libva decoding performance regression with kernel 4.0-rc

[Olivier Crête]

Hello,

Using an Atom E3845 board, we had a pretty bad performance regression
when upgrading to 4.0-rc6 from 3.19. With the help of git bisect, I
traced it back to commit 78a42377. Reverting this commit and subsequent
related commits (b9ffd80, 71745376, etc) fixes the performance
regression for me.

Without those patches, I can play 8-9 1080p MPEG2 streams, after them,
it's down to 5-6.

I tested using a libdrm checkout from Feb 16, and the latest git master
of libva, libva-intel-driver and gst-plugins-vaapi. The "identity
drop-probability=1" is to prevent anything from being displayed, so it's
purely decoding performance.

Pure decode, single stream not displayed:
time gst-launch-1.0 filesrc location=18Mbps_CBR_MPEG2_Main-High_1920x1080p_16x9_29-97fps.m2t ! tsdemux ! mpegvideoparse ! vaapidecode ! identity drop-probability=1 ! vaapisink

With kernel 3.18.0-rc7-01052-g493018d
real	0m11.429s
user	0m6.516s
sys	0m1.640s

With kernel 3.18.0-rc7-01053-g78a4237
real	0m12.694s
user	0m6.744s
sys	0m2.680s


8 simultaneous streams displayed:
time gst-launch-1.0 filesrc location=18Mbps_CBR_MPEG2_Main-High_1920x1080p_16x9_29-97fps.m2t ! tsdemux ! mpegvideoparse ! vaapidecode ! vaapisink sync=0 \
  filesrc location=18Mbps_CBR_MPEG2_Main-High_1920x1080p_16x9_29-97fps.m2t ! tsdemux ! mpegvideoparse ! vaapidecode ! vaapisink sync=0 \
  filesrc location=18Mbps_CBR_MPEG2_Main-High_1920x1080p_16x9_29-97fps.m2t ! tsdemux ! mpegvideoparse ! vaapidecode ! vaapisink sync=0 \
  filesrc location=18Mbps_CBR_MPEG2_Main-High_1920x1080p_16x9_29-97fps.m2t ! tsdemux ! mpegvideoparse ! vaapidecode ! vaapisink sync=0 \
  filesrc location=18Mbps_CBR_MPEG2_Main-High_1920x1080p_16x9_29-97fps.m2t ! tsdemux ! mpegvideoparse ! vaapidecode ! vaapisink sync=0 \
  filesrc location=18Mbps_CBR_MPEG2_Main-High_1920x1080p_16x9_29-97fps.m2t ! tsdemux ! mpegvideoparse ! vaapidecode ! vaapisink sync=0 \
  filesrc location=18Mbps_CBR_MPEG2_Main-High_1920x1080p_16x9_29-97fps.m2t ! tsdemux ! mpegvideoparse ! vaapidecode ! vaapisink sync=0 \
  filesrc location=18Mbps_CBR_MPEG2_Main-High_1920x1080p_16x9_29-97fps.m2t ! tsdemux ! mpegvideoparse ! vaapidecode ! vaapisink sync=0

With kernel 3.18.0-rc7-01052-g493018d
real	2m45.317s
user	1m21.296s
sys	0m51.080s

With kernel 3.18.0-rc7-01053-g78a4237
real	3m1.275s
user	1m24.336s
sys	1m38.360s


-- 
Olivier Crête
olivier.crete at collabora.com