Comment 7 for bug 1532202

Notes from experimentation:

1. I've been unable to reproduce this effect without a nested server.

2. The slowdown manifests with the client on either the internal or the external display (or with clients on both).

3. There's a further (more dramatic) slowdown on the primary display if a second client connects to the host requesting the external display. Vis: bin/mir_demo_client_egltriangle -p -o2 -f

3. "--nbuffers = 0" doesn't help

4. "--disable-overlays on" reduces FPS further, but seems to cure the jerkiness

5. I sometimes see a crash on exiting the host server: *** Error in `mir_demo_server': corrupted double-linked list: 0x01e72d70 ***