[PATCH v2 0/7] A few drm_syncobj optimisations

[Tvrtko Ursulin]

On 06/01/2025 10:55, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
> 
> 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. It
> would be best if someone could verify or suggest a more heavy workload for
> syncobjs.
> 
> *)
> Before average fps after 200s: 22102
> After: 22426

Copying over from the discussion on v1 of the series:

Five ~100 second runs each kernel. Absolute numbers are a bit different 
before I turned *off* some kernel hardening options since.

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)


> 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 | 281 ++++++++++++++++++----------------
>   1 file changed, 147 insertions(+), 134 deletions(-)
>