Commen=
t # 23
on bug 79850<=
/a>
from Michel D=C3=A4nzer
(In reply to comment #=
21)
> It would mean the pixmap transformation is costi=
ng too much in time
> regarding vblank time, making happen the swap in the middle of the vis=
ible
> screen.
When the window pixmap is not the screen pixmap, a GLX/DRI2 buffer swap
involves two copies: one from the DRI2 back buffer to the window pixmap, and
one from the window pixmap to the screen pixmap. It's unrealistic for the
second copy to finish before the end of the vertical blank period, resultin=
g in
the visible tearing.
(In reply to comment #22)
> - I did swap my TAHITI XT (7970) with a JUNIPER=
PRO (5750), the pixmap
> transformation seems GPU bound since the tearing appears quite lower on
> JUNIPER PRO than with TAHITI XT.
Could be due to EXA vs. glamor. In the latter case, the copies described ab=
ove
are rasterized as two triangles each, which makes the tearing more noticeab=
le.