How fast is the D-Bus reference implementation?
Of course it depends a bit on what you’re doing. This mail contains some benchmarking. At the time of that benchmark, D-Bus one-to-one communication was about 2.5x slower than simply pushing the data raw over a socket. After the recent rewrite of the marshaling code, D-Bus is slower than that because a lot of optimization work was lost. But it can probably be sped up again. D-Bus communication with the intermediate bus daemon should be (and as last profiled, was) about twice as slow as one-to-one mode, because a round trip involves four socket reads/writes rather than two socket reads/writes. The overhead comes from a couple of places; part of it is simply “abstraction penalty” (there are layers of code to support multiple main loops, multiple transport types, security, etc.). Probably the largest part comes from data validation (because the reference implementation does not trust incoming data). It would be simple to add a “no validation” mode, but probably not a good idea all things
