Re: [linux-audio-dev] News about sequencers (not my own though!)

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Subject: Re: [linux-audio-dev] News about sequencers (not my own though!)
From: jfm3 (jfm3_AT_acm.org)
Date: to tammi  20 2000 - 12:00:59 EST


David Olofson wrote:

> Interpreted languages (and actually any language that uses garbage
> collection and similar techniques) have inherent problems with real
> time - you never know when the garbage collector steps in for some
> cleaning! I some implementations, you can force a garbage collection
> when it won't disturb the real time processing, but you may not be
> able to guarantee that it won't happen an extra time in the middle of
> the real time code...

One can use an incremental collector, which causes all allocations to happen
in constant bounded time.

For time critical real time sections, one can just lock a larger portion of
memory (and other resources) before entering the section, then prohibit
garbage collection until the section is complete.

With multiple processors, one can use a threaded collector, which will not
interfere with the running of the main computation.

> Further, speed might be a serious problem.
> Even if it could be acceptable to eat 80% of the CPU time, you have to
> buffer the results (and output them using some streamlined function,
> preferably in native code), to get rid of the jitter that grows with
> execution time.

In my experience, most modern interpreted language systems don't have this
problem. Guile in SND is the exception. Newer GCs and experimental Guile
implementations go much faster than the precompiled binaries do.

(jfm3)


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