bug#28695: 26.0.60; Rendering lag spikes caused by double-buffering on Linux

[Bryan Gilbert]

> Bryan, which revision/year is it? I also have an XPS 15 (with Skylake 
> CPU) with 4K resolution, and at worst, I see the minor stutters you show 
> in the 1080p video (after adding the advice, yes).

I'm using the newest model: XPS 9560 (Kaby Lake).

> Ubuntu 17.04 with Unity 7 here.

I'm running Arch Linux w/ XMonad.

> Personally, I can stand a few minor glitches, given that double 
> buffering saves me from flickering, which has been an annoyance for years.

I've never actually noticed flickering with Emacs in the ~2 years that I've
been using it, although I've seen it brought up often. One thing that is
unique about my setup compared to yours is that I have no compositor running,
and I'd assume that since you're running Unity that you most likely do. I'm
not sure if that would have any effect on this issue or the flickering though.
In either case I'll do a few tests with compton running to see if that makes
a difference.

I also have a co-worker with an identical computer running Gnome on X11, so
I'll see if I can get ahold of his computer and test this as well.