From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:42973 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753472Ab1BUTAg (ORCPT ); Mon, 21 Feb 2011 14:00:36 -0500 Date: Mon, 21 Feb 2011 13:47:17 -0500 From: "John W. Linville" To: Nathaniel Smith Cc: linux-wireless@vger.kernel.org, bloat-devel@lists.bufferbloat.net, johannes@sipsolutions.net, nbd@openwrt.org 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 In-Reply-To: Sender: linux-wireless-owner@vger.kernel.org List-ID: 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.