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Re: gEDA-user: My Xorg uses large amounts of CPU when using PCB



Hi Peter,

Thanks for your help. I tried your advice and found the problem. Turns out there must be some glitch in EXA acceleration that causes it to spend 96% of processor time doing memcpy; google led me to some people with memcpy problems related to EXA. So I changed to XAA acceleration and the problem is gone.

Thank you,
Cory

Oh, and for the curious, this may be the bug:
https://bugzilla.redhat.com/show_bug.cgi?id=242386

Peter Clifton wrote:
On Thu, 2010-10-07 at 14:41 -0700, Cory Cross wrote:

Laptop&  Desktop both run Debian unstable with Linux 2.6.32 for 686,
Xorg 1.7.7
Laptop uses intel driver for 945GM/GMS/GME, 943/940GML Express
Desktop uses open-source radeon driver for Radeon 9250

Are you using compositing? (e.g. compiz / kwin with desktop effects?)
No.

If I'm reading your hardware matrix right, the problem is with the
machine with the Radeon card?
Yes.

I'm well out of date with ATI/AMD cards.. how fast is the 9250, are the
drivers "any good"? A cursory search suggests they have full accelerated
3D support. I'm not sure how this transfers to accelerated 2D support,
or importantly - whether the XOR operations PCB uses to redraw its
cross-hair would be hardware accelerated.

I'm noticing a trend for features which used to be the fastest way of
doing something are sometimes less performant on newer hardware.
It's several years old, AGP card. Full 3D hardware acceleration.

I think the most useful debugging aid you could get to help diagnose the
problem would be a trace from "sysprof".  <snip>
Get a profile trace for the system whilst Xorg is thrashing, and let us
see where the CPU time is going. Unfortunately, you may well have to
install quite a lot of -dbg packages to get a meaningful backtrace.
These are something us developers tend to accumulate over time, but I
couldn't give you a canonical list of which -dbg packages you will need.

Perhaps starting with xserver-xorg-core-dbg would be a good start.


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