[linux-audio-user] Graphics card an realtime performance

[Gerrit Niestijl]

On Tue, Feb 07, 2006 at 10:06:46PM +0100, Florian Schmidt wrote:
> > Hi all,
> > 
> > Could a better graphics card result in better realtime performance? I can
> > get a good realtime performance on my box (buffersize 64 and less) but
> > when using X some display activity seems to cause xruns. E.g sooperlooper
> > is far more usable without it's gui.
> > 
> > This is on a pentium3 600Mhz PC, running gentoo kernel 2.6.14 with rt22
> > patch applied. I also prioritize the irq's as documented on this list. The
> > graphics card is a Nvidia Vanta LT with 16 Mb memory.
> 
> What software do you use? I assume JACK? If so, setting up the irq's is
> not enough. You also need to run jackd with the right prio (below
> soundcard irq, but above all others)
> 
> See 
> 
> http://tapas.affenbande.org/?page_id=40
> 
> for a little more exhaustive info.

Yes, i use jack. I also use the rtirq package. Here is the relevant
info:

reus ~ # cat /proc/interrupts 
           CPU0       
  0:    1009634  XT-PIC         [........N/  0]  pit
  1:        727  XT-PIC         [........./  0]  i8042
  2:          0  XT-PIC         [........N/  0]  cascade
  4:          0  XT-PIC         [........./  0]  Serial MIDI
  5:       1661  XT-PIC         [........./  0]  eth0
  8:          2  XT-PIC         [........./  0]  rtc
  9:          1  XT-PIC         [........./  0]  acpi, ICE1712
 10:        121  XT-PIC         [........./  0]  uhci_hcd:usb1, EMU10K1
 12:       3651  XT-PIC         [........./  0]  i8042
 14:       4926  XT-PIC         [........./  0]  ide0
 15:        653  XT-PIC         [........./  0]  ide1

reus ~ # /etc/init.d/rtirq status
 * status:  started

  PID CLS RTPRIO  NI PRI %CPU STAT COMMAND
  200 FF      80   - 120  0.0 S<   IRQ 8
   14 FF      70   - 110  0.0 S<   IRQ 9
  262 FF      60   - 100  0.0 S<   IRQ 10
  277 FF      50   -  90  0.0 S<   IRQ 1
  206 FF      49   -  89  0.0 S<   IRQ 12
  209 FF      46   -  86  0.0 S<   IRQ 6
  240 FF      45   -  85  0.0 S<   IRQ 14
  242 FF      44   -  84  0.0 S<   IRQ 15
 6472 FF      41   -  81  0.0 S<   IRQ 5
 6635 FF      40   -  80  0.0 S<   IRQ 4

Not exactly the same numbers as yours, but it looks ok to me.
I was trying to avoid the route Lee mentions, debugging using the
latency tracer, but it looks like i have to find some time to study
it. Anyway, thanks a lot all of you for your input, i will let you know
when i have made some progress.

-- 
gerrit