Hi, > (but it is still limited to 256 x 16 notes !)
Houps , i must correct me. Please read 128 as ofc there are only 128 notes maximum per MIDI channel. jjc > Message du 15/04/18 00:00 > De : "Ceresa Jean-Jacques" > A : "FluidSynthmailinglist" > Copie à : > Objet : Re: [fluid-dev] Parallelize rendering using openMP > > > Thanks for yours awswers > > >Apparently the soundfonts I used were not polyphonic enough > >Using FluidR3_GM.sf2 the cpu load looks better, but I'm yet quite far from > >the "perfect" scalability that your profiling interface gives you JJC. > > Effectivelly, your machine is fast and in this case playing MIDI file to > simulate a notes (voices) generator isn't not efficient. This is why the > profiling interface have is own notes generator (but it is still limited to > 256 x 16 notes !). > The most important is that fluidsynth are able to play constant number of > voices during measurement. This gives consecutives measurement the same cpu > load result. This makes any future performances measurements easily much more > predictive. > Note:During my experiment, initially i have noticed that result between > consecutives measurement was not constant. Quickly, i realized that a > backgroud process was running. The job of this process was to economize > energy . It was doing this by stealing cpu cycle!. Of course any performance > measurement aren' possible with this kind of jobs or services running > silently behind the scene. > > >Additionally I want to revise the current implementation, like using a > >parallel logarithmic buffer reduction to mix audio between threads or > >rethinking data layout and memory accesses in general, >hoping this makes it > >more efficient. > Interresting. Looking the code (in the past) i have noticed that a lot of > things perhaps could be enhanced arround the following subject: > 1) avoiding mutual access to the "active list of voices" between "primary > tasks" and the pool of "extra tasks". > - breaking the unique list in local list for each task. > - load balancing (same number of voices in each local list). > 2) optimizing mixing of buffers between "primary" task and "extra task" (to > avoid actual possible synchronization overhead domination). > 3) optimizing fluid_cond_signal(), fluid_cond_wait() each time the associated > mutex is pointless. > Of course all this is easier to say than to do :). > jjc > Message du 14/04/18 17:58 > De : "Tom M." > A : fluid-dev@nongnu.org > Copie à : > Objet : Re: [fluid-dev] Parallelize rendering using openMP > > Thanks for the feedback so far. > > > Please are you using a very fast machine ? did you ask to fluidsynth to > > play sufficient number of notes ? > > I'm on a Intel Core i5-3570K @ 3.40GHz. I tested several midi files that have > instruments playing on all 16 channels. Apparently the soundfonts I used were > not polyphonic enough, you're right. Using FluidR3_GM.sf2 the cpu load looks > better, but I'm yet quite far from the "perfect" scalability that your > profiling interface gives you JJC. > > > How did you come to the conclusion that the synchronization overhead > > dominates? > > Admittedly this might be a wrong/premature conclusion based on my > observations + looking at the source code. I took a look at the callgraph > generated with valgrind --tool=callgrind ./fluidsynth. Synchronization > functions like g_mutex_lock() or g_cond_wait() are called quite often by > fluid_mixer_thread_func(). Although it also reports to be not that expensive. > Still I think it's worth evaluating what job openMP and other refactorings > can do here. David Henningsson once told me that the parallel renderer was > more like a (failed) experiment. So please see this current work as my little > experiment. > > > I do wonder though why OpenMP can do a better job than the current code. > > openMP provides different scheduling strategies to process for loops. Also > this restriction VOICES_PER_THREAD (==8) to avoid thread overhead seems quite > magic to me (it probably worked well when David tested it, still, why is 8 > the right number?). Overall I'm not sure whether openMP alone can do a better > job. It definitely reduces complexity of the code. Additionally I want to > revise the current implementation, like using a parallel logarithmic buffer > reduction to mix audio between threads or rethinking data layout and memory > accesses in general, hoping this makes it more efficient. > > Tom > > > _______________________________________________ > fluid-dev mailing list > fluid-dev@nongnu.org > https://lists.nongnu.org/mailman/listinfo/fluid-dev > _______________________________________________ fluid-dev mailing list fluid-dev@nongnu.org https://lists.nongnu.org/mailman/listinfo/fluid-dev
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