[CM] some questions re S7, real-time use, and memory allocation

Christos Vagias chris.actondev at gmail.com
Mon Nov 23 03:41:49 PST 2020

Hey Iain,

I'm indeed using s7 in the audio thread (and another instance in separate
thread for the GUI) but I've just used simple midi input to make some
nothing in the area of audio generation/output so didn't have any problems
Also, didn't extensively test it with real time audio in mind, just wanted
to get it working. And it'll be quite some time until I get to work with it
again I'm afraid.

Regarding your question of turning off the GC, there's a way of doing it! I
think it's the (gc) function which accepts a boolean argument (to turn on
or off) or
none to just run the GC.

On Mon, 23 Nov 2020 at 00:27, Iain Duncan <iainduncanlists at gmail.com> wrote:

> Another thought, my use case is mostly to make sequencers and algo
> composition aids, not to render real time audio, so while timing is
> important, I'm not going to be running a lot of code in the RT thread. It
> will likely run once per minimum time unit, ie maybe 24 parts per quarter,
> or something. Is there any reason I could not just have that function
> (clocked from max) turn off the GC, do it's work, and then turn the GC back
> on to clean up at the end of every tick? is that crazy talk?
> Christos, I think you are using S7 in the audio thread in your VST thing
> right? How are you dealing with that issue, or has it not bitten you?
> iain
> On Sun, Nov 22, 2020 at 3:21 PM Iain Duncan <iainduncanlists at gmail.com>
> wrote:
>> Thanks Bill, that sounds promising on the malloc front then. I'll take a
>> look at the code.
>> What I'm imagining right now is two s4m objects, one in high priority
>> thread and one in the low, so that the majority of stuff is done in the low
>> and the high is only used for lightweight timing critical tasks. If this
>> doesn't pan out, I can always do the high priority thread stuff in Max or C
>> instead, but it would be nice to be able to use S7 if possible. I *think* I
>> should be able to keep the stuff in the high priority thread minimal enough
>> to keep a handle on the garbage collection side, but dealing first hand
>> with a garbage collector is new to me. (As in, I've done some soft
>> realtime in C, and I've done work in GC'd languages, but none of that was
>> in situations where I cared when the GC ran). If you (or anyone else) has
>> pointers on how to learn more about that sort of thing, or how to watch
>> when the GC runs, I'm all ears.
>> thanks
>> iain
>> On Sun, Nov 22, 2020 at 3:05 PM <bil at ccrma.stanford.edu> wrote:
>>> s7 calls malloc very infrequently; it has its own
>>> malloc (mallocate and friends), calling malloc
>>> only to get large blocks that it handles after that.
>>> More likely to be a problem is garbage collection.
>>> I haven't tried to use s7 in real-time, but I
>>> would expect it to be a struggle.
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