[mythtv-commits] Ticket #13170: Restore realtime priority capability for vsync thread

[MythTV]

#13170: Restore realtime priority capability for vsync thread
-----------------------------------+--------------------------------
 Reporter:  Doug Larrick <doug@…>  |          Owner:  pbennett
     Type:  Patch - Feature        |         Status:  infoneeded_new
 Priority:  minor                  |      Milestone:  needs_triage
Component:  Ports - rPi            |        Version:  Master Head
 Severity:  medium                 |     Resolution:
 Keywords:                         |  Ticket locked:  0
-----------------------------------+--------------------------------

Comment (by pbennett):

 I tried with and without this patch, also I tried without the patch and
 running sudo renice -20  and the pid of mythfrontend after starting the
 frontend. I did not see any visible or audible difference. With the patch
 the standard deviations are fractionally smaller. see below. Do you set
 the governor before using frontend (see
 https://www.mythtv.org/wiki/Raspberry_Pi#System_Performance)? That makes a
 huge difference in the cases where the raspberry pi has decided on its own
 authority to go into power saving mode. Before I discovered that I was
 tearing my hair out because sometimes playback was perfectly smooth and
 sometimes it was awful.

 I would like to get rid of the extra log message, Buffering:
 !ValidVideoFrames: 0. It floods the log if you have -v playback. It always
 shows zero because I believe that this code is only entered when there are
 0 frames available. There are so many repetitions of waiting buffers
 condition that the original authors instituted the code just below it to
 only display the buffering messages every 100ms (code starting with if
 (last_msg > 100)), but this message is displaying way more often than
 that.

 Reaspberry pi normal
 {{{
 FPS:   30.32 Mean: 32981 Std.Dev: 10157 CPUs: 11% 17% 11% 12%
 FPS:   29.98 Mean: 33350 Std.Dev:  8692 CPUs: 1% 10% 14% 8%
 FPS:   30.12 Mean: 33202 Std.Dev:  6688 CPUs: 1% 9% 10% 9%
 FPS:   29.86 Mean: 33490 Std.Dev:  8148 CPUs: 4% 7% 14% 13%
 FPS:   29.97 Mean: 33370 Std.Dev:  7488 CPUs: 0% 7% 7% 15%
 FPS:   29.99 Mean: 33344 Std.Dev:  6871 CPUs: 1% 9% 10% 12%
 FPS:   30.00 Mean: 33336 Std.Dev:  9016 CPUs: 1% 9% 13% 11%
 FPS:   29.97 Mean: 33368 Std.Dev:  6448 CPUs: 4% 9% 9% 8%
 FPS:   29.89 Mean: 33454 Std.Dev:  8882 CPUs: 1% 9% 13% 10%
 }}}
 Reaspberry pi  with sudo renice -20
 {{{
 FPS:   29.92 Mean: 33424 Std.Dev: 12287 CPUs: 9% 14% 10% 11%
 FPS:   29.84 Mean: 33514 Std.Dev:  8227 CPUs: 12% 13% 7% 6%
 FPS:   30.10 Mean: 33227 Std.Dev:  5612 CPUs: 5% 6% 9% 11%
 FPS:   29.93 Mean: 33412 Std.Dev:  7575 CPUs: 8% 7% 9% 11%
 FPS:   29.98 Mean: 33350 Std.Dev:  8207 CPUs: 7% 11% 12% 7%
 FPS:   30.10 Mean: 33221 Std.Dev:  7890 CPUs: 4% 8% 10% 14%
 FPS:   29.93 Mean: 33405 Std.Dev:  5628 CPUs: 8% 5% 12% 13%
 FPS:   29.92 Mean: 33418 Std.Dev:  8680 CPUs: 3% 9% 14% 11%
 FPS:   29.89 Mean: 33451 Std.Dev:  7740 CPUs: 7% 8% 14% 7%
 FPS:   30.15 Mean: 33172 Std.Dev:  7769 CPUs: 10% 4% 11% 9%
 }}}
 Reaspberry pi with Realtime patch
 {{{
 FPS:   27.94 Mean: 35787 Std.Dev: 14939 CPUs: 2% 2% 2% 2%
 FPS:   30.02 Mean: 33316 Std.Dev:  6928 CPUs: 4% 12% 8% 8%
 FPS:   30.10 Mean: 33228 Std.Dev:  4389 CPUs: 8% 10% 8% 6%
 FPS:   29.99 Mean: 33342 Std.Dev:  7143 CPUs: 4% 10% 8% 10%
 FPS:   29.98 Mean: 33359 Std.Dev:  6930 CPUs: 6% 8% 13% 9%
 FPS:   29.98 Mean: 33358 Std.Dev:  7713 CPUs: 11% 9% 11% 6%
 FPS:   29.67 Mean: 33701 Std.Dev:  7610 CPUs: 11% 12% 8% 8%
 FPS:   30.32 Mean: 32982 Std.Dev:  7176 CPUs: 7% 11% 10% 11%
 FPS:   29.97 Mean: 33368 Std.Dev:  6449 CPUs: 4% 11% 9% 11%
 FPS:   30.01 Mean: 33324 Std.Dev:  7169 CPUs: 6% 10% 7% 7%
 }}}
 Laptop computer no patch or renice, for comparison
 {{{
 FPS:   30.26 Mean: 33045 Std.Dev:  2893 CPUs: 4% 4% 3% 5%
 FPS:   30.03 Mean: 33299 Std.Dev:   261 CPUs: 11% 29% 9% 9%
 FPS:   30.03 Mean: 33301 Std.Dev:   264 CPUs: 15% 26% 11% 9%
 FPS:   29.90 Mean: 33441 Std.Dev:  1534 CPUs: 12% 33% 10% 9%
 FPS:   30.03 Mean: 33301 Std.Dev:   268 CPUs: 15% 28% 11% 10%
 FPS:   30.03 Mean: 33301 Std.Dev:   272 CPUs: 15% 23% 12% 14%
 FPS:   30.03 Mean: 33300 Std.Dev:   275 CPUs: 10% 31% 7% 7%
 FPS:   29.90 Mean: 33441 Std.Dev:  1549 CPUs: 10% 31% 7% 11%
 FPS:   30.03 Mean: 33300 Std.Dev:   271 CPUs: 14% 24% 10% 12%
 FPS:   30.03 Mean: 33299 Std.Dev:   395 CPUs: 22% 31% 18% 18%
 }}}

--
Ticket URL: <https://code.mythtv.org/trac/ticket/13170#comment:8>
MythTV <http://www.mythtv.org>
MythTV Media Center