问题
What is a "bottleneck", particularly when used in terms of network bandwidth?
回答1:
A bottleneck is the "slowest" part of a system. If you examine a beer bottle, the neck is smaller than the base and so limits the amount of sweet wonderful nectar that you can drink. Mmmm! Beeer! (sorry, got carried away).
In terms of bandwidth, it's the slowest device in the chain. For example, it makes little difference having gigabit ethernet on your PC if your router only runs at 10meg. The router there is the bottleneck.
And it doesn't matter how fast your ethernet card and router and internet infrastructure are, if the site you're trying to download from is running with a 1200/75 acoustic modem from the early '80s. The other end is the bottleneck in that case.
Bottlenecks are everywhere. Your network devices, the disk in your PC, having to fetch from RAM rather than L2 cache, critical paths on your Gantt chart, trying to walk your kids to school when one is a 7yo speed daemon and the other a 5yo "want to stop and look at every single god-damned flower"-type :-)
Basically, it's the thing that, if it was faster, would make the system (as a whole) faster. It's the bottlenecks where you need to optimise since the return on investment should be higher there.
来源：https://stackoverflow.com/questions/5062325/what-does-bottleneck-mean-in-terms-of-bandwidth