very bad, and very weird, scrolling text performance xorg 1.5.3 intel 2.5.1 GM965

Eric Anholt eric at
Sun Dec 14 16:21:15 PST 2008

On Sun, 2008-12-14 at 16:08 -0800, Jeffrey Baker wrote:
> On Sun, Dec 14, 2008 at 3:48 PM, Thomas Jaeger <thjaeger at> wrote:
> > You really need the glyph cache in the X server to get decent text
> > performance out of the 2.5 intel driver.  The patches are pretty
> > straightforward to backport, but it is my understanding that a 1.6
> > server will be uploaded to jaunty soon, so you might want to wait for that.
> >
> I'm sure the glyph cache is a big help, but I don't think it's able to
> explain the nonlinear performance difference between scrolling in
> 80x24 (nearly adequate) and 80x48 (horrifying).

You've got 20% of your cpu being used from pixmap memory management in
compositing, which would be gone with GEM+DRI2.

You've got syncing happening in the 2D driver in glyph drawing, which is
fixed in 2.6.

And since you've got a server with no glyph cache, you're syncing per
glyph even if you fix the driver.

Eric Anholt
eric at                         eric.anholt at

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