On Fri, Oct 02, 2020 at 03:20:36PM +0100, Laurence Tratt wrote: >> For the past couple of weeks I've been encountering a weird problem on >> -current amd64 -- my screen intermittently blanks for around 2-4 seconds >> when running xorg. At first I thought this was a hardware problem (the >> machine isn't a spring chicken), but then ffmpeg caught the blanking while >> I was doing a screencast (i.e. the recording of the xorg part of things >> goes entirely blank for a couple of seconds), so it seems to be a software >> problem. >> >> Unfortunately I can't seem to find any obvious trigger. It seems to happen >> more often when the machine is under heavy load, but sometimes it happens >> under light load. Frankly, I don't have any real idea *what* could be >> causing it, and I'm hoping that someone else might have seen this, and >> perhaps have been equally baffled as to the cause! > I have now found a semi-reliable way of triggering this with the following > ffmpeg command on a decent length video file: > > ffmpeg -i <video> -c:a flac out.flac > > The blanking effect is not consistent or continuous: sometimes the display > will blank every few seconds, sometimes it might go 30 seconds without > doing so. > > I'm running on a 4 core machine, and this task maxes out all 4 cores. > Interestingly, however, other tasks which use all 4 cores do not cause the > display blanking problem as often. I don't know what ffmpeg is doing > differently, other than 'top' shows that it's often 'fsleep'ing (which may > well be completely irrelevant to the problem I'm seeing).
For the record, I've not had this problem in the last week or so -- hopefully it's disappeared for good! Laurie
