Jettisoning Vanilla Kernel?

[Ralf Mardorf]

On Sat, 2012-12-22 at 18:37 +0800, Ho Wan Chan wrote:
> Also, can you provide us a comparesent on the performance and audio
> recording on both the 3.5-lowlatency and the 3.6-rt kernel:-P

My audio card does not work properly. It doesn't matter what kernel is
booted, I always get xruns. Latency is bad with both kernels.
Linux can use 2 of 8 ADAT channels only. RME is willing to help, but I
don't have the abilities to write a driver and nobody from ALSA did
reply.
At the moment I don't have a Linux production environment and I don't
see that this will change in the near future, so I'll test FreeBSD as
soon as possible.
The developer of the FreeBSD driver is interested in testers, I don't
had to write him, he did wrote me.
Unfortunately FreeBSD isn't a real-time OS.

However, I can't give any valid information about kernel performance.
Before I bought my card, I did a lot of research and asked the
community. Shit happens, the information was wrong.

I only can inform everybody that the RME HDSPe AIO does not work for
Linux and all the time people claim that all RME PCIe cards should be
supported by Linux, I only can correct them, to avoid that other users
spend that much money for a card that isn't supported by Linux.

For sure, even for this RME cards there are differences regarding to the
Linux distro and/or kernel I use.

So one big difference between kernels is, that later kernels handle the
graphics IRQ. I can't reboot right now, but IIRC Quantal's lowlatency
kernel already does ensure that the graphics gets it's own IRQ too. The
3.6-rt kernel at all events does ensure it.

So, for hobby usage there isn't really a difference (did not test with
external MIDI equipment, there might be a difference) between the both
kernels.

With both kernels, professional usage is completely impossible.

I tweaked my Ubuntu completely.

$ 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

Other things, e.g. frequency scaling and enabling
hr timer is done by the scripts, to start my audio sessions.

I can stop network-manager too, but this will not change anything,
disabling networking does cause issues. Usually I would not disable the
TerraTec EWX 24/96 cards, because I still like to use them as MIDI
interfaces.

Regards,
Ralf