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[85.204.121.218]) by smtp.gmail.com with ESMTPSA id y5sm1078673lfg.5.2019.11.21.02.05.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Nov 2019 02:05:17 -0800 (PST) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 65D611818B9; Thu, 21 Nov 2019 11:05:16 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Kan Yan Cc: Dave Taht , Rajkumar Manoharan , Kevin Hayes , Make-Wifi-fast , linux-wireless , Yibo Zhao , John Crispin , Johannes Berg , Lorenzo Bianconi , Felix Fietkau Subject: Re: [Make-wifi-fast] [PATCH v8 0/2] Implement Airtime-based Queue Limit (AQL) In-Reply-To: References: <20191115014846.126007-1-kyan@google.com> <8736eiam8f.fsf@toke.dk> X-Clacks-Overhead: GNU Terry Pratchett Date: Thu, 21 Nov 2019 11:05:16 +0100 Message-ID: <87a78p8rz7.fsf@toke.dk> MIME-Version: 1.0 X-MC-Unique: 8EZ2ZZ0iMW2yjXcmvsm7Dg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org Kan Yan writes: >> It would be interesting to get some samples of the actual sojourn time >> as seen by CoDel in mac80211. Might be doable with bpftrace... > > I will try to add some trace event to get the sojourn time for the > next round of tests. In theory, this ought to produce a histogram of sojourn times (in microseconds): bpftrace -e 'kretprobe:codel_skb_time_func { @sojourn =3D lhist((nsecs - (r= etval << 10))/1000, 0, 100000, 1000); }' Can't get the CoDel drop mechanism to trigger on my system at all, though (a laptop running on iwl). I guess because there's queue backpressure to userspace first? It would be interesting to see if it works for you, assuming you can get bpftrace to work on your test system :) -Toke