From owner-freebsd-net@freebsd.org Mon Aug 17 15:44:38 2015 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 33D049BBFC5; Mon, 17 Aug 2015 15:44:38 +0000 (UTC) (envelope-from haramrae@gmail.com) Received: from mail-io0-x233.google.com (mail-io0-x233.google.com [IPv6:2607:f8b0:4001:c06::233]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id EF46F1647; Mon, 17 Aug 2015 15:44:37 +0000 (UTC) (envelope-from haramrae@gmail.com) Received: by iods203 with SMTP id s203so156015012iod.0; Mon, 17 Aug 2015 08:44:37 -0700 (PDT) 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=j/eS1ITatBCtcp/wsRl5hVp7ISn540RkaGwxK3hNflo=; b=VglJYEwaPEp3ZXnd/a6DatLJOosZE4TVCTgnRRnDRmiymDOwtP+csGGhprqQKap0yJ eVejujHCBVKa5F+BnHeUw6242XVbqTXkLrPenwGwnOZHRcrJPvb/jt4TIQW+4zYG0SDv jI5yquL8Mt5EAbUcZRoegYQXA2XFk0g4/8PTUDD9Pl3IfB3iR8XfuBk+Vd96QFjYnEAc p04Np8CdfuwQtpz4Y4pY+TUi69GuZRgxcmvAaXeAn1hvkLNDldltngUojoMS6oJKyhcr BocNqkNzOL4pRdPFI6+ka33rch4h5OnwXP4B5QMnR7v7h6HzlV8n44opaT0JgeQGqiBD OOxg== MIME-Version: 1.0 X-Received: by 10.107.169.215 with SMTP id f84mr2330734ioj.42.1439826277490; Mon, 17 Aug 2015 08:44:37 -0700 (PDT) Received: by 10.64.80.197 with HTTP; Mon, 17 Aug 2015 08:44:37 -0700 (PDT) In-Reply-To: <20150817115405.GL1872@zxy.spb.ru> References: <1D52028A-B39F-4F9B-BD38-CB1D73BF5D56@cs.huji.ac.il> <20150817094145.GB3158@zxy.spb.ru> <197995E2-0C11-43A2-AB30-FBB0FB8CE2C5@cs.huji.ac.il> <20150817113923.GK1872@zxy.spb.ru> <20150817115405.GL1872@zxy.spb.ru> Date: Mon, 17 Aug 2015 17:44:37 +0200 Message-ID: Subject: Re: ix(intel) vs mlxen(mellanox) 10Gb performance From: Alban Hertroys To: Slawa Olhovchenkov Cc: Daniel Braniss , FreeBSD Net , FreeBSD stable Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.20 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, 17 Aug 2015 15:44:38 -0000 On 17 August 2015 at 13:54, Slawa Olhovchenkov wrote: > On Mon, Aug 17, 2015 at 01:49:27PM +0200, Alban Hertroys wrote: > >> On 17 August 2015 at 13:39, Slawa Olhovchenkov wrote: >> >> > In any case, for 10Gb expect about 1200MGB/s. >> >> Your usage of units is confusing. Above you claim you expect 1200 > > I am use as topic starter and expect MeGaBytes per second That's a highly unusual way of writing MB/s. There are standards for unit prefixes: k means kilo, M means Mega, G means Giga, etc. See: https://en.wikipedia.org/wiki/International_System_of_Units#Prefixes >> million gigabytes per second, or 1.2 * 10^18 Bytes/s. I don't think >> any known network interface can do that, including highly experimental >> ones. >> >> I suspect you intended to claim that you expect 1.2GB/s (Gigabytes per >> second) over that 10Gb/s (Gigabits per second) network. >> That's still on the high side of what's possible. On TCP/IP there is >> some TCP overhead, so 1.0 GB/s is probably more realistic. > > TCP give 5-7% overhead (include retrasmits). > 10^9/8*0.97 = 1.2125 In information science, Bytes are counted in multiples of 2, not 10. A kb is 1024 bits or 2^10 b. So 10 Gb is 10 * 2^30 bits. It's also not unusual to be more specific about that 2-base and use kib, Mib and Gib instead. Apparently you didn't know that... Also, if you take 5% off, you are left with (0.95 * 10 * 2^30) / 8 = 1.1875 B/s, not 0.97 * ... Your calculations were a bit optimistic. Now I have to admit I'm used to use a factor of 10 to convert from b/s to B/s (that's 20%!), but that's probably no longer correct, what with jumbo frames and all. -- If you can't see the forest for the trees, Cut the trees and you'll see there is no forest.