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. Thanks, Miquèl
