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

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Date:   Thu, 24 Oct 2019 15:23:52 +0000
From:   Vlad Buslov <vladbu@...lanox.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>
CC:     Jiri Pirko <jiri@...nulli.us>, 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

On Thu 24 Oct 2019 at 10:35, Jiri Pirko <jiri@...nulli.us> wrote:
> 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.

Jamal, can we reach some conclusion? Do you still suggest to refactor
the patches to use TCA_ROOT_FLAGS and parse it in act API instead of
individual actions?

Thanks,
Vlad