Re: [linux-audio-dev] Client/Server audio system

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Subject: Re: [linux-audio-dev] Client/Server audio system
From: Paul Barton-Davis (pbd_AT_Op.Net)
Date: Mon Mar 13 2000 - 12:06:21 EST


>I think there is already a context switch when a user space application
>read or write the /dev/dsp device.

This is false. There is a system call, but under Linux, this is not
even close to the costs of a context switch. On my PII-450, a context
switch (between two kernel threads) takes about 22usec. A simple
system call (e.g gettimeofday) takes less than 12usec. A read/write
system call to an ALSA DSP device can take much less than that,
believe it or not.

>Also a plug-in based architecture would need to use callback. Having a
>client/server based system would require context switches + callback for
>all running clients.
>I'm not sure at all that a system like that can work, but i think having a
>time-stamped event based audio system +scheduler could be very interesting.
>Of course a lot of question are not solved : synchronisation, memory
>sharing between several applications...

I think that from our discussions about the server/client version of
the Mythical Universal Communication Official Software (MuCoS), we
concluded the a server/client model is no good for low latency
work. Thats why we settled on some kind of model that would allow
things (plugins, i guess) to be relatively switched from operating as
a plugin in a host to a client, and other things (host engines, i
suppose) to be altered fairly easily to run as a server rather than a host.

That way, things can be used as appropriate to the context.

--p


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