[LAD] "enhanced event port" LV2 extension proposal

David Olofson david at olofson.net
Thu Nov 29 00:49:02 UTC 2007

On Thursday 29 November 2007, Dave Robillard wrote:
> Well, sure, but big data is big data. In the typical case plugin
> buffers are much smaller than the cache

Of course, but that's exactly what I'm talking about - large buffers, 
and why it doesn't make sense to support them. :-)

If you're using 65536 samples per buffer, it just takes a plugin with 
four audio inputs and you're up to 1 MB of intermediate buffers. Even 
if that does fit in the cache, in a real life situation, with other 
threads working, most of it will be cold again every time the audio 
thread starts. So, your processing speed is potentially capped at the 
memory bandwidth throughout the buffer cycle, or at least until you 
start reusing buffers in the graph. And what is supposed to be gained 
by this...?

I don't see why a plugin API of this type should support nonsense like 
that at all, and thus, it shouldn't affect event timestamps either - 
but well, now it's there, and there isn't really any Right Thing(TM) 
to do here, I guess.

> crunching away on plain old audio here is definitely CPU bound (with
> properly written RT safe host+plugins anyway).

Last time I looked into this, a reasonably optimized resampler with 
cubic interpolation and some ramped parameters was memory bound even 
on a lowly P-III CPU, at least with integer processing. (Haven't 
actually tested this on my AMD64...)

I think floating point should be as fast or faster in most cases, at 
least on P-III CPUs and better - and with SIMD, you may get another 
2x-4x higher throughput at that.

Could be way off here, though. Do you have benchmark figures?

//David Olofson - Programmer, Composer, Open Source Advocate

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