[asterisk-dev] nVidia Cuda

Wai Wu wkwu at calltrol.com
Mon Mar 5 08:27:03 MST 2007

Someone once told me that g729 talkes 35mhz per channel. GPU wasting
cycles is not a concern since when the GPU is waiting for the cpu to
complete it tast, the GPU can take on other tasts or doing
transformation for other channels. This is exactly why I think the GPU
is perfect for Asterisk type of system. I are not trying to speed up
coding/decoding here, but rather, doing it for all channels at the same
time. As a matter of fact, if one has a 3ghz cpu, transcoding can be
done faster on the cpu than the g80 is the code is a straight port.

-----Original Message-----
From: asterisk-dev-bounces at lists.digium.com
[mailto:asterisk-dev-bounces at lists.digium.com] On Behalf Of Matthew
Sent: Monday, March 05, 2007 8:32 AM
Cc: Asterisk-Dev
Subject: Re: [asterisk-dev] nVidia Cuda

	Do you know the relative MIPS consumed by G.729 in each of the
decoding and the transformation phases? If the decoding is a significant
percentage, then it will block the CPU process while the GPU waits a
long time. While a really fast GPU can afford to waste cycles in
inefficient logic if it's still faster than the CPU.

On Mon, 2007-03-05 at 09:13 +0100, CA DM wrote:
> You don't need to port the entire codec code to a GPU. GPU aren't good

> general purpose processors, such as CPU aren't good stream processors.
> Code need to be cleaverly distributed across the specific abilities of

> CPU and GPU (eg.: decoding and unpacking the data stream is a task 
> suited for the CPU, like data block transformations are for the GPU) 
> if you want to get the most from both.
> At 20.38 04/03/2007, you wrote:
> >         Compression algorithms have generally not been ported to  
> >GPUs like the G80. They're usually more logic and branch oriented 
> >than just brute force multiply-accumulates that GPUs specialize in. I

> >also haven't seen any of the popular Asterisk codecs, like G.729 or 
> >GSM, ported to any GPU. Is there a source for codecs ported to GPUs? 
> >Or any research showing a good approach?
> >
> >
> >On Sun, 2007-03-04 at 10:12 -0700, 
> >asterisk-dev-request at lists.digium.com
> >wrote:
> > > Date: Sat, 03 Mar 2007 22:05:19 -0500
> > > From: Wai Wu <wkwu at calltrol.com>
> > > Subject: [asterisk-dev] nVidia Cuda
> > > To: asterisk-dev at lists.digium.com
> > > Message-ID: 
> > > <B0430B20D208514CB2AFF57E81645C3101B970 at k3-1.Calltrol.com>
> > > Content-Type: text/plain; charset="iso-8859-1"
> > >
> > > Hi devs,
> > >
> > > Has any one looked into cuda to see if cpu intensive part of 
> > > asterisk(like codecs and conference) can be moved to the G80 
> > > processor? I found that the GF8800 cards are very inexpensive 
> > > (around 400 USDs per). I have ported some of our financial 
> > > applications to this board and found almost 10x performance 
> > > improvement over the 3GHz C2D host processor. I would like to do
the same for asterisk.
> > >
> > > To start. I have been looking into the asterisk code and have no 
> > > crew how it is structured except the addon applications. Here I 
> > > have two questions.
> > >
> > > 1) Is each channel use their own thread if a codec is used?
> > > 2) Which part of the asterisk code actually makes the call to the 
> > > necessary codec? I notice in the applications. They save and set 
> > > the frame format, then read from the channel. So I trace the read 
> > > function, but all it does is reading from a file descriptor. So I 
> > > need some help here.
> >--
> >
> >(C) Matthew Rubenstein
> >
> >_______________________________________________
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(C) Matthew Rubenstein

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