[PATCH v2 4/5] fbdev: Improve performance of cfb_imageblit()

[Thomas Zimmermann]

Hi

Am 22.02.22 um 14:01 schrieb Pekka Paalanen:
> On Mon, 21 Feb 2022 20:54:09 +0100
> Thomas Zimmermann <tzimmermann at suse.de> wrote:
> 
>> Improve the performance of sys_imageblit() by manually unrolling
> 
> sys?
> 
>> 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().
> 
> This is correct here.
> 
>>
>> A microbenchmark measures the average number of CPU cycles
>> for sys_imageblit() after a stabilizing period of a few minutes
> 
> sys?
> 
>> (i7-4790, FullHD, simpledrm, kernel with debugging).
>>
>> sys_imageblit(), new: 15724 cycles
> 
> sys?
> 
>> cfb_imageblit(): old: 30566 cycles
>>
>> In the optimized case, cfb_imageblit() is now ~2x faster than before.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>> ---
>>   drivers/video/fbdev/core/cfbimgblt.c | 51 +++++++++++++++++++++++-----
>>   1 file changed, 42 insertions(+), 9 deletions(-)
> 
> Just noticed some confusion in the commit message.

I copied some of the text from the other commit and I could have sworn I 
updated it. But apparently not.

Best regards
Thomas

> 
> 
> Thanks,
> pq

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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