Linux sounds fast. 50ns is blazingly fast. Benchmarks I surveyed show figures around 1-10usec but they are old and processors are faster now.
Kernel entry and exit are of course contributors to i/o overhead. Also include data copy time (2K times all those main memory flushes), ip stack time (well into scores of usec now) and driver overhead.
Add the latency of the result being signalled to your user-mode application. Interrupt latency, user-mode task scheduling time and if a receive then data copy time again.
Of course router delays are negligible on the backbone, but your local cable modem etc will add something.
I think we're over 16usec now, which if I did the math right is the wire time.
Another way to estimate all this is to benchmark achieved transfer rate peer-to-peer on an otherwise idle link. Folks report from 100mbit to 300mbit depending on other bottlenecks (disk speed, bus etc), but that's often using very large block sizes, not our 2K. Even so we see most of the Gigabit rate whittled away.
Kernel entry and exit are of course contributors to i/o overhead. Also include data copy time (2K times all those main memory flushes), ip stack time (well into scores of usec now) and driver overhead.
Add the latency of the result being signalled to your user-mode application. Interrupt latency, user-mode task scheduling time and if a receive then data copy time again.
Of course router delays are negligible on the backbone, but your local cable modem etc will add something.
I think we're over 16usec now, which if I did the math right is the wire time.
Another way to estimate all this is to benchmark achieved transfer rate peer-to-peer on an otherwise idle link. Folks report from 100mbit to 300mbit depending on other bottlenecks (disk speed, bus etc), but that's often using very large block sizes, not our 2K. Even so we see most of the Gigabit rate whittled away.