netdev - Re: [PATCH net-next] vxlan: distribute vxlan tunneled traffic across multiple TXQs

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Message-Id: <20140102.013637.1024370036672354197.davem@davemloft.net>
Date:	Thu, 02 Jan 2014 01:36:37 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	stephen@...workplumber.org, sathya.perla@...lex.com,
	netdev@...r.kernel.org, edumazet@...gle.com
Subject: Re: [PATCH net-next] vxlan: distribute vxlan tunneled traffic
 across multiple TXQs

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Wed, 01 Jan 2014 21:56:46 -0800

> On Tue, 2013-12-31 at 13:56 -0500, David Miller wrote:
>> From: Eric Dumazet <eric.dumazet@...il.com>
>> Date: Tue, 24 Dec 2013 10:39:06 -0800
>> 
>> > On Mon, 2013-12-23 at 11:28 -0800, Stephen Hemminger wrote:
>> > 
>> >> The idea is good, but without the destructor there is nothing to keep
>> >> the UDP socket from being destroyed while packet is being sent on another
>> >> CPU.
>> > 
>> > I see no requirement of holding a reference on the vxlan UDP socket in
>> > transmit path.
>> 
>> I'm trying to figure out how leaving a dangling socket attached to
>> skb->sk, as in this original patch, can be OK.
> 
> Sorry, I lost track here (vacation time...), what patch are you
> referring to ?

http://patchwork.ozlabs.org/patch/304767/

> Once we pass the tunnel, we can either :
> 
> 1) Leave skb->sk set to the original socket sk1 (Say TCP or UDP
> producer)
> 
> 2) Assign skb->sk to the 'socket' used in vxlan (after orphaning and
> releasing reference on socket sk1)
 ...
> If we chose 1), it makes more sense, because each producer will be
> effectively limited by the proper sk->sk_sndbuf limit.
> 
> And a socket cannot be destroyed anyway as long as at least one skb is
> in flight (with skb->sk set to this socket)
> 
> Really, I do not think vxlan should behave in a different way than other
> tunnels (GRE, IPIP, SIT, ...), which chose 1) 

Ok, agreed.
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