From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-x22d.google.com (mail-it0-x22d.google.com [IPv6:2607:f8b0:4001:c0b::22d]) (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 B1DF53B2B0 for ; Sun, 12 Jun 2016 12:31:27 -0400 (EDT) Received: by mail-it0-x22d.google.com with SMTP id e5so28229906ith.0 for ; Sun, 12 Jun 2016 09:31:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:subject:from:to:cc:date:in-reply-to:references :mime-version:content-transfer-encoding; bh=s7VkhmlT+PI5Do89Vh9RHUbGhan/Y7Bgp+rKvqRxnYw=; b=jBTniAZnCyQCsF8uJb+GqYrZA/pd0J7hQUjER/OunVQjUxvFNs7dq3FBfjlHbvyz4u sCLHsqn5E1gqFxLPHRYFQjybk7HF1LoQWCUICBMznmatG76dlLUkVmJjct0PMJqRR1kT 9TtgT+NqAw+Gdckt6bR7aYCvqVT7r9B7jTjSofsZ+n9qIF7yPbVy+gJm5V+W9S79zBXN iSLGxrWYxvaUkrCSvVszaCaigO6rK+Wqzfm1pQSiGbBai+Z4U1vI71Q3iouu+wZPtEcS et3aibchBSyqHaTiJdFki5OIISS9KmC45LYWwvLd8PFqXp0Ml8C9PRhiRkJLdxUZgR1a gdHg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=s7VkhmlT+PI5Do89Vh9RHUbGhan/Y7Bgp+rKvqRxnYw=; b=GF34YwPPhsYgfqjVW/SDO3rsHNPv6MZYmRw/vsH7r5KlemgLSSjZoXTrHqiX2kVKC0 qJcke7vCoUaGBhXkO6hs9HZnRepYcWJxDA7nSY4fOGP7nWmFQUnb5Oe2oLk2h8MXQ8Qs JltCAvrDPLuzkQtXnAqe3ee9VEHEMmpGEnP2AffGOWeuAV6f/EzxcPQ3NSXkkTEqrK0c aUbanTo1foa4XFjm2d0Nm387scsOcF/kF3QwNY+zaVbUGxJ55I5fXUhuhRv9kTmKUnSs 5hJPuM+sU/09/AFdwUyPfebbuFd2YFGaLh6p50e+iBxPZvNUZa5++NrgO9F6iHQ8C7c3 3uFQ== X-Gm-Message-State: ALyK8tJKNe8PhlQfxAjY9Oi4wc2VAfllgd5JgW+X7+/vWTxlWrs6txID/kpwIwSVCtf2YA== X-Received: by 10.36.208.135 with SMTP id m129mr11755870itg.56.1465749087165; Sun, 12 Jun 2016 09:31:27 -0700 (PDT) Received: from [172.26.50.149] ([172.26.50.149]) by smtp.googlemail.com with ESMTPSA id e7sm10301518iof.12.2016.06.12.09.31.25 (version=TLSv1/SSLv3 cipher=OTHER); Sun, 12 Jun 2016 09:31:26 -0700 (PDT) Message-ID: <1465749085.7945.81.camel@edumazet-glaptop3.roam.corp.google.com> From: Eric Dumazet To: Jonathan Morton Cc: Kevin Darbyshire-Bryant , cake@lists.bufferbloat.net Date: Sun, 12 Jun 2016 09:31:25 -0700 In-Reply-To: <98AFD8C3-2343-4B8B-BFB0-6F877161A039@gmail.com> References: <5756ADEC.9070305@darbyshire-bryant.me.uk> <8EE35B4F-5C28-41C7-8795-93A6F606B3A8@gmail.com> <5756E2CA.2020700@darbyshire-bryant.me.uk> <575BD5D0.4060702@darbyshire-bryant.me.uk> <98AFD8C3-2343-4B8B-BFB0-6F877161A039@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: Re: [Cake] Possible BUG - parent backlog incorrectly updated in case of NET_XMIT_CN 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: Sun, 12 Jun 2016 16:31:27 -0000 On Sat, 2016-06-11 at 19:41 +0300, Jonathan Morton wrote: > > On 11 Jun, 2016, at 12:11, Kevin Darbyshire-Bryant wrote: > > > > And now there's a version 2 of Eric's fix: http://marc.info/?l=linux-netdev&m=146507012302643&w=2 > > > > Does this change apply to cake? > > I suppose this answers the question of which packet’s size should be > used in the correction factor. Of course, by this time in the enqueue > process, the original packet length has been replaced by the > overhead-corrected one in Cake, though I can save a copy for this > purpose. > > And there’s also the problem that we might not need to drop packets as > large as the incoming packet in order to fit the latter into the queue > - so this corrected correction may be *negative* (the queue is longer > than before) - but qdisc_tree_reduce_backlog() only takes an unsigned > parameter here. That's a very minor detail. If the code does : reduce_backlog(unsigned quantity) { q->backlog -= quantity; } Then the fact that @quantity is signed or unsigned is irrelevant. You can submit a patch if you want ;) > > IMHO the NET_XMIT_CN semantics are broken. It might be better to drop > support for it, since it should rarely be triggered. What exact part is broken ? Semantic looks good to me. Implementations might be broken after recent Cong Wang patches.