Subject: Re: [alsa-devel] Re: [linux-audio-dev] laaga, round 2
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Tue May 15 2001 - 17:39:54 EEST
On Tue, May 15, 2001 at 09:15:03AM -0400, Paul Davis wrote:
> Whether we retain busses or not, I propose the following: unlike the
> context switch costs that we've been discussing, the cost of zeroing
> memory goes down more or less linearly with processor speed (helped
> along by RAM speed, which is increasing much more slowly). Because of
> this, we should consider the cost to zero a buffer to be an
> essentially vanishing item in the overall operation of an audio
> system. Because of this, all output memory buffers should be used as
> "busses" - they are, as tom put it, "summing nodes". All operations to
> store data in them should use "+=", and not "=". The host will provide
> buffers, and will ensure that they are zeroed when appropriate.
I couldn't agree more. Even in LADSPA plugins there are very few cases
where the extra work done in summing to the buffer is significant compared
to the actual work done in the processing loop.
- Steve
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