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Comment by steveklabnik | Hacker News Reader

Iron is still using sync IO, and while Ruby isn't great at parallel stuff, it at least does async IO, IIRC. That's going to be a huge difference.

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It depends what you're doing. If you're running a ruby web app server and talking to the database, all the io you're doing is most likely synchronous. In the one-server-per-cpu model, anyway.

It's been a while, but I thought that MRI basically slept during IO and released the GIL so that other threads could do work. In that case, you'd still be handling more requests while the IO was performed. I could be wrong. This kind of thing: http://ablogaboutcode.com/2012/02/06/the-ruby-global-interpr...

You're right that it can do async io. But you compared a framework to a language. Rust has Tokio for async - Iron is just not using it.

It's similar with Ruby/RoR - yeah, they can do async. But not on their own. With unicorn server, you still get no threading and just a bunch of processes. With puma you can do threading (async cooperative really) - as long as you keep the configuration/code within the limits of what's allowed.

And due to the extra care needed whenever you do caching/storage things, I expect unicorn is still the king in RoR deployments. (GH uses that for example)

It's definitely preemptive rather than cooperative. Ruby/Puma is actually using one OS thread per Ruby thread, so when one hits a DB call and blocks on sync IO, it releases the GVL and another Ruby thread can proceed. There's a timer thread Ruby runs and pre-empts each thread to schedule them.

Yeah, I guess I moved to Puma long enough ago that I forgot about this. Good points, thank you.

Yeah, that's pretty much what happens. There's also non-blocking IO you can use with EventMachine but the DB drivers are a bit of an issue AFAIK.

Wow, steveklabnik replied to my comment! Unfortunately, both implementations of the service are CPU bound. I think we're running 25 threads in Iron but I'll have to check.

Ah interesting! With that being true, then yes, I'd be surprised that it isn't faster too.

What about memory usage? That's an un-appreciated axis, IMO: for example, all of crates.io takes ~30mb resident, which is roughly the overhead for MRI itself, let alone loading code.

Anyway, the Rust team loves helping production users succeed, so if there's anything we can do, please let us know!

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