linux-kernel - Re: [PATCH net-next 0/3] make skip

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Date: Fri, 16 Feb 2024 10:44:36 +0200
From: Vlad Buslov <vladbu@...dia.com>
To: Marcelo Ricardo Leitner <mleitner@...hat.com>
CC: Asbjørn Sloth Tønnesen
	<ast@...erby.net>, Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang
	<xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, Daniel Borkmann
	<daniel@...earbox.net>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <llu@...erby.dk>
Subject: Re: [PATCH net-next 0/3] make skip_sw actually skip software


On Thu 15 Feb 2024 at 10:00, Marcelo Ricardo Leitner <mleitner@...hat.com> wrote:
> Hi,
>
> On Thu, Feb 15, 2024 at 04:04:41PM +0000, Asbjørn Sloth Tønnesen wrote:
> ...
>> Since we use TC flower offload for the hottest
>> prefixes, and leave the long tail to Linux / the CPU.
>> we therefore need both the hardware and software
>> datapath to perform well.
>>
>> I found that skip_sw rules, are quite expensive
>> in the kernel datapath, sice they must be evaluated
>> and matched upon, before the kernel checks the
>> skip_sw flag.
>>
>> This patchset optimizes the case where all rules
>> are skip_sw.
>
> The talk is interesting. Yet, I don't get how it is set up.
> How do you use a dedicated block for skip_sw, and then have a
> catch-all on sw again please?
>
> I'm missing which traffic is being matched against the sw datapath. In
> theory, you have all the heavy duty filters offloaded, so the sw
> datapath should be seeing only a few packets, right?

Yeah, I also didn't get the idea here. The cited paragraphs seem to
contradict each other.