Question

I have been developing in Node.js recently and have a good idea of what is going on as far as the event loop. Given that I had experience with javascript, Node made sense for me to use, but I wonder, has anyone ever stopped using a multithreading system and went to async for PERFORMANCE? Or made a choice to go with async instead of multithreading for performance?

What are real-life examples of async non-blocking I/O triumphing over multithreading in the real world?

Answer 1

Regardless you do multithreading or not, all modern operating system I/O operations are inherently async. So saying that “async is faster” is not actually true. However, async programming allows you to conserve threads with almost the same performance. That’s important on a server because number of threads you can get is finite (limited by available memory).

So with async you don’t necessarily get better performance but better scalability on I/O heavy tasks. Async could even perform worse on CPU-intensive tasks since you don’t benefit of parallelizing work between server cores. I/O on the other hand, works with interrupts and DMA which does not involve CPU. That’s how you can get good-enough performance because you can keep executing until hardware notifies you of I/O completion by signaling an interrupt.

Edit: I just figured out that I did not answer your actual question. But as long as you know how async benefits you, you may not need real world examples on that. Just know that:

• communicating with database is I/O
• reading from or writing to disk is I/O
• sending/receiving packets over network is I/O
• the rest is CPU

Depending on if you use I/O or CPU more async could give you great scalability or worse performance. Typically web applications are I/O intensive, which benefits from async programming.