From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id F0C6D3B360 for ; Fri, 8 Apr 2016 09:17:55 -0400 (EDT) Received: from [172.17.3.193] ([134.2.189.253]) by mail.gmx.com (mrgmx003) with ESMTPSA (Nemesis) id 0M243n-1bgbv82GuB-00u3Ms; Fri, 08 Apr 2016 15:17:53 +0200 User-Agent: K-9 Mail for Android In-Reply-To: <57079B2F.8070607@gmail.com> References: <57066793.5050608@gmail.com> <056D9AAF-85E2-4849-A3EC-4CE77276DF24@gmx.de> <57079B2F.8070607@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable From: Sebastian Moeller Date: Fri, 08 Apr 2016 15:17:51 +0200 To: Richard Smith CC: "cerowrt-devel@lists.bufferbloat.net" Message-ID: <66A42333-0801-45AF-B67E-B7CFAF22FE43@gmx.de> X-Provags-ID: V03:K0:HWuUZcBFM6dMPONoKlsV/I2/DJgH+WYl9+/mqpKYDSxzfOwsV+H va2VdRLSPfDfjyLFQbbrdpSkJhC9Fwel55ccz5IlRLhg9gO5I0elbrXc7LxgOLsUV/xKYER vhXbRsI2JgzUWC6MycjbP3BHlaAae9RVqnkUNwSL7Hn1FJ4LlLJibqBbcZER6/TfEKsHR0M 9qF2HVZtkvVyQKUgoGTsQ== X-UI-Out-Filterresults: notjunk:1;V01:K0:ts6SpiIfToc=:Lo2nmvl6vWon3tqWhVVGOI A1gpu45PQ+Y4lAclAJcxlrYOMJ06knqEQQ8rIXkHhrXdHkgkwf4EtP/982JfHNMgZBswHY12o HJh2FPS6Mwcxh/NHq+pgyD4p7Pz+1MVVcTMxu4JcBY7ucyIZs8dcfAvga7guZC8qQihYzBsf0 DyN9t/wcqw4aCRpJi+j0JlTHvx0kIznqu9qn0dCJ3vYD484t32PPszTKWE8glu6dQ+7ZmVFMK 7/fGrvwi3y5R1k71XgmOHv0xu6IJyn7YtMJ6UaDUUUK0Mgf3uO+8we8Fz75Mq3U3R4DF0XaUj k/8uHAGbjUJKx55dhavxWyW+FuA2pMgtFhjXy0eItKJ6ZEAFCaj2D9RHjWSRK/Kr+ePmxgMSX /sqd6OM2wrl2wtzZkb85PXnCPylCK9lnvoCIIZBO/Dpp4B+bsqsMG8jQRQZk65C5fBak2nIrv Qsosghv+15f8ANhq7sglxT8ecq5svjUm+FxfxidposUX8SdqHcAB6UxLg9GG/OMC6R365KmEu 1SpzdBBjqUU/IPzlY7XSRhb/iYQ8YgSXFx8l7ZApFgG9KI1qaOkcUoy7zL2Uranf8tyac9lKZ z3cTvOY0MK00bHgFmojyEe3OXZmuZkGdbEd1rk9xeobrOziFSjnCBAdiko7lHPRxdaUZ/5S5J LmJN2h5zPJW/HkSUBloWEclUK6c9vRdZv+wqZgAo3QYrbMengkpQziF02MprbhVAXGY7Zf6O3 G5fJAwBZqpr5pglepZDBbgyaGw1+YqUna2lnunTAYs3Zw9zkQWRqIi8rVwErnNVpWEE1obzFP rbbn3QF Subject: Re: [Cerowrt-devel] Linksys wrt1900acs rrul traces X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.20 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: Fri, 08 Apr 2016 13:17:56 -0000 Hi Richard,=20 On April 8, 2016 1:51:11 PM GMT+02:00, Richard Smith wrote: >On 04/07/2016 12:16 PM, moeller0 wrote: >> Hi Richard, >> >>> For these tests I had the inbound and outbound limits set to 975000 >>> kbps=2E 975000 was somewhat arbitrary=2E I wanted it below 1Gbps >>> enough that I could be sure it was the router as the limit but yet >>> fast enough that I would be able to see the peak transfer rates=2E >> >> All of the following might be old news to you, but please let me >> elaborate for others on this list (well, most folks here know way >> more about these things than I do)=2E I believe Gbit ethernet is >> trickier than one would guess, the 1 Gbit rate contains some overhead >> that one typically does not account for=2E Here is the equivalent >> on-the-wire size of a full MTU non-jumbo ethernet frame: Layer =E2=80= =9C1+": >> 1500 (payload pMTU) + 6 (dest MAC) + 6 (src MAC) + 2 (ethertype) + 4 >> (FCS) + 7 (preamble) + 1 (start of frame delimiter) + 12 (interframe >> gap)) =3D 1500+6+6+2+4+7+1+12 =3D 1538 =E2=80=9DEquivalent=E2=80=9D in = that the >> interframe gap is not really used, but filled with silence but it has >> the duration one would need for 12 bytes=2E > >I knew there was a bit of overhead but thanks for laying out the >details=20 >and why it matters=2E > >> 975000 * (1538/1514) =3D 990455=2E746367 (which still is below the 1GBi= t >> Layer1+ ceiling that GbE has)=2E At 985000 * (1538/1514) =3D >> 1000614=2E26684 you would already have slowly caused the NIC=E2=80=99s = buffer >> to fill ;) > >So by luck I just barely made it=2E :)the Yes, for full MTU-sized packets you made it, but try the same with= say 150 Byte packets: 975000 * (183/164) =3D 1117682=2E9=2E=2E=2E That will nicely Show bloated = Buffets in the Ethernet driver, but should still work well for drivers usi= ng BQL=2E IMHO opinion proper shaping requires to take overhead into accoun= t=2E > >> Luckily sqm-scripts will allow you to specify any >> additional per-packet overhead so just set this to 24 and things >> should just work out I believe=2E > >I knew that there might need to be some overhead accounting and I >looked=20 >at Link Layer Adaption tab in the options when I set up the SQM but the > >info in that menu isn't quite descriptive enough for for my setup=2E > >It has a box for "Ethernet with overhead, select for eg VSDL2"=2E I'm=20 >using Ethernet but I don't know about VSDL2=2E If I select it then I get > >a 2nd box that asks for the per packet overhead=2E Even if I had tried >to=20 >fill that out then I would have gotten it wrong=2E :) Fair enough, we actually multiplex two related things with that drop down = menu, whether to account for per packet overhead or not, and whether to als= o account for ATMs AAL5 cell wonkiness=2E In retrospect we should have sepa= rated these=2E=2E=2E In your case select Ethernet with overhead, and manually put 24 into these= packet overhead field, as the kernel already accounted for 14 of the total= of 38=2E > >The other option is "ATM" which I know I'm not using=2E > >Not knowing what I really should select I just left it at None=2E > >Perhaps there are too many combinations to add items mol for everything b= ut > >a few more options and more descriptions of scenarios might be helpful=2E > >So now that I have that set at 24 is it worth re-running some of the >tests? I assume in your case this will not change your results a lot, as you most= likely used full MTU packets in the test flows, I believe your low latency= under load increases show that you have not much buffer bloat left=2E=2E= =2E I would still recommend to use the correct per packet overhead to be on= the right side=2E=2E=2E Best Regards Sebastian --=20 Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E