From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-x22c.google.com (mail-qk0-x22c.google.com [IPv6:2607:f8b0:400d:c09::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 D79643BA8E for ; Thu, 26 Jul 2018 00:42:12 -0400 (EDT) Received: by mail-qk0-x22c.google.com with SMTP id 26-v6so237921qks.9 for ; Wed, 25 Jul 2018 21:42:12 -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=hBJGn3Rqpr9Lc0MGRAReL1MTxnHlMwcGnjec9FBe2pE=; b=Q2VA7vbEwVSNjW96AL80EWBLlur3uRgyk7gzGGgf9BMAFAqsw/yDTp3cJ5gQFoJjkg +rM7HuYY6kq27hLCOVwYjrNccg2u7AwyOkpoTxLE89GX4klbx9tQhqrXLpx2EHXZJ9cz c0x26RcB74bZjG1JE9Gw0iLxBA62+rnJu5b9jz6T3K2WNo9SvbrkEyzMADRBWSj7/d10 z0SWpK/RBNgOXjjOdaENfIBJMHFSEfTqa8lP9nkBcb769unVei3pvHeSzFYdHNm2ZxNO kKMtYYlj1tog7BR3lJ4inzrow76CSBE43UoKd12x07AceIAuezf8l6dcurTFTc72byOY 3TLw== 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=hBJGn3Rqpr9Lc0MGRAReL1MTxnHlMwcGnjec9FBe2pE=; b=HQpmE5pbZRDUF8vRmVlPs/g9CU6doZkTYDTqSGqO6/ZKnWupID5Q70mnTfu7eHxuQx ZDzNWT6yV0892HwmNdVxyBrh15hx5JwVAuGMi05FQsnO4JxrLst5tosf2JlNvgWu/1mk cx9C+wqfN8hvveLhlzdySP0rIzuawD1k6wtcLGlBhWb4HBtit3j2G3fnpZeJoQK2jaHE 5GuLiP4u30KUiWFCXI4B+zsg+JdBx0R/pddWnmqjgXhDyNpXNdF74aS6lJGC6Rg50eyZ PVY57S2HOmfSAWYTSdxUb0TqrI0WM8jV6SubXTNJJXsNSkxH1aj3VpCdFadaFChWvssx ayEg== X-Gm-Message-State: AOUpUlFl4wmY6kyEh038QZ6EOOm7TxjNOIsn9u9HSiLIwMw/D1OhYjQI m9sWxZkxqn0yp5NYvdsQZdwaYRwGV19ChlD5o1M= X-Google-Smtp-Source: AAOMgpc31r9NjXeXCgsEtOsZgA0In4P+pXhpMHx45KlB2asvFZT8tII8TvSE5KYiCcJ9AM+e/wtxrKC+PkyyAUJNxQo= X-Received: by 2002:a37:4d1:: with SMTP id 200-v6mr304480qke.35.1532580132344; Wed, 25 Jul 2018 21:42:12 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Dave Taht Date: Wed, 25 Jul 2018 21:42:00 -0700 Message-ID: To: Benjamin Cronce Cc: bloat Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: Re: [Bloat] No backpressure "shaper"+AQM X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 26 Jul 2018 04:42:12 -0000 On Tue, Jul 24, 2018 at 2:31 PM Dave Taht wrote: > > I'd actually written some code for this way back when, if you want to > know how policers currently work, > google for "tri-color policer". They worked ok in the T1 era, but suck > rocks now. > > TL;DR > > Earlier this week while we (ended up) debugging a buggy comcast modem > I was desparate enough to resume thinking it was time to revisit the > concept as a first stage filter prior to hitting cake. > > I did think that an *aqm* that aimed for defeating a burst policer > rate (much like BBR is doing now) would be a goodness. Say you know > there is a policer upstream configured like yours... > > Then... I thought we could build something lighter weight than > shaping, but the feature set built and built... A few useful > enhancements to the standard policer like deficits rather than tbf, > adding ECN, shooting equally at all flows it sees (fq), not shooting > at one flow for more than one packet in 4 (thus, voip suffers not), > trying to wait an RTT before shooting again (codel - actually pie in > this case). I don't want this convo to die on details. Having a less cpu intensive than shaping yet more effective than policing "thing" would be a goodness. > As one example I controlled the shooting schedule with a 2048 bit, (2 > bits per flow) bitmap sampling every 5ms, keeping around 16 versions > (thus 80ms of history) Another variant was bloom filters. I'd played with murmur as an alternate hash simply because this pull request was a gas: https://github.com/bitly/dablooms/pull/19 > I discarded the idea for several other reasons back then > > ENOFUNDING > TBF Policers generally are used in switches and routers that do it in > hardware. Everything I came up with > was doable in HW (O1) (which cake/fq_codel are not), but waiting 10 > years for it to show up in ISP hardware seemed harder than waiting 10 > years to see ISP shapers get fixed. > Shaping, given the growing amounts of multi-core underutilized cpus, > allowed us to be more gentle and achieve > goals like better e2e host and flow fq, while allowing sparse flows to > not be delayed very much. > ENOFUNDING > Identifying flows required taking a hash which slows things down. > > Still, a "slightly better" bobbie aqm influenced policer has long > seemed doable so long as it's extremely lightweight. --=20 Dave T=C3=A4ht CEO, TekLibre, LLC http://www.teklibre.com Tel: 1-669-226-2619