From owner-freebsd-net@FreeBSD.ORG Wed Jul 2 05:10:09 2008 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 279D41065680 for ; Wed, 2 Jul 2008 05:10:09 +0000 (UTC) (envelope-from mcdouga9@egr.msu.edu) Received: from mx.egr.msu.edu (surfnturf.egr.msu.edu [35.9.37.164]) by mx1.freebsd.org (Postfix) with ESMTP id DD9928FC22 for ; Wed, 2 Jul 2008 05:10:08 +0000 (UTC) (envelope-from mcdouga9@egr.msu.edu) Received: from localhost (localhost [127.0.0.1]) by mx.egr.msu.edu (Postfix) with ESMTP id C173D71F092; Wed, 2 Jul 2008 00:53:29 -0400 (EDT) X-Virus-Scanned: amavisd-new at egr.msu.edu Received: from mx.egr.msu.edu ([127.0.0.1]) by localhost (surfnturf.egr.msu.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id WTLFQJi+xn1s; Wed, 2 Jul 2008 00:53:29 -0400 (EDT) Received: from localhost (daemon.egr.msu.edu [35.9.44.65]) by mx.egr.msu.edu (Postfix) with ESMTP id 8BD7D71F08A; Wed, 2 Jul 2008 00:53:29 -0400 (EDT) Received: by localhost (Postfix, from userid 21281) id 896DF34A; Wed, 2 Jul 2008 00:53:29 -0400 (EDT) Date: Wed, 2 Jul 2008 00:53:29 -0400 From: Adam McDougall To: David Kwan Message-ID: <20080702045329.GT23350@egr.msu.edu> References: <486A91B0.6040505@gtcomm.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Cc: freebsd-net@freebsd.org Subject: Re: Poor network performance for clients in 100MB toGigabit environment 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: Wed, 02 Jul 2008 05:10:09 -0000 Are the NFS mounts UDP or TCP on Linux and FreeBSD? I believe FreeBSD still defaults to UDP which can act differently especially for NFS. On Tue, Jul 01, 2008 at 05:30:35PM -0700, David Kwan wrote: I've attempt many standard and non-standard permutations of the tcp tuning parameters without much successful via sysctl. It feels like FreeBSD is not handling the congestion very well and is beyond tuning sysctl. It's just clients on the 100MB networks has slow/erratic reads; Clients on the Gigabit network are fine and screams, so the original tcp parameters are just fine for them. David K. -----Original Message----- From: owner-freebsd-net@freebsd.org [mailto:owner-freebsd-net@freebsd.org] On Behalf Of Paul Sent: Tuesday, July 01, 2008 1:21 PM To: David Kwan Cc: freebsd-net@freebsd.org Subject: Re: Poor network performance for clients in 100MB toGigabit environment What options do you have enabled on the linux server? sysctl -a | grep net.ipv4.tcp and on the bsd sysctl -a net.inet.tcp It sounds like a problem with BSD not handing the dropped data or ack packets so what happens is it pushes a burst of data out > 100mbit and the switch drops the packets and then BSD waits too long to recover and doesn't scale the transmission back. TCP is supposed to scale down the transmission speed until packets are not dropped to a point even without ECN. Options such as 'reno' and 'sack' etc. are congestion control algorithms that use congestion windows. David Kwan wrote: > I have a couple of questions regarding the TCP Stack: > > > > I have a situation with clients on a 100MB network connecting to servers > on a Gigabit network where the client read speeds are very slow from the > FreeBSD server and fast from the Linux server; Write speeds from the > clients to both servers are fast. (Clients on the gigabit network work > fine with blazing read and write speeds). The network traces shows > congestion packets for both servers when doing reads from the clients > (dup acks and retransmissions), but the Linux server seem to handle the > congestion better. ECN is not enabled on the network and I don't see any > congestion windowing or clients window changing. The 100MB/1G switch > > is dropping packets. I double checked the network configuration and > also swapped swithports for the servers to use the others to make sure > the switch configuration are the same, and the Linux always does better > than FreeBSD. Assuming that the network configuration is a constant for > all clients and servers (speed, duplex, and etc...), the only variable > is the servers themselves (Linux and FreeBSD). I have tried a couple of > FreeBSD machines with 6.1 and 7.0 and they exhibit the same problem, > with no luck matching the speed and network utilization of Linux (2 > years old). The read speed test I'm referring is doing transferring of > a 100MB file (cifs, nfs, and ftp), and the Linux server does it > consistently in around 10 sec (line speed) with a constant network > utilization chart, while the FreeBSD servers are magnitudes slower with > erratic network utilization chart. I've attempted to tweak some network > sysctl options on the FreeBSD, and the only ones that helped were > disabling TSO and inflight; which leads me to think that the > inter-packet gap was slightly increased to partially relieve congestion > on the switch; not a long term solution. > > > > My questions are: > > 1. Have you heard of this problem before with 100MB clients to Gigabit > servers? > > 2. Are you aware of any Linux fix/patch in the TCP stack to better > handling congestion than FreeBSD? I'm looking to address this issue in > the FreeBSD, but wondering if the Linux stack did something special that > can help with the FreeBSD performance. > > > > David K. > > > > _______________________________________________ > 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" > > _______________________________________________ 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" _______________________________________________ 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"