netdev - Re: tc mqprio offload command error

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Date:   Mon, 16 Jul 2018 10:57:38 -0700
From:   Jesus Sanchez-Palencia <jesus.sanchez-palencia@...el.com>
To:     Alexander Duyck <alexander.duyck@...il.com>,
        "Chopra, Manish" <Manish.Chopra@...ium.com>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        David Miller <davem@...emloft.net>,
        Jiri Pirko <jiri@...nulli.us>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: tc mqprio offload command error

Hi,


On 07/16/2018 10:20 AM, Alexander Duyck wrote:
> On Sun, Jul 15, 2018 at 6:30 PM, Chopra, Manish
> <Manish.Chopra@...ium.com> wrote:
>> Hello Folks,
>>
>> I am trying to set below command to try mqprio offload on 4.18 kernel. It is throwing the flowing error.
>>
>> # tc qdisc add dev eth0 root mqprio num_tc 2 map 1 1 1 1 0 0 0 0
>> RTNETLINK answers: Numerical result out of range
>>
>> I can't really make out what's wrong with the above command, since this works fine with other OS kernels.
>> Any thoughts if it is something broken on upstream kernel ?
>>
>> Thanks,
>> Manish
> 
> You might need to specify the traffic class for the 8 remaining
> priorities. The full map size is 16 entries, not just 8. The default
> value for the last 4 mapping entries is TC 3 which would be out of
> range if you only have 2 TCs specified.


In addition to that, you might hit the same bug we brought up [1] a while ago.
If that is the case, a fix was just proposed here [2]. Note that other qdiscs
might be broken as well, but we could only spot the issue with mqprio and netem
so far.

[1] https://patchwork.ozlabs.org/patch/867860/#1893405
[2] https://patchwork.ozlabs.org/patch/944565/


Regards,
Jesus


> 
> - Alex
>