[LAU] Qjackctl 3.2, QT4, KDE 3.5.9, high CPU usage

[Reuben Martin]

I just ran into this issue as well on my Gentoo system after a fresh system 
install. I started jack from the command line to see if the problem had to do 
with qjackctl and it didn't cause any excess CPU usage, but then when I 
started Ardour, the excess CPU usage started up again.

If I'm having the same issue as you, it would seem that the problem occurs 
when a GUI based jack app starts up. Perhaps it's a jack related issue with 
realtime and GUI libs?

-Reuben

Back on Sunday 30 March 2008, hanaghan at starband.net was like:
> Hi Rui,
> thanks for the reply.
>
> Ok...just to add, I rebuilt from the SRPM (same spec file though) and no
> change. I also installed Gnome and it does it from there as well, just to
> further support your point.
>
> I will email thac and see if we can figure it out.
>
> thanks,
> R
>
> > hanaghan at starband.net wrote:
> >> Hi folks...
> >>
> >> I still running PCLinuxOS and using Thacś RPMś.
> >>
> >> Without version numbers of lots of libs, the version numbers in the
> >> subject line are relevant to my system. Hopefully thatś enough.
> >>
> >>
> >> I set up a new box from the live CD and added all the audio stuff from
> >> apt. Everything worked fine...I updated to Qjackctl 3.2 from and older
> >> version even and still no problems. I then did a jumbo update out of
> >> Synaptic...
> >>
> >> When I run Qjackctl or Qsynth in KDE, the CPU usage shoots to the
> >> moon. This has happened on another install of the same distro in the
> >> the very same sequence and manner. I dont think itś Qjackctl that
> >> is the issue..otherwise it would have done it when i first upgraded to
> >> 3.2 using QT4. Even though Qsynth shows the same symptoms, pointing
> >> toward a possible QT4 issue, that makes no sense either...again, it
> >> would have done it before.
> >>
> >> I suspect something in KDE is doing it. I tried running from Fluxbox,
> >> and same thing...but doesn Fluxbox use some KDS libs anyway?
> >>
> >> I guess I can install Gnome and try that but really dont want the
> >> clutter on the machine. Anyone know anything about this? I saw another
> >> post on Linuxquestions.org about the same thing on another distro...
> >>
> >> TIA for any help.
> >
> > a very similar issue has been experienced before, iirc. it has been
> > reported that on debian etch and ubuntu, qjackctl 0.3.x was peaking to
> > 100%cpu usage (not %dsp load) and right after jackd is started.
> >
> > this issues blame has been pointed to libqt4 itself, more specifically
> > to the QProcess class wich deals to process interface coordination and
> > to the extent of my knowledge a mere qt4 upgrade, from the testing (or
> > lenny) repositories, sufficed for the issue go away.
> >
> > so it seems to be a strict qt4 issue, maybe related to the way it's
> > built but not sure (i never had the issue duplicated myself)
> >
> > hth
> >
> > cheers
> > --
> > rncbc aka Rui Nuno Capela
> > rncbc at rncbc.org
>
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