Bug#451571: xserver-xorg-video-intel: uses lots of CPU with Compiz and (new default) EXA
On Sat, 2007-11-17 at 02:55 +0000, brian m. carlson wrote:
> The intel video driver now uses EXA by default. When using Compiz as
> my window manager, Xorg consistently uses >50% of the CPU when scrolling
> in Firefox or doing other simple (and formerly efficient) operations.
> This did not occur with XAA, because I used XAANoOffscreenPixmaps, which
> is recommended with Compiz. Now, using EXA, offscreen memory is
> allocated, which I believe to be the cause of the CPU waste.
Not really; the problem is that GLX_EXT_texture_from_pixmap is
implemented inefficiently. XaaNoOffscreenPixmaps just happens to make it
usable, at the cost of basically disabling 2D acceleration. While the
same workaround could be implemented for EXA, there's little point in
using it (or XAA, for that matter) at all in that case. So there's
really no point in implementing such an option for EXA, compared to just
switching to XAA.
With the i915tex Mesa driver (or the i915 driver from upstream Git, but
that also requires xserver Git), EXA allows for more efficient
GLX_EXT_texture_from_pixmap together with 2D acceleration, but
unfortunately this is difficult to set up.
It's all kind of messy at the moment, but work is going on upstream to
make it all work nicely out of the box in the hopefully not too distant
Earthling Michel Dänzer | http://tungstengraphics.com
Libre software enthusiast | Debian, X and DRI developer