netdev - Re: [net-next PATCH v3 3/8] net: sched: add cls

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Date:	Fri, 19 Feb 2016 10:16:10 +0200
From:	Or Gerlitz <gerlitz.or@...il.com>
To:	Amir Vadai <amir@...ai.me>,
	John Fastabend <john.fastabend@...il.com>
Cc:	Jamal Hadi Salim <jhs@...atatu.com>,
	Jiří Pírko <jiri@...nulli.us>,
	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: Re: [net-next PATCH v3 3/8] net: sched: add cls_u32 offload hooks for netdevs

On Thu, Feb 18, 2016 at 11:23 AM, Amir Vadai" <amir@...ai.me> wrote:
> On Wed, Feb 17, 2016 at 03:07:23PM -0800, John Fastabend wrote:

>> Actually thinking about this a bit more I wrote this thinking
>> that there existed some hardware that actually cared if it was
>> a new rule or an existing rule. For me it doesn't matter I do
>> the same thing in the new/replace cases I just write into the
>> slot on the hardware table and if it happens to have something
>> in it well its overwritten e.g. "replaced". This works because
>> the cls_u32 layer protects us from doing something unexpected.

>> I'm wondering (mostly asking the mlx folks) is there hardware
>> out there that cares to make this distinction between new and
>> replace? Otherwise I can just drop new and always use replace.
>> Or vice versa which is the case in its current form.

> I don't see a need for such a distinction in mlx hardware.

If you (say) have the same match and different action for a given rule
we have HW API to modify existing steering entry under which we would
end up calling the FW once instead of twice (delete old, add new).

Or.