[Mesa-dev] [Bug 47375] Blender crash on startup after upgrade to mesa 8.0.1

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=47375

--- Comment #31 from Roland Scheidegger <sroland at vmware.com> 2012-07-26 20:10:28 PDT ---
(In reply to comment #29)

> I compiled mesa lib, Blender runs without crash, but it still very slow in the
> GUI ( too much lag when I click in the gui, menus ), it's not normal because
> with 7.11 mesa lib Blender was much more fast,
Unfortunately I think this is expected. Previously swrast didn't map whole
buffers, only parts of them. For much simpler and more robust code though
swrast fallbacks now maps the full buffers, an operation which is hideously
expensive at least with radeons (as you've got to blit back the buffers from
the card memory to system memory). I believe blender draws some little things
on a large buffer, so the performance of the swrast fallback is fully dominated
by copying the buffers around, the actual cost of the drawing operation in the
swrast fallback is completely irrelevant. This is also why it's much faster to
just use swrast to begin with as then you don't need to copy the buffers around 
(you should see this if you some some profiling tool like sysprof, oprofile,
perf).
I'm not sure how this could be solved really, I think the best option would be
to modify blender so it doesn't rely on these legacy features leading to
fallbacks. Or similarly try to accelerate these in metaops so it doesn't need
to fallback.
A third option would be to try to figure out the area accessed and only map
those parts (to swrast it would still look like the whole buffer would be
mapped to keep things simple, but the driver would only blit the needed parts).
The infrastructure for that isn't there and I'm not sure it's desired in any
case, and it would probably only work for the draw buffers and not for textures
neither.


> 
> I notice also some errors message in the console :
> 
> Mesa: User error: GL_INVALID_ENUM in
> glGetIntegerv(pname=GL_MAX_TEXTURE_IMAGE_UNITS)
> Error: Not freed memory blocks: 2
> IDProperty group len: 108 0xb91d808
> uiAfterFunc len: 616 0xb9e5f88
I don't think this is related to this issue.

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