Hi Miquel,
On 2/2/24 06:26, Miquel Raynal wrote:
Hi Pekka,
pekka.paalanen@xxxxxxxxxxxxx wrote on Fri, 2 Feb 2024 10:55:22 +0200:
On Thu, 01 Feb 2024 18:31:32 +0100
Louis Chauvet <louis.chauvet@xxxxxxxxxxx> wrote:
Change the composition algorithm to iterate over pixels instead of lines.
It allows a simpler management of rotation and pixel access for complex formats.
This new algorithm allows read_pixel function to have access to x/y
coordinates and make it possible to read the correct thing in a block
when block_w and block_h are not 1.
The iteration pixel-by-pixel in the same method also allows a simpler
management of rotation with drm_rect_* helpers. This way it's not needed
anymore to have misterious switch-case distributed in multiple places.
Hi,
there was a very good reason to write this code using lines:
performance. Before lines, it was indeed operating on individual pixels.
Please, include performance measurements before and after this series
to quantify the impact on the previously already supported pixel
formats, particularly the 32-bit-per-pixel RGB variants.
VKMS will be used more and more in CI for userspace projects, and
performance actually matters there.
I'm worrying that this performance degradation here is significant. I
believe it is possible to keep blending with lines, if you add new line
getters for reading from rotated, sub-sampled etc. images. That way you
don't have to regress the most common formats' performance.
While I understand performance is important and should be taken into
account seriously, I cannot understand how broken testing could be
considered better. Fast but inaccurate will always be significantly
less attractive to my eyes.
I am in favor of making this working first, and then improving the code
for faster results. Maybe the line-driven approach can be dedicated to
"simpler" formats where more complex corner cases do not happen. But
for now I don't see the point in comparing performances between broken
and (hopefully) non broken implementations.
We still haven't landed the YUV series for VKMS. Therefore, the code
available in the repository is not broken.
Performance is crucial for VKMS, as Pekka mentioned. First, because it
will be used more and more in CI. Second, because I wouldn't like to see
IGT tests timing out in VKMS.
Best Regards,
- Maíra
Thanks,
Miquèl
