Re: [LAU] Realtime latency kernel testing

From: Robin Gareus <robin@email-addr-hidden>
Date: Fri Jan 07 2011 - 19:41:59 EET

Hi again,

OOPS, I made lots of typos in that email this morning (please do send
some coffee). I hope you understood the content of it anyway. If not:
please excuse my sloppiness and read on:

best,
robin

On 01/07/2011 02:43 PM, Robin Gareus wrote:
> On 01/07/2011 01:32 PM, torbenh wrote:
>> On Sun, Dec 12, 2010 at 07:22:28PM +0100, Jeremy Jongepier wrote:
>>> On 12/12/2010 06:42 PM, Ronald Stewart wrote:
>>>> Hi,
>>>>
>>>> I would go with what Robin said. That being said, Robin's tweaks on
>>>> Transmission last year on 89 set the pace for our build (brilliant!). Since
>>>> then tuning jack2 (jackdmp) Rui's rtirq, plus tuning for specific chips /
>>>> computer hardware makes a difference. If you want something now that truly
>>>> stands up and has had some of the best Linux developers touch the project,
>>>> go with Transmission 4.2. I know Paul will jump in and tune us all up with
>>>> our thoughts (go Paul!) but it should be stated again we are getting lights
>>>> out performance without RT on our new multi-touch Tablets for Pro Audio with
>>>> 2.6.35, Meego/AtomN450.
>>>
>>> So with 2.6.35 rtirq also works with a non real-time kernel?
>>
>> i am not aware of normal kernels having threaded irq handlers.
>
> No it they do not.

The vanilla kernel (<=2.6.37 - currently latest version) has no threaded
IRQ handlers and does not support rtirq.

>> additionally jack2 does not mlockall clients.
>
> If the machine as enough RAM or no SWAP partition this won't be a problem.

s/as/has/

> The ability to distribute audio load over multiple CPU cores is a big
> pro. (tschak was not packaged when building the Transmission disto and
> we were somewhat conservative, as well).

s/tschak/tschack/

>> so basically i would say, that this configuration works is pretty much
>> luck.
>
> Vanilla kernels > 2.6.33 do offer great overall performance: smooth
> Destkop and acceptable audio performance. Peak performance is for sure
> better than with the latest RT kernel (2.6.33.7.2-rt30).

s/Destkop/Desktop/

> However that it works _reliable_ is indeed luck.
>
>> maybe robin can clarify this.
>
> I don't know the details for the new Indamixx tablets, maybe the
> sound-card (and USB ports for external audio interfaces) are on a
> dedicated IRQ (they were not on the first generation Indamixx netbooks:
> the audio IRQ was shared with the graphics card and WiFi; a RT kernel
> and rtirq was pretty much a requirement)
>
> I don't think reliable low latency is a major goal for Indamixx. Most
> use-cases are quite fine with high latency that can be compensated for.
>
> Also see an article I'm just writing with Luis:
> http://wiki.linuxaudio.org/wiki/jack_latency_tests#does_latency_really_really_matter
>
> An occasional rare x-run is probably sth. Indamixx users can live with.
> After all it is a portable studio, not something super-pro-high-end to
> be mounted in a studio or used on-stage. Besides overall performance is
> for sure better than on comparable windows products even without RT kernel.
>
> FWIW: Thomas Gleixer has announced that he's working on a RT patch for
> 2.6.37 but there's no ETA.
>
> ciao,
> robin
>
>>> Best,
>>>
>>> Jeremy
>>> _______________________________________________
>>> Linux-audio-user mailing list
>>> Linux-audio-user@email-addr-hidden
>>> http://lists.linuxaudio.org/listinfo/linux-audio-user
>>

-- 
Robin Gareus
web: http://gareus.org/                mail: robin@email-addr-hidden
lab: http://citu.fr/                   chat: xmpp:rgareus@email-addr-hidden
Public Key at http://pgp.mit.edu/  http://gareus.org/public.asc
Fingerprint : 7107 840B 4DC9 C948 076D 6359 7955 24F1 4F95 2B42
_______________________________________________
Linux-audio-user mailing list
Linux-audio-user@email-addr-hidden
http://lists.linuxaudio.org/listinfo/linux-audio-user
Received on Fri Jan 7 20:15:03 2011

This archive was generated by hypermail 2.1.8 : Fri Jan 07 2011 - 20:15:03 EET