seconds. Then still a lot of memory is in use, but a compiz --replace solves the job. That doesn't work if compiz hangs, then I won't get new frames and a KILL is required. I think the hanging happens after a longer period of inactivity.

If the problem is indeed the graphic driver putting the monitor into sleep, another workaround should also be to disable sleep in the power management settings and turn off the monitor manually. I will test this next time.