currently involved professionally in a software architecture based on pretty much raw shared memory IPC, it's still too slow compared to in-process.
See also VST hosts that allow grouping plug-ins together in one process or separating them in distinct processes, like Bitwig: for just a few dozen plug-ins you can very easily get 10+% of CPU impact (and CPU is an extremely dire commodity when making pro audio, it's pretty much a constant fight against high CPU usage in larger music making sessions)
Why? Relative to the in-process case, properly done multi-process data flow pipelines don't necessarily incur extra copies. Sure, switching to a different process is somewhat more expensive than switching to a different thread due to page table changes, but if you're doing bulk data processing, you amortize any process-separation-driven costs across lots of compute anyway --- and in a many-core world, you can run different parts of your system on different cores anyway and get away with not paying context-switch costs at all.
Also, 10% is actually a pretty modest price to pay for increased software robustness and modularity. We're paying more than that for speculative execution vulnerability anyway. Do you run your fancy low-level audio processing pipeline with "mitigations=off" in /proc/cmdline?
> Also, 10% is actually a pretty modest price to pay for increased software robustness and modularity. We're paying more than that for speculative execution vulnerability anyway.
it's a completely crazy price to pay in a field where people routinely spend thousands of $$$ for <5% improvement
> Do you run your fancy low-level audio processing pipeline with "mitigations=off" in /proc/cmdline?
obviously yes! along with power saving CPU C-states or anything throttling-related disabled, specific real-time IRQ and threading configuration (e.g. making sure that the sound card interrupts aren't going to happen on a core handling network interrupts) and two dozen other optimizations (which do make a difference, I regularly set-up new machines from scratch for shows, art installations, etc. and always do this setup step-by-step to see if things are finally "good enough" and they always make a difference, in really a make-or-break sense).
