[Codel] fq_codel_drop vs a udp flood

[Eric Dumazet]

On Thu, 2016-05-05 at 17:53 +0300, Roman Yeryomin wrote:

> 
> qdisc fq_codel 0: dev eth0 root refcnt 2 limit 1024p flows 1024
> quantum 1514 target 5.0ms interval 100.0ms ecn
>  Sent 12306 bytes 128 pkt (dropped 0, overlimits 0 requeues 0)
>  backlog 0b 0p requeues 0
>   maxpacket 0 drop_overlimit 0 new_flow_count 0 ecn_mark 0
>   new_flows_len 0 old_flows_len 0


Limit of 1024 packets and 1024 flows is not wise I think.

(If all buckets are in use, each bucket has a virtual queue of 1 packet,
which is almost the same than having no queue at all)

I suggest to have at least 8 packets per bucket, to let Codel have a
chance to trigger.

So you could either reduce number of buckets to 128 (if memory is
tight), or increase limit to 8192.