From owner-freebsd-current@FreeBSD.ORG Thu Jun 9 13:22:46 2011 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B6386106564A for ; Thu, 9 Jun 2011 13:22:46 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id 8EA8A8FC19 for ; Thu, 9 Jun 2011 13:22:46 +0000 (UTC) Received: from bigwig.baldwin.cx (66.111.2.69.static.nyinternet.net [66.111.2.69]) by cyrus.watson.org (Postfix) with ESMTPSA id 4562B46B0A; Thu, 9 Jun 2011 09:22:46 -0400 (EDT) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id A9CE08A01F; Thu, 9 Jun 2011 09:22:45 -0400 (EDT) From: John Baldwin To: freebsd-current@freebsd.org Date: Thu, 9 Jun 2011 09:11:51 -0400 User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110325; KDE/4.5.5; amd64; ; ) References: <20110609035952.GA30464@onelab2.iet.unipi.it> In-Reply-To: <20110609035952.GA30464@onelab2.iet.unipi.it> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201106090911.51817.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.6 (bigwig.baldwin.cx); Thu, 09 Jun 2011 09:22:45 -0400 (EDT) Cc: Luigi Rizzo Subject: Re: any place to look at for PCI-express performance issues ? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 09 Jun 2011 13:22:46 -0000 On Wednesday, June 08, 2011 11:59:52 pm Luigi Rizzo wrote: > hi, > during my tests with netmap with 10Gbit cards (82599, dual port), > i notice that a motherboard with an AMD 880G chipset > is performing significantly worse than an intel based one. > In both cases the NIC is mounted on a 16x PCIe slot, > and in both cases the driver reports the use 5Gb/4x per port. > > On the intel i reach easily 14.88Mpps, on the AMD the card tops > at 1.8Mpps, and is not CPU limited (changing dev.cpu.0.freq does not change > the throughput). > Disabling flow control does not help (and in any case > the other end of the link is the same), and since > I am using the same picobsd image (based on FreeBSD/i386 > head w/ my netmap code) i suspect that the difference in > performance has to do with the PCIe controller. > My netmap code > http://info.iet.unipi.it/~luigi/netmap/ > does nothing special on the bus. > > Now, the question is, is there any place in FreeBSD sources that > might be related to PCIe performance, e.g. initialising specific > features in one or another northbridge, etc ? No, in general we rely on the firmware (BIOS, etc.) to configure those bits. You might take a gander at comparing 'pciconf -lc' output as that displays a few of the PCI-e settings such as the actual number of lanes used, etc. -- John Baldwin