[Cake] and the bad cpu news on arm is

Dave Taht dave.taht at gmail.com
Sat Dec 19 15:03:40 EST 2015

is that bcake configured via sqm to do 200mbit/20mbit, rings
in at 82% idle over a 2 minute period over a 1 minute rrul test.
cake, in all it's glory of statistics, extra features, bells, and whistles...

is also 82% idle.

vs sqm's htb + fq_codel at 86% idle.

(in other words, this is not a direct measurement of the code under
'load' but over a large sampling interval comparing idle with the
loaded state, AND (sigh) htb + fq_codel uses less cpu. am using the
mpstat 1 120 test for this from the openwrt sysstat package)

The good news from my perspective:

A) that it works at all with linux 4.4rc4 on the linksys 1200ac, which
was certainly not the case til last week
B) We CAN profile now
C) All systems for bandwidth (htb and cake) are accurate to 200mbit at
least, on this hardware

The bad news from my perspective:

A) I ran out of time for this back in august. Really have a ton of
wifi work stacked up.

B) I'd like to see someone show an instance where cake uses less cpu
or is better in any way than htb+ fq_codel.

There is a very small latency improvement (.8ms vs 1ms on this path).

I do not see any other appreciable difference in cpu usage or network
behavior... aside from negative ones.

Someone that's saying "ooh cake's better" *please* go measure rrul_be
while running "mpstat 1 120" for both sqm with fq_codel and sqm with

C) I will try to summon the energy to try it on mips myself, tomorrow.

Dave Täht
Let's go make home routers and wifi faster! With better software!

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