From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-14-ewr.dyndns.com (mxout-039-ewr.mailhop.org [216.146.33.39]) by lists.bufferbloat.net (Postfix) with ESMTP id F34292E016E for ; Mon, 21 Feb 2011 11:00:36 -0800 (PST) Received: from scan-12-ewr.mailhop.org (scan-12-ewr.local [10.0.141.230]) by mail-14-ewr.dyndns.com (Postfix) with ESMTP id 0BC689CDDF4 for ; Mon, 21 Feb 2011 19:00:36 +0000 (UTC) X-Spam-Score: 0.0 () X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 70.61.120.58 Received: from smtp.tuxdriver.com (charlotte.tuxdriver.com [70.61.120.58]) by mail-14-ewr.dyndns.com (Postfix) with ESMTP id D287D9CDCEC for ; Mon, 21 Feb 2011 19:00:35 +0000 (UTC) Received: from uucp by smtp.tuxdriver.com with local-rmail (Exim 4.63) (envelope-from ) id 1Prazn-0006eK-5B; Mon, 21 Feb 2011 14:00:31 -0500 Received: from linville-8530p.local (localhost.localdomain [127.0.0.1]) by linville-8530p.local (8.14.4/8.14.4) with ESMTP id p1LIlH5n013793; Mon, 21 Feb 2011 13:47:18 -0500 Received: (from linville@localhost) by linville-8530p.local (8.14.4/8.14.4/Submit) id p1LIlHm7013791; Mon, 21 Feb 2011 13:47:17 -0500 Date: Mon, 21 Feb 2011 13:47:17 -0500 From: "John W. Linville" To: Nathaniel Smith Subject: Re: [RFC v2] mac80211: implement eBDP algorithm to fight bufferbloat Message-ID: <20110221184716.GD9650@tuxdriver.com> References: <1297907356-3214-1-git-send-email-linville@tuxdriver.com> <1298064074-8108-1-git-send-email-linville@tuxdriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Cc: bloat-devel@lists.bufferbloat.net, johannes@sipsolutions.net, linux-wireless@vger.kernel.org X-BeenThere: bloat-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: "Developers working on AQM, device drivers, and networking stacks" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 21 Feb 2011 19:00:37 -0000 On Fri, Feb 18, 2011 at 07:44:30PM -0800, Nathaniel Smith wrote: > On Fri, Feb 18, 2011 at 1:21 PM, John W. Linville > wrote: > > +       /* grab timestamp info for buffer control estimates */ > > +       tserv = ktime_sub(ktime_get(), skb->tstamp); > [...] > > +               ewma_add(&sta->sdata->qdata[q].tserv_ns_avg, > > +                        ktime_to_ns(tserv)); > > I think you're still measuring how long it takes one packet to get > from the end of the queue to the beginning, rather than measuring how > long it takes each packet to go out? Yes, I am measuring how long the driver+device takes to release each skb back to me (using that as a proxy for how long it takes to get the fragment to the next hop). Actually, FWIW I'm only measuring that time for those skb's that result in a tx status report. I tried to see how your measurement would be useful, but I just don't see how the number of frames ahead of me in the queue is relevant to the measured link latency? I mean, I realize that having more packets ahead of me in the queue is likely to increase the latency for this frame, but I don't understand why I should use that information to discount the measured latency...? John -- John W. Linville Someday the world will need a hero, and you linville@tuxdriver.com might be all we have. Be ready.