Re: [fluid-dev] parallel loading of soundfont samples

[Marcus Weseloh]

Am Mi., 28. Okt. 2020 um 20:11 Uhr schrieb Tom M. via fluid-dev
<fluid-dev@nongnu.org>:
> 1. The samplecache is guarded by a mutex that prevents naïve
> parallelization.

Yes, and that is a difficult lock to remove, I think. But as a quick
check for a possible speedup factor with parallel loading, your branch
is a good test.

> 2. If we relax that mutex we get a strange race condition, resulting in
> various failed sample decodings.

That is because all threads use the same file pointer and thrash each
others file position all the time.
If you modify the vorbis loader code so that it opens a new file
pointer before doing the virio stuff, it loads without errors.

Here's the comparison...

Current master:
$ time ./fluidsynth -a file MuseScore_General.sf3 -i
real 0m6,689s
user 0m6,381s
sys 0m0,185s

parallelize-sf3-loading (with separate file per worker fix):
$ time ./fluidsynth -a file MuseScore_General.sf3 -i
real 0m2,795s
user 0m9,512s
sys 0m0,260s

When using the parallel loading my 4 cores are completely maxed out
and I get around double the speed. Probably not enough speedup to
remove the OPs problem, I guess?

Cheers
Marcus