[Bloat] AQM creeping into L2 equipment

[Eric Dumazet]

On Thu, 2014-03-20 at 13:23 -0700, Dave Taht wrote:

> Well there is some good work in linux 3.14 and beyond, and there was also
> some interesting work on "initial spreading" presented at ietf.
> 
> Hopefully patches for this will be available soon.
> 
> http://tools.ietf.org/html/draft-sallantin-iccrg-initial-spreading-00
> 
> I would certainly like to be able to sanely measure the impact of
> hundreds or thousands of flows in slow start, rather than/in addition to 8 flows
> in congestion avoidance.

As mentioned elsewhere, FQ/pacing does exactly this 'spreading', and not
only for the 'initial' burst, but on all the lifetime of tcp flow, for
example after recovery or idle period.

FQ/pacing is part of linux kernel since 3.12

To play with it, you can set it like that :

tc qdisc replace dev eth0 root fq quantum 1514 initial_quantum 1514

http://lwn.net/Articles/564978/

I believe Steinar had success using FQ/pacing lately, presumably using
SO_MAX_PACING_RATE as well.