From patchwork Thu Feb 28 12:36:54 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Leslie Monis X-Patchwork-Id: 1049435 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@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; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="ATgPEIF8"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 449Bt8273lz9s1B for ; Thu, 28 Feb 2019 23:38:24 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731643AbfB1MiW (ORCPT ); Thu, 28 Feb 2019 07:38:22 -0500 Received: from mail-pf1-f193.google.com ([209.85.210.193]:45624 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730931AbfB1MiW (ORCPT ); Thu, 28 Feb 2019 07:38:22 -0500 Received: by mail-pf1-f193.google.com with SMTP id v21so9662468pfm.12 for ; Thu, 28 Feb 2019 04:38:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id; bh=2wg1eG2u82x3gKNDULLmM+y3RjkqZYYE5LF01PvFSCQ=; b=ATgPEIF8cQeHPxZaFzIzrareui4L6cz3N336i7daHEmMsDKQoJZ4JM9gfUhGvFRqc3 9xBGl2UuJy2mWVhOeEXC/yBySs9odaLFRwF4PqvMg/yezPENjzN9kDJRY3azpLBffMMe ER/YZ7u5WZySA51UAwYfoC/9Ru+ZMWn9uyiDxSc6HfXJJGX6dmqbh5Bz5eVkFYAExwiP U+Zi2a5wEUNQ4+cASp27lrFAmLESs0m0dH2VCna0xJ/UBzn+YWE3VmeL+SFhf7HFkr2N ZCpI+uI/SbsJxaPMCXCw2XQKX2jSGnr8NMO9NXaN8+TG3ZS6qu+ftNjY9qoxIEjZspzv W5cQ== 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=2wg1eG2u82x3gKNDULLmM+y3RjkqZYYE5LF01PvFSCQ=; b=a7Rm+ZYB/S4Ow0H+RNYxbqjKwuEOD2IsqWU/SaFDkdrn+D8fNVaawFl+mo6Ve5Sv9C M2XNhFPzgJnhuT0/VmscpcN47fWt9rllhSK90BmbwUPwy4MLso8cYC6XVZXFXHhMSYmE 52Qm7QQ4+VxeZGA7iwLGUC60ajfddycVpDwSqiXLSOtdzQHnYytjyuAOyvV1HGCCaAqR JLFitoEHUdnoltfFX0+xuLlhnJEdRqa5xKKfZAm3+oF2scSwJncZREZ0ey9oeJFtYIdA Q3NGS+CzN5qO+XHDyngLcNLMDb+esE3PgtS7fv3KQAEbFJgQ20V4rlQYVC5ZorkaXFci qVnA== X-Gm-Message-State: AHQUAuaiGYUqYOK5xWOw15zkdDnciCPyzlMdANw9JoB595z9i+gdOyi2 hRHPLhcR5olyK2LikhAc1fw= X-Google-Smtp-Source: AHgI3IberpRG9mFMZ9mT+Y3/ZvTfztZd6XpyZIMpRh4lg8G06r1jUMnhFMLv0+TyMGH/wwbfrr0jhQ== X-Received: by 2002:a63:c449:: with SMTP id m9mr8231643pgg.41.1551357501850; Thu, 28 Feb 2019 04:38:21 -0800 (PST) Received: from localhost.localdomain ([223.186.159.144]) by smtp.gmail.com with ESMTPSA id x23sm47297709pfe.0.2019.02.28.04.38.18 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Feb 2019 04:38:21 -0800 (PST) From: Leslie Monis To: davem@davemloft.net Cc: netdev@vger.kernel.org, tahiliani@nitk.edu.in, dave.taht@gmail.com, Leslie Monis Subject: [PATCH net-next] net: sched: pie: avoid slow division in drop probability decay Date: Thu, 28 Feb 2019 18:06:54 +0530 Message-Id: <20190228123654.26330-1-lesliemonis@gmail.com> X-Mailer: git-send-email 2.17.1 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org As per RFC 8033, it is sufficient for the drop probability decay factor to have a value of (1 - 1/64) instead of 98%. This avoids the need to do slow division. Suggested-by: David Laight Signed-off-by: Leslie Monis --- net/sched/sch_pie.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c index f93cfe034c72..1cc0c7b74aa3 100644 --- a/net/sched/sch_pie.c +++ b/net/sched/sch_pie.c @@ -429,7 +429,8 @@ static void calculate_probability(struct Qdisc *sch) */ if (qdelay == 0 && qdelay_old == 0 && update_prob) - q->vars.prob = 98 * div_u64(q->vars.prob, 100); + /* Reduce drop probability to 98.4% */ + q->vars.prob -= q->vars.prob / 64u; q->vars.qdelay = qdelay; q->vars.qlen_old = qlen;