[ardour-dev] Ancient history? - Problem identified

[R Parker]

Hi Joel,

--- cv223 at comcast.net wrote:

> A few days ago I posted the following message about
> tracking down xruns using Ardour to record to a SCSI
> Raid0.  At the end of the message, I asked whether
> anyone had any ideas about why commenting out a
> single line in streamview.cc (which at the very
> least eliminates updating the "progress" rectangles
> during recording) completely eliminates my xrun
> problem, in a rather dramatic fashion (dozens of
> xruns per min to none).  Since I got a goose egg in
> response, I thought I would try again because I've
> run out of things to test and don't know where to
> look next.  

I took note of your first message. It's certainly an
interesting discovery. 

> Basically, how can display updates in Ardour during
> recording cause xruns with writes to the hard
> drives?

I'm not a programmer but we have to imagine the
function operates outside the realtime threads. If
that's correct and all is well within the code, then
Ardour isn't the cause but does trigger the symptom.

It would seem to indicate xruns caused by the video
driver but you have narrowed it down to a hardware
scsi raid event where the problem occurs.

Being pretty clueless, perhaps all I'm doing is trying
to add some life to your thread. Incidentally, the
region drawing code was written by Jesse Chappel--I
think. If you do IRC, he can often be found on
freenode.net #ardour.

Sorry I can't be very helpful, more sorry than you
know because I also run hardware raid and have xrun
problems.

ron

> Since this problem doesn't seem to be common, it
> seems that it has more to do with my system/hardware
> configuration than with Ardour/jack.  But what, I
> don't know.
> 
> Any suggestions would be greatly appreciated. 
> Thanks for your time.
> 
> Joel
> -------------- Original message -------------- 
> 
> > (Note that I didn't write "Problem solved" - I
> don't know how to solve 
> > it, besides a hack described below) 
> > 
> > About a week ago, I posted a message asking about
> possible reasons why 
> > xruns seen using 0.9beta11.2 when recording to a
> SCSI Raid0 went away 
> > with 0.9beta12 (on a 2.4.23 kernel). Paul took
> pity on my poor, 
> > tormented soul and let me have cvs access (thanks
> again, Paul!) so I 
> > could try and track down the problem. I went
> through a number of old 
> > cvs versions by the dates of "CVS commit" messages
> to the ardour-dev 
> > list (not sequentially - I don't have _that_ much
> time!) and found the 
> > smoking gun to be on May 7, 2004, when Jesse
> Chappell committed code to 
> > put waveforms into regions while recording. That
> code pointed out where 
> > the problem was. 
> > 
> > To make a long story somewhat shorter, it turns
> out that on my system, 
> > updating the regions during recording (even with
> "Follow playhead" 
> > turned off) generates xruns when the SCSI Raid is
> written to (i.e., 
> > xruns occur when the drives chirp). Specifically,
> if I comment out line 
> > 700 in streamview.cc (this is in routine
> StreamView::update_rec_box() 
> > in 0.9beta19): 
> > 
> > // gtk_canvas_item_set (rect, "x2", xend, NULL); 
> > 
> > and run Ardour with the Display Option "Show
> waveforms while recording" 
> > turned off, I get no (zero!) xruns while recording
> to the SCSI Raid, 
> > where before I got > 25 per 1 minute of recording.
> Of course, I don't 
> > get the pinkish boxes growing across the screen,
> but I can live with that. 
> > 
> > If I don't comment out that line, I get just as
> many xruns on the newer 
> > versions of Ardour as before - I hadn't tried
> turning "Show 
> > waveforms..." off before I started on my cvs
> quest. I guess I thought 
> > the waveforms during recording were too cool. 
> > 
> > Turning on the "Show waveforms..." still generates
> about 3 xruns per 
> > minute of recording, so I still don't know what's
> going on there (other 
> > gtk canvas access, perhaps?). Also, running under
> the 
> > 2.6.9-rc2-mm4-VP-S7 kernel still generates a
> handful of xruns per minute 
> > on either Raid or IDE drives even with the above
> hack, so something 
> > different still seems to be happening with that
> kernel. I'll stick with 
> > 2.4.23 for now. 
> > 
> > If anybody has any ideas about what may be going
> on (how gtk canvas 
> > access + SCSI Raid writes = xruns), I'm still
> curious. Also, I'm 
> > willing to try additional tests, if it would be
> helpful. 
> > 
> > BTW, this is with gtk+ version 1.2.10. 
> > 
> > Thanks for your time, 
> > 
> > Joel 
> > 
> > 
> > 
> > _______________________________________________ 
> > ardour-dev mailing list 
> > ardour-dev at lists.ardour.org 
> >
>
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