Missing the AF_BUS

Posted Jul 6, 2012 15:03 UTC (Fri) by pspinler (subscriber, #2922)
In reply to: Missing the AF_BUS by josh
Parent article: Missing the AF_BUS

I'm not sure if linux's tcp stack is inefficient or not compared to other tcp stacks, but the networking stack is certainly is complex and multi-layered. Consider all the basic tcp protocol code (reliability, packet frag and reassembly, etc), then layer on top netfilter, underneath it routing logic, the ip stack, and etc, and it's easy to construct packets that go through possibly significant code paths.

Certainly all that complexity can't be great for performance.

It's the argument I make for fibre channel v. iscsi. It's true that iscsi hardware (being just standard networking stuff) is a lot cheaper and does the job 90-95% of the time. But in the edge case, especially w.r.t latency, fibre still wins, largely because it's simple in comparison.

-- Pat

Missing the AF_BUS

Posted Jul 9, 2012 2:35 UTC (Mon) by raven667 (subscriber, #5198) [Link]

> Certainly all that complexity can't be great for performance.

That's something worth testing, scientifically.

> It's the argument I make for fibre channel v. iscsi. It's true that iscsi hardware (being just standard networking stuff) is a lot cheaper and does the job 90-95% of the time. But in the edge case, especially w.r.t latency, fibre still wins, largely because it's simple in comparison.

One thing about this example that I would like to point out. FC implements much of the features of Ethernet and TCP/IP ... differently, so in that sense the complexity is at least comparable though probably not equal. As far as the implementation complexity I think that FC can get off easier because as a practical matter it is used in closed networks often with all components from the same vendor. Ethernet and TCP/IP have to deal with a lot more varied equipment and varied networks and have to be battle tested against _anything_ happening, all that extra implementation complexity has a real reason for being there.