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by ashf023 289 days ago
Interesting that very few people in that thread seem to understand Go's model, especially the author of this proposal. If you don't allow preemption, you still have a sort of coloring because most non async functions aren't safe to call in a virtual thread - they may block the executor. If you call C code, you need to swap out stacks and deal with blocking by potentially spawning more OS threads - that's what CGo does. Maybe preemption is harder in Python, but that's not clearly expressed - it's just rejected as obviously unwanted.

Ultimately Python already has function coloring, and libraries are forced into that. This proposal seems poorly thought out, and also too little too late.
2 comments
rsyring 289 days ago
I can't speak to the more technical aspects you bring up b/c I'm not that well versed in the underlying implementations and tradeoffs.

> and also too little too late.

I think it very likely that Python will still be around and popular 10 years from now. Probably 20 years from now. And maybe 30 years from now. I think that's plenty of time for a new and good idea that addresses significant pain points to take root and become a predominant paradigm in the ecosystem.

So I don't agree that it's too little too late. But whether or not a Virtual Threads implementation can/will be developed and be good enough to gain wide adoption, I just can't speak to. If it's possible to create a better devx than async and get multi-core performance and usage, I'm all for the effort.

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ashf023 287 days ago
Fair enough, I was a little too negative. It is good they're thinking about improvements
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Dagonfly 288 days ago
I'm also surprised how often the preemptive vs. cooperative angle gets ignored in favor of the stackful vs stackless debate.

If you choose a non-preemptive system, you naturally need yield points for cooperation. Those can either be explicit (await) or implicit (e.g. every function call). But you can get away with a minimal runtime and a stackless design.

Meanwhile, in a preemptive system you need a runtime that can interrupt other units of work. And it pushes you towards a stackful design.

All those decisions are downstream of the preemptive vs. cooperative.

In either case, you always need to be able to interface with CPU-heavy work. Either through preemption, or by isolating the CPU-heavy work.

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