Re: [PATCH] packed pixel image blit optimizations.

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

On Tue, 2007-05-08 at 20:58 +0100, James Simmons wrote:
> > On Thu, 2007-05-03 at 20:55 +0100, James Simmons wrote:
> > > > > > I don't have to test the patch to see that it is not endian-correct and
> > > > > > that it will be many times slower than the old code.
> > > > > 
> > > > > I have tested on big endian framebuffers and it does work.
> > > > 
> > > > How about little-endian?
> > > 
> > > Worked as well.
> > >  
> > 
> > Not for me, vesafb 8x16 font at 1024x768-8.
> 
> How did you do the test below if it doesn't work on little endian? If you 
> are the only one allowed to work on the core system you need to make 
> people aware of it. I won't invade you space anymore.

I get corrupted characters and this is with vesafb, the most widely used
framebuffer driver. I just copied the last screen output to a text file
and opened it in X.  Look, everyone is free to try your patch for
testing, and if they report that it works for them with no speed
degradation, then I'll examine it further where it failed.

So people, can you try James Simmon's patch posted here?

http://marc.info/?l=linux-fbdev-devel&m=117821517710515&w=2

Tony

PS: The reason your patch is slow is because you are using swab32().

The old code does this:

table lookup

Your patch does this:

table lookup + swab32()

And swab32 consists of 4 OR's, 4 bitshifts, and 2 ANDS. This is very
expensive especially if this is done for each 4 bytes of data (thats 1
pixel in 32 bpp).



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