Re: [PATCH] Preemption Latency Measurement Tool

Oliver Xymoron
2001-09-20T23:16:19Z

On Fri, 21 Sep 2001, Dieter Nützel wrote:

> > > > Right, the patch is returning the length preemption was unavailable
> > > > (which is when a lock is held) in us. So it is indded 4ms.
> > > >
> > > > But, I think Dieter is saying he _sees_ 0.5~1s latencies (in the form
> > > > of audio skips). This is despite the 4ms locks being held.
> > >
> > > Yes, that's the case. During dbench 16,32,40,48, etc...
> >
> > You might actually be waiting on disk I/O and not blocked.
> >
> > Does your audio source depend on any files (eg mp3s) and if so, could they
> > be moved to a ramfs? Do the skips go away then?
>
> Good point.
>
> I've copied one video (MP2) and one Ogg-Vorbis file into /dev/shm.
> Little bit better but hiccup still there :-(

Is anything else freezing up? Do you see your mouse stop moving, for
instance? Do other apps stop getting scheduled (eg, ico)?

You might try stracing artsd to see if it hangs at a particular syscall.
Use -tt or -r for timestamps and pipe the output through tee (to a file on
your ramfs).

--
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