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

Jeffrey Baker jwbaker at
Sun Dec 14 22:54:20 PST 2008

On Sun, Dec 14, 2008 at 4:21 PM, Eric Anholt <eric at> wrote:
> 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.

Here's a more complete profile, with symbols in the xorg core.  It
does seem to support the glyph caching theory.


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