From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-x22c.google.com (mail-qt0-x22c.google.com [IPv6:2607:f8b0:400d:c0d::22c]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 8D6733BA8E for ; Wed, 25 Jul 2018 12:01:06 -0400 (EDT) Received: by mail-qt0-x22c.google.com with SMTP id d4-v6so8113852qtn.13 for ; Wed, 25 Jul 2018 09:01:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=uAseau2PSzlJMPybVY1Srd9qF1JTN3X+hGKKjxVkVj0=; b=M4ZcQ3ubnXmoJOj00Jnw5v+SECLW9gr69babSsKLeBUiM9PZk0fligMUJ8hWwLIwDp diTE8CsXAug6SzFuubpxSUW28JG5kaGbKtyPlPB6Q7f0op+BFtGQCIhbt7l0TBzK07fk LaA6N7DwucN7szO75bYfCKhzf8c8ibHPB+SKOkXPr0zpAYNAuezed7bq5jr/IBspaffT MINWzPNY6v+KP9Ogs8rhAutfsGV4mbHQPgdcffDet9S4e8iewe5mWZf4kk/2a4HP0Rbw VRoCbusiiUiFO1S6YeeQd+UcTq0IVNFx3xklGOiqS5FRqvzXyYPBPFpthLwCOarrISI3 C6hQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=uAseau2PSzlJMPybVY1Srd9qF1JTN3X+hGKKjxVkVj0=; b=fPSU0ziJU6ZmDYxLXXYsnrchd87yUYo/0uFMvtVjL7+eHoTLZuHPXW/7xuaXLVHhPp spHw/HCGWB8L5k5ajHlVcV4j1poNKndJrRNviOeWZZRtGMDX9UAyjUZmn4yepe8aeWn0 oVZQkN12EGfJjCkc/eEORKiWFJ7TpAN++gWjxzWPKFtcvHBj+hQQFc16DoYqdeVTqhsx wkK5g2v5/NYhYu/cks4w0HdQTej6uPgLu2kEGWDwcr2fSAJYg3D8yKPk6l+zz7W+9qP8 LrOduLHH396jCZx2ZuQsox+vOmBdvxbG4zQt3hLugNVJ3QfPspDETjLspyf9Fz7oErQS fOIg== X-Gm-Message-State: AOUpUlGF2vF1DntA7miPzYkhBT/qvMqrhwwKt71uaTxZSSarPpXGr20r wiHx8XOqllELJJlEYUuecataYkWPkZaxL7ErNHs= X-Google-Smtp-Source: AAOMgpdmA7pm3uF/7KBCpxlhoqlNZh92Fzr0AaoyJhURn7IMqrjVIGm/zPIk8LPJO/CiL2/DScoOkaJiONpF9HPZQwQ= X-Received: by 2002:ac8:354e:: with SMTP id z14-v6mr21849222qtb.261.1532534465894; Wed, 25 Jul 2018 09:01:05 -0700 (PDT) MIME-Version: 1.0 References: <87effr3a72.fsf@toke.dk> <6495D4D7-0920-43C7-A92E-3027102E723D@gmx.de> In-Reply-To: <6495D4D7-0920-43C7-A92E-3027102E723D@gmx.de> From: Dave Taht Date: Wed, 25 Jul 2018 09:00:54 -0700 Message-ID: To: Sebastian Moeller Cc: =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= , Cake List Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: Re: [Cake] making split_gso_threshold configurable 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: Wed, 25 Jul 2018 16:01:06 -0000 On Wed, Jul 25, 2018 at 3:07 AM Sebastian Moeller wrote: > > Hi Toke, > > > > On Jul 25, 2018, at 12:02, Toke H=C3=B8iland-J=C3=B8rgensen wrote: > > > > Dave Taht writes: > > > >> I really wanted cake to always optimize for low latency. I wanted it > >> to "just work" at line rate on dsl, on 100mbit, even 10mbit ethernet, > >> to work against pause frames, etc, without configuration. I wanted to > >> defeat drivers like the mvneta that can do 64k of software GRO > >> automagically. > > > > So I think that Eric's point was that the GSO logic itself should > > throttle back and not build so big packets when the link rate is lower. > > Might be worth it to check if this is actually the case, and if not to > > get GSO fixed rather than disabling it. It doesn't and I think I should just put forth the patch and face the howling from the 40gbit guys. > > > > Also, are there actually any modems that will negotiate ethernet line > > rates less than a gigabit? > > Yes, there are XDSL Modem(routers) that only have fast-ethernet p= orts. Not sure how rare these are though. And there are also many devices that ecert hardware flow control. > Best Regards > Sebastian > > > > > >> Along the way to mainlining it, cake's behavior got changed, to scale > >> well to 50Gbit by allowing GSO above a 1gbit shaped rate, and *always > >> allowing GSO at line rate*. > >> > >> if (q->rate_bps && q->rate_bps <=3D CAKE_SPLIT_GSO_THRESHOLD) > >> q->rate_flags |=3D CAKE_FLAG_SPLIT_GSO; > >> else > >> q->rate_flags &=3D ~CAKE_FLAG_SPLIT_GSO; > >> > >> I don't care about 50gbit. I'm delighted, even astonished, it does > >> 50Gbit. I want it to do 1mbit with 13ms interpacket latency when hit > >> by an IW10 burst from somewhere else, not 130, with hardware pause > >> frames in use on the dsl modem or elsewhere. > > > > Getting pause frames to work properly in this setup kinda requires the > > buffering in the modem to be reasonable in the first place... > > > >> so, I'd like to A) default to always split shaped or unshaped. And B) > >> expose the split threshold to be configured via userspace. This latter > >> option would give a tunable for those struggling a bit for cpu to play > >> with, also. > > > > I very much doubt that we can get upstream to accept split as the > > default. It may be possible to get it to be user tunable. I don't think > > we should deviate from upstream unless we absolutely have to (that was > > kinda the whole point of the upstreaming exercise), and I'm not > > convinced that this is a good enough reason... > > > > -Toke > > _______________________________________________ > > Cake mailing list > > Cake@lists.bufferbloat.net > > https://lists.bufferbloat.net/listinfo/cake > --=20 Dave T=C3=A4ht CEO, TekLibre, LLC http://www.teklibre.com Tel: 1-669-226-2619