[Cake] the meta problem of memory, locks, and multiple cpus

[Jonathan Morton]

> On 3 Nov, 2015, at 02:55, Stephen Hemminger <stephen at networkplumber.org> wrote:
> 
> Why not measure the egress rate like PIE?

Because there is often quite a lot of buffering in the device and/or driver which can easily mask the true link rate, by absorbing bursts of traffic at extremely high rates.  This is a greater problem in ordinary Ethernet NICs than in cable modems.  It is likewise (and more obviously) a problem when a fast Ethernet link exists between the router and a slow last-mile modem.

> Also many devices (like wifi) can't report real link rate.

On the contrary, Minstrel knows what rate it has (momentarily) selected for the wifi device to use (though it is then diluted by contention for the medium).  Exposing that to other layers of the network stack is the challenge.

 - Jonathan Morton