From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) (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 83DF13CB37 for ; Wed, 7 Feb 2024 07:05:40 -0500 (EST) Received: by mail-pj1-x102f.google.com with SMTP id 98e67ed59e1d1-2909a632e40so384107a91.0 for ; Wed, 07 Feb 2024 04:05:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1707307539; x=1707912339; darn=lists.bufferbloat.net; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=DSE2XmBMEltANkF9P4I3aPhVXTVM0rcH+dYTDjdh++Q=; b=lkqD/SVTJzGrjdC5qGGwTqt5CTPiHljyDIXmziIaTsdYmhyOdv9O9+Hw+IKJkUGu0N OukrDGPq7bQ0XltfmCwUSs2r6eRRm19F+OuoWk8rJJCQgcHC87ugOycYQ0bbsrvRonTP 6LBl+reF2JIYKOOhipiIli8Pc46YVWDMW0GvTGH9eFlnrq8S8F7k4y+5p3wn7xpuC7xq J5WIylr6ZtUcRjnAx/1YAgowMP8xkvugj0LC94oVparFozyo6lxlfkbX1SXRQsDfAPwT /AqfCHys3+SxrdhXPuHNYIjfRbVn3qjt/l+lXCmbZw/dqYdqjyvHLuPeTT7qjwIwtGJa PC+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707307539; x=1707912339; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=DSE2XmBMEltANkF9P4I3aPhVXTVM0rcH+dYTDjdh++Q=; b=rAdNie7heZ2j1WoELZw2MzbnYBqfwqtxqTMRaLHndf+ALvbVSt1gT1lgO0Juao8ysz IN19oRKIJBRLZU1PzTL4FMVuuplaTTVrdZhraUtDcptJ6havmVEkGrQxMDnlnIBQPQDo cAMStE6OiA2cgkVu41+EVi4+nbhVBNElk5KKzUgG3wPKqB73lf2qYAJ71n5uYRTmS8zq 2CWchc3GeqFQ//r/RhhptZTqUl7sqlRqd3ou2lsnheAe+4BGRive2XOPyirH9H04DPyi EsDlDE4tHYQUWptxNtO/zU/RydmuJsD10up6BhkXw/AN9NxL75Ko5Yql/7IyX+lxABia 0USQ== X-Gm-Message-State: AOJu0YzVziOPb32lrIMnay1ITlvqvKMS3CNPP+mtQifN5u2WHAOsYnN8 2P728pcn5QNkO0EZFhsM6C5qCvgVuQLqzd6f57IDUgex/YSGDaZ+EWGmnYWITSqVt8zmXB4kfen uLMMnzidDeVIqcSkS1Dg+jaK1yH0= X-Google-Smtp-Source: AGHT+IGTgw0yWuFN9zUPvBl9pNX6+xU7nYAe4RzYAVoL9RdZyVoAHak1niaNVSdbVF2ZUQ8/xVpwDgHoMS1dpJvjD8g= X-Received: by 2002:a17:90b:480b:b0:296:6a36:a615 with SMTP id kn11-20020a17090b480b00b002966a36a615mr2257342pjb.34.1707307539225; Wed, 07 Feb 2024 04:05:39 -0800 (PST) MIME-Version: 1.0 References: <1BAA689A-D44E-4122-9AD8-25F6D024377E@ifi.uio.no> In-Reply-To: <1BAA689A-D44E-4122-9AD8-25F6D024377E@ifi.uio.no> From: Dave Taht Date: Wed, 7 Feb 2024 07:05:27 -0500 Message-ID: To: Michael Welzl , Linux Kernel Network Developers Cc: bloat@lists.bufferbloat.net Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: Re: [Bloat] Trying to *really* understand Linux pacing 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: Wed, 07 Feb 2024 12:05:40 -0000 Dear Michael: Thank you for digging deeply into packet pacing, TSQ, etc. I think there are some interesting new possibilities in probing (especially during slow start) that could make the core idea even more effective than it is. I also tend to think that attempting it in various cloudy environments and virtualization schemes, and with certain drivers, the side effects are not as well understood as I would like. For example, AWS's nitro lacks BQL as does virtio-net. I think the netdev community, now cc'd, would be interested in your document and explorations so far, below. I hope for more enlightenment. On Wed, Feb 7, 2024 at 6:57=E2=80=AFAM Michael Welzl via Bloat wrote: > > Dear de-bloaters of buffers, > Esteemed experts of low delay and pacing! > > I have no longer been satisfied with high-level descriptions of how pacin= g works in Linux, and how it interacts with TSQ (I=E2=80=99ve seen some, in= various papers, over the years) - but I wanted to REALLY understand it. So= , I have dug through the code. > > I documented this experience here: > https://docs.google.com/document/d/1-uXnPDcVBKmg5krkG5wYBgaA2yLSFK_kZa7xG= DWc7XU/edit?usp=3Dsharing > but it has some holes and may have mistakes. > > Actually, my main problem is that I don=E2=80=99t really know what goes o= n when I configure a larger IW=E2=80=A6 things seem to get quite =E2=80=9Co= ff=E2=80=9D there. Why? Anyone up for solving that riddle? ;-) > (see the tests I documented towards the end of the document) > > Generally, if someone who has their hands on files such as tcp_output.c a= ll the time could take a look, and perhaps =E2=80=9Cfill=E2=80=9D my holes,= or improve anything that might be wrong, that would be fantastic! I thin= k that anyone should be allowed to comment and make suggestions in this doc= . > > MANY thanks to whoever finds the time to take a look ! > > Cheers, > Michael > > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat --=20 40 years of net history, a couple songs: https://www.youtube.com/watch?v=3DD9RGX6QFm5E Dave T=C3=A4ht CSO, LibreQos