Subject: Re: [linux-audio-dev] Re: costs of IPC
From: Abramo Bagnara (abramo_AT_alsa-project.org)
Date: Sun May 13 2001 - 10:02:15 EEST
Kai Vehmanen wrote:
>
> On Sat, 12 May 2001, Abramo Bagnara wrote:
>
> > This thread is becoming more and more instructive ;-)
>
> Yes indeed! But I think you've forgotten one aspect of this IPC issue: how
> the audio system (= referring to the whole single/multi-threaded/process
> system) behaves under heavy load?
>
> As I've mentioned in my earlier message today, multiple threads means
> multiple deadlines. Even if we assume IPC has zero cost, scheduling is
> still a problem. If you have 30 threads/processes participating in the
> audio processing, that means each of those threads must get enough
> processor time during the <5ms timeframe we have...
>
> Now I'm not saying it's impossible to have those 30 threads. It might be
> that by using user-space threads (or something else that gives you control
> over thread scheduling) might enable you to solve the problem. I've
> understood that gstreamer does something along these lines. But you can't
> deny that it's much easier and simpler to solve the problem by running one
> thread with sched_fifo priority...
Please note that I'm not suggesting a solution or another for "The
Thing(TM)" I'm only saying that its design/API need to be compatible
with both.
The little program I've written is only a tool we may use to have real
numbers for our decisions.
-- Abramo Bagnara mailto:abramo_AT_alsa-project.orgOpera Unica Phone: +39.546.656023 Via Emilia Interna, 140 48014 Castel Bolognese (RA) - Italy
ALSA project http://www.alsa-project.org It sounds good!
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