Re: [LAU] kernel changes -was - So what do you think sucks about Linux audio ?

I've actually seen some dramatic changes myself. I had great luck with
an ICE1724 based card, but I've noticed that multiple USB audio
devices don't perform as well on the 3.x series kernels compared to my
old trusty 2.6.33, which I realize is ancient now :) I'm wondering if
anyone else has had the same experience. It's only really noticeable
if you're pushing the CPU hard-- it's not a "set to 4x latency" kind
of thing.

But I'd say make super sure you're running at realtime priority. I
can't emphasize how much of a difference that makes. If you're unsure,
do this at a terminal:

ps -eLo cmd,rtprio | grep APPLICATION_NAME_HERE.

Check for your app and for JACK's prio.

Also, grab rtirq and run that if you haven't. I'd assume if you're
using a music-oriented distro that this is all already done.

-Louis

On Sun, Feb 10, 2013 at 9:25 AM, Len Ovens <len@email-addr-hidden> wrote:
>
> On Sun, February 10, 2013 8:59 am, Ralf Mardorf wrote:
>> On Sun, 2013-02-10 at 08:14 -0800, Len Ovens wrote:
>>> On Sun, February 10, 2013 2:57 am, Folderol wrote:
>>>
>>> > One thing I find confusing is the way the kernel performance changes
>>> so
>>> > dramatically from one version to the next.
>>> >
>>> > In debian testing, 64bit V3.1 vanilla works beautifully on my current
>>> > machine, but V3.2 requires jack to be set to 4x the latency! That's
>>> for
>>> > both
>>> > vanilla & RT.
>>>
>>> This may or not be it, but try looking at the irq assignment from one to
>>> the next. The kernel sets IRQs for at least some of the devices.
>>
>> The only difference for the IRQ I noticed between older and newer kernel
>> versions are different IRQs for the graphics. The graphics on my machine
>> doesn't share it's IRQ with another device any more.
>
> Ok, your machine, but the reply was for someone else. No matter you do say
> irqs did change which is what I was saying.
>
> What I am says though is that I'm not sure these problems are kernel
> problems. They may be kernel module problems or something else. I have
> used all of these kernel versions and been able to run low latency on all
> of them no problems (ICE1712 based card). Other people on this list have
> had no problems too. Yet there is not just one person with this same
> problem. We (on this list) might do well to explore the differences
> between our hardware/software to see if we can find the problem.
>
> --
> Len Ovens
> www.OvenWerks.net
>
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> Linux-audio-user@email-addr-hidden
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Received on Sun Feb 10 20:15:11 2013