[PATCH 2/2] fbdev: Improve performance of sys_imageblit()

[Javier Martinez Canillas]

Hello Thomas,

On 2/17/22 11:34, Thomas Zimmermann wrote:
> Improve the performance of sys_imageblit() by manually unrolling
> the inner blitting loop and moving some invariants out. The compiler
> failed to do this automatically. The resulting binary code was even
> slower than the cfb_imageblit() helper, which uses the same algorithm,
> but operates on I/O memory.
> 
> A microbenchmark measures the average number of CPU cycles
> for sys_imageblit() after a stabilizing period of a few minutes
> (i7-4790, FullHD, simpledrm, kernel with debugging). The value
> for CFB is given as a reference.
> 
>   sys_imageblit(), new: 25934 cycles
>   sys_imageblit(), old: 35944 cycles
>   cfb_imageblit():      30566 cycles
> 
> In the optimized case, sys_imageblit() is now ~30% faster than before
> and ~20% faster than cfb_imageblit().
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> ---

This patch looks good to me as well.

Reviewed-by: Javier Martinez Canillas <javierm at redhat.com>

Best regards,
-- 
Javier Martinez Canillas
Linux Engineering
Red Hat