Date: Wed, 2 Jul 2008 10:48:32 +0200 (CEST) From: Ingo Flaschberger <if@xip.at> To: David Kwan <david.kwan@isilon.com> Cc: freebsd-net@freebsd.org Subject: Re: Poor network performance for clients in 100MB to Gigabit environment Message-ID: <alpine.LFD.1.10.0807021048040.557@filebunker.xip.at> In-Reply-To: <E83E80FC158BCA4F921B1349E38866B802A6DE1A@seaxch07.desktop.isilon.com> References: <E83E80FC158BCA4F921B1349E38866B802A6DE1A@seaxch07.desktop.isilon.com>
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Dear David,
try to enable flow-control at the gig-e switch and freebsd network card.
Kind regards,
ingo flaschberger
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On Tue, 1 Jul 2008, 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.
>
>
>
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