[Python-ideas] Concurrency Modules

Nikolaus Rath Nikolaus at rath.org
Sun Jul 26 02:58:09 CEST 2015

On Jul 25 2015, "Sven R. Kunze" <srkunze-7y4VAllY4QU at public.gmane.org> wrote:
> startup impact | biggest                 | medium                     | smallest
> cpu impact     | biggest                 | medium                     | smallest
> memory impact  | biggest                 | medium                     | smallest
> purpose        | cpu-bound tasks         | i/o-bound tasks            | ???

I don't think any of these is correct. Unfortunately, I also don't think
there even is a correct version, the differences are simply not so

On Unix, Process startup-cost can be high if you do fork() + exec(), but
if you just fork, it's as cheap as a thread. With asyncio, it's not
clear to me what exactly you'd define as the "startup impact" (the
creation of a future maybe? Or setting up the event loop?).

"CPU impact" as a category doesn't make any sense to me. If you execute
the same code it's going to take the same amount of (cumulative) CPU
time, no matter if this code runs in a separate thread, separate
process, or asynchronously.

"memory impact" is probably highest for separate processes, but I don't
see an obvious difference when using threads vs asyncio. Where did you
get this from?

As far as purpose is concerned, pretty much the only limitation is that
asyncio is not suitable for cpu-bound tasks. Any other combination is
possible and also most appropriate in specific circumstances.

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