netdev - Re: [PATCH net-next] net: openvswitch: Set OvS recirc

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Date:   Mon, 19 Aug 2019 22:50:54 -0700
From:   Pravin Shelar <pshelar@....org>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     Paul Blakey <paulb@...lanox.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Justin Pettit <jpettit@...ira.com>,
        Simon Horman <simon.horman@...ronome.com>,
        Vlad Buslov <vladbu@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>, Roi Dayan <roid@...lanox.com>,
        Yossi Kuperman <yossiku@...lanox.com>,
        Rony Efraim <ronye@...lanox.com>, Oz Shlomo <ozsh@...lanox.com>
Subject: Re: [PATCH net-next] net: openvswitch: Set OvS recirc_id from tc chain

On Mon, Aug 19, 2019 at 10:42 AM Marcelo Ricardo Leitner
<marcelo.leitner@...il.com> wrote:
>
> On Sun, Aug 18, 2019 at 07:00:59PM +0300, Paul Blakey wrote:
> > What do you guys say about the following diff on top of the last one?
> > Use static key, and also have OVS_DP_CMD_SET command probe/enable the feature.
> >
> > This will allow userspace to probe the feature, and selectivly enable it via the
> > OVS_DP_CMD_SET command.
>
> I'm not convinced yet that we need something like this. Been
> wondering, skb_ext_find() below is not that expensive if not in use.
> It's just a bit check and that's it, it returns NULL.
>
> And drivers will only be setting this if they have tc-offloading
> enabled (assuming they won't be seeing it for chain 0 all the time).
> On which case, with tc offloading, we need this in order to work
> properly.
>
> Is the bit checking really that worrysome?
>
Point is this would be completely unnecessary check for software only
cases, that is what static key is used for, when you have a feature in
datapath that is not used by majority of users. So I do not see any
downside of having this static key.