[LAD] LV2 realtime safe memory pool extension

David Olofson david at olofson.net
Thu Nov 8 12:34:39 UTC 2007

On Thursday 08 November 2007, Stefano D'Angelo wrote:
> I'm not a plugin developer and I have nothing to do with LV2, but
> anyway I think it can be a useful thing and that it is good to have
> one "standard protocol" for this in LV2, instead of letting plugins
> rely on external libraries or, even worse, include their own rt-safe
> memory allocator.

Yes, that's exactly my point, but I think it needs to deal with 
arbitrary size chunks to actually be able to serve that purpose in 
real applications.

To avoid plugins effectively allocating private pools (just as if 
they'd implemented it internally), a host would have to use a proper 
real time memory manager, and then, whey not just make that available 
directly to plugins?

> However, I see the atomic and sleepy version of allocate but only
> one deallocate, why?

Because it's never needed. When you free a memory block you're really 
just saying "I don't need this any more", and you don't care if/when 
the host does anything about it.

BTW, are the blocking allocation calls intended for background 

Wouldn't it be more useful with some interface that allows plugins to 
request memory in a non-blocking manner, and if instant allocation 
fails, have the host notify the plugin when the memory is available? 
Basically, a malloc() call that means "If I can't have this memory 
right away, please expand the pool so I can have it later!"

The alternative would be to use the blocking version only 
in "background" threads, but unless you need background threads 
anyway, to do actual work, this is just moving complexity into 
plugins for no gain. If a plugin wants some memory to play around 
with "in the near future", it shouldn't have to implement it's own 
asynchronous memory management just to avoid stalling the host's 
audio thread.

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

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