[LAU] xruns with m-audio fast track pro on fedora 8 ccrma->periods/buffer = 3, proper rtirq setup, idle=poll kernel parameter

[Florent Berthaut]

Fernando Lopez-Lezcano a écrit :
> On Thu, 2008-01-24 at 08:51 +0100, Florent Berthaut wrote:
>   
>> Fernando Lopez-Lezcano a écrit : 
>>     
>>> On Wed, 2008-01-23 at 16:44 +0100, Florent Berthaut wrote:
>>>       
>>>> Florent Berthaut a écrit : 
>>>>         
>>>>> Florent Berthaut a écrit : 
>>>>>           
>>>>>> Hartmut Noack a écrit : 
>>>>>>             
>>>>>>> -----BEGIN PGP SIGNED MESSAGE-----
>>>>>>> Hash: SHA1
>>>>>>> Florent Berthaut schrieb:
>>>>>>>               
>>>>>>>> Fernando Lopez-Lezcano a écrit :
>>>>>>>>                 
>>>>>>>>> A more basic question... what parameters are you using when you start
>>>>>>>>> jackd?
>>>>>>>>>       
>>>>>>>>>               
>>>>>>>>>                   
>>>>>>>> .jackdrc:
>>>>>>>>
>>>>>>>> /usr/bin/jackd -R -P70 -t1000 -u -dalsa -r44100 -p64 -n2 -D -Chw:0,1 
>>>>>>>> -Phw:0,0 -S -i2 -o2
>>>>>>>>             
>>>>>>>>                 
>>>>>>> USB-Devices often perform much better with -n3. Furthermore I would try
>>>>>>> to eliminate any flag, that is not absolutely needed such as:
>>>>>>>
>>>>>>> /usr/bin/jackd -R -dhw:1 -dalsa -r44100 -p64 -n3
>>>>>>>
>>>>>>> BTW: this would compute to around 4 ms latency - is that good enough for
>>>>>>> you?
>>>>>>>           
>>>>>>>               
>>>>>> Okay, i had forgot to turn off the system "bips" and esd (it
>>>>>> reduced the number of xruns)
>>>>>> And yep with -n3 i 've got even less xruns and it seems they're
>>>>>> not audible. 
>>>>>> I don't know if the latency is low enough though, i'll test this
>>>>>> evening with my drum pads.
>>>>>>
>>>>>> Thanks everyone , it's really great to get so much help so
>>>>>> quickly. 
>>>>>>
>>>>>>         
>>>>>>             
>>>>> Argh, actually i still have audible xruns. And i don't think i'd be
>>>>> able to play correctly with a higher latency anyway...
>>>>> Think i'll have to get back to ubuntu studio ... :( 
>>>>>       
>>>>>           
>>>> Actually after a reboot and some more tweakings, things have been
>>>> running without a xrun for an hour now, even with periods/buffer=2.
>>>>
>>>> So finally, i'll stay with planet ccrma ;) 
>>>>     
>>>>         
>>> You might want to try the 2.6.22.x based kernel for f8 as stated
>>> somewhere else in the thread. In my experience it has better performance
>>> latency-wise. 
>>>
>>> What other tweakings did you do?
>>>       
>> Ok finally, i tried to disable the second core ( i have a dual core
>> 2GHz) and things get really better this way, i can lauch more
>> applications with 4,8ms latency and no xruns. I had already disabled
>> cpuspeed but it looks like it was not enough. 
>>     
>
> That points to a realtime kernel problem with (probably) timekeeping in
> two core processors (ie: "time of day" is not perfectly synchronized
> between the processors so that if jack migrates from one to another it
> appears as there has been too much delay and things don't work as
> intended). I have seen this happen in 2.6.23.x + rt14. 
>
> What happens if you boot dual core with the "idle=poll" kernel
> parameter? (I assume this happens with 2.6.22.x). 
>
> -- Fernando
>   

Looks like it solves the problem, even the 2.6.23.x (latest ccrma 
kernel) works well with this parameter.
Thanks.

Florent








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