EXA performance problem

[Maarten Maathuis]

On Mon, Nov 28, 2011 at 2:41 AM, Christoph Bartoschek
<bartoschek at or.uni-bonn.de> wrote:
> I have new information. I am no longer sure whether it is a problem with
> EXA.
>
> I have a testcase that currently takes 90 seconds to draw all rectangles. I
> see that in damage.c two functions are mainly used:
>
> damagePolyRectangle
> damagePolyFillRectangle
>
> The first function calls for each given rectangle up to four times
> damageDamageBox (pDrawable, &box, pGC->subWindowMode);
> which adds the box to a region. The function then calls damageRegionAppend.
>
> This part takes in sum 30 seconds of my testcase. I think the code has
> quadratic behaviour here becuase it adds rectangle by rectangle instead of
> first adding them to a region and then calling damageRegionAppend. I think
> removing the quadratic behaviour can reduce the runtime significantly.
>
> About 60 seconds are spent in the calls
>
> (*pGC->ops->PolyRectangle)(pDrawable, pGC, nRects, pRects);
> (*pGC->ops->PolyFillRect)(pDrawable, pGC, nRects, pRects);
>
> However I do not yet know why they are so slow.
>
> Is damage.c part of EXA?
>
> Christoph
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No, damage is an extention, it is called by EXA, it's probably adding
all you rectangles to a damage region used to determine how much data
is actually valid (needed for ram<-->vram migrations for example).

One thing that just comes to mind, if you are rendering a million
rectangles, how many of those do you actually see on your screen?

Anyway, you can try optimizing damaga, exa and either fb or mi (for
PolyRectangle PolyFillRect software ops). I don't know how efficient
the region code is at reducing the number of rectangles if they
overlap, a region is built up out of rectangles as well.

-- 
Far away from the primal instinct, the song seems to fade away, the
river get wider between your thoughts and the things we do and say.