[LAU] Fwd: [linux-audio-user] Real-time kernel

[Mark Knecht]

Hi Chuck,
   A few comments embedded below.
- MArk

On 6/26/07, Chuckk Hubbard <badmuthahubbard at gmail.com> wrote:
<SNIP>
> 64studio:/mnt/win/Linux# uname -a
> Linux 64studio 2.6.22-rc4.062107 #1 PREEMPT Thu Jun 21 23:28:59 EDT 2007
> x86_64 GNU/Linux

OK, running 64-bit. I do also, although I'm Gentoo.

I'm not certain from this kernel name that this is a real-time kernel.
Most of the time they include some form or '-rt' in the name. Not a
requirement that the name say -rt but if you're not running a real
time kernel then all bets are off for real time performance.

>
>
> 64studio:/mnt/win/Linux# lspci
<SNIP>
> 00:14.2 Audio device: ATI Technologies Inc SB450 HDA Audio (rev 01)
<SNIP>
> 02:00.0 Ethernet controller: Marvell Technology Group Ltd. 88E8038 PCI-E
> Fast Ethernet Controller (rev 14)
> 05:00.0 Network controller: Broadcom Corporation Dell Wireless 1390 WLAN
> Mini-PCI Card (rev 01)
<SNIP>

OK, so you are running the Intel-HDA which lots of other folks have
had problems with. My son's machine has one and has trouble with
real-time performance although I haven't tried to fix it yet.

>
>
> 64studio:/mnt/win/Linux# cat /proc/asound/cards
>  0 [SB             ]: HDA-Intel - HDA ATI SB
>                       HDA ATI SB at 0xc0000000 irq 16
>
>
<SNIP>

OK, looking at the list above you have a *lot* of modules loaded.
Again, not necessarily a problem but when I see things like

> thermal                15376  0
> fan                     5896  0
> button                  9312  0
> processor              26940  1 thermal
> ac                      6280  0
> battery                11464  0

this makes me think about power management which has caused me and
others problems with RT performance over the years. Do you need them?
At least for debugging it might be wise to not use anything you don't
absolutely need until you get to the root of the problem.

>
>
> 64studio:/mnt/win/Linux# cat /proc/interrupts
<SNIP>
>  16:        429   IO-APIC-fasteoi   eth0, HDA Intel
<SNIP>

You are sharing the sound card's hardware interrupt line with a NIC.
If this is a desktop machine you might want to change the NIC's slot
and share it with something else for simplicity.

>
> ====================
> qjackctl messages:
>
<SNIP>
> Creating link /home/chuckk/.kde/socket-64studio.
> 05:00:31.211 Startup script terminated with exit status=256.
> 05:00:31.211 JACK is starting...
> 05:00:31.211 /usr/bin/jackd -dalsa -dhw:0 -r44100 -p1024 -n2
>

And finally it seems that Jack is not running with real-time turned
on. If it was I would expect to see

/usr/bin/jackd -R .......

Check how you are starting Jack in QJC. There is a button you must
push to turn on real time performance.

Also I'm thinking that someone else recently said they had to run the
Intel-HDA with variables like:

-r48000 -n3

or possibly

-r44100 n3

You should Google a bit for specifics on that. Some on-board sound
cards don't work well at all sample rates.

Hope this helps,
Mark