Re: [LAD] PCI MIDI jitter - comparison Ubuntu (bad) and Suse (might be ok)

Hi Ralf,

You are comparing a banana and an orange to find out which one is
sweeter. Given the nature of the problem it would help a lot to have as
little differences between the systems under test, otherwise it's
impossible to track it down.

I hazard a guess that it's Ubuntu's 2.6.32 realtime-preemt-kernel.
There are no official 2.6.32 rt-patches and it's likely that some of the
back/forward ports have screwed things up.

Is 'cat /proc/interrupts' identical on both systems?
what about 'ps ax | wc -l' and
'ps -eo pid,class,rtprio,ni,pri,pcpu,stat,comm --sort -rtprio'
Are there high-priority jobs present on Ubuntu which are not on SuSE?

What happens if you use the same kernel (SuSE's kernel on Ubuntu, or
vice versa) but different disto user-lands? Is there still a difference
in your measurements?

ciao,
robin

On 07/11/2010 04:53 PM, Ralf Mardorf wrote:
> Hi :)
>
> today I compared a default Ubuntu Studio with and without the
> proprietary NVIDIA driver. Note that for Ubuntu Studio 2 tests failed
> because of time out errors, but even the tests that were passed with
> success are significantly less good, than the tests with openSUSE, were
> I set up audio myself.
> Ubuntu based Linux until now were my music Linux, e.g 64 Studio 3.0 and
> 3.3, but I wonder if bad MIDI latency is depending to Ubuntu.
> For Ubuntu Studio even PCI MIDI has got more jitter, but USB MIDI for
> Suse, see older test in the archives.
>
> What might be the difference between Ubuntu and Suse?
>
> Could anybody compare different distros too?
>
> ------------------------------------------------------------------------
> Ubuntu Studio 10.04 amd64
> 2 x Terratec EWX 24/96 (2 single cards, but 1 virtual card)
> Frequency scaling ?
> ------------------------------------------------------------------------
>
> spinymouse@email-addr-hidden:~$ hwinfo --gfxcard
> Driver: "nouveau"
> Driver Modules: "drm"
> IRQ: 18
> spinymouse@email-addr-hidden:~$ alsa-midi-latency-test -l
> Port Client name Port name
> 14:0 Midi Through Midi Through Port-0
> 16:0 TerraTec EWX24/96 TerraTec EWX24/96 MIDI
> 20:0 TerraTec EWX24/96 TerraTec EWX24/96 MIDI
> 128:0 TiMidity TiMidity port 0
> 128:1 TiMidity TiMidity port 1
> 128:2 TiMidity TiMidity port 2
> 128:3 TiMidity TiMidity port 3
> spinymouse@email-addr-hidden:~$ alsa-midi-latency-test -Rrw=2 -o20:0 -i20:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 1.00 ms
> worst latency was 1.97 ms, which is great.
>
> spinymouse@email-addr-hidden:~$ alsa-midi-latency-test -Rrw=2 -o20:0 -i20:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 1.00 ms
> worst latency was 3.36 ms, which is great.
>
> spinymouse@email-addr-hidden:~$ alsa-midi-latency-test -Rrw=2 -o16:0 -i16:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 0.99 ms
> worst latency was 1.93 ms, which is great.
>
> spinymouse@email-addr-hidden:~$ alsa-midi-latency-test -Rrw=2 -o16:0 -i16:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 0.99 ms
> worst latency was 1.74 ms, which is great.
>
> spinymouse@email-addr-hidden:~$ uname -a
> Linux ubuntu 2.6.32-23-preempt #37-Ubuntu SMP PREEMPT Fri Jun 11
> 10:19:07 UTC 2010 x86_64 GNU/Linux
> spinymouse@email-addr-hidden:~$ envy24control
> 0xcf00, irq 20, Master Clock int 44100
>
> No envy24control for
> 0xcb00, irq 21, Master Clock ?
>
> 20:0 opto S/PDIF out --> 16:00 opto S/PDIF in
>
> ------------------------------------------------------------------------
> Ubuntu Studio 10.04 amd64
> 2 x Terratec EWX 24/96 (2 single cards, but 1 virtual card)
> Frequency scaling ?
> ------------------------------------------------------------------------
>
> spinymouse@email-addr-hidden:~$ hwinfo --gfxcard
> Driver: "nvidia"
> Driver Modules: "nvidia"
> IRQ: 18
> spinymouse@email-addr-hidden:~$ alsa-midi-latency-test -l
> Port Client name Port name
> 14:0 Midi Through Midi Through Port-0
> 16:0 TerraTec EWX24/96 TerraTec EWX24/96 MIDI
> 20:0 TerraTec EWX24/96 TerraTec EWX24/96 MIDI
> 128:0 TiMidity TiMidity port 0
> 128:1 TiMidity TiMidity port 1
> 128:2 TiMidity TiMidity port 2
> 128:3 TiMidity TiMidity port 3
> pinymouse@email-addr-hidden:~$ alsa-midi-latency-test -Rrw=2 -o20:0 -i20:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 1.00 ms
> worst latency was 1.84 ms, which is great.
>
> spinymouse@email-addr-hidden:~$ alsa-midi-latency-test -Rrw=2 -o20:0 -i20:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 1.00 ms
> worst latency was 1.27 ms, which is great.
>
> spinymouse@email-addr-hidden:~$ alsa-midi-latency-test -Rrw=2 -o16:0 -i16:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 0.99 ms
> worst latency was 1.92 ms, which is great.
>
> spinymouse@email-addr-hidden:~$ alsa-midi-latency-test -Rrw=2 -o16:0 -i16:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 0.99 ms
> worst latency was 1.72 ms, which is great.
>
> spinymouse@email-addr-hidden:~$ uname -a
> Linux ubuntu 2.6.32-23-preempt #37-Ubuntu SMP PREEMPT Fri Jun 11
> 10:19:07 UTC 2010 x86_64 GNU/Linux
> spinymouse@email-addr-hidden:~$ envy24control
> 0xcf00, irq 20, Master Clock int 44100
>
> No envy24control for
> 0xcb00, irq 21, Master Clock ?
>
> 20:0 opto S/PDIF out --> 16:00 opto S/PDIF in
>
> ------------------------------------------------------------------------
> openSUSE 11.2 amd64
> 2 x Terratec EWX 24/96 (2 single cards, but 1 virtual card)
> Frequency scaling performance
> ------------------------------------------------------------------------
>
> spinymouse11.2@email-addr-hidden-2:~> su -c "hwinfo --gfxcard"
> Driver: "nvidia"
> Driver Modules: "nvidia"
> IRQ: 18
> spinymouse11.2@email-addr-hidden-2:~> alsa-midi-latency-test -l
> Port Client name Port name
> 14:0 Midi Through Midi Through Port-0
> 16:0 TerraTec EWX24/96 TerraTec EWX24/96 MIDI
> 24:0 TerraTec EWX24/96 TerraTec EWX24/96 MIDI
> spinymouse11.2@email-addr-hidden-2:~> alsa-midi-latency-test -l
> Port Client name Port name
> 14:0 Midi Through Midi Through Port-0
> 16:0 TerraTec EWX24/96 TerraTec EWX24/96 MIDI
> 24:0 TerraTec EWX24/96 TerraTec EWX24/96 MIDI
> spinymouse11.2@email-addr-hidden-2:~> alsa-midi-latency-test -Rrw=2 -o24:0 -i24:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 0.99 ms
> worst latency was 1.07 ms, which is great.
>
> spinymouse11.2@email-addr-hidden-2:~> alsa-midi-latency-test -Rrw=2 -o24:0 -i24:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 0.99 ms
> worst latency was 1.08 ms, which is great.
>
> spinymouse11.2@email-addr-hidden-2:~> alsa-midi-latency-test -Rrw=2 -o16:0 -i16:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 0.99 ms
> worst latency was 1.06 ms, which is great.
>
> spinymouse11.2@email-addr-hidden-2:~> alsa-midi-latency-test -Rrw=2 -o16:0 -i16:0
>> alsa-midi-latency-test 0.0.3
>> set_realtime_priority(SCHED_FIFO, 99).. done.
>> clock resolution: 0.000000001 s
>> SUCCESS
>
> best latency was 0.99 ms
> worst latency was 1.05 ms, which is great.
>
> spinymouse11.2@email-addr-hidden-2:~> uname -a
> Linux suse11-2 2.6.31.6-rt19 #1 SMP PREEMPT RT Wed Nov 18 16:59:26 CET
> 2009 x86_64 x86_64 x86_64 GNU/Linux
> spinymouse11.2@email-addr-hidden-2:~> envy24control
> spinymouse@email-addr-hidden:~$ envy24control
> 0xcf00, irq 20, Master Clock int 44100
>
> No envy24control for
> 0xcb00, irq 21, Master Clock ?
>
> 24:0 opto S/PDIF out --> 16:00 opto S/PDIF in
>
> I still have got some tests to do, e.g. a real test by listening to MIDI
> music and I'll test what happens if two sound cards become one virtual
> sound card, http://www.jrigg.co.uk/linuxaudio/ice1712multi.html and
> before doing this I need to test if the second, new second hand card
> from Ebay isn't broken for audio, resp. I'll compare the sound quality
> for my old and the new Terratec EWX 24/96 sound card, before they become
> one virtual sound card.
>
> Cheers!
>
> Ralf
>
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Received on Sun Jul 11 20:15:05 2010