Performance drop when updating > 500k pixels

[Adam Jackson]

On Fri, 2017-01-13 at 15:07 +0100, Pierre Ossman wrote:

> I'll answer myself here...
> 
> This seems to be a CPU cache issue. Below this limit I see:
> 
>          4,469,985      cache-misses:u            #    0.336 % of all cache refs    
>     35,279,259,258      instructions:u            #    1.70  insn per cycle                                              (100.00%)
> 
> Above the limit I get:
> 
>        194,571,782      cache-misses:u            #   30.322 % of all cache refs    
>     18,084,891,734      instructions:u            #    0.73  insn per cycle                                            
> 
> So no wonder things take a turn for the worse.
> 
> I'll have to think a bit on how to make this more efficient. Ideas are always welcome.

Seems like a job for non-temporal stores?

- ajax