Date: Fri, 04 Jul 2008 20:31:49 +0200 From: Kris Kennaway <kris@FreeBSD.org> To: David Kwan <david.kwan@isilon.com> Cc: freebsd-performance@freebsd.org Subject: Re: TCP stack in FreeBSD poor performance in 100MB to Gigabit environment. Message-ID: <486E6C95.1020509@FreeBSD.org> In-Reply-To: <E83E80FC158BCA4F921B1349E38866B802A6DD77@seaxch07.desktop.isilon.com>
index | next in thread | previous in thread | raw e-mail
David Kwan wrote: > > > I have a few questions regarding the TCP: > > > > 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 100/1G 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 show 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 > constantly 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? The key point seems to be that the switch is dropping packets. If you have packet loss then TCP is not going to perform well. Krishome | help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?486E6C95.1020509>