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Open Source and information security mailing list archives
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Date: Wed, 9 Dec 2020 12:37:29 -0500 From: Willem de Bruijn <willemdebruijn.kernel@...il.com> To: "Geva, Erez" <erez.geva.ext@...mens.com> Cc: Network Development <netdev@...r.kernel.org>, linux-kernel <linux-kernel@...r.kernel.org>, "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>, Alexey Kuznetsov <kuznet@....inr.ac.ru>, Arnd Bergmann <arnd@...db.de>, Cong Wang <xiyou.wangcong@...il.com>, "David S . Miller" <davem@...emloft.net>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, Jakub Kicinski <kuba@...nel.org>, Jamal Hadi Salim <jhs@...atatu.com>, Jiri Pirko <jiri@...nulli.us>, Alexei Starovoitov <ast@...nel.org>, Colin Ian King <colin.king@...onical.com>, Daniel Borkmann <daniel@...earbox.net>, Eric Dumazet <edumazet@...gle.com>, Eyal Birger <eyal.birger@...il.com>, "Gustavo A . R . Silva" <gustavoars@...nel.org>, Jakub Sitnicki <jakub@...udflare.com>, John Ogness <john.ogness@...utronix.de>, Jon Rosen <jrosen@...co.com>, Kees Cook <keescook@...omium.org>, Marc Kleine-Budde <mkl@...gutronix.de>, Martin KaFai Lau <kafai@...com>, Matthieu Baerts <matthieu.baerts@...sares.net>, Andrei Vagin <avagin@...il.com>, Dmitry Safonov <0x7f454c46@...il.com>, "Eric W . Biederman" <ebiederm@...ssion.com>, Ingo Molnar <mingo@...nel.org>, John Stultz <john.stultz@...aro.org>, Miaohe Lin <linmiaohe@...wei.com>, Michal Kubecek <mkubecek@...e.cz>, Or Cohen <orcohen@...oaltonetworks.com>, Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Richard Cochran <richardcochran@...il.com>, Stefan Schmidt <stefan@...enfreihafen.org>, Xie He <xie.he.0141@...il.com>, Stephen Boyd <sboyd@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Vladis Dronov <vdronov@...hat.com>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Frederic Weisbecker <frederic@...nel.org>, Vinicius Costa Gomes <vinicius.gomes@...el.com>, Vedang Patel <vedang.patel@...el.com>, "Molzahn, Ines" <ines.molzahn@...mens.com>, "Sudler, Simon" <simon.sudler@...mens.com>, "Meisinger, Andreas" <andreas.meisinger@...mens.com>, "Bucher, Andreas" <andreas.bucher@...mens.com>, "henning.schild@...mens.com" <henning.schild@...mens.com>, "jan.kiszka@...mens.com" <jan.kiszka@...mens.com>, "Zirkler, Andreas" <andreas.zirkler@...mens.com>, "Sakic, Ermin" <ermin.sakic@...mens.com>, "anninh.nguyen@...mens.com" <anninh.nguyen@...mens.com>, "Saenger, Michael" <michael.saenger@...mens.com>, "Maehringer, Bernd" <bernd.maehringer@...mens.com>, "gisela.greinert@...mens.com" <gisela.greinert@...mens.com>, Erez Geva <ErezGeva2@...il.com> Subject: Re: [PATCH 1/3] Add TX sending hardware timestamp. On Wed, Dec 9, 2020 at 10:25 AM Geva, Erez <erez.geva.ext@...mens.com> wrote: > > > On 09/12/2020 15:48, Willem de Bruijn wrote: > > On Wed, Dec 9, 2020 at 9:37 AM Erez Geva <erez.geva.ext@...mens.com> wrote: > >> > >> Configure and send TX sending hardware timestamp from > >> user space application to the socket layer, > >> to provide to the TC ETC Qdisc, and pass it to > >> the interface network driver. > >> > >> - New flag for the SO_TXTIME socket option. > >> - New access auxiliary data header to pass the > >> TX sending hardware timestamp. > >> - Add the hardware timestamp to the socket cookie. > >> - Copy the TX sending hardware timestamp to the socket cookie. > >> > >> Signed-off-by: Erez Geva <erez.geva.ext@...mens.com> > > > > Hardware offload of pacing is definitely useful. > > > Thanks for your comment. > I agree, it is not limited of use. > > > I don't think this needs a new separate h/w variant of SO_TXTIME. > > > I only extend SO_TXTIME. The patchset passes a separate timestamp from skb->tstamp along through the ip cookie, cork (transmit_hw_time) and with the skb in shinfo. I don't see the need for two timestamps, one tied to software and one to hardware. When would we want to pace twice? > > Indeed, we want pacing offload to work for existing applications. > > > As the conversion of the PHC and the system clock is dynamic over time. > How do you propse to achive it? Can you elaborate on this concern? The simplest solution for offloading pacing would be to interpret skb->tstamp either for software pacing, or skip software pacing if the device advertises a NETIF_F hardware pacing feature. Clockbase is an issue. The device driver may have to convert to whatever format the device expects when copying skb->tstamp in the device tx descriptor. > > > It only requires that pacing qdiscs, both sch_etf and sch_fq, > > optionally skip queuing in their .enqueue callback and instead allow > > the skb to pass to the device driver as is, with skb->tstamp set. Only > > to devices that advertise support for h/w pacing offload. > > > I did not use "Fair Queue traffic policing". > As for ETF, it is all about ordering packets from different applications. > How can we achive it with skiping queuing? > Could you elaborate on this point? The qdisc can only defer pacing to hardware if hardware can ensure the same invariants on ordering, of course. Btw: this is quite a long list of CC:s
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