From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH net-net] net: loopback: set default mtu to 64K
Date: Mon, 24 Sep 2012 22:33:16 +0200
Message-ID: <1348518796.26828.1651.camel@edumazet-glaptop>
References: <1348475339.26828.188.camel@edumazet-glaptop>
	 <20120924.162442.1381532664983403691.davem@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Cc: netdev@vger.kernel.org
To: David Miller <davem@redhat.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mail-bk0-f46.google.com ([209.85.214.46]:49547 "EHLO
	mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1757626Ab2IXUdU (ORCPT
	<rfc822;netdev@vger.kernel.org>); Mon, 24 Sep 2012 16:33:20 -0400
Received: by bkcjk13 with SMTP id jk13so1171933bkc.19
        for <netdev@vger.kernel.org>; Mon, 24 Sep 2012 13:33:19 -0700 (PDT)
In-Reply-To: <20120924.162442.1381532664983403691.davem@redhat.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Mon, 2012-09-24 at 16:24 -0400, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@gmail.com>
> Date: Mon, 24 Sep 2012 10:28:59 +0200
> 
> > From: Eric Dumazet <edumazet@google.com>
> > 
> > loopback current mtu of 16436 bytes allows no more than 3 MSS TCP
> > segments per frame, or 48 Kbytes. Changing mtu to 64K allows TCP
> > stack to build large frames and significantly reduces stack overhead.
> > 
> > Performance boost on bulk TCP transferts can be up to 30 %, partly
> > because we now have one ACK message for two 64KB segments, and a lower
> > probability of hitting /proc/sys/net/ipv4/tcp_reordering default limit.
> > 
> > Signed-off-by: Eric Dumazet <edumazet@google.com>
> 
> This gives a nice %13 improvement on my SPARC-T4 box as well.
> 
> Applied, thanks Eric.

the biggest increase is with

netperf -- -m 63K

I reach 50000 Mbytes/second