netdev - Re: [PATCH v3] net:Add sysctl_max_skb

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Date:	Wed, 3 Feb 2016 10:24:20 -0800
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Hans Westgaard Ry <hans.westgaard.ry@...cle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	Tom Herbert <tom@...bertland.com>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Florian Westphal <fw@...len.de>, Jiri Pirko <jiri@...nulli.us>,
	Alexander Duyck <alexander.h.duyck@...hat.com>,
	Michal Hocko <mhocko@...e.com>,
	Linus Lüssing <linus.luessing@...3.blue>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Kodanev <alexey.kodanev@...cle.com>,
	Håkon Bugge <haakon.bugge@...cle.com>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>
Subject: Re: [PATCH v3] net:Add sysctl_max_skb_frags

On Wed, Feb 3, 2016 at 9:54 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Wed, 2016-02-03 at 09:43 -0800, Alexander Duyck wrote:
>
>> Read the history.  I still say it is best if we don't accept a partial
>> solution.  If we are going to introduce the sysctl as a core item it
>> should function as a core item and not as something that belongs to
>> TCP only.
>
>
> But this patch is the base, adding both the core sysctl and its first
> usage.
>
> Do we really need to split it in 2 patches ? Really ?
>
> The goal is to use it in all skb providers were it might be a
> performance gain, once they are identified.

That is what I thought.  So why are we trying to sell this as a core
change then.  All I am asking for is the sysctl to be moved and
renamed since based on all of your descriptions this clearly only
impacts TCP.

> Your points were already raised and will be addressed, by either me or
> you. And maybe others.

Please don't sign me up for work I didn't volunteer for.  I already
have enough broken code to try and fix.  I'm pretty sure I need to go
in and fix the gso_max_size code for starters.

If this is only meant to be a performance modification and is only
really targeted at TCP TSO/GRO then all I ask is that we use a name
like tcp_max_gso_frags and relocate the sysctl to the TCP section.
Otherwise if we are actually going to try to scope this out on a wider
level and limit all frags which is what the name implies then the
patch set needs to make a better attempt at covering all cases where
it may apply.

- Alex