Unity8-dash render time is too high, causing frame skipping

[Daniel van Vugt]

Unity8-dash render time is too high, causing frame skipping

On a 60Hz display you have 16.6ms per frame. So to keep things running smoothly your render time should be much lower than 16.6ms.

$ restart unity8-dash MIR_CLIENT_PERF_REPORT=log MIR_CLIENT_FORCE_SWAP_INTERVAL=0
$ tail -f ~/.cache/upstart/unity8-dash.log

MAKO:

[2016-04-01 11:38:54.086901] perf: : 69.00 FPS, render time 13.96ms, buffer lag 29.76ms (3 buffers)
[2016-04-01 11:38:55.103637] perf: : 73.81 FPS, render time 13.00ms, buffer lag 27.33ms (3 buffers)
[2016-04-01 11:38:56.111953] perf: : 67.46 FPS, render time 14.19ms, buffer lag 30.60ms (3 buffers)

ARALE:

[2016-04-01 11:41:43.467067] perf: : 52.31 FPS, render time 18.54ms, buffer lag 61.60ms (3 buffers)
[2016-04-01 11:41:44.491750] perf: : 53.71 FPS, render time 18.01ms, buffer lag 37.43ms (3 buffers)
[2016-04-01 11:41:45.504621] perf: : 55.33 FPS, render time 17.53ms, buffer lag 37.03ms (3 buffers)

Note(1): I have used MIR_CLIENT_FORCE_SWAP_INTERVAL=0 because it works around a problem with the Android platform's MIR_CLIENT_PERF_REPORT=log being rounded up to the next frame interval. It also has the nice benefit of showing peak frame rate possible on a device (e.g. 73 FPS on mako above).

Note(2): Yes you can use the same benchmark on 'unity8' instead of 'unity8-dash' however the results will be inaccurate -- limited and rounded to whole frames due to bug 1369763.

Note(3): This is all possibly related to bug 1494795.

[Daniel van Vugt (vanvugt)]

It's worth noting that mako just sneaking under 16ms sounds good, but also needs to do better. Because that still means it's using most of the time available to render a frame. And if the system had to do anything else at all during that time, you likely would take longer and miss a frame.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[kevin gunn (kgunn72)]

@duflu - just to double check, have you verified the actual refresh rate config of arale screen/display?

[Daniel van Vugt (vanvugt)]

Yes, the arale display is 60.72Hz as shown by 'mirout'. But that's also irrelevant here as I'm using MIR_CLIENT_FORCE_SWAP_INTERVAL=0 to collect peak numbers that are independent of the physical refresh rate.

More data points for the sake of comparison (also running under Unity8 on the same phones):

MAKO:
mir_demo_client_egltriangle (about the simplest and fastest client imaginable):
[2016-04-04 10:46:20.018850] perf: : 282.60 FPS, render time 2.43ms, buffer lag 8.10ms (3 buffers)
[2016-04-04 10:46:21.023429] perf: : 332.66 FPS, render time 2.07ms, buffer lag 6.98ms (3 buffers)
[2016-04-04 10:46:22.024222] perf: : 297.70 FPS, render time 2.32ms, buffer lag 7.81ms (3 buffers)
mir_demo_client_eglplasma (a pathologically heavy fragment shader):
[2016-04-04 10:46:54.638567] perf: : 165.83 FPS, render time 4.78ms, buffer lag 13.32ms (3 buffers)
[2016-04-04 10:46:55.644152] perf: : 161.19 FPS, render time 4.88ms, buffer lag 13.79ms (3 buffers)
[2016-04-04 10:46:56.645983] perf: : 163.83 FPS, render time 4.84ms, buffer lag 13.49ms (3 buffers)

ARALE:
mir_demo_client_egltriangle (about the simplest and fastest client imaginable):
[2016-04-04 10:25:12.224706] perf: : 245.26 FPS, render time 3.24ms, buffer lag 8.98ms (3 buffers)
[2016-04-04 10:25:13.227914] perf: : 246.26 FPS, render time 3.21ms, buffer lag 8.97ms (3 buffers)
[2016-04-04 10:25:14.231324] perf: : 244.26 FPS, render time 3.25ms, buffer lag 9.02ms (3 buffers)
mir_demo_client_eglplasma (a pathologically heavy fragment shader):
[2016-04-04 10:26:35.991810] perf: : 90.81 FPS, render time 10.16ms, buffer lag 22.90ms (3 buffers)
[2016-04-04 10:26:37.001922] perf: : 91.08 FPS, render time 10.10ms, buffer lag 22.95ms (3 buffers)
[2016-04-04 10:26:38.004405] perf: : 90.81 FPS, render time 10.19ms, buffer lag 22.84ms (3 buffers)

So this shows it's possible to render super-smooth graphics in a Unity8 client on mako and arale. Only unity8-dash is letting us down.