netdev - Re: [PATCH net-next 00/13] Control action percpu counters allocation by netlink flag

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Date:   Sat, 26 Oct 2019 10:52:58 -0400
From:   Roman Mashak <mrv@...atatu.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>
Cc:     Vlad Buslov <vladbu@...lanox.com>, Jiri Pirko <jiri@...nulli.us>,
        "netdev\@vger.kernel.org" <netdev@...r.kernel.org>,
        "xiyou.wangcong\@gmail.com" <xiyou.wangcong@...il.com>,
        "davem\@davemloft.net" <davem@...emloft.net>,
        "mleitner\@redhat.com" <mleitner@...hat.com>,
        "dcaratti\@redhat.com" <dcaratti@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next 00/13] Control action percpu counters allocation by netlink flag

Jamal Hadi Salim <jhs@...atatu.com> writes:

> On 2019-10-26 5:44 a.m., Vlad Buslov wrote:
>>
>
>> Okay, I understand now what you suggest. But why not unify cls and act
>> API, and always have flags parsed in tcf_action_init_1() as
>> TCA_ACT_ROOT_FLAGS like I suggested in one of my previous mails? That
>> way we don't have to pass pointers around.
>
> That would work.
> I am being a sucker for optimization - one flag for a batch
> of actions vs one per action.
> It is a good compromise, go for it.

But why do we need to have two attributes, one at the root level
TCA_ROOT_FLAGS and the other at the inner TCA_ACT_* level, but in fact
serving the same purpose -- passing flags for optimizations?

The whole nest of action attributes including root ones is passed as 3rd
argument of tcf_exts_validate(), so it can be validated and extracted at
that level and passed to tcf_action_init_1() as pointer to 32-bit flag,
admittedly it's ugly given the growing number of arguments to
tcf_action_init_1(). With old iproute2 the pointer will always be NULL,
so I think backward compatibilty will be preserved.