From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-net] net: loopback: set default mtu to 64K Date: Mon, 24 Sep 2012 16:38:46 -0400 (EDT) Message-ID: <20120924.163846.351381312643475595.davem@davemloft.net> References: <1348475339.26828.188.camel@edumazet-glaptop> <20120924.162442.1381532664983403691.davem@redhat.com> <1348518796.26828.1651.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: eric.dumazet@gmail.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:54266 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757999Ab2IXUiu (ORCPT ); Mon, 24 Sep 2012 16:38:50 -0400 In-Reply-To: <1348518796.26828.1651.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet Date: Mon, 24 Sep 2012 22:33:16 +0200 > On Mon, 2012-09-24 at 16:24 -0400, David Miller wrote: >> From: Eric Dumazet >> Date: Mon, 24 Sep 2012 10:28:59 +0200 >> >> > From: Eric Dumazet >> > >> > 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 >> >> 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 I tested with lmbench bw_tcp, which gives me about 1308 MB/sec. And indeed that netperf command line gives superior numbers, about 11747 MB/sec