[Cake] lan keyword affects host fairness

Dave Taht dave.taht at gmail.com
Fri Nov 24 15:03:12 EST 2017

I support removing metro and below as keywords.

Note: I am more interested in throughput (w/ecn) at the lower rtt
settings than flow fairness (is the aqm scaling?). If we can have
shorter queues overall while not taking a throughput hit, in the
datacenter, that's a win.

I have a hope, however, that at 10GigE we have sufficient queue size
for both fairness and throughput, with even a 1ms rtt setting (50us
target) but most of us lack the hardware that can test anything at
those rates, and there are other problems in that Linux can't do more
than about 4m PPS, so it is presently impossible, to my knowledge, to
drive 10GigE to saturation with small packets using any qdisc.

And there are many other overheads - notably qdisc locking and, fib
lookup, in the way. It had been my hope that cake could be poured into
ethernet hardware one day, but it has sprouted too many non O(1)
things of late.

On Fri, Nov 24, 2017 at 11:41 AM, Pete Heist <peteheist at gmail.com> wrote:
> On Nov 24, 2017, at 2:49 PM, Pete Heist <peteheist at gmail.com> wrote:
> Removing the bandwidth keywords altogether and going back to fq_codel’s
> specification of target and interval would be my personal preference (unless
> we can figure out how to make the keywords work well with one another in all
> cases).
> To add to my comments, this probably came across as too harsh or
> discontinuous an idea at this stage when we’re in the process of shoring
> things up- that wasn’t my intent!
> There is the other side that these keywords save people from having to know
> more. Which is better, explaining target and interval to everyone or having
> them use these? I imagine that was the logic that went into it. Also, if
> it’s not a good idea to be changing the configuration interface at this
> point (and it may not be), then there are alternatives, and the man page
> addition will definitely help people. Maybe I’ll make some runs across a
> range of rtts to understand this better…
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Dave Täht
CEO, TekLibre, LLC
Tel: 1-669-226-2619

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