[linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch

[Benno Senoner]

Lee Revell wrote:

>anyway.
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>>Plus what's very important is that every kernel developer and driver 
>>developer (even thirdparty, especially those
>>that do closed source stuff like Nvidia etc) takes into account the 
>>latency problems that code paths that run for
>>too long time (or disable IRQs for too long etc) might create.
>>While I'm not a kernel expert I assume the premptible kernel alleviates 
>>this problem but I guess it still cannot
>>completely get rid of low latency-unfriendly routines and drivers.
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>Yes, this is important.  One problem I had recently with the Via EPIA
>board was that unless 2D acceleration was disabled by setting 'Option
>"NoAccel"' in /etc/X11/XF86Config-4, overloading the X server would
>cause interrupts from the soundcard to be completely disabled for tens
>of milliseconds.  Users should keep in mind that by using 2D or 3D
>hardware acceleration in X, you are allowing the X server to directly
>access hardware, which can have very bad results if the driver is
>buggy.  I am not sure the kernel can do anything about this.
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that's bad news.
VIA markets those mini-itx mainboards (with onboard audio/video/network) 
as multimedia appliances and
therefore I'd expect the hardware providing low latencies  when both 
video acceleration and audio is used.
Hopefully only a driver issue (as in most of cases)

Since VIA released the unichrome (the gfx chipset contained in their 
mainboards) sources someone should
contact these folks :
http://unichrome.sourceforge.net/
to check what is causing those latency spikes ?
Any unichrome developer lurking on LKML ?

cheers,
Benno
http://www.linuxsampler.org

>Lee
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