netdev - Re: [net-next sample action optimization 3/3] openvswitch: Optimize sample action for the clone use cases

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Message-ID: <CABKoBm01ieuSrbhf7yZH9AzZkTNB=kiOAhYTDoinXRtDhQoFoQ@mail.gmail.com>
Date:   Mon, 13 Mar 2017 16:39:08 -0700
From:   Andy Zhou <azhou@....org>
To:     Pravin Shelar <pshelar@....org>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Joe Stringer <joe@....org>
Subject: Re: [net-next sample action optimization 3/3] openvswitch: Optimize
 sample action for the clone use cases

>>> -       skb = skb_clone(skb, GFP_ATOMIC);
>>> -       if (!skb)
>>> -               /* Skip the sample action when out of memory. */
>>> -               return 0;
>>> +       if (key) {
>>> +               err = do_execute_actions(dp, skb, key, actions, rem);
>>> +       } else if (!add_deferred_actions(skb, orig, actions, rem)) {
>>>
>> We can refactor this code to avoid duplicate code all actions
>> implementation. This way there could be single function dealing with
>> both defered action and key fifo arrays.
>
> O.K. I will make the change in the next version.

After looking more at it, the sample action and recirc action are different
enough that I don't see clean ways refactor them. For example, recirc
needs to deal with setting recirc_id.  recirc calls
ovs_dp_process_packet, and sample calls do_execute_action.

>> I am not sure if we can put sample or recirc in "may not change flow"
>> actions list. Consider following set of actions:
>> sample(sample(set-IP)),userpsace(),...
>> In this case the userspace action could recieve skb with inconsistent
>> flow due to preceding of set action nested in the sample action.
>
> Good catch.  Will fix.

What's the objection on recirc action? It always works on clone key.