Overhead of X?

Bilderbeek, Manuel manuel.bilderbeek at oce.com
Thu Apr 20 05:05:54 PDT 2006


> X does a little more than just a memset() of the enitre framebuffer.
> Filling the entire framebuffer with just one solid color is 
> nothing that
> the solid fill code in fb (that's what you are using unaccelerated) is
> really optimized for. Therefore it will perform some tests 
> and operations
> that are not required for this particular operation.

Would all those tests take so much CPU that it makes it 3 times slower?
So, 2/3 of the time is used for calculations and checks?
After all, the fill code is just supposed to fill a solid rectangle, so
the filling itself should be comparable. Or not?

> This doesn't seem to be a very common use either.

Isn't an application mainly painting filled rectangles, copying images
and drawing lines?
> Furthermore memset() is ususally higly optimized for your 
> architecture.

If the fb fill routine would use memset, would that matter? (I don't
know if it does that, but I don't see why it couldn't...)
> This seems to be a poor comparison.

How can I make it better?

Maybe running the application in the root window might help? (Could save
some checks!)
How would I do that, anyway? (Run a Java app in the root window...)

Kind regards,

Manuel Bilderbeek

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