From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net-next-2.6] net: Increase NET_SKB_PAD to 64 bytes Date: Fri, 07 May 2010 11:55:14 +0200 Message-ID: <1273226114.2261.42.camel@edumazet-laptop> References: <20100506.220221.90798296.davem@davemloft.net> <1273209321.2222.36.camel@edumazet-laptop> <4BE3C70C.4060705@monstr.eu> <20100507.013216.133893678.davem@davemloft.net> <4BE3E1D6.30907@monstr.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: David Miller , netdev@vger.kernel.org, hadi@cyberus.ca, therbert@google.com, microblaze-uclinux@itee.uq.edu.au To: monstr@monstr.eu Return-path: Received: from mail-bw0-f219.google.com ([209.85.218.219]:52580 "EHLO mail-bw0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753670Ab0EGJzS (ORCPT ); Fri, 7 May 2010 05:55:18 -0400 Received: by bwz19 with SMTP id 19so466712bwz.21 for ; Fri, 07 May 2010 02:55:16 -0700 (PDT) In-Reply-To: <4BE3E1D6.30907@monstr.eu> Sender: netdev-owner@vger.kernel.org List-ID: Le vendredi 07 mai 2010 =C3=A0 11:48 +0200, Michal Simek a =C3=A9crit : > David Miller wrote: > > From: Michal Simek > > Date: Fri, 07 May 2010 09:53:48 +0200 > >=20 > >> I will add this Microblaze patch to my repo for testing and anyway > >> should go through my repo. > >=20 > > It's already in the net-next-2.6 tree. >=20 > Anyway. >=20 > I am ok with removing NET_IP_ALIGN because it is already defined in=20 > skbuff.h to 2. > But increasing NET_SKB_PAD to 64 caused that Microblaze extends skb=20 > buffers for some bytes. > I measured it by iperf and netperf and I see regression around 1-2Mbi= t/s=20 > that's why I would like to ask you to revert this patch or keep at le= ast=20 > NET_SKB_PAD part. Interesting. Increasing NET_SKB_PAD to say 128 or 256 should not have performance impact, but reserve a bit more ram. (truesize...) Investigation is needed. Maybe your NIC now allocates high order pages = ? What driver are you using ?