From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-x235.google.com (mail-wi0-x235.google.com [IPv6:2a00:1450:400c:c05::235]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 54E7621F1EF; Wed, 30 Oct 2013 12:29:21 -0700 (PDT) Received: by mail-wi0-f181.google.com with SMTP id ex4so1995943wid.2 for ; Wed, 30 Oct 2013 12:29:18 -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:content-transfer-encoding; bh=2uwtoo5Lu378Hzl5iaolx5my83y7S4j76mAqKO5yWH4=; b=oelTSxk9+E+Mbu4aWpK7Z1FJjwvO9EqNksnriCf7zW1gSqWzo5T5gOEJEG1SpoEBIP 8+H6Tdqq5tcq68y2igDrVdnRPIVQMF5knI37y5FSNurTY1b6DF8K6KC1pOlnf0CPwQms 1XWp6ofhTpLjUBfduQAewOfj+O07hr+nMyYKziS4Wp/UCiobIic5Cw4tnQR+LKzNBWvZ mwiDyczOhQvLnww6TxNkg6ei7QwTREfOQEOLb1276E2+HDceywUxhOg8Ow2YMVWmlwEM 6JuI+5FEB28N9RDJ8w7ApfK7CptUTr02wzs2i/qakA7nVfeAUL3sdi4I3efXvG2OIyHk azww== MIME-Version: 1.0 X-Received: by 10.194.219.70 with SMTP id pm6mr4250416wjc.47.1383161358685; Wed, 30 Oct 2013 12:29:18 -0700 (PDT) Received: by 10.217.67.202 with HTTP; Wed, 30 Oct 2013 12:29:18 -0700 (PDT) In-Reply-To: <20131030183629.GB4316@ens-lyon.fr> References: <20131030183629.GB4316@ens-lyon.fr> Date: Wed, 30 Oct 2013 12:29:18 -0700 Message-ID: From: Dave Taht To: Baptiste Jonglez Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: bloat-devel , "babel-users@lists.alioth.debian.org" , "cerowrt-devel@lists.bufferbloat.net" Subject: Re: [Cerowrt-devel] =?iso-8859-1?q?=5BBabel-users=5D_Follow-up_on_the?= =?iso-8859-1?q?_new_babel-rtt_branch=3A_=B5s_resolution?= X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 30 Oct 2013 19:29:22 -0000 On Wed, Oct 30, 2013 at 11:36 AM, Baptiste Jonglez wrote: > Dear Babel hackers, > > I'm currently testing my new babel-rtt code, which uses 32-bits > timestamps to achieve a =B5s-resolution on RTT. > > A graph showing the RTT between two directly-connected hosts (Gigabit > Ethernet) can be found in [1]. > > The two hosts are laptops, directly connected with an Ethernet cable. > Both have Gigabit interfaces. One has a fast Intel Core2 duo CPU (2.4 > GHz), while the other has a slow AMD E2-1800 APU (1.7 GHz). > > Do note that the RTT is expressed in =B5s, not ms. A few comments, > prompted by a discussion with Juliusz and Matthieu: I am pretty curious if you can tell the difference between 10GigE, GigE, and 100Mbit under various loads. > - the ping6 result is surprising, as two groups of points clearly > appear, separated by about 200 =B5s. It seems that interrupts might > be responsible for this, but it's still somewhat unclear. It could be caused by napi. There is also some parameter to ethtool (?) to tell it to return pings more immediately (that I recall was specific to the e1000e network card). I'm pretty sure it was the --coalesce some_option You might find it easier to verify your measurement with owamp and gps synced clocks. I'm delighted to see this measurement as collected by babel as my sekret plan was to be able to measure heavy traffic benchmarks vs various qdiscs like the new "fq" and older fq_codel ones... > - Babel sees a RTT that is 400 =B5s higher than ping6. The babel-rtt > implementation timestamps outgoing message as late as possible, and > timestamps incoming messages as early as possible, but it's not > perfect. Did you try hardware timestamping on rx? (this is a kernel compile option) > Context-switching and syscalls can probably account for > these 400 =B5s: a quick test, on the slower laptop, showed that > calling the gettimeofday() syscall takes about 100 =B5s. Kernel version? This was sped up in some fairly recent kernel version (?) > > Further comments are welcome. > > [1] http://ze.polyno.me/babel/32bits-rtt-ethernet.pdf > > _______________________________________________ > Babel-users mailing list > Babel-users@lists.alioth.debian.org > http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/babel-users --=20 Dave T=E4ht Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.= html