From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-x22e.google.com (mail-qt0-x22e.google.com [IPv6:2607:f8b0:400d:c0d::22e]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id F3CA53B29E for ; Sun, 8 Oct 2017 21:54:14 -0400 (EDT) Received: by mail-qt0-x22e.google.com with SMTP id k31so5191141qta.6 for ; Sun, 08 Oct 2017 18:54:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to :content-transfer-encoding; bh=9trQ02KiQCGu1REpBTcro7l2hqJjV5MW+ScaGrOPvPA=; b=IvIG4Rp3NIgY1z3cApPb/VmnDgsYduB/MjoWsqRDO6Yam6hwyWF7yvhJx7+ia7MfZM EIXjKuhPor4VGa01bVANNGLWKLgUWOdNDjWhUkDNrxWdhQJxSeWI2sB/XF2zdgixnYyj 3Ikby8JDf3Ag1/SFTK2ADhNR04I3xW3rMc/0WU6A7B2SKzs2Q9ilaMilZbUPBHXG+Ajg 55qPtKYkbUcDW1VqpkB7Ti6ZRURl7yupoki+hd5Sr/ATM/+pxjIo2fUZ8QfelIJnutJn Y4GnNC27FplpDN39awncDWEU5J8bGLEKBwqzpo5I5T2T50LrPIL7lmjl6dPqXWJREi5a DMmQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to :content-transfer-encoding; bh=9trQ02KiQCGu1REpBTcro7l2hqJjV5MW+ScaGrOPvPA=; b=Z42sHdq6mD2VHph84rc4GFh8eKSCvz2thJWsnwhdXZmrtDciHmaiYfsWjGeuXPi7XP 1HZWdZYrRzaWQ73prQzBKX48iZiN4+msJs2cRVG/kajwYxAhR9iRWqAFvh+B5ZjDrE8i 4FBew4siLnBJjR+tUdckf2nXIPKjThj8m4s24uNyHRIn/xZzTIjVL6/hZqAx734UGX24 +kh9hzWqXCxTg3jxq+a/DamZBmvKaURR9lyBR/rW7B7LWqtzsBYEt6uLo/3goIWrIMdY aT1Bw0EP+mXpluwYhasCiybZWJYYlRLkthhF42xCCtGy2KUiNIzbNKu+i64KFy4q8/JQ 3uzA== X-Gm-Message-State: AMCzsaXjS0Gqg+Xo/tI+Ux4np8P0tW5mq+Cneuv0f8MdZQAm7Aq/oklo t5izuq0DaPLi5CHDOKvDmeDm24wcE59a0m6dQRs= X-Google-Smtp-Source: AOwi7QC2vlthn/OSwkVXjLQTZNLkjwVyN/9GYaIBBuLe7vFABlaS/jMIGtCjB22dYBfYkofTp5M03u1D/XMdcJ7mCHk= X-Received: by 10.200.40.120 with SMTP id 53mr11064629qtr.164.1507514054422; Sun, 08 Oct 2017 18:54:14 -0700 (PDT) MIME-Version: 1.0 Received: by 10.12.193.115 with HTTP; Sun, 8 Oct 2017 18:54:12 -0700 (PDT) From: Dave Taht Date: Sun, 8 Oct 2017 18:54:12 -0700 Message-ID: To: bloat Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: [Bloat] emulating non-duplex media in linux qdiscs X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Oct 2017 01:54:15 -0000 I have been hacking away at netem for a while now in the hope that eventually - with a great deal more hacking - it could be used to more accurately emulate shared media like wifi and lte. (Some people try to describe these as simplex (which is not true because you can have multiple destinations), and they certainly are not duplex, so I tend to say non-duplex and still hope some better word emerges) So... one sticking point for me has been wanting to emulate the fact that on shared media, that you cannot transmit and receive at the same time; that these are "coupled" events, and what I'd like to be able to express might be something like: tc qdisc add dev eth0 root netem rate 100mbit coupled some_identifier ... some tc mirred magic for ifb here ... tc qdisc add dev ifb0 root netem rate 10mbit coupled the_same_identifier "some_identifier" would be a mutex of some sort, and I confess to not having much grip on the kernel outside of the net/sched directory. What facility would be best to try and leverage? It would be created (globally) on first use, ref-counted (thus destroyed when it goes to zero), atomically updated... posix shared memory seems too heavyweight to use.... --=20 Dave T=C3=A4ht CEO, TekLibre, LLC http://www.teklibre.com Tel: 1-669-226-2619