netdev - RE: [PATCH] mlx4_en: Setting RSS hash result to skb->rxhash field

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Date:	Thu, 05 May 2011 08:55:18 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Yevgeny Petrilin <yevgenyp@...lanox.co.il>
Cc:	Ben Hutchings <bhutchings@...arflare.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] mlx4_en: Setting RSS hash result to skb->rxhash field

Le jeudi 05 mai 2011 à 06:47 +0000, Yevgeny Petrilin a écrit :
> > 
> Eric, you are correct.
> We do plan to enable full 32 bit hash for our devices.
> Once it is done, we will naturally use the whole 32 bits.
> In the meanwhile, even with this change we see improved performance when enabling RPS.

Hmm, thats strange because you have only 256 possible values for rxhash,
and it's OK for maybe one hundred flows. (I am talking not of RPS but
RFS here)

So your patch is a win only for small hosts, or particular workloads
(did I say biased benchmarks ? ;) )

Really, we better use the linux/software full 32bit rxhash in this case,
and wait for your 32bit full support.

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