[PATCH v3 0/7] few drm_syncobj optimisations

[Tvrtko Ursulin]

On 28/03/2025 16:46, Tvrtko Ursulin wrote:
> A small set of drm_syncobj optimisations which should make things a tiny bit
> more efficient on the CPU side of things.
> 
> Improvement seems to be around 1.5%* more FPS if observed with "vkgears
> -present-mailbox" on a Steam Deck Plasma desktop, but I am reluctant to make a
> definitive claim on the numbers since there is some run to run variance. But, as
> suggested by Michel Dänzer, I did do a five ~100 second runs on the each kernel
> to be able to show the ministat analysis.
> 
> x before
> + after
> +------------------------------------------------------------+
> |                          x         +                       |
> |                   x      x         +                       |
> |                   x      xx      ++++                      |
> |                 x x      xx x    ++++                      |
> |                 x xx   x xx x+   ++++                      |
> |                xxxxx   xxxxxx+   ++++ + +                  |
> |                xxxxxxx xxxxxx+x  ++++ +++                  |
> |              x xxxxxxxxxxx*xx+* x++++++++   ++             |
> |        x x   xxxxxxxxxxxx**x*+*+*++++++++ ++++ +           |
> |       xx x   xxxxxxxxxx*x****+***+**+++++ ++++++           |
> |x     xxx x   xxxxx*x****x***********+*++**+++++++   +  +  +|
> |               |_______A______|                             |
> |                             |______A_______|               |
> +------------------------------------------------------------+
>      N           Min           Max        Median           Avg        Stddev
> x 135      21697.58     22809.467     22321.396     22307.707     198.75011
> + 118     22200.746      23277.09       22661.4     22671.442     192.10609
> Difference at 95.0% confidence
>      363.735 +/- 48.3345
>      1.63054% +/- 0.216672%
>      (Student's t, pooled s = 195.681)

Intel Alderlake laptop, KDE Wayland:

x base
+ syncobj
+--------------------------------------------------------------+
|                                                       +      |
|                                                       +   +  |
|                                                       +   +  |
|                                                       +  ++  |
|                                                       ++ ++  |
|                                       x               ++ ++  |
|                       x               x             + ++ ++  |
|                       x          xx   xx x x        +++++++  |
|                       x   x   xx xxx xxxx*xxx      +++++++++ |
|x       xx x  x    x  xx xxxxxxxxxx*xxx****xxx  +x+ ++++++++++|
|                      |__________A_M_______|     |____A_M___| |
+--------------------------------------------------------------+
     N           Min           Max        Median           Avg        Stddev
x  55      7158.232      8058.753      7803.506     7754.5195     191.69526
+  55       7801.23      8272.271      8172.435     8150.6303     105.84085
Difference at 95.0% confidence
	396.111 +/- 57.8717
	5.10813% +/- 0.746296%
	(Student's t, pooled s = 154.838)

* Scores may seem low but I had to fix CPU freq to avoid some pretty 
strong thermal throttling causing wild swings within a run.

Benchmarking script:

#! /bin/sh

base=$1

for i in $(seq 5)
do
	timeout 60 vkgears -present-mailbox | tee -a "vkbench-$base.log"
	sleep 5
done

Regards,

Tvrtko

> 
> v2:
>   * Implemented review feedback - see patch change logs.
> 
> v3:
>   * Moved #define DRM_SYNCOBJ_FAST_PATH_ENTRIES one patch earlier for less churn.
> 
> Cc: Maíra Canal <mcanal at igalia.com>
> 
> Tvrtko Ursulin (7):
>    drm/syncobj: Remove unhelpful helper
>    drm/syncobj: Do not allocate an array to store zeros when waiting
>    drm/syncobj: Avoid one temporary allocation in drm_syncobj_array_find
>    drm/syncobj: Use put_user in drm_syncobj_query_ioctl
>    drm/syncobj: Avoid temporary allocation in
>      drm_syncobj_timeline_signal_ioctl
>    drm/syncobj: Add a fast path to drm_syncobj_array_wait_timeout
>    drm/syncobj: Add a fast path to drm_syncobj_array_find
> 
>   drivers/gpu/drm/drm_syncobj.c | 286 ++++++++++++++++++----------------
>   1 file changed, 154 insertions(+), 132 deletions(-)
>