From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: Poor TCP bandwidth between network namespaces Date: Fri, 08 Feb 2013 17:33:38 -0800 Message-ID: <1360373618.6696.2.camel@edumazet-glaptop> References: <20130204144320.GG1353@tostaky> <20130204225227.GC6898@order.stressinduktion.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Emmanuel Jeanvoine , netdev@vger.kernel.org To: Hannes Frederic Sowa Return-path: Received: from mail-pa0-f47.google.com ([209.85.220.47]:55392 "EHLO mail-pa0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758593Ab3BIBdm (ORCPT ); Fri, 8 Feb 2013 20:33:42 -0500 Received: by mail-pa0-f47.google.com with SMTP id bj3so2325265pad.20 for ; Fri, 08 Feb 2013 17:33:41 -0800 (PST) In-Reply-To: <20130204225227.GC6898@order.stressinduktion.org> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2013-02-04 at 23:52 +0100, Hannes Frederic Sowa wrote: > On Mon, Feb 04, 2013 at 03:43:20PM +0100, Emmanuel Jeanvoine wrote: > > I'm wondering why the overhead is so high when performing TCP > > transfers between two network namespaces. Do you have any idea about > > this issue? And possibly, how to increase the bandwidth (without > > modifying the MTU on the veths) between network namespaces? > > You could try Eric's patch (already in net-next) and have a look at the rest > of the discussion: > > http://article.gmane.org/gmane.linux.network/253589 Another thing to consider is the default MTU value : 65536 for lo, and 1500 for veth It easily explains half performance for veth One another thing is the tx-nocache-copy setting, this can explain some extra percents.