Default to high thread priority of the KMS thread instead of realtime priority
In contrast to realtime scheduling, this doesn't risk us getting SIGKILL:ed when the kernel is doing busy looping in drmModeAtomicCommit() for some reason, but will according to testing, right now, give us more or less the same benefit when it comes to dispatch lateness and commit lateness.
Stats measured by @daenzer when frantically moving the mouse cursor while compiling mesa in the background, which roughly matched what happened on my system as well with the same reproduction steps:
x high-lateness.txt
+ rt-lateness.txt
+------------------------------------------------------------------------------+
| * |
| x * |
| xx*xx + x |
| *****++ x + + + + + x xx x + x|
||____|_____M_M__________AA_________________|______| |
+------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 22 62 4029 235 1062.0909 1440.673
+ 17 77 3902 352 981.94118 1086.0443
No difference proven at 95.0% confidence
---
x high-duration.txt
+ rt-duration.txt
+------------------------------------------------------------------------------+
| xx+ |
| xx*+ |
| ***+ |
| ***** * x + x x + x x + +|
||___|______MM___A___A______|____________| |
+------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 22 145 2488 225 480.36364 601.16122
+ 17 135 3617 275 698.70588 1014.6407
No difference proven at 95.0% confidence
Edited by Jonas Ådahl