[Cake] [PATCH 0/3] Add Common Applications Kept Enhanced (sch_cake) qdisc

Dave Taht dave.taht at gmail.com
Tue Nov 21 19:09:39 EST 2017

sch_cake is intended to squeeze the most bandwidth and lowest latency out
of even the slowest ISP links and routers, while presenting an API simple
enough that even an ISP can configure it.

Example of use on an ISP uplink:

tc qdisc add dev eth0 cake bandwidth 20Mbit nat docsis ack-filter

Cake can also be used in unlimited mode to drive packets at the speed
of the underlying link.

Cake is filled with:

* A hybrid Codel/Blue AQM algorithm, “Cobalt”, tied to an FQ_Codel
  derived Flow Queuing system, which autoconfigures based on the bandwidth.
* A unique "triple-isolate" mode (the default) which balances per-flow
  and per-host flow FQ even through NAT.
* An integral deficit based shaper with extensive dsl and docsis support
  that can also be used in unlimited mode.
* 8 way set associative queuing to reduce flow collisions to a minimum.
* A reasonable interpretation of various diffserv latency/loss tradeoffs.
* Support for washing diffserv for entering and exiting traffic.
* Perfect support for interacting with Docsis 3.0 shapers.
* Extensive support for DSL framing types.
* (New) Support for ack filtering.
  - 20 % better throughput at a 16x1 down/up ratio on the rrul test.
* Extensive statistics for measuring loss, ecn markings, latency variation.

There are some features still considered experimental, notably the
ingress_autorate bandwidth estimator and cobalt itself.

Various versions shipping have been available as an out of tree build for
kernel versions going back to 3.10, as the embedded router world has been
running a few years behind mainline Linux. A stable version has been
generally available on lede-17.01 and later.

sch_cake replaces a combination of iptables, tc filter, htb and fq_codel in
the sqm-scripts, with sane defaults and vastly easier configuration.

Cake's principal author is Jonathan Morton, with contributions from
Kevin Darbyshire-Bryant, Toke Høiland-Jørgensen, Sebastian Moeller,
Ryan Mounce, Dean Scarff, Guido Sarducci, Nils Andreas Svee, Dave Täht, and
Loganaden Velvindron.

Dave Taht (3):
  pkt_sched.h: add support for sch_cake API
  Add Common Applications Kept Enhanced (sch_cake) qdisc
  Add support for building the new cake qdisc

 include/net/cobalt.h           |  152 +++
 include/uapi/linux/pkt_sched.h |   58 +
 net/sched/Kconfig              |   11 +
 net/sched/Makefile             |    1 +
 net/sched/sch_cake.c           | 2551 ++++++++++++++++++++++++++++++++++++++++
 5 files changed, 2773 insertions(+)
 create mode 100644 include/net/cobalt.h
 create mode 100644 net/sched/sch_cake.c


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