Running with the brakes on ...

[William Cohen]

Adam Jackson wrote:
> On Mon, 2006-12-04 at 02:13 -0500, Paul Michael Reilly wrote:
> 
> 
>>When running top, I see that X is consuming 40% of memory which is not
>>surprising since I am running two X sessions with 3200x1200 (dual
>>head, radeon, open source) along with long running firefox,
>>thunderbird and VNC (also 3200x1200) apps).  But when I bring up the
>>Soundcard Detection tool under KDE top shows Xorg is consistently
>>grabbing 93% of the CPU even when all I am doing is typing this
>>message.  That would certainly explain a lot of the lag in response to
>>mouse clicks from the app. :-)  Switching to Gnome and running top
>>there shows varying, but high (60%ish) CPU use with the Soundcard
>>Detection tool still running in both sessions.  But with Gnome,
>>response to mousee clicks is fine, even with the high X CPU use.
> 
> 
> So you've found that some use profile makes X use all the CPU.  Now you
> need to find out _what_ in X is taking all the time.  You need to either
> use a tool like oprofile or sysprof to extract that information, or you
> need to instrument the X server to report on what requests and clients
> are using most of its time.  The latter requires code changes to a
> project that many people find intimidating and/or unpleasant to work
> with, which is why I suggested using oprofile in the first place.
> 
> - ajax
> 

Yes, certainly use OProfile to narrow down what code/package is using the CPU. 
If you are not familar with OProfile, there are some writeup on how to use 
OProfile to track down this kind of problem at:

http://people.redhat.com/wcohen/

In particular the following articles would be a good place to start:

http://people.redhat.com/wcohen/FedoraCore2OProfileTutorial.txt
http://www.redhat.com/magazine/012oct05/features/oprofile/

You will probably need to install some debuginfo RPMs when doing the analysis of 
the collected data to see exactly which functions are using up the time. These 
can be install via yum.

-Will