From owner-freebsd-net@FreeBSD.ORG Mon Dec 31 15:58:59 2012 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 8AC8FEA; Mon, 31 Dec 2012 15:58:59 +0000 (UTC) (envelope-from yanegomi@gmail.com) Received: from mail-ob0-f182.google.com (mail-ob0-f182.google.com [209.85.214.182]) by mx1.freebsd.org (Postfix) with ESMTP id 24DB58FC0A; Mon, 31 Dec 2012 15:58:58 +0000 (UTC) Received: by mail-ob0-f182.google.com with SMTP id 16so11683165obc.13 for ; Mon, 31 Dec 2012 07:58:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=X/q3A751zpVv5Xs0RVkLzcaR6+vHngASADyAhZuEUJE=; b=hZRNx6T6TWQR1VOeRCbwpVglH2wYa3ImEBoq1t3GbOJ8nLb+HqRt0dLgSZCx/RX+Wz n0x/GX7LXmCwbdM6ppHWw+w5b1xLTSWUSL/txrTwQ2zEylq8QLe580jhxxT7+7itfy67 YuaZjPZwvSsAaGXNuPElmqFjHS6IerVzYUCS8nhahTJNUPdSMsVgNb/U8Gmdd9yuJNSg jYH0sW0gMOYEHO+g4TqbpkZj1vak6rNhrtucYqoh5WPPXein1g5NXO7mY0bX5Dw4eFXr 4meDggNZjXgUBKhNtfGdK0q7dwa3Q7d+d1GZfzPvf/uqhTnU8zrkUQDp0JaeI2wTWZBw 4RQw== MIME-Version: 1.0 Received: by 10.182.194.2 with SMTP id hs2mr34008384obc.97.1356969532596; Mon, 31 Dec 2012 07:58:52 -0800 (PST) Received: by 10.76.143.33 with HTTP; Mon, 31 Dec 2012 07:58:52 -0800 (PST) In-Reply-To: <1356969238.85857.YahooMailClassic@web121602.mail.ne1.yahoo.com> References: <201212310728.qBV7SPKC064686@freefall.freebsd.org> <1356969238.85857.YahooMailClassic@web121602.mail.ne1.yahoo.com> Date: Mon, 31 Dec 2012 07:58:52 -0800 Message-ID: Subject: Re: kern/174851: [bxe] [patch] UDP checksum offload is wrong in bxe driver From: Garrett Cooper To: Barney Cordoba Content-Type: text/plain; charset=ISO-8859-1 Cc: freebsd-net@freebsd.org, David Christensen , linimon@freebsd.org X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 31 Dec 2012 15:58:59 -0000 On Mon, Dec 31, 2012 at 7:53 AM, Barney Cordoba wrote: ... > Has anyone done an analysis on modern hardware as to whether udp csum > offloading is actually beneficial? Even on 2007 hardware I came to the > conclusion that using offloading was a negative. > > Reminds me of the days when people were using "intelligent" ethernet cards > that were slower than the host cpu. The handshaking cost you more than > just using shared memory. I would ask David about whether or not there was a performance difference because they might have some numbers for if_bxe. Not sure about the concept in general, but it seems like a reasonable application protocol specific request. But by and large, I agree that UDP checksumming doesn't make logical sense because it adds unnecessary overhead on a L3 protocol that's assumed to be unreliable. Thanks, -Garrett