From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-x235.google.com (mail-oi0-x235.google.com [IPv6:2607:f8b0:4003:c06::235]) (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 A7DE33B260 for ; Fri, 6 May 2016 03:38:59 -0400 (EDT) Received: by mail-oi0-x235.google.com with SMTP id x19so130198980oix.2 for ; Fri, 06 May 2016 00:38:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-transfer-encoding; bh=ltkjKRgexIlxhAPEWV+nyIh4Ckv3cOBF0zhydTZeotA=; b=myA0slpX/oImZErPX2wqVZL6jx0nu0Zn+UgXsHQi3PffqEFJguZB7hn/IeG/2+DCpp 6JGY8Lf+zcniuNzRcw4zGQGntrPBq6ICDKufa3fLsKaVMZx3/O+t9h2koVExOPQsYTRV +Tvlf6sKx4LfkEywOABE6WolbNVpvfAywWEU4m6Fwi+AGIb1c/qlbkGLSY2sBdq9tNI4 +4rWsYpU46NC1FQ70qTyr8ibvICs0C6GOjrZyBam9DRVUbtCNC2PpHLjBTOG528zGlgO Cvu3o3nMuyC2YASlY7kdRlK2mbJgLQgN3XSAi9wnl8ixp2QhowHWVZIQyQG+ct52Xer+ hpqg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-transfer-encoding; bh=ltkjKRgexIlxhAPEWV+nyIh4Ckv3cOBF0zhydTZeotA=; b=PpXfhqOYzJOS+p6m9bkcX8tUTiGxsDQ1n1dby797nIIac3wDTxx/qfPAubof5UBg/D rdQyqUmOrCjvFkrtbgfU+pYbUS3fRO+zWQ0C3ycuOzZiaQIq/lZtIOpZwDb7WHxSUlK2 yMWr36johLYcm0deuo7t2aJyQtY4+pRwEQ/ak7CMUjR1IAm2ERwBQ7u+Zs4uuHLTWUYW AWNBpilHOdKRPY8QN8rHB3pnpPHI3ZZ7T5qmg0w3Vr5rsfJgpyXq616NO397xOEJpZta vACgDh1VdM6lDHK/kQednYwkuSnApgWjTy+hUviE8ppw9DbVs06cr6v61Y8IdUnKDlpi 6FJA== X-Gm-Message-State: AOPr4FWd47s3sEPYek251niPsRRkXrVDr9q8yTP9qCy8+IuS0rGX17XvbuMCZQLRb/ZdD3IRklgXc0OTLQRJUg== MIME-Version: 1.0 X-Received: by 10.202.217.67 with SMTP id q64mr9055297oig.151.1462520339122; Fri, 06 May 2016 00:38:59 -0700 (PDT) Received: by 10.202.229.210 with HTTP; Fri, 6 May 2016 00:38:59 -0700 (PDT) In-Reply-To: <0eca51dc-694b-6a85-d56d-1ed19e9fc2ef@darbyshire-bryant.me.uk> References: <0eca51dc-694b-6a85-d56d-1ed19e9fc2ef@darbyshire-bryant.me.uk> Date: Fri, 6 May 2016 00:38:59 -0700 Message-ID: From: Dave Taht To: Kevin Darbyshire-Bryant Cc: cake@lists.bufferbloat.net Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Cake] UDP floods and taking advantage of egress signalling at ingress 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: Fri, 06 May 2016 07:38:59 -0000 On Fri, May 6, 2016 at 12:29 AM, Kevin Darbyshire-Bryant wrote: > Hi All, > > My brain woke up with this idea rattling around in it this > morning...obviously the subconscious has been busy. So here it is: > > Is there any way to use the egress drop signalling at ingress time to dro= p > stuff before it gets into the queue so then we don't have to drop it at > egress? > > Something like: At enqueue if we've a matching flow check to see if that > flow had been in egress 'fast dropping' state *and* know how much data in > terms of time it had to fast drop to get the queue back under the nominal > time threshold. If say it had to drop 10ms worth of packets to get back = to > the nominal 5ms threshold then it dropped 67% of the packets/data. I'd l= ike > to think of that as an 'unresponsive flow'...hence could it be possible t= o > use that information at ingress time and in essence drop (some? 66%?) of > them there, we can also signal congestion to the stack at that point to > (cake already does this signalling when getting to its buffer size limit) > > > Probably a very silly idea. No, actualy, I'd been thinking about the same thing myself for days. :) I've always wanted a way to notify userspace that I was dropping (the heck out of) something on egress to try and stuff it up on ingress, or do something more intelligent like re-route the traffic elsewhere. There was a lot of talk about adding the ability to drop stuff really fast in the rx ring recently using the jit BPF stuff. I was at a meeting where tom herbert talked about that, and I confess, extremely dubious. Then... well, I see lots of drops on ingress already I don't want, the udp flooding episode made me go look harder at whole system behavior... and I can't find the lwn article about it. > > -- > Thanks, > > Kevin@Darbyshire-Bryant.me.uk > M: +44 7947 355344 H: +44 1256 478597 > > > _______________________________________________ > Cake mailing list > Cake@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/cake > --=20 Dave T=C3=A4ht Let's go make home routers and wifi faster! With better software! http://blog.cerowrt.org