From patchwork Tue Jan 16 23:08:50 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jakub Kicinski X-Patchwork-Id: 861931 X-Patchwork-Delegate: dsahern@gmail.com Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=netronome-com.20150623.gappssmtp.com header.i=@netronome-com.20150623.gappssmtp.com header.b="hq1QIGzN"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3zLmB63j3dz9s7n for ; Wed, 17 Jan 2018 10:09:02 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751211AbeAPXI7 (ORCPT ); Tue, 16 Jan 2018 18:08:59 -0500 Received: from mail-pl0-f66.google.com ([209.85.160.66]:40782 "EHLO mail-pl0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750750AbeAPXI6 (ORCPT ); Tue, 16 Jan 2018 18:08:58 -0500 Received: by mail-pl0-f66.google.com with SMTP id g18so1706763plo.7 for ; Tue, 16 Jan 2018 15:08:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netronome-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id; bh=8gMRYrL8eiErJdrvnqef/7wGCQaSxBznbeY9ajanzx4=; b=hq1QIGzN3T8AH82Jz4eBCl9Hn338zdeTvp/O2rJiWKagjShvf0RPxV8TgtTYLneXe9 uM+jeboC9rpWNS96RXgzTl8QipeC63OW9lLv5Fn9w8krV5ddfQ49Rb53pFaaLXeEHeGu x1m2cXvOfw2oXeRj2CrsM6sKRg+U0QONJYm7QklugkU8Tm31VCziBr9pGAmkeKg5gwke Ky1rWRSyqczuFSxtKHIJyz6MMO7RtYOprG0kDYqPmxJmUUBPVuQphKUPmLNbW19DhA40 gKZQ4CvWsD7i5Zy1qXe8TdJUFnEvFgUKGXSLacZt5QamOcUvTvC1iQzmFGQoZJjzRKAB MDJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=8gMRYrL8eiErJdrvnqef/7wGCQaSxBznbeY9ajanzx4=; b=U8HGOkT/eln3hliCpNYQIWDePDC4R6P5KfMX6BuNn4AS5i/gkqcvDyg/wHLUe1+BvM 9VUqK6jE/A8r6LBHc/TADxqN3cfDiuCyWm1hfjk/meEKq+voz8zYLHnclG4SkQcpjiyp XBpsVrCbBP8ppxF3zaxxMs1xBaC+yJ860LsD32RofyRHiVq3jZdu9YHuWvfQHhu2bC6s NEmimyyK5Lgsf1Ojitd5oxzh/o1dMRS+uXFoVac+6Rmyhu5P50fL2hiUdJcMJpmJSac5 jhHnsbqKlhRaSbXEpqA8gkO7+YJ8qyqLg/uETke20vMTWIl1FowzHPM9nhv4XqYyYyKu gMtg== X-Gm-Message-State: AKwxytefNH2UxzX4lu5XIfhmiSdOmDFEqOfszEaHWj5oPujf2UJV0+40 TpbuET6IOc21kOX/o9dz1Hj6Ww== X-Google-Smtp-Source: ACJfBovbet7i3MlQMQ8rnNyPbGGd8Bf/CdUrycJlO1TrJfwyUYb2UAaXLl/riyVS4uePXEcrIZhMrw== X-Received: by 10.84.232.9 with SMTP id h9mr27567873plk.46.1516144138285; Tue, 16 Jan 2018 15:08:58 -0800 (PST) Received: from jkicinski-Precision-T1700.netronome.com ([75.53.12.129]) by smtp.gmail.com with ESMTPSA id k9sm4265096pgo.33.2018.01.16.15.08.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 16 Jan 2018 15:08:57 -0800 (PST) From: Jakub Kicinski To: dsahern@gmail.com, stephen@networkplumber.org Cc: netdev@vger.kernel.org, oss-drivers@netronome.com, Jakub Kicinski Subject: [PATCH iproute2-next] tc: red: allow setting th_min and th_max to the same value Date: Tue, 16 Jan 2018 15:08:50 -0800 Message-Id: <20180116230850.25802-1-jakub.kicinski@netronome.com> X-Mailer: git-send-email 2.15.1 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Setting th_min and th_max to the same value may be useful for DCTCP deployments. The original DCTCP paper describes it as a simplest way of achieving simple ECN threshold marking. Indeed, there doesn't seem to be any simpler qdisc in Linux which would allow such a setup today. Signed-off-by: Jakub Kicinski Reviewed-by: Dirk van der Merwe --- Or should I go ahead and add a DCTCP qdisc? :) tc/tc_red.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/tc/tc_red.c b/tc/tc_red.c index 1f82ef1aec65..178fe088f732 100644 --- a/tc/tc_red.c +++ b/tc/tc_red.c @@ -30,7 +30,9 @@ int tc_red_eval_P(unsigned int qmin, unsigned int qmax, double prob) { int i = qmax - qmin; - if (i <= 0) + if (!i) + return 0; + if (i < 0) return -1; prob /= i;