[Iproute2]: failed replacing internal netem qdisc with pfifo

[Iproute2]: failed replacing internal netem qdisc with pfifo

[Marcela Maslanova]

Hello,
I've received bug report about not being replaced netem with pfifo
anymore: https://bugzilla.redhat.com/show_bug.cgi?id=515522
This should be possible according to documentation [1].
Is this intentional change or is it a bug?

It worked with kernel-2.6.27.5-117.fc10 and iproute-2.6.27. The problem
is still present with current iproute and kernel-2.6.29.6-217.2.3.fc11.

Best regards,
Marcela Mašláňová

[1] http://www.linuxfoundation.org/en/Net:Netem#How_to_reorder_packets_based_on_jitter.3F

Re: [Iproute2]: failed replacing internal netem qdisc with pfifo

[Jarek Poplawski]

On 13-08-2009 12:26, Marcela Maslanova wrote:
> Hello,
> I've received bug report about not being replaced netem with pfifo
> anymore: https://bugzilla.redhat.com/show_bug.cgi?id=515522
> This should be possible according to documentation [1].
> Is this intentional change or is it a bug?

It's intentional:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=02201464119334690fe209849843881b8e9cfa9f

> 
> It worked with kernel-2.6.27.5-117.fc10 and iproute-2.6.27. The problem
> is still present with current iproute and kernel-2.6.29.6-217.2.3.fc11.

Yes, netem is classless since 2.6.29, so this documentation needs
updating.

Best regards,
Jarek P.

Re: [Iproute2]: failed replacing internal netem qdisc with pfifo

[Jarek Poplawski]

Jarek Poplawski wrote, On 08/13/2009 02:03 PM:

> On 13-08-2009 12:26, Marcela Maslanova wrote:
>> Hello,
>> I've received bug report about not being replaced netem with pfifo
>> anymore: https://bugzilla.redhat.com/show_bug.cgi?id=515522
>> This should be possible according to documentation [1].
>> Is this intentional change or is it a bug?
> 
> It's intentional:
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=02201464119334690fe209849843881b8e9cfa9f
> 
>> It worked with kernel-2.6.27.5-117.fc10 and iproute-2.6.27. The problem
>> is still present with current iproute and kernel-2.6.29.6-217.2.3.fc11.
> 
> Yes, netem is classless since 2.6.29, so this documentation needs
> updating.


Hmm... I see this is passed to the user as "notabug". On the other hand,
since this functionality looks like useful (and used), I wonder if "we"
weren't too strict, and maybe it should be at least partially restored.
The clasfullness isn't actually a big problem if we skip reordering
(done by putting packets to the head of the queue) for such external
qdiscs. Alternatively we could modify netem's tfifo behavior (to pfifo)
with some option. Any suggestions?

Jarek P.

Re: [Iproute2]: failed replacing internal netem qdisc with pfifo

[Jarek Poplawski]

Jarek Poplawski wrote, On 08/13/2009 11:32 PM:

...
> The clasfullness isn't actually a big problem if we skip reordering
> (done by putting packets to the head of the queue) for such external
> qdiscs. Alternatively we could modify netem's tfifo behavior (to pfifo)
> with some option. Any suggestions?


...or something in between like classfulness limited to fifos only?

Jarek P.