[PATCH 3/6] drm/syncobj: Do not allocate an array to store zeros

[Tvrtko Ursulin]

On 06/01/2025 17:16, Michel Dänzer wrote:
> On 2025-01-02 20:44, Tvrtko Ursulin wrote:
>>
>> "vkgears -present-mailbox" average framerate:
>>
>>    Before: 21410.1089
>>    After:  21609.7225
>>
>> With a disclaimer that measuring with vkgears feels a bit variable,
>> nevertheless it did not look like noise.
> 
> That's ~1% difference. IME the frame rate can easily vary more than that during a single run.
> 
> The frame rate surely varies by more than 1 fps during each run, so comparing such large average values down to 4 digits after the decimal point doesn't seem very useful.
> 
> Doing multiple (at least 3 or more each) before & after runs and comparing the distribution of individual measured values using something like ministat might confirm it's essentially noise, or give more confidence it's not.

I did multiple runs and I thought from the code changes it would be 
obvious there is some code there which should go.

But fair enough, I agree ministat is common practice so I re-did it. 
Five ~100 second runs each kernel. Absolute numbers are a bit different 
before I turned on 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)

It's a small difference but every little helps.

Regards,

Tvrtko