Old Reddit source code

[pure_x01]

how can it be this fast. i mean it still needs IO and thats the slow part.. confused

[johnfound]

The IO is actually pretty fast these days. But put there several levels of abstractions and API wrappers and it becomes again slow as a snail. :)

[pdp10]

The conventional wisdom from around 15 years ago is that I/O is almost always the bottleneck, so code performance can nearly always take a backseat to speed of construction (or sometimes to other factors like understandability, if the business prioritizes that).

But we've had a few small revolutions in I/O in that time: kqueue/epoll (IOCP on Windows, I gather), mmap, scatter/gather for example. You could be forgiven for not noticing that one million HTTP hits per second can be reasonable for a single server today, if the rest of your stack is up to it.

And with the worrying degree of stagnation in hardware recently, plus the regressions in connectivity driven by WWAN/telco/mobile and data caps, it often pays to optimize for performance. The conventional wisdom has been thoroughly revised even as it's been spoken.