netdev - Re: [PATCH iproute2-next v2] tc: add skip_hw and skip

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Message-ID: <280e716c-a588-5c7b-d77e-d5d09bb0148b@mojatatu.com>
Date:   Wed, 16 Feb 2022 07:51:04 -0500
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Baowen Zheng <baowen.zheng@...igine.com>,
        Roi Dayan <roid@...dia.com>,
        Victor Nogueira <victor@...atatu.com>
Cc:     David Ahern <dsahern@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        oss-drivers <oss-drivers@...igine.com>,
        Simon Horman <simon.horman@...igine.com>
Subject: Re: [PATCH iproute2-next v2] tc: add skip_hw and skip_sw to control
 action offload

On 2022-02-11 05:01, Baowen Zheng wrote:
> Hi Jamal:
> Sorry for the delay of the reply.
>

I guess it is my turn to say sorry for the latency ;->

> On February 2, 2022 7:47 PM, Jamal wrote:
>> On 2022-02-02 04:37, Baowen Zheng wrote:
>>> Hi Roi:
>>> Thanks for bring this to us, please see the inline comments.
>>>

[..]
>>
>> Probably the language usage is causing the confusion and I missed this detail
>> in the output as well. Let me see if i can break this down.
>>
>> Either both action and  filter are in h/w or they are not. i.e
>>
>> action in h/w  + filter in h/w == GOOD
>> action in h/w  + filter in s/w == BAD
>> action in s/w  + filter in h/w == BAD
>> action in s/w  + filter in s/w == GOOD
>>
>> The kernel patches did have those rules in place - and Baowen added tdc tests
>> to check for this.
>>
>> Now on the workflow:
>> 1) If you add an action independently to offload before you add a filter when
>> you dump actions it should say "skip_sw, ref 1 bind 0"
>> i.e information is sufficient here to know that the action is offloaded but there
>> is no filter attached.
>>
>> 2) If you bind this action after to a filter which _has to be offloaded_
>> (otherwise the filter will be rejected) then when you dump the actions you
>> should see "skip_sw ref 2 bind 1"; when you dump the filter you should see
>> the same on the filter.
>>
>> 3) If you create a skip_sw filter without step #1 then when you dump you
>> should see "skip_sw ref 1 bind 1" both when dumping in IOW, the not_in_hw
>> is really unnecessary.
>>
>> So why not just stick with skip_sw and not add some new language?
>>
> If I do not misunderstand, you mean we just show the skip_sw flag and do not show other information(in_hw, not_in_hw and in_hw_count), I think it is reasonable to show the action information as your suggestion if the action is dumped along with the filters.
> 

Yes, thats what i am saying - it maintains the existing semantics people
are aware of for usability.

> But as we discussed previously, we added the flags of skip_hw, skip_sw, in_hw_count mainly for the action dump command(tc -s -d actions list action xxx).
> We know that the action can be created with three flags case: skip_sw, skip_hw and no flag.
> Then when the actions are dumped independently, the information of skip_hw, skip_sw, in_hw_count will become important for the user to distinguish if the action is offloaded or not.
> 
> So does that mean we need to show different item when the action is dumped independent or along with the filter?
> 

I see your point. I am trying to visualize how we deal with the
tri-state  in filters and we never considered what you are suggesting.
Most people either skip_sw or skip_hw in presence of offloadable hw.
In absence of hardware nobody specifies a flag, so nothing is displayed.
My eyes are used to how filters look like. Not sure anymore tbh. Roi?

cheers,
jamal