Running with the brakes on ...

[Arjan van de Ven]

On Mon, 2006-12-04 at 11:44 -0500, 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, 

one easy way that might give a good clue is cstop (for context-switch
top); it's a system tap script that reports the top context switchers

http://www.fenrus.org/cstop.stp

run this as
stap -v cstop.stp

(you need the kernel-debuginfo rpm installed for this to work)

X will probably be way high up there, but so will the culprit which
makes X do a lot of work, at least that's my experience....