From owner-freebsd-performance@FreeBSD.ORG Sat Nov 17 22:32:49 2012 Return-Path: Delivered-To: freebsd-performance@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 465797B9; Sat, 17 Nov 2012 22:32:49 +0000 (UTC) (envelope-from zbeeble@gmail.com) Received: from mail-lb0-f182.google.com (mail-lb0-f182.google.com [209.85.217.182]) by mx1.freebsd.org (Postfix) with ESMTP id 534648FC08; Sat, 17 Nov 2012 22:32:48 +0000 (UTC) Received: by mail-lb0-f182.google.com with SMTP id go10so1015089lbb.13 for ; Sat, 17 Nov 2012 14:32:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:content-type; bh=1U7bqcNKpRacRZNLh2nUOIrmeOQ4DEB+vByKc0f41Do=; b=DKFPjdAhc1Ft9KJIe/LyXjAciPcSLu2VAu84KJAaytQyEmQPPajagbr3LyU1/xE2kd TReXE5FZhPfDJDGjdX1ujaNLagYPjdBNOmVb9UGLh6F5QL36Vdhhmn5lCaOUII5/5PDv qdNg2tDXSbu+/+H4Yv6/C7A6eLGSBZynPCirOIe0cDniBDVQyqoRCo5tO/TCU8WdZsDR 2nxHW7/pKXjxHgl45Bq7Cp8V5km/eH6n5RfNANcWNHvIFmNgIz5C/eiC3SEhsQJHjD83 OiO5aBch75wVGH3BLM2SWfk2WaefF6C6zuJUwWHINk5PmIsdhZS3cHRaK/eDcnRhBj4r JmmA== MIME-Version: 1.0 Received: by 10.112.30.195 with SMTP id u3mr3328589lbh.37.1353191567036; Sat, 17 Nov 2012 14:32:47 -0800 (PST) Received: by 10.112.49.138 with HTTP; Sat, 17 Nov 2012 14:32:46 -0800 (PST) Date: Sat, 17 Nov 2012 17:32:46 -0500 Message-ID: Subject: Jumbo Packet fail. From: Zaphod Beeblebrox To: freebsd-hackers@freebsd.org, freebsd-fs , FreeBSD Mailing Lists Content-Type: text/plain; charset=ISO-8859-1 X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 17 Nov 2012 22:32:49 -0000 I recently started using an iSCSI disk on my ZFS array seriously from a windows 7 host on the network. The performance is acceptable, but I was led to believe that using Jumbo packets is a win here. My win7 motherboard adapter did not support jumbo frames, so I got one that did... configured it, etc. Just in case anyone cares, the motherboard had an 82567V-2 (does not support jumbo frames) and I added in an intel 82574L based card. Similarly, I configured em0 on my FreeBSD host to have an MTU of 9014 bytes (I also tried 9000). The hardware on the FreeBSD 9.1RC2 side is: em0: port 0xdc00-0xdc1f mem 0xfcfe0000-0xfcffffff,0xfcfc0000-0xfcfdffff irq 16 at device 0.0 on pci3 pciconf -lv identifies the chipset as 82572EI Now... my problem is that the windows machine correctly advertises an MSS of 8960 bytes in it's SYN packet while FreeBSD advertises 1460 in the syn-ack. [1:42:342]root@vr:/usr/local/etc/istgt> ifconfig em0 em0: flags=8843 metric 0 mtu 9014 options=4019b ether 00:15:17:0d:04:a8 inet 66.96.20.52 netmask 0xffffffe0 broadcast 66.96.20.63 inet6 fe80::215:17ff:fe0d:4a8%em0 prefixlen 64 scopeid 0x5 inet6 2001:1928:1::52 prefixlen 64 inet 192.168.221.2 netmask 0xffffff00 broadcast 192.168.221.255 nd6 options=21 media: Ethernet autoselect (1000baseT ) status: active I have tested this with both ipv4 and ipv6 connections between the win7 host and the FreeBSD server. win7 always requests the larger mss, and FreeBSD the smaller.