[Bug 13801] Very slow text rendering in AutoCAD

[wine-bugs at winehq.org]

http://bugs.winehq.org/show_bug.cgi?id=13801





--- Comment #30 from Jan Ploski <jpljpl at gmx.de>  2008-09-20 09:27:16 ---
(In reply to comment #29)
> Overall, it seems to me like some sort of lock contention problem, with
> NtProtectVirtualMemory being called a lot of times from the execution path
> containing DrawTextExA, X11DRV_XRender_ExtTextOut, X11DRV_LockDIBSection,
> X11DRV_DIB_Coerce.

I have to retract that. Further experiments reveal that the locking mechanism
per se does not cause trouble. The bad performance can be instead attributed to
the call to XShmGetImage in X11DRV_DIB_GetImageBits (which is invoked a lot
from X11DRV_DIB_Coerce when text rendering operations are performed).
Commenting out just that call makes, like the previously described actions, all
text disappear and restores good performance.

Elsewhere I read that XShmGetImage may be slow because of pixel data being
stored directly in the video memory and having to be transferred to the main
memory. Inspired by this explanation, I switched from the proprietary nvidia
driver 96.43.07 (my video card is a GeForce4 MX 440 AGP) to the framebuffer
device driver. Lo and behold, it also restored good performance! This
workaround is easy and good enough for playing the TSE2 game, but probably too
drastic in general. However, it could also be that the particular versions of
the nvidia driver and video hardware are to blame, so it is recommended that
other people try to reproduce this bug to help estimate its significance.


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