Subject: Re: [linux-audio-user] xruns vs. disk activity
From: Mark Knecht (markknecht_AT_attbi.com)
Date: Thu Apr 24 2003 - 04:49:59 EEST
> On Wed, 23 Apr 2003, rob fell wrote:
>
> > Hi Alex
> >
> > > i see that both your mouse (?!) and your network card seem to have
> > > higher priority than your IDE channels (harddisks).
> > > i would advice you to try without the network card and not to move
> > > your mouse =)
Normally there isn't much you can do about this, other than put in some
other ATA disk controller or go SCSI, which I wouldn't recommend just
yet. Fortunately I don't think any of that is really necessary just yet.
These are good experiments though. On the NIC side, just unpluging the
cable would normally be enough to test.
> >
> > when Mark suggested that the card might not be man-enough for the job i
> > realised that my internal model of how a soundcard works might be a little
> > naive - i suspect it has more than a lump of DP ram and some counters :)
This is where I think we really start getting into PC chipset design.
(something I used to do for AMD.) Without belaboring the details, a good
card is capable of getting data to and from memory without much
processor interaction and very efficiently on the PCI bus. If it does
that, then what's left is basically how it tells the processor what's
going on, which is the interrupt service routine's job. However, even a
great sound card can be hindered by other parts of the PC (like other
PCI cards) usign the bus badly.
You don't happen to be using a PCI VGA adapter, do you? I Cannot
remember at this point.
> >
> > i set the buffersize smaller to try to act as a crude filter to make my awk
> > script simpler - though this neglects the effect on the card itself of
> > running at a higher rate.
> >
> > the most success so far with the testing seems to be at 1024 - though large
> > file copies causes massive xruns at any rate (BTW: how large would a 'large'
> > file be?).
This sounds like an interrupt problem, or else a bad set of hard disk
device drivers. If you sound card want to interrupt, it should get
serviced even if the hard disk was on the bus. Possibly the DMA
controller in this ATA chipset isn't very efficient....
> >
> > i can't decide whether to gamble on the purchase of a decent card and hope
> > this all goes away, or whether to read the alsa driver code for the card to
> > see if i can work out just how bad the card really is :(
I think I'd maybe try running Benno's disk latency test first. IF it
says you have long latency issues in your disk subsystem, then a newer
sound card isn't going to do you much good.
> >
> > >
> > > and ofcourse... good luck.
> >
> > looks like i may need it - and some more spare time. thanks.
>From me also...
Cheers,
Mark
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