netdev - Re: [PATCH] net: fix saving TX flow hash in sock for outgoing connections

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Date:	Wed, 22 Oct 2014 10:39:02 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Sathya Perla <sathya.perla@...lex.com>
Cc:	netdev@...r.kernel.org, therbert@...gle.com
Subject: Re: [PATCH] net: fix saving TX flow hash in sock for outgoing
 connections

On Wed, 2014-10-22 at 21:42 +0530, Sathya Perla wrote:
> The commit "net: Save TX flow hash in sock and set in skbuf on xmit"
> introduced the inet_set_txhash() and ip6_set_txhash() routines to calculate
> and record flow hash(sk_txhash) in the socket structure. sk_txhash is used
> to set skb->hash which is used to spread flows across multiple TXQs.
> 
> But, the above routines are invoked before the source port of the connection
> is created. Because of this all outgoing connections that just differ in the
> source port get hashed into the same TXQ.

Acked-by: Eric Dumazet <edumazet@...gle.com>

Are you really using the socket/flow hash to select a TXQ ?

Even with this patch, you have a good probability of multiple
cpus hitting same TXQ.




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