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[185.193.85.130]) by smtp.gmail.com with ESMTPSA id p6sm61863260wrx.50.2019.01.05.12.01.32 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 05 Jan 2019 12:01:32 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\)) From: Pete Heist In-Reply-To: Date: Sat, 5 Jan 2019 21:01:31 +0100 Cc: =?utf-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , Cake List Content-Transfer-Encoding: quoted-printable Message-Id: References: <5482A3CA-9C36-4DDE-A858-24D8467F70C7@heistp.net> <8736q8yumt.fsf@toke.dk> <4C422792-7E51-4DBA-A229-FA7D3F987FB6@heistp.net> <87zhsgxdao.fsf@toke.dk> <87wonjxvss.fsf@toke.dk> <0077CC34-490F-4D76-82D3-BE37B27F2E1C@heistp.net> <49A6DCF8-BE98-47F4-9C66-6B4288390A58@heistp.net> <87tvinxos7.fsf@toke.dk> <87r2drxnal.fsf@toke.dk> <45D43135-318B-48AD-B09B-69BBB034CE12@heistp.net> <87o98vxm57.fsf@toke.dk> <797FCC60-0048-4EF6-80BC-19707E9173FB@heistp.net> <87lg3zxdyr.fsf@toke.dk> To: Sebastian Moeller X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Cake] cake infinite loop(?) with hfsc on one-armed router X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 05 Jan 2019 20:01:34 -0000 That first bug report looks decidedly similar to mine, but Toke would = have to comment on the specifics. So far I see the patch to sch_codel.c = you mentioned and another two-liner to remove the warning in hfsc.c = (https://patchwork.ozlabs.org/patch/933611/). It would be really good to = know that that warning is truly bogus, that it wasn=E2=80=99t put there = by the author for good reason, as Toke may have been thinking of a = different way to fix hfsc. Thanks for bringing this up! I see that I ought to search = OpenWRT/kernel.org next time=E2=80=A6 :) > On Jan 5, 2019, at 8:27 PM, Sebastian Moeller wrote: >=20 > Dear all, >=20 > I am most likely wrong, but did you have a look at = https://bugs.openwrt.org/index.php?do=3Ddetails&task_id=3D1136 yet? > Especially https://bugzilla.kernel.org/show_bug.cgi?id=3D109581 and = https://www.spinics.net/lists/netdev/msg450655.html might be related to = Pete's bug. > Then again, I might be wrong as the whole flurry of emails went past = my head quickly. >=20 > Best Regards > Sebastian >=20 >=20 >> On Jan 5, 2019, at 17:32, Toke H=C3=B8iland-J=C3=B8rgensen = wrote: >>=20 >> Pete Heist writes: >>=20 >>>> On Jan 5, 2019, at 2:35 PM, Toke H=C3=B8iland-J=C3=B8rgensen = wrote: >>>>=20 >>>> Pete Heist writes: >>>>=20 >>>>>> On Jan 5, 2019, at 2:10 PM, Toke H=C3=B8iland-J=C3=B8rgensen = wrote: >>>>>>=20 >>>>>> Hmm, that's odd. Could you try adding this debugging line in >>>>>> adjust_parent_qlen(), right before the sch->q.qlen +=3D n line: >>>>>>=20 >>>>>> net_info_ratelimited("Adjusting parent qdisc %d with pkt = +=3D %d, len +=3D %d", >>>>>> parentid, n, len); >>>>>>=20 >>>>>> And see if you actually get any of those lines in your dmesg? >>>>>=20 >>>>> I do see the messages twice, then not after that in the rest of = the >>>>> output... >>>>=20 >>>> Right. Looking at the HFSC code some more, I think the bug is = actually >>>> caused by another, but related, interaction between HFSC and CAKE. >>>>=20 >>>> Specifically, this line: >>>>=20 >>>> = https://elixir.bootlin.com/linux/v3.16.7/source/net/sched/sch_hfsc.c#L1605= >>>>=20 >>>> where HFSC checks whether the child queue len is 1, which it = interprets >>>> as the event that activates that queue. However, because CAKE = splits the >>>> packet, this check will fail, and the HFSC class will not be = activated. >>>> This also explains why you only see the bug with HFSC, and not with = HTB >>>> (although I do think that we still need to update the hierarchy). >>>>=20 >>>> The good news it that it is a fairly simple to fix in HFSC. The bad = news >>>> is that it's something that's hard to work around from the = out-of-tree >>>> CAKE... >>>=20 >>> Aha, well, I wonder if we=E2=80=99ll see this problem with other = qdiscs- maybe >>> cbq, if I ever get a chance to try it (not hurrying yet). Ideally = this >>> interaction between qdiscs would be clarified somewhere, at some >>> point. :) >>>=20 >>> Thanks a lot for doing the discovery though! >>=20 >> You're welcome, and thanks for you help :) >>=20 >>> We may not have hfsc+cake with GSO splitting on older kernels very >>> soon, but what should we do with this? There=E2=80=99s nobody in = MAINTAINERS >>> for hfsc, so we may not get much of a response to any bug >>> submissions... >>=20 >> $ ./scripts/get_maintainer.pl net/sched/sch_hfsc.c=20 >> Jamal Hadi Salim (maintainer:TC subsystem) >> Cong Wang (maintainer:TC subsystem) >> Jiri Pirko (maintainer:TC subsystem) >> "David S. Miller" (maintainer:NETWORKING = [GENERAL]) >> netdev@vger.kernel.org (open list:TC subsystem) >>=20 >> I'll submit a patch sometime next week, and also look into the qlen >> adjustment for CAKE GSO splitting... >>=20 >> -Toke >> _______________________________________________ >> Cake mailing list >> Cake@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/cake >=20