Comment 6 for bug 1661072

It appears Unity8 is unthrottled, as in swap interval 0. So when I drag a window around rapidly it matches the USB mouse event rate rather than the display's refresh rate. MIR_CLIENT_PERF_REPORT shows:

[2017-02-02 10:29:02.531811] perf: : 131.00 FPS, render time 7.61ms, buffer lag 22.92ms (4 buffers)
[2017-02-02 10:29:03.547757] perf: : 119.21 FPS, render time 8.36ms, buffer lag 25.21ms (4 buffers)
[2017-02-02 10:29:04.551850] perf: : 95.61 FPS, render time 10.42ms, buffer lag 31.74ms (4 buffers)
[2017-02-02 10:29:05.564508] perf: : 96.83 FPS, render time 10.30ms, buffer lag 30.72ms (4 buffers)
[2017-02-02 10:29:06.579804] perf: : 94.58 FPS, render time 10.54ms, buffer lag 31.32ms (4 buffers)
[2017-02-02 10:29:07.583854] perf: : 95.61 FPS, render time 10.42ms, buffer lag 32.15ms (4 buffers)
[2017-02-02 10:29:08.584909] perf: : 131.86 FPS, render time 7.55ms, buffer lag 22.92ms (4 buffers)
[2017-02-02 10:29:09.589854] perf: : 107.56 FPS, render time 9.26ms, buffer lag 27.92ms (4 buffers)
[2017-02-02 10:29:10.603679] perf: : 120.43 FPS, render time 8.28ms, buffer lag 24.52ms (4 buffers)
[2017-02-02 10:29:11.619541] perf: : 117.24 FPS, render time 8.50ms, buffer lag 25.68ms (4 buffers)
[2017-02-02 10:29:12.628505] perf: : 120.03 FPS, render time 8.31ms, buffer lag 25.00ms (4 buffers)
[2017-02-02 10:29:13.635706] perf: : 93.34 FPS, render time 10.67ms, buffer lag 31.79ms (4 buffers)
[2017-02-02 10:29:14.643575] perf: : 122.14 FPS, render time 8.16ms, buffer lag 24.94ms (4 buffers)
[2017-02-02 10:29:15.643621] perf: : 93.00 FPS, render time 10.72ms, buffer lag 32.28ms (4 buffers)
[2017-02-02 10:29:16.647720] perf: : 108.56 FPS, render time 9.18ms, buffer lag 27.95ms (4 buffers)
[2017-02-02 10:29:17.648820] perf: : 92.90 FPS, render time 10.73ms, buffer lag 32.17ms (4 buffers)