Not getting expected performance improvement after accelerating bitBlit through KAA

Adam Jackson ajax at
Mon Nov 2 08:31:34 PST 2009

On Fri, 2009-10-30 at 13:12 +0530, prudhvi raj wrote:
> Thanks for the response mr. Daniel.
> According to my understanding KDrive has been developed with more
> focus on embedded systems. So why do u want me to go for XOrg ( u mean
> XAA??) instead of KDrive??

Because the major tradeoffs made for kdrive (not building XKB and GLX,
for example) are either generally recognized to be false economies, or
are achievable with Xorg too.  And because nobody is maintaining kdrive,
or wants to.

> Do u have any ided why the mapping    pScreen->PaintWindowBackground =
> kaaPaintWindow; has been removed in the next versions??

commit e4d11e58ce349dfe6af2f73ff341317f9b39684c
Author: Eric Anholt <eric at>
Date:   Wed Sep 12 13:58:46 2007 +0000

    Remove the PaintWindow optimization.
    This was an attempt to avoid scratch gc creation and validation for paintwindow
    because that was expensive.  This is not the case in current servers, and the
    danger of failure to implement it correctly (as seen in all previous
    implementations) is high enough to justify removing it.  No performance
    difference detected with x11perf -create -move -resize -circulate on Xvfb.
    Leave the screen hooks for PaintWindow* in for now to avoid ABI change.

> and why is the function kaaFillRegionTiled() is left unimplemented and
> commented??

Probably because it was only ever called from the PaintWindow screen

As to your initial question:

> > Can you provide more clarity why are most of the Blit calls are
> > routed through software fallbacks.

fbBlt is called from more places than just the screen-to-screen copy
path.  In particular, it's called from the PutImage path (host to GPU
upload), which KAA does not (did not) accelerate.

- ajax

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