From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0FADBC388F3 for ; Tue, 1 Oct 2019 10:52:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ACA392133F for ; Tue, 1 Oct 2019 10:52:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=nbd.name header.i=@nbd.name header.b="Q6uUxIAP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731252AbfJAKwQ (ORCPT ); Tue, 1 Oct 2019 06:52:16 -0400 Received: from nbd.name ([46.4.11.11]:55780 "EHLO nbd.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726885AbfJAKwP (ORCPT ); Tue, 1 Oct 2019 06:52:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=nbd.name; s=20160729; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:To:Subject:Sender:Reply-To:Cc: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=Ca5yI2RNFSqrsK9sm6nitHIALj8F0DAqbPKRja6JU9A=; b=Q6uUxIAPqJmNTT/yz+3L64E/30 pRIJjan1QAiTKhYc3UvU0gH9il5+qwA75MpRQJG2qSTpnTGSCeOkakFbNTYUz0t8ckypF3QoYiELI 7zM9+RnJB+SufP9T3E/zQcIiijHKy9UTwya0Tb6o+237L3S1WAMWs3Q6lUZHzyKyylRk=; Received: from p5b20652d.dip0.t-ipconnect.de ([91.32.101.45] helo=nf.local) by ds12 with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.89) (envelope-from ) id 1iFFlN-0007nt-Qq; Tue, 01 Oct 2019 12:52:13 +0200 Subject: Re: [PATCH 2/2] mac80211: minstrel_ht: replace rate stats ewma with a better moving average To: Johannes Berg , linux-wireless@vger.kernel.org References: <20190929154646.90901-1-nbd@nbd.name> <20190929154646.90901-2-nbd@nbd.name> From: Felix Fietkau Autocrypt: addr=nbd@nbd.name; prefer-encrypt=mutual; keydata= xsDiBEah5CcRBADIY7pu4LIv3jBlyQ/2u87iIZGe6f0f8pyB4UjzfJNXhJb8JylYYRzIOSxh ExKsdLCnJqsG1PY1mqTtoG8sONpwsHr2oJ4itjcGHfn5NJSUGTbtbbxLro13tHkGFCoCr4Z5 Pv+XRgiANSpYlIigiMbOkide6wbggQK32tC20QxUIwCg4k6dtV/4kwEeiOUfErq00TVqIiEE AKcUi4taOuh/PQWx/Ujjl/P1LfJXqLKRPa8PwD4j2yjoc9l+7LptSxJThL9KSu6gtXQjcoR2 vCK0OeYJhgO4kYMI78h1TSaxmtImEAnjFPYJYVsxrhay92jisYc7z5R/76AaELfF6RCjjGeP wdalulG+erWju710Bif7E1yjYVWeA/9Wd1lsOmx6uwwYgNqoFtcAunDaMKi9xVQW18FsUusM TdRvTZLBpoUAy+MajAL+R73TwLq3LnKpIcCwftyQXK5pEDKq57OhxJVv1Q8XkA9Dn1SBOjNB l25vJDFAT9ntp9THeDD2fv15yk4EKpWhu4H00/YX8KkhFsrtUs69+vZQwc0cRmVsaXggRmll dGthdSA8bmJkQG5iZC5uYW1lPsJgBBMRAgAgBQJGoeQnAhsjBgsJCAcDAgQVAggDBBYCAwEC HgECF4AACgkQ130UHQKnbvXsvgCgjsAIIOsY7xZ8VcSm7NABpi91yTMAniMMmH7FRenEAYMa VrwYTIThkTlQzsFNBEah5FQQCACMIep/hTzgPZ9HbCTKm9xN4bZX0JjrqjFem1Nxf3MBM5vN CYGBn8F4sGIzPmLhl4xFeq3k5irVg/YvxSDbQN6NJv8o+tP6zsMeWX2JjtV0P4aDIN1pK2/w VxcicArw0VYdv2ZCarccFBgH2a6GjswqlCqVM3gNIMI8ikzenKcso8YErGGiKYeMEZLwHaxE Y7mTPuOTrWL8uWWRL5mVjhZEVvDez6em/OYvzBwbkhImrryF29e3Po2cfY2n7EKjjr3/141K DHBBdgXlPNfDwROnA5ugjjEBjwkwBQqPpDA7AYPvpHh5vLbZnVGu5CwG7NAsrb2isRmjYoqk wu++3117AAMFB/9S0Sj7qFFQcD4laADVsabTpNNpaV4wAgVTRHKV/kC9luItzwDnUcsZUPdQ f3MueRJ3jIHU0UmRBG3uQftqbZJj3ikhnfvyLmkCNe+/hXhPu9sGvXyi2D4vszICvc1KL4RD aLSrOsROx22eZ26KqcW4ny7+va2FnvjsZgI8h4sDmaLzKczVRIiLITiMpLFEU/VoSv0m1F4B FtRgoiyjFzigWG0MsTdAN6FJzGh4mWWGIlE7o5JraNhnTd+yTUIPtw3ym6l8P+gbvfoZida0 TspgwBWLnXQvP5EDvlZnNaKa/3oBes6z0QdaSOwZCRA3QSLHBwtgUsrT6RxRSweLrcabwkkE GBECAAkFAkah5FQCGwwACgkQ130UHQKnbvW2GgCfTKx80VvCR/PvsUlrvdOLsIgeRGAAn1ee RjMaxwtSdaCKMw3j33ZbsWS4 Message-ID: <017c1a59-edf2-0a1a-aa8c-3c32e57d6cd0@nbd.name> Date: Tue, 1 Oct 2019 12:52:13 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On 2019-10-01 12:17, Johannes Berg wrote: > >> This change replaces the EWMA implementation with a moving average that's >> designed to significantly reduce lag while keeping a bigger window size >> by being better at filtering out noise. >> >> It is only slightly more expensive than the simple EWMA and still avoids >> divisions in its calculation. >> >> The algorithm is adapted from an implementation intended for a completely >> different field (stock market trading), where the tradeoff of lag vs >> noise filtering is equally important. It is based on the "smoothing filter" >> from http://www.stockspotter.com/files/PredictiveIndicators.pdf. >> >> I have adapted it to fixed-point math with some constants so that it uses >> only addition, bit shifts and multiplication >> > > Would it be worth pulling that out into similar helpers to EWMA in > average.h, perhaps even in the same file? > > You need to keep a bit more state, but essentially the same API should > work since EWMA already declares the "struct ewma_something" once you > use the DECLARE_EWMA(). Might be useful, yes. The main issue here is that the period / window size has to be hardcoded through the coefficient values, unless we find a way to do floating point math, including exp() and cos() at compile time, including conversion to fixed point. - Felix