Unity8's blur effect slows the system down too much

Unity8's blur effect (such as in the app drawer) slows the system down too much. I get 20 FPS with the blur, and 60 FPS+ without it.

Here's my unity8.log output (with MIR_CLIENT_PERF_REPORT=log) on a 6-year old laptop, rendering egltriangle before and after the app drawer opens above it:

[2017-02-22 17:25:09.160680] perf: : 60.03 FPS, render time 1.52ms, buffer lag 65.11ms (4 buffers)
[2017-02-22 17:25:10.160958] perf: : 60.00 FPS, render time 1.56ms, buffer lag 65.11ms (4 buffers)
[2017-02-22 17:25:11.176709] perf: : 60.09 FPS, render time 1.58ms, buffer lag 65.02ms (4 buffers)
[2017-02-22 17:25:12.193072] perf: : 60.03 FPS, render time 1.23ms, buffer lag 65.39ms (4 buffers)
[2017-02-22 17:25:13.209314] perf: : 60.03 FPS, render time 1.22ms, buffer lag 65.42ms (4 buffers)
[2017-02-22 17:25:14.225774] perf: : 60.03 FPS, render time 1.40ms, buffer lag 65.23ms (4 buffers)
[2017-02-22 17:25:15.241893] perf: : 60.03 FPS, render time 1.31ms, buffer lag 65.32ms (4 buffers)
[2017-02-22 17:25:16.258348] perf: : 60.03 FPS, render time 1.23ms, buffer lag 65.41ms (4 buffers)
[2017-02-22 17:25:17.275305] perf: : 60.03 FPS, render time 1.45ms, buffer lag 65.20ms (4 buffers)
[2017-02-22:17:25:18.223] qml: pushing right edge without mouse actually being at right edge!
[2017-02-22 17:25:18.292455] perf: : 59.98 FPS, render time 1.36ms, buffer lag 65.33ms (4 buffers)
[2017-02-22:17:25:18.586] [PERFORMANCE]: Last frame took 44 ms to render.
[2017-02-22:17:25:18.625] [PERFORMANCE]: Last frame took 37 ms to render.
[2017-02-22:17:25:18.714] [PERFORMANCE]: Last frame took 42 ms to render.
[2017-02-22:17:25:18.766] [PERFORMANCE]: Last frame took 43 ms to render.
[2017-02-22:17:25:18.818] [PERFORMANCE]: Last frame took 50 ms to render.
[2017-02-22:17:25:18.867] [PERFORMANCE]: Last frame took 44 ms to render.
[2017-02-22:17:25:18.920] [PERFORMANCE]: Last frame took 51 ms to render.
[2017-02-22:17:25:18.920] [PERFORMANCE]: Last 10 frames took over 17 ms to render (last frame: 51 ms)
[2017-02-22:17:25:18.968] [PERFORMANCE]: Last frame took 45 ms to render.
[2017-02-22:17:25:19.020] [PERFORMANCE]: Last frame took 34 ms to render.
[2017-02-22:17:25:19.319] [PERFORMANCE]: Last frame took 33 ms to render.
[2017-02-22 17:25:19.319652] perf: : 27.26 FPS, render time 31.01ms, buffer lag 108.55ms (4 buffers)
[2017-02-22:17:25:19.418] [PERFORMANCE]: Last 10 frames took over 17 ms to render (last frame: 31 ms)
[2017-02-22:17:25:19.919] [PERFORMANCE]: Last 10 frames took over 17 ms to render (last frame: 31 ms)
[2017-02-22:17:25:20.071] [PERFORMANCE]: Last frame took 32 ms to render.
[2017-02-22:17:25:20.167] [PERFORMANCE]: Last frame took 44 ms to render.
[2017-02-22:17:25:20.215] [PERFORMANCE]: Last frame took 47 ms to render.
[2017-02-22:17:25:20.215] [PERFORMANCE]: Too many warnings were given. Performance monitoring stops.
[2017-02-22 17:25:20.361137] perf: : 20.17 FPS, render time 47.32ms, buffer lag 151.76ms (4 buffers)
[2017-02-22 17:25:21.384374] perf: : 20.52 FPS, render time 43.28ms, buffer lag 149.30ms (4 buffers)
[2017-02-22 17:25:22.402890] perf: : 20.62 FPS, render time 44.51ms, buffer lag 151.61ms (4 buffers)
[2017-02-22 17:25:23.419072] perf: : 20.66 FPS, render time 43.71ms, buffer lag 147.78ms (4 buffers)
[2017-02-22 17:25:24.433844] perf: : 20.71 FPS, render time 44.63ms, buffer lag 143.52ms (4 buffers)
[2017-02-22 17:25:25.450279] perf: : 20.66 FPS, render time 44.08ms, buffer lag 154.40ms (4 buffers)
[2017-02-22 17:25:26.468114] perf: : 20.64 FPS, render time 43.97ms, buffer lag 145.19ms (4 buffers)
[2017-02-22 17:25:27.481509] perf: : 20.73 FPS, render time 44.42ms, buffer lag 153.57ms (4 buffers)
[2017-02-22 17:25:28.500612] perf: : 20.60 FPS, render time 44.28ms, buffer lag 147.28ms (4 buffers)
[2017-02-22 17:25:29.516410] perf: : 20.68 FPS, render time 44.19ms, buffer lag 151.85ms (4 buffers)
[2017-02-22 17:25:30.534662] perf: : 20.62 FPS, render time 44.74ms, buffer lag 151.19ms (4 buffers)

And while we still render the cursor manually this means the mouse cursor also now moves at only 20 FPS.