From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [PATCH 2/2] NET: Accurate packet scheduling for ATM/ADSL (userspace) Date: Wed, 14 Jun 2006 15:18:02 +0200 Message-ID: <1150291082.26186.88.camel@localhost.localdomain> References: <1150278040.26181.37.camel@localhost.localdomain> <1150282625.3490.23.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-41hGIGQHvr3hTqy3Q0B/" Cc: Stephen Hemminger , Jamal Hadi Salim , netdev@vger.kernel.org, lartc@mailman.ds9a.nl, russell-tcatm@stuart.id.au, hawk@diku.dk, linux-kernel@vger.kernel.org, hawk@comx.dk Return-path: Received: from ex001a.cxnet.dk ([195.135.216.13]:43724 "EHLO comxexch01.comx.local") by vger.kernel.org with ESMTP id S964910AbWFNNSE (ORCPT ); Wed, 14 Jun 2006 09:18:04 -0400 To: Alan Cox In-Reply-To: <1150282625.3490.23.camel@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org --=-41hGIGQHvr3hTqy3Q0B/ Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Wed, 2006-06-14 at 11:57 +0100, Alan Cox wrote: > Ar Mer, 2006-06-14 am 11:40 +0200, ysgrifennodd Jesper Dangaard Brouer: > > option to calculate traffic transmission times (rate table) > > over all ATM links, including ADSL, with perfect accuracy. > > The other problem I see with this code is it is very tightly tied to ATM > cell sizes, not to solving the generic question of packetisation.=20 Well, we did consider to do so, but we though that it would be harder to get it into the kernel. Actually thats the reason for the defines: #define ATM_CELL_SIZE 53 #define ATM_CELL_PAYLOAD 48 Changing these should should make it possible to adapt to any other SAR (Segment And Reasembly) link layer. > I'm > not sure if that matters but for modern processors I'm also sceptical > that the clever computation is actually any faster than just doing the > maths, especially if something cache intensive is also running. I guess you are refering to the rate table lookup system, that is based upon array lookups. I do think that the rate table array lookup system has been outdated, as memory access is the bottleneck on modern CPUs. But its design by Alexey for a long time ago where the hardware restrictions were different. It also avoids floting point operations in the kernel. Thanks for your comments. --=20 Med venlig hilsen / Best regards Jesper Brouer ComX Networks A/S Linux Network developer Cand. Scient Datalog / MSc. Author of http://adsl-optimizer.dk --=-41hGIGQHvr3hTqy3Q0B/ Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (GNU/Linux) iD8DBQBEkAyKwuVH+NB3fZkRAspAAJ491JxslgE27tm4XgIBsm8ioSp8yACfXfI9 0E2FZkM/s1qb12g027c19VY= =pnha -----END PGP SIGNATURE----- --=-41hGIGQHvr3hTqy3Q0B/--