fc2, xorg, 2.6.x, scheduling latency peaks
Arjan van de Ven
arjanv at redhat.com
Wed Jun 2 07:38:41 UTC 2004
> In [c] and [d] I'm applying an additional latency patch to the drm
> kernel driver that affects radeon, r128 and mga based cards. The patch
> is old and _illegal_ as it does reschedules with a lock on. So far the
> computer has not locked up but I guess it is a matter of time :-)
can you send me that patch (or point at an URL) ?
> A real test with the Jack low latency server reveals that something else
> is creating latency hits.
do you run Jack as realtime process ??
> So, latencytest is happy but a real test with real applications is not.
>
it might be an application artifact/interaction
> Other important data points:
>
> - xruns seem to be related to graphics activity
> - booting FC2 into 2.4.26 with the low latency and preempt patches gives
> me similar results (latency hits when running jack and jack apps)
> - booting FC1 into 2.4.26 (same hardware, just replace the hard disk)
> gives me a rock solid system (no xruns whatsoever, down to 128x2).
>
> So, it would seem to me that it is not (only) the kernel..........
>
> Things I could not make work:
> - testing 2.6.6-1.391.x in FC1. For some reason init does not get
> executed, probably a library problem somewhere...
you need to pass vdso=0 to the kernel there.
> Any ideas on what could cause this????
>
try disabling DRI.
DRI sometimes can "hold" the pci bus for quite some time, which by
definition causes latency since no IO can be done
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