netdev - Re: [jkirsher/next-queue PATCH v4 0/6] tc-flower based cloud filters in i40e

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Date:   Wed, 11 Oct 2017 10:46:27 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     Amritha Nambiar <amritha.nambiar@...el.com>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        "Duyck, Alexander H" <alexander.h.duyck@...el.com>,
        Netdev <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>
Subject: Re: [jkirsher/next-queue PATCH v4 0/6] tc-flower based cloud filters
 in i40e

On Wed, Oct 11, 2017 at 5:56 AM, Jiri Pirko <jiri@...nulli.us> wrote:
> Wed, Oct 11, 2017 at 02:24:12AM CEST, amritha.nambiar@...el.com wrote:
>>This patch series enables configuring cloud filters in i40e
>>using the tc-flower classifier. The classification function
>>of the filter is to match a packet to a class. cls_flower is
>>extended to offload classid to hardware. The offloaded classid
>>is used direct matched packets to a traffic class on the device.
>>The approach here is similar to the tc 'prio' qdisc which uses
>>the classid for band selection. The ingress qdisc is called ffff:0,
>>so traffic classes are ffff:1 to ffff:8 (i40e has max of 8 TCs).
>
>
> NACK. This clearly looks like abuse of classid to something
> else. Classid is here to identify qdisc instance. However, you use it
> for hw tclass identification. This is mixing of apples and oranges.
>
> Why?
>
> Please don't try to abuse things! This is not nice.

This isn't an abuse. This is reproducing in hardware what is already
the behavior for software. Isn't that how offloads are supposed to
work?

This is exactly how prio currently handles this. We are essentially
doing the exact same thing in the hardware where we are choosing a
queueing group based on the class ID. You could setup a prio qdisc. If
you are offloading a qdisc behavior into hardware how are you supposed
to emulate the behavior if you aren't allowing the offload to use the
same mechanism?

- Alex