HTB + netem - weird be haviour of a queue size

HTB + netem - weird be haviour of a queue size

[Ewa Janczukowicz]

Hello,

I want to emulate ADSL link behaviour.
For that I decided to use netem and configure its rate and delay parameters.

Additionally I test different queuing configurations e.g. htb.
Since if I use htb, I can only configure netem on leaves, I decided to
create a virtual bridge.
As a results I have the following configuration:
- I have virtual bridge (br0) and I attached the phycical inerface to it.
- On virtual bridge I configure htb
- On physical interface I configure netem.

However using htb and netem changes the queue size.

If I only use htb, the queue size is 1000. The same happens if I only use netem.
However when I use both of them, the queue size becomes much shorter.

Is there any way I can check what queue size is configured?
I know I can overwrite this configuration, however finally I am not
sure how netem and htb interact and what queue I configure.

Thank you in advance for any help.

Re: HTB + netem - weird be haviour of a queue size

[Ewa Janczukowicz]

Ok, I have just realized by doing ifconfig that the queue length of my
bridge (br0) was 0. So I suppose this was causing the problem.

However I still do not know whant happens it I use htb and netem in
the above configuration and e.g. I change the queue length of htb to
1000. Will it be applicable to both netem and htb queueus? Or will I
have one two queues of 1000, on after another.

Thank you in advance.



On Thu, Feb 11, 2016 at 11:34 AM, Ewa Janczukowicz
<janczukowicz.ewa@gmail.com> wrote:
> Hello,
>
> I want to emulate ADSL link behaviour.
> For that I decided to use netem and configure its rate and delay parameters.
>
> Additionally I test different queuing configurations e.g. htb.
> Since if I use htb, I can only configure netem on leaves, I decided to
> create a virtual bridge.
> As a results I have the following configuration:
> - I have virtual bridge (br0) and I attached the phycical inerface to it.
> - On virtual bridge I configure htb
> - On physical interface I configure netem.
>
> However using htb and netem changes the queue size.
>
> If I only use htb, the queue size is 1000. The same happens if I only use netem.
> However when I use both of them, the queue size becomes much shorter.
>
> Is there any way I can check what queue size is configured?
> I know I can overwrite this configuration, however finally I am not
> sure how netem and htb interact and what queue I configure.
>
> Thank you in advance for any help.

Re: HTB + netem - weird be haviour of a queue size

[Andy Furniss]

Ewa Janczukowicz wrote:
> Ok, I have just realized by doing ifconfig that the queue length of
> my bridge (br0) was 0. So I suppose this was causing the problem.
>
> However I still do not know whant happens it I use htb and netem in
> the above configuration and e.g. I change the queue length of htb to
> 1000. Will it be applicable to both netem and htb queueus? Or will I
> have one two queues of 1000, on after another.
>
> Thank you in advance.

Not sure about that specifically.

Maybe you don't even need htb as netem now has a rate option which will
be useful to emulate bitrate latency and wasn't there when I tried this
around a decade ago.

I am not sure whether or not netem will work with stab (which lets you
accurately add ATM/PPP overheads).

With htb you can specify child qdiscs anyway to control length, I don't
know about netem - if you can't find a way you could try changing txqlen
on br0/eth0 with ip link set ...

If bridging doesn't work out for some reason you can double queue using ifb.



> On Thu, Feb 11, 2016 at 11:34 AM, Ewa Janczukowicz
> <janczukowicz.ewa@gmail.com> wrote:
>> Hello,
>>
>> I want to emulate ADSL link behaviour. For that I decided to use
>> netem and configure its rate and delay parameters.
>>
>> Additionally I test different queuing configurations e.g. htb.
>> Since if I use htb, I can only configure netem on leaves, I decided
>> to create a virtual bridge. As a results I have the following
>> configuration: - I have virtual bridge (br0) and I attached the
>> phycical inerface to it. - On virtual bridge I configure htb - On
>> physical interface I configure netem.
>>
>> However using htb and netem changes the queue size.
>>
>> If I only use htb, the queue size is 1000. The same happens if I
>> only use netem. However when I use both of them, the queue size
>> becomes much shorter.
>>
>> Is there any way I can check what queue size is configured? I know
>> I can overwrite this configuration, however finally I am not sure
>> how netem and htb interact and what queue I configure.
>>
>> Thank you in advance for any help.
> -- To unsubscribe from this list: send the line "unsubscribe lartc"
> in the body of a message to majordomo@vger.kernel.org More majordomo
> info at  http://vger.kernel.org/majordomo-info.html
>

Re: HTB + netem - weird be haviour of a queue size

[Ewa Janczukowicz]

Thank you for your answer.
You're right. I also figured out that precising the qdisc kind of
solves the problem.
Thus, I make sure to configure the queue length in htb so the default
queue length of a bridge is overwritten.




On Sat, Feb 13, 2016 at 12:00 AM, Andy Furniss <adf.lists@gmail.com> wrote:
> Ewa Janczukowicz wrote:
>>
>> Ok, I have just realized by doing ifconfig that the queue length of
>> my bridge (br0) was 0. So I suppose this was causing the problem.
>>
>> However I still do not know whant happens it I use htb and netem in
>> the above configuration and e.g. I change the queue length of htb to
>> 1000. Will it be applicable to both netem and htb queueus? Or will I
>> have one two queues of 1000, on after another.
>>
>> Thank you in advance.
>
>
> Not sure about that specifically.
>
> Maybe you don't even need htb as netem now has a rate option which will
> be useful to emulate bitrate latency and wasn't there when I tried this
> around a decade ago.
>
> I am not sure whether or not netem will work with stab (which lets you
> accurately add ATM/PPP overheads).
>
> With htb you can specify child qdiscs anyway to control length, I don't
> know about netem - if you can't find a way you could try changing txqlen
> on br0/eth0 with ip link set ...
>
> If bridging doesn't work out for some reason you can double queue using ifb.
>
>
>
>> On Thu, Feb 11, 2016 at 11:34 AM, Ewa Janczukowicz
>> <janczukowicz.ewa@gmail.com> wrote:
>>>
>>> Hello,
>>>
>>> I want to emulate ADSL link behaviour. For that I decided to use
>>> netem and configure its rate and delay parameters.
>>>
>>> Additionally I test different queuing configurations e.g. htb.
>>> Since if I use htb, I can only configure netem on leaves, I decided
>>> to create a virtual bridge. As a results I have the following
>>> configuration: - I have virtual bridge (br0) and I attached the
>>> phycical inerface to it. - On virtual bridge I configure htb - On
>>> physical interface I configure netem.
>>>
>>> However using htb and netem changes the queue size.
>>>
>>> If I only use htb, the queue size is 1000. The same happens if I
>>> only use netem. However when I use both of them, the queue size
>>> becomes much shorter.
>>>
>>> Is there any way I can check what queue size is configured? I know
>>> I can overwrite this configuration, however finally I am not sure
>>> how netem and htb interact and what queue I configure.
>>>
>>> Thank you in advance for any help.
>>
>> -- To unsubscribe from this list: send the line "unsubscribe lartc"
>> in the body of a message to majordomo@vger.kernel.org More majordomo
>> info at  http://vger.kernel.org/majordomo-info.html
>>
>