How to disable BBR module in kernel?

[Ray Zhang]

Hi,

I am trying to do some testing to see if there is benefit from BBR, a little disapointed,  please help me to check if there is something wrong

1.  upgrade kernel to 4.9

2.  echo bbr > /proc/sys/net/ipv4/tcp_congestion_control  

~ # cat /proc/sys/net/ipv4/tcp_congestion_control

bbr

do testing get the data1

3.  echo cubic > /proc/sys/net/ipv4/tcp_congestion_control   <----  can it disable BBR?

cat /proc/sys/net/ipv4/tcp_congestion_control

cubic

do testing and get data2

didn't see much difference between data1 and data2,  maybe BBR is not disabled in step3? 

Regards,

Lei 

     

    

[Kevin Bowling]

What are you testing and what are you looking to improve?

BBR helps in at least the following dimensions right now: dealing
with packet loss, avoiding buffer bloat, RTT measurement. Perhaps
flow fairness and dealing with other problems described on the mailing
list soon.

Regards,
Kevin Bowling - Senior Manager, Engineering
+1 602 850 5036 +1 480 227 1233
www.limelight.com Delivering Faster Better

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[Eric Dumazet]

Hi Ray.

It seems you forgot to setup FQ packet scheduler ?

You also can retry the experiment using latest kernel (linux-4.13) to
avoid to deal with FQ

Note that BBR helps tremendously in presence of losses and long RTT.

Thanks !

[Ray Zhang]

thank you for your info~ I will do more investigation for next post. 

[Ray Zhang]

cat /proc/sys/net/core/default_qdisc

fq

FQ is set to fq. It should be OK, I will do more investigation about BBR for next testing

[Neal Cardwell]

On Thu, Sep 14, 2017 at 5:48 AM, Ray Zhang <bzl...@gmail.com> wrote:

cat /proc/sys/net/core/default_qdisc

fq

FQ is set to fq. It should be OK, I will do more investigation about BBR for next testing

Keep in mind that /proc/sys/net/core/default_qdisc does not take effect immediately. It only takes effect after the qdiscs for a network device are rebuilt. The easiest way to make sure this happens is to reboot.

You can check if fq is in place with:

   tc qdisc show

You may find the BBR quick-start guide helpful:

  https://github.com/google/bbr/blob/master/Documentation/bbr-quick-start.md

cheers,

neal