netdev - Re: [PATCH net-next v8 2/3] net sched actions: dump more than TCA_ACT_MAX

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Date:   Wed, 26 Apr 2017 16:07:08 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     davem@...emloft.net, xiyou.wangcong@...il.com,
        eric.dumazet@...il.com, netdev@...r.kernel.org,
        Simon Horman <simon.horman@...ronome.com>,
        Benjamin LaHaise <bcrl@...ck.org>
Subject: Re: [PATCH net-next v8 2/3] net sched actions: dump more than
 TCA_ACT_MAX_PRIO actions per batch

On 17-04-26 09:56 AM, Jiri Pirko wrote:
> Wed, Apr 26, 2017 at 03:14:38PM CEST, jhs@...atatu.com wrote:
>> On 17-04-26 08:08 AM, Jiri Pirko wrote:

[..]

>> Jiri, what are you arguing about if you have done the math? ;->
>
> I can do 3*2*64. What I cannot do is to figure out the real performance
> impact.
>

Jiri, I do a lot of very large data dumping and setting towards the
kernel. You know that. It is why I even have these patches to begin
with.

The math should be convincing enough.
48B per rule extra for just MPLS in a filter rule. I havent started
testing the overhead of flower but i do plan to use it - with about a
million rules for offloading. I will give you the numbers then.

I think we are at a stalemate.
You are not going to convince me to use an attribute with a
u8 for a bit flag when I can fit 32 of them in one attribute (with
the same cost). And I am not able to convince you that you are
wrong to put beauty first.

>> Again: You are looking at this from a manageability point of view which
>> is useful but not the only input into a design. If i can squeeze more
>> data without killing usability - I am all for it. It just doesnt
>> compute that it is ok to use a flag per attribute because it looks
>> beautiful.
>
> Hmm. Now that I'm thinking about it, why don't we have NLA_FLAGS with
> couple of helpers around it? It will be obvious what the attr is, all
> kernel code would use the same helpers. Would be nice.
>

I think to have flags at that level is useful but it
is a different hierarchy level. I am not sure the
"actions dump large messages" is a fit for that level.

cheers,
jamal