From owner-freebsd-net@FreeBSD.ORG Sat Jan 2 19:42:30 2010 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C56EB106568B for ; Sat, 2 Jan 2010 19:42:30 +0000 (UTC) (envelope-from barney_cordoba@yahoo.com) Received: from web63905.mail.re1.yahoo.com (web63905.mail.re1.yahoo.com [69.147.97.120]) by mx1.freebsd.org (Postfix) with SMTP id 729238FC15 for ; Sat, 2 Jan 2010 19:42:30 +0000 (UTC) Received: (qmail 48986 invoked by uid 60001); 2 Jan 2010 19:42:25 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1262461344; bh=9D7o4Laqmxel9bfREa/KZplSVP36bFS3d7ctQLT1JYI=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:MIME-Version:Content-Type; b=NnXWXgwqR8Bqr0IqZbsQoO4HZEkdKfKiwCjSW4496Xs+/c+NMbCIXi5uTDY/ltx/xJsO48ADwMh3P5ulEjCKW2EgtKgNoHF5AP55s4owmmMw30fWnR6vD+7ZkCiapXExsI0Rrg5BaeLAWw6YextWUpX86dO+BSRxvE/yA1Xm8fM= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:MIME-Version:Content-Type; b=kq1Y9wU5qZTWJU/2qF2hjPgwrgeSPXu/frqpI+syQee+LhU94XTTjtFvgXQeQKkKhkTX67Qb/U/IG1dAxUOqtu8j8UHEl/uv/MXIE60g9BkYISLvMVvwOtk+4vqBtQUrUTso3mhP72YTwK373QmlhI4KUg43cv+xW5GyrPGWf+A=; Message-ID: <969646.48748.qm@web63905.mail.re1.yahoo.com> X-YMail-OSG: bM.DR0MVM1lf.BXF_nCcaPRv8befPguMBC.FwumyZ3CZn6NffeS.Hh7fTBNVTlGtWrdGaWMFzukRlPY2batK7Efsb_hW9ARR3cflQVInpiPheWcB6WBUyYtJbxx9qTcJ4qXtGJySxN2K4g.RJM7WhIqSds8YnF1IppF8WmByqBdJudqaQzmJIY7uQ_zW28NWPizcM06MneGV5MqJSkmRTvIToxkTSRiF7Ami29zU8ZwRNtqkddNUWA.ZwsmC Received: from [98.203.21.152] by web63905.mail.re1.yahoo.com via HTTP; Sat, 02 Jan 2010 11:42:24 PST X-Mailer: YahooMailClassic/9.0.20 YahooMailWebService/0.8.100.260964 Date: Sat, 2 Jan 2010 11:42:24 -0800 (PST) From: Barney Cordoba To: freebsd-net@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: jfvogel@gmail.com Subject: igb interrupt moderation X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 02 Jan 2010 19:42:30 -0000 Jack, I'm trying to get some clarification on differences I'm finding between the 82575 and 82576 parts with respect to interrupt moderation. The spec I have for the 82576 (82576_Datasheet_v2p1.pdf) indicates that the ITR algorithm is different than the one used (I don't have one of the secret copies of the 82575 spec). The algorithm shown is interrupts/sec = 1/(2 * 10-6sec x interval) (page 295, Section 7.3.4) which is clearly wrong from practice. I have an 82576 (device id 10C9) if I use the 125d setting in the example get just under 32000 interrupts per second. Clearly your code doesnt implement this, nor do you have different settings for the 82575 and 82576 parts. So I assume that the same formula for the em parts hold for the igb parts, and that the datasheet is wrong? There does seem to be a slight difference. The setting that gets 1000 ints/second on the 82575 generates about 1020 on the 82576. Not a big deal but I wonder why there's a difference? Is the reference clock for these something that may not be fixed and could vary from board to board? Note that both devices are on the same MB. Also, it seems that settings to EITR over 32767 wrap on the 82576 (for example writing 32768 to EITR is the same as writing a 1). So the minimum setting on the 82576 is around 125 ints/second. The 82575 can accept values up the 65535 before wrapping. The 82576 document doesn't have a map of the register that I can find, so Im curious as to whether these observations are something I can assume is true across all parts and motherboards/cards, or is there some implementation variance that will cause these to only apply to the ones I happen to be testing? Thanks, Barney