From owner-freebsd-stable@FreeBSD.ORG Thu May 29 14:30:50 2008 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3E5621065674 for ; Thu, 29 May 2008 14:30:50 +0000 (UTC) (envelope-from arnaud.houdelette@tzim.net) Received: from alaranth.tzim.net (alaranth.tzim.net [91.121.97.143]) by mx1.freebsd.org (Postfix) with ESMTP id E70E28FC1E for ; Thu, 29 May 2008 14:30:49 +0000 (UTC) (envelope-from arnaud.houdelette@tzim.net) Received: from localhost ([127.0.0.1]) by alaranth.tzim.net with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.69 (FreeBSD)) (envelope-from ) id 1K1j4R-0004o2-LO for freebsd-stable@freebsd.org; Thu, 29 May 2008 16:25:35 +0200 Message-ID: <483EBCDD.2070408@tzim.net> Date: Thu, 29 May 2008 16:25:33 +0200 From: Arnaud Houdelette User-Agent: Thunderbird 2.0.0.14 (Windows/20080421) MIME-Version: 1.0 To: freebsd-stable@freebsd.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated-User: tzim@tzim.net X-Authenticator: plain Subject: Bad TCP performance with large MTU on 7-stable. X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 29 May 2008 14:30:50 -0000 I got really poor performance when I try to upload files to the box (via pureFTP or Samba) when using jumbo frames somewhat above 2k. uname -a : FreeBSD carenath.tzim.net 7.0-STABLE FreeBSD 7.0-STABLE #4: Wed May 28 17:45:14 CEST 2008 tzim@carenath.tzim.net:/usr/obj/usr/src/sys/CARENATH amd64 It seems that TCP acks are delayed for about a second, so the upload rate nevers goes above 60kB/s. I can provide wireshark captures done on the box uploading the files if necessary. The client is a Windows XP64 box, but I do not recall having the same problem on 6.2. I did got about 100 MB/s for similar file transfers, but I had to disable jumbo frames when I upgraded to 7.0-Release because of some bug on txcsum/rxcsum on re(4) so I only noticed the issue recently. The txcsum bug doesn't seem to occur anymore, but now I have this strange rate issue, with or without checksum offloading disabled. I also tried with tso disabled. Same results. Is it related to the re(4) driver ? Or to the TCP stack ? Arnaud Houdelette