[LAU] Realtime latency kernel testing

[Gabriel M. Beddingfield]

On Fri, 7 Jan 2011, 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.
> additionally jack2 does not mlockall clients.

Indamixx/Transmission 4 has a PREEMPT_RT kernel and utilizes 
rtirq.

Indamixx 2/Transmission 5 (MeeGo) has a PREEMPT kernel, and 
therefore rtirq won't work with it.  We've spent a lot of 
time tuning this kernel, and while there have been no 
clinical tests... we're experiencing performance very close 
to Transmission 4's PREEMPT_RT kernel (With jack running at 
512x2 frames/buffer and 44100 Hz) on various machines.

We are required by MeeGo to have a kernel >= 2.6.35.  In 
addition, to use 2.6.33 we would have to backport a 
boat-load of device drivers.  If an PREEMPT_RT patch appears 
for 2.6.35 or 2.6.37, you can bet that we'll be all over it 
and doing side-by-side comparisons.

-gabriel