On Sat, 2012-12-01 at 01:07 +0100, berenger.mo...@neutralite.org wrote:
> I have questions about why are you needing so much kernels.
My apologies, I'm short in time, so my off-list mail also is short and
slightly OT.
On the quick:
I need that much kernels, because I've got issues with audio latency and
had issues with MIDI jitter.
I try to keep the most stable Linux for my needs and try to get a Linux,
that will fit better to my needs.
I've got no experiences with FreeBSD, I don't know the difference
myself.
IOW I try to fix issues, without buying hardware. On old computers it
was easy to get hard real-time, because the software directly was
connected with the hardware and the kernels where optimized to the
hardware. Computers today have many layers, different chipsets, do real
multitasking, but this does cause timing issues.
For example, using older kernels my graphics and the audio card do share
the same IRQ, with the new kernel the graphics get another IRQ:
spinymouse@q:~$ uname -a
Linux q 3.6.5-rt14 #1 SMP PREEMPT RT Fri Nov 2 21:36:37 CET 2012 x86_64
x86_64 x86_64 GNU/Linux
spinymouse@q:~$ service rtirq status
PID CLS RTPRIO NI PRI %CPU STAT COMMAND
62 FF 90 - 130 0.0 S irq/8-rtc0
799 FF 85 - 125 0.0 S irq/18-snd_hdsp
830 FF 85 - 125 0.0 S irq/20-snd_ice1
832 FF 85 - 125 0.0 S irq/21-snd_ice1
54 FF 80 - 120 0.0 S irq/19-ehci_hcd
55 FF 80 - 120 0.0 S irq/16-ohci_hcd
56 FF 79 - 119 0.0 S irq/17-ohci_hcd
58 FF 78 - 118 0.0 S irq/18-ohci_hcd
59 FF 78 - 118 0.0 S irq/17-ohci_hcd
60 FF 77 - 117 0.0 S irq/18-ohci_hcd
61 FF 75 - 115 0.0 S irq/1-i8042
24 FF 50 - 90 0.0 S irq/9-acpi
46 FF 50 - 90 0.0 S irq/22-ahci
216 FF 50 - 90 0.0 S irq/14-pata_ati
218 FF 50 - 90 0.0 S irq/15-pata_ati
302 FF 50 - 90 0.0 S irq/22-firewire
580 FF 50 - 90 0.0 S irq/7-parport0
782 FF 50 - 90 0.0 S irq/43-radeon
1313 FF 50 - 90 0.0 S irq/42-eth0
3 FF 1 - 41 0.1 S ksoftirqd/0
15 FF 1 - 41 0.1 S ksoftirqd/1
If I would make music, I would unbind other things that share IRQ 18 too
by running a script:
spinymouse@q:/mnt/music/quantal/01song$ cat tuning
#!/bin/bash
# sudo bash tuning - Ubuntu Studio Quantal
# 2012/Nov/04
### http://www.mythtv.org/wiki/PCI_Latency
###
http://wiki.linuxmusicians.com/doku.php?id=system_configuration#pci_bus_latency
### Bluetooth
service bluetooth stop
### Network
#service network-manager stop
#service networking stop # does cause serious issues
#modprobe -r r8169 # Ethernet NIC driver
### TerraTec EWX 24/96
modprobe -r snd_ice1712
### Others
modprobe -r firewire-ohci
modprobe -r firewire_core
service cups stop
modprobe -r ppdev # parallel port
modprobe -r lp # printer
### Unbinding devices
echo -n "0000:00:13.2" > /sys/bus/pci/drivers/ohci_hcd/unbind
echo -n "0000:00:13.4" > /sys/bus/pci/drivers/ohci_hcd/unbind
### Log file
l="log/tuning.log"
#echo "$ lspci -v " > $l
#lspci -v >> $l
#echo >> $l
echo "$ /etc/init.d/rtirq status " > $l
/etc/init.d/rtirq status >> $l
echo "$ grep 18: /proc/interrupts" >> $l
grep 18: /proc/interrupts >> $l
echo >> $l
echo -n $(date)" - "$(uname -r)" - " >> $l
cat /etc/issue >> $l
echo "##############################" ; cat $l
exit 0
This is neither needed for professional servers nor needed for averaged
desktop usage. Real-time audio is a special task. For real-time CNC
there is another real-time kernel. This are things most users don't need
to care about.
Regards,
Ralf
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