netdev - Re: [PATCH v2] net:Add sysctl_tcp_sg_max_skb

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Date:	Mon, 1 Feb 2016 14:12:36 +0100
From:	Hans Westgaard Ry <hans.westgaard.ry@...cle.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"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>,
	"open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	Haakon Bugge <haakon.bugge@...cle.com>
Subject: Re: [PATCH v2] net:Add sysctl_tcp_sg_max_skb_frags



On 01/27/2016 07:12 PM, Hannes Frederic Sowa wrote:
> On 27.01.2016 16:15, Eric Dumazet wrote:
>>
>> If it is a common one, it should be /proc/sys/net/core/... instead
>> of /proc/sys/net/ipv4/tcp_....
> >
>> Other providers include :
>>
>> 1) GRO stack
>> 2) callers of sock_alloc_send_pskb(), alloc_skb_with_frags(),
>> sock_alloc_send_skb() ..
>
> I agree, this knob should get a generic name and live in a generic 
> net/ directory to control this globally, so things don't break during 
> forwarding etc.
>
> It does not solve the problem completely, e.g. when VMs send gso 
> packets through a vhost-net onto IPoIB, no?
>
> Thanks,
> Hannes
>
I have understood more of the problem Hannes raises and I realize that 
we need a slowpath in IPoIB to handle the problem
in question. I will make a new version of this patch with a more correct 
position/name of the sysctl-variable.
I'll also make a separate patch adding the slowpath i IPoIB.

Hans