[Users] oVirt 3.5 planning - bandwidth accounting

[Dan Kenigsberg]

There are users that would like to tell how much traffic each vnic of
each VM has consumed in a period of time. Currently, we report only
bitrate as a percetage of an estimated vnic "speed". Integrating this
value over time is inefficent and error prone.

I suggest to have all the stack (Vdsm, Engine, dwh) report the
actually-trasmitted (and actually-received) byte count on each vnic, as
well as the time when the sample was taken.

Currently, Vdsm reports

                   'eth0': {'rxDropped': '0',
                            'rxErrors': '0',
                            'rxRate': '8.0',
                            'speed': '1000',
                            'state': 'up',
                            'txDropped': '0',
                            'txErrors': '0',
                            'txRate': '10.0'},

but it should add rxKiBytes, txKiBytes and time to the frill.

GUI could still calculate the rate for illustration, based on the raw
trasmission and the sample time.

Until we break backward compatibility, we'd keep reporting the flaky
rxRate/txRate, too.

I can think of only two problems with this approach: Linux byte counters would
eventually reset when they overflow. This is currently hidden by Vdsm, but with
the suggested change, would have to be handled by higher levels of the stack.

A similar problem appears on migration: the counters would reset and Engine
would need to know how to keep up the accounting properly.

I've opened

    Bug 1066570 - [RFE] Report actual rx_byte instead of a false rxRate

to track this request of mine.