Re: [PATCH v3 4/5] fbdev: Improve performance of cfb_imageblit()

On Wed, Feb 23, 2022 at 08:38:03PM +0100, Thomas Zimmermann wrote:

Improve the performance of cfb_imageblit() by manually unrolling
the inner blitting loop and moving some invariants out. The compiler
failed to do this automatically. This change keeps cfb_imageblit()
in sync with sys_imagebit().

A microbenchmark measures the average number of CPU cycles
for cfb_imageblit() after a stabilizing period of a few minutes
(i7-4790, FullHD, simpledrm, kernel with debugging).

cfb_imageblit(), new: 15724 cycles
cfb_imageblit(): old: 30566 cycles

In the optimized case, cfb_imageblit() is now ~2x faster than before.

v3:
	* fix commit description (Pekka)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

Acked-by: Sam Ravnborg <redacted>

The code looks equally complicated now in the sys and cfb variants.

Question: What is cfb an abbreviation for anyway?
Not related to the patch - but if I have known the memory is lost..

	Sam