[LARTC] HTB traffic shaping odd effects

[Andy Furniss]

Oliver Hookins wrote:
> Hi,
> 
> I'm trying to perform some (what I consider) basic traffic shaping on 
> our network utilising HTB. I have mostly reused the example on the 
> lartc.org site:
> 
> tc qdisc add dev eth0 root handle 1: htb default 10
> tc class add dev eth0 parent 1: classid 1:1 htb rate 100mbit burst 24k
> tc class add dev eth0 parent 1:1 classid 1:10 htb rate 50mbit ceil
> 80mbit burst 19k

burst 19k will limit you unless your HZ=1000


> tc class add dev eth0 parent 1:1 classid 1:20 htb rate 1mbit ceil
> 1mbit
> tc qdisc add dev eth0 parent 1:10 handle 10: sfq perturb 10
> tc qdisc add dev eth0 parent 1:20 handle 20: sfq perturb 10
> tc filter add dev eth0 protocol ip parent 1:0 prio 1 u32 match ip src
> X.X.X.X flowid 1:20
> 
> So we have a total of 100mbit to be used, the default class 1:10 gets 
> 50mbit and a ceiling of 80mbit whereas my test host X.X.X.X gets only 
> 1mbit in any situation. Some rate limiting is definitely happening, but 
> I am finding the outbound traffic is limited to 2mbit instead of 1mbit. 
> If I change the rate (to say 10mbit) the outbound traffic gets up to 
> again twice the rate (in this case 20mbit).

Not sure can you show output of tc -s -d class ls dev eth0 while it's 
running at 2x speed.

> 
> Any thoughts? I have had a look at the tc statistics but it doesn't 
> appear as I would expect it to. Class 1:10 shows a lot of dropped 
> packets but it is only averaging around 30mbit constantly. On the other 
> hand class 1:20 doesn't show any dropped packets. Similarly there are no 
> packets marked as overlimit for any class.

Apart from the 30mbit that would be normal.

Andy.


  I occasionally see the tokens
> for 1:20 go negative... everything is quite strange.
> 
> Any help would be appreciated.
>