[PD-dev] why must one never send a message from a perform routine ?

[Day Rush]

On Wed, 23 Aug 2023 at 23:24, Christof Ressi <info at christofressi.com> wrote:

> I actually get fewer xruns in callback mode,
>
> This sounds highly unlikely. Maybe your "delay" setting is too low? Or Pd
> is not actually running with realtime priority?
>

I spent a lot of time testing this on an ancient laptop running a
fairly modern kernel because I was deeply frustrated with general PD
performance on that machine. "unlikely" it may have been. True, it most
certainly was.

> I also bump the sound-generation process up to realtime priority.
>
> Pd itself already tries to raise the thread priority; if this fails, you
> might not have sufficient permissions.
>

 Perhaps. But I was definitely able to manually bump the priority without
sudo. I did a *lot* of system optimization trying to squeeze good
performance out of various moderately complicated physical models. From
this
I learned a few things:

1 - the PD UI will absolutely kill performance
2 - because of 1, plan to run the sound gen in [pd~]
3 - pd patch and file lookup is a nightmare, especially in [pd~]
4  - real-time priority + callbacks usually produces clean sound on a clean
system

And now you know why I want multi-threaded pd audio.

- d
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