[bruce343434]

> However, if you are doing web apps or any networking stuff, massive concurrency benefits are almost always too important to ignore

No, you will benefit from parallelism/multithreading. Why only use 1 core? Multitasking as it was once called, or "async" as it is now, is fundamentally _synchronous_ because everything still happens on one core. Just that the order of execution may be a bit wonky, which technically all code already suffers from at the microscopic level with instruction reordering and out of order execution. You almost certainly don't need multitasking unless you are writing an OS for embedded.

[solar-ice]

Async in Rust usually runs across many cores, using a work-stealing scheduler, fwiw.

[lalaithion]

Even if you use N cores, you still get a massive benefit from being able to let >N threads wait on IO events simultaneously using concurrency/multitasking/async.

[bruce343434]

There's only so much a "apache" or "nginx" can do though in between io operations right? And there's only so much io per second a whole system can do. Basically, from disk to memory, maybe run a language interpreter if the site is not static, then from memory to the internet. Maybe if your pages are very dynamic and involve a lot of scripts it could be worthwhile. Do you have any numbers to back up your claim?

[lalaithion]

I don’t have a reference offhand to hard numbers, but I’ve definitely run webservers which have a significantly higher number of concurrent in-flight requests than number of cores.

Even for a static site, what you’re basically doing is

    page = readFile(“foo.txt”)
    response.write(page)

That’s no CPU usage at all. ~Zero time spent in process. All the time is spent waiting on the data to be loaded into memory from disk, and then copied from memory out onto the network. If you use concurrency for those two functions, then you can handle ~100s of in-flight requests at the same time.

[bkolobara]

Almost all async Rust runtimes use a multithreaded work stealing schedulers by default, to equally utilise all available cores.

[maleldil]

Tokio has a multi-threaded scheduler.