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

Stephen Hemminger stephen at networkplumber.org
Mon Nov 2 19:55:32 EST 2015

On Thu, 29 Oct 2015 12:00:38 +0100
Jesper Dangaard Brouer <brouer at redhat.com> wrote:

> On Thu, 29 Oct 2015 10:08:34 +0100
> Dave Taht <dave.taht at gmail.com> wrote:
> > The real problem A) that I wish we could solve at the qdisc layer
> > 
> > is that we could size everything more appropriately if we actually
> > *knew* the physical link rate in many cases. It is *right there* in
> > the sys filesystem for ethernet devices, if only there was some way to
> > get at it, and get notifications if it changed.... or merely to know
> > the underlying operating range of the device at qdisc init time. It is
> > dumb to allow 50MB of memory for a 10mbit device just to make the
> > 10GigE folk happy.  
> Well, do you really need to know the link rate?  One of the lessons
> learned from codel (by Kathleen/Van) is that we should not trie to
> measure the link rate, but instead simply look at the time spend in
> queue.

Why not measure the egress rate like PIE?
It is right there in the same code.

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

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