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

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Date:   Thu, 24 Oct 2019 09:35:57 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jamal Hadi Salim <jhs@...atatu.com>
Cc:     Vlad Buslov <vladbu@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "mleitner@...hat.com" <mleitner@...hat.com>,
        "dcaratti@...hat.com" <dcaratti@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next 00/13] Control action percpu counters allocation
 by netlink flag

Wed, Oct 23, 2019 at 04:21:51PM CEST, jhs@...atatu.com wrote:
>On 2019-10-23 9:04 a.m., Vlad Buslov wrote:
>> 
>> On Wed 23 Oct 2019 at 15:49, Jamal Hadi Salim <jhs@...atatu.com> wrote:
>> > Hi Vlad,
>> > 
>
>> > I understand your use case being different since it is for h/w
>> > offload. If you have time can you test with batching many actions
>> > and seeing the before/after improvement?
>> 
>> Will do.
>
>Thanks.
>
>I think you may have published number before, but would be interesting
>to see the before and after of adding the action first and measuring the
>filter improvement without caring about the allocator.
>
>> 
>> > 
>> > Note: even for h/w offload it makes sense to first create the actions
>> > then bind to filters (in my world thats what we end up doing).
>> > If we can improve the first phase it is a win for both s/w and hw use
>> > cases.
>> > 
>> > Question:
>> > Given TCA_ACT_FLAGS_FAST_INIT is common to all actions would it make
>> > sense to use Could you have used a TLV in the namespace of TCA_ACT_MAX
>> > (outer TLV)? You will have to pass a param to ->init().
>> 
>> It is not common for all actions. I omitted modifying actions that are
>> not offloaded and some actions don't user percpu allocator at all
>> (pedit, for example) and have no use for this flag at the moment.
>
>pedit just never got updated (its simple to update). There is
>value in the software to have _all_ the actions use per cpu stats.
>It improves fast path performance.
>
>Jiri complains constantly about all these new per-action TLVs
>which are generic. He promised to "fix it all" someday. Jiri i notice
>your ack here, what happened? ;->

Correct, it would be great. However not sure how exactly to do that now.
Do you have some ideas.

But basically this patchset does what was done many many times in the
past. I think it was a mistake in the original design not to have some
"common attrs" :/ Lesson learned for next interfaces.