Re: [Bloat] SFQRED or SFQARED?

[Dave Taht <dave.taht@gmail.com>]

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On Tue, Aug 27, 2013 at 9:29 AM, Naeem Khademi <naeem.khademi@gmail.com>wrote:

> Hi
>
> Slide 37 of below link mentions that SFQRED implemented in Linux 3.4
> upwards, "Utilized a better version of RED (“ARED”) from Sally Floyd
> in 2002". However I'm unable to find the "adaptive" bit of SFQRED in
> the kernel and iproute code. Can anyone (Dave or Eric) confirm that
> the mentioned statement is correct?
>
> http://netseminar.stanford.edu/seminars/Inside_Codel_and_Fq_Codel.pdf
>
>
I think you are correct in that the adaptive RED code never formally made
it into SFQRED. SFQRED was a brief blip in time before codel showed up...
I'd talked about it in that talk as a steppingstone in hybrid fq+aqm
history. (prior to that we were working with qfq + red as entirely
separate, modular qdiscs). So... oops.

I think the work was interesting and valuable, and if you want to play with
the ARED variant probably all you have to do is OR in the TC_ADAPTATIVE
value into the flags on the red setup in sch_sfq.c

Eric added ARED support to sch_red in kernel commit:
8af2a218de38f51ea4b4fa48cac1273319ae260c

https://android.googlesource.com/kernel/exynos/+/8af2a218de38f51ea4b4fa48cac1273319ae260c

and some ip route version later corrected "adaptive" to be the user-facing
syntax. I just ran a quick, dirty and (nonsensical*) rrul test with this:

tc qdisc add dev eth0 root red limit 40000 min 30000 max 90000 avpkt 1000
burst 55 ecn adaptive bandwidth 10Mbit

tc -s qdisc show dev eth0
qdisc red 8005: root refcnt 2 limit 40000b min 30000b max 90000b ecn
adaptive
 Sent 858913226 bytes 823269 pkt (dropped 4866, overlimits 123 requeues 0)
 backlog 0b 0p requeues 0
  marked 0 early 123 pdrop 4743 other 0

which "just worked" with ubuntu 13.4.

The ARED option could be enabled with GRED/SFQRED with adding the right
knob to iproute2.


Regards,
> Naeem
>


* I have thankfully managed to completely forget how to configure RED or
ARED to what little extent I understood it in the first place
-- 
Dave Täht

Fixing bufferbloat with cerowrt:
http://www.teklibre.com/cerowrt/subscribe.html

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