From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: RE: [PATCH] mlx4_en: Setting RSS hash result to skb->rxhash field
Date: Thu, 05 May 2011 08:55:18 +0200
Message-ID: <1304578518.32152.794.camel@edumazet-laptop>
References: <4DC156AF.4050807@mellanox.co.il>
	 <1304520260.3203.34.camel@localhost>
	 <1304527586.32152.5.camel@edumazet-laptop>
	 <953B660C027164448AE903364AC447D2070B8E35@mtldag01.mtl.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: QUOTED-PRINTABLE
Cc: Ben Hutchings <bhutchings@solarflare.com>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>
To: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mail-wy0-f174.google.com ([74.125.82.174]:49438 "EHLO
	mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752029Ab1EEGzY (ORCPT
	<rfc822;netdev@vger.kernel.org>); Thu, 5 May 2011 02:55:24 -0400
Received: by wya21 with SMTP id 21so1368471wya.19
        for <netdev@vger.kernel.org>; Wed, 04 May 2011 23:55:23 -0700 (PDT)
In-Reply-To: <953B660C027164448AE903364AC447D2070B8E35@mtldag01.mtl.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

Le jeudi 05 mai 2011 =C3=A0 06:47 +0000, Yevgeny Petrilin a =C3=A9crit =
:
> >=20
> 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 w=
hen 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.