From owner-freebsd-net@FreeBSD.ORG Sat Apr 14 19:11:25 2012 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 9B1F7106564A for ; Sat, 14 Apr 2012 19:11:25 +0000 (UTC) (envelope-from leschnik@gmail.com) Received: from mail-gx0-f182.google.com (mail-gx0-f182.google.com [209.85.161.182]) by mx1.freebsd.org (Postfix) with ESMTP id 57BBB8FC12 for ; Sat, 14 Apr 2012 19:11:25 +0000 (UTC) Received: by ggnk4 with SMTP id k4so2513438ggn.13 for ; Sat, 14 Apr 2012 12:11:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=xNSKk85jjpILTmPDdbL8/yReAcA1IPqIKTiIvv19zFY=; b=NIbV2dwGNPjcuK24fFBsFAHyyFyvKZUKL2v6uFUX08Vw3ECYSW6N5mIruA1EhlmMGQ BdlEiZ2g1lZ2LWC4vMZyRqGGPnxkN4iXcGZ4EbCC1L75pZ2FPwLvFJy9yhKszggT6TCE Ft18JDALnWvl2FSG4xTAVCl2xkOHRnY0fFa0kzc9/wALP3gWM+5x9qSqeTzjspaDoWAJ z51qsf9tlIbNHufn0PW/nLXjm/pXJmy9QyMtJPwcBvy5bRDQibUfkyXoWDyVgvAi+R2q KxkUU7rrnJK2VIMyffuNL64VzADn7kO+RjKvlxBgn+ytJvpKFzNVJ4w1drSPpnIxkxgx M95g== MIME-Version: 1.0 Received: by 10.101.8.37 with SMTP id l37mr1039661ani.49.1334430684676; Sat, 14 Apr 2012 12:11:24 -0700 (PDT) Received: by 10.100.210.4 with HTTP; Sat, 14 Apr 2012 12:11:24 -0700 (PDT) In-Reply-To: <4F89C005.2020304@rawbw.com> References: <4F89C005.2020304@rawbw.com> Date: Sun, 15 Apr 2012 05:11:24 +1000 Message-ID: From: Jason Leschnik To: Yuri Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: freebsd-net@freebsd.org Subject: Re: Why host transmit rate on 1Gb ethernet is only ~750Mbps ? X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 Apr 2012 19:11:25 -0000 I would first start by doing a point-to-point link between your two end nodes to rule out your network gear as being the problem On Sun, Apr 15, 2012 at 4:20 AM, Yuri wrote: > I am running some tests with gigabit switch between two 9.0 hosts using > iperf. > The best UDP transmit rate I am getting is 753 Mbits/sec with ~3-6% packe= t > loss @1500 MTU @ 2.5GHz CPU, even though command 'iperf -c X.X.X.X -u -b > 1000m' requests the full gigabit. > > I am trying to understand what exactly usually limits the speed with one = way > ethernet traffic and also what causes the packet loss. > Is it the host's CPU or rather the need to make ~83K system calls in orde= r > to send 1Gb of UDP data at 1500 MTU? > Is it the NIC or it's driver ('re' on source and 'em' on destination in m= y > case)? > Is it the router which is maybe too old? (Linksys EG008W, with tcpdump I > made sure there is no ICMP traffic that is coming back from the router > during the test). > > Why can't NIC send say 900 Mbps with MTU 1500 since the only overhead is > ethernet+UDP headers which are ~120bytes out of 1500? > Why packet loss occurs in such a simple network with just one switch and > speeds of 75% of the maximum? > How can I troubleshoot such situation and understand the reasons? > > Yuri > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" --=20 Regards, Jason Leschnik. [m] 0432 35 4224 [w@] jason dot leschnik ansto dot gov dot au [U@]=A0jml974@uow.edu.au