Re: Blitter speed tests (was: smart blitter usage for scrolling)

["Antonino A. Daplas" <adaplas@gmail.com>]

On Thu, 2007-05-10 at 18:48 +0200, Krzysztof Helt wrote:
> Hi,
> 
> Below are tests of different scrolling methods for cards I have.
> 
> All tested drivers use SCROLL_REDRAW method. I forced SCROLL_MOVE 
> method by adding flag FB_READS_FAST. 
> 
> Here are some conclusions:
> Comparing two new methods: smart blitting and smart blitting with 
> merge, the merge of blits gives some speed up at lower bit 
> depths, but it is usually lost at higher ones. So we can choose 
> both ways (with or without the merge).
> 
> The smart blitting is so much faster in many cases comparing to 
> the current dump SCROLL_MOVE, that it can replace the current 
> method. For some cards it is even faster than SCROLL_REDRAW with 
> accelerated fb_imageblit().
> 
> The drivers tdfxfb and nvidiafb will benefit from switching to 
> SCROLL_MOVE method if the smart blitting is added (the tdfxfb  
> even without it). I wonder if Geforce cards also shows this speed 
> up if switched to the SCROLL_MOVE method but I have no card to 
> test.
> 
> The mach64 case is strange: it gives upper hand to smart blitting 
> but not at 32-bit depth.
> 
> I will prepare a patch with drop-in replacement for current 
> SCROLL_MOVE method without blits merging (it is the cleanest 
> solution).

Nice benchmarks and results!

The test is done on cards with both accelerated imageblit and copyarea.
Do you get the same results in unaccelerated drivers (vesafb)?  

If you do, it might even be wise to change the default from
SCROLL_REDRAW to SCROLL_MOVE...?

Tony



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