Received: by 2002:a05:6a10:d5a5:0:0:0:0 with SMTP id gn37csp4460553pxb; Tue, 5 Oct 2021 03:40:33 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzUNvBkcpH+lR3bXdWclZHspiMVFyxGbgwsy9A1cTFNbjRbIEdcU6aZRfLkD7xqkacthj5h X-Received: by 2002:a17:902:b20e:b029:12b:fd6f:44c3 with SMTP id t14-20020a170902b20eb029012bfd6f44c3mr4628364plr.36.1633430432785; Tue, 05 Oct 2021 03:40:32 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1633430432; cv=none; d=google.com; s=arc-20160816; b=P+b61ja1eVnGqx0lyXd768AaEzK7yUHzV44fpylU0V0tTVQQiqkHbpf/4zh4hNW/lE zKyBPh8/ZIX8SJ3h3QbmxgT7nQ5jhdurqy27JbBXwaP8wAUT6ph2cchz8IR2tN7vjFRt 6HSWG7cieJrd7Wiar6IWGJ+DILZMj/y9treLYIqs0qwNI4pUDLD+wwFj5A3qbNH6+TfC LYjRs0aAufCRjgNkXEesega3QyhqKl4YwcHSvF3qgq56aEdVLiVxo4+78XFKNF1kREEZ 7Ics2R9l8jekqPwCrjnsdAyAxcfBri/ZJihiWLi4Q8NCOpiWr7rBgg5Hgz2P8otjmSl5 GdMQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:in-reply-to:content-disposition:mime-version :references:message-id:subject:cc:to:from:date:dkim-signature; bh=t9uwTcpRAkuxtDd8N8WgM5ZhUGx0canA4I39+YkmP/0=; b=0SPRtoUxdThSm4wwi54v0l7wJ1tie2iRezNTH+PMenpeBXXNSAUJNcAUySqETGfjxJ oRplWToF0gIB2VVZEx5VLDzH4as2jyO8+py20y/zEghT7/gQCf7WQG/IfntpsCZj3at4 7LUTCygqYKJ11s/DVBCgP27aQrWA3JRSS+O6f/z//s7Wmht3VTcMgWT+mziZmid5X5wr iP+YjxVzjTsDXfjtNuH5x/WtxkEGVZcnHIqHp6XbvYbfdFOM1wLr7E7cjnnpPkd/Mpvd dMYfygEU29kGWm2P5hXekXWhbvXAQG36luqtwsFtvn2g8mQjy4xxFZPWm4oi1+Fh6ScR CyHQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=casper.20170209 header.b=kTqPsDsF; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id il18si902013pjb.53.2021.10.05.03.40.19; Tue, 05 Oct 2021 03:40:32 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=casper.20170209 header.b=kTqPsDsF; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233576AbhJEKkN (ORCPT + 99 others); Tue, 5 Oct 2021 06:40:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46966 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233290AbhJEKkM (ORCPT ); Tue, 5 Oct 2021 06:40:12 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0C03BC06161C for ; Tue, 5 Oct 2021 03:38:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=t9uwTcpRAkuxtDd8N8WgM5ZhUGx0canA4I39+YkmP/0=; b=kTqPsDsFhZu+P+KsHET12MMsJb MJ2cUoF7pzVQQUry2j8Ms7vabgpWxJLV38z4/yS0SmuvKY+Osxx3Dz+WFy+lu0BmCV92F5OUvcE8R tYTZEhhLDp0fIyrreBbxljABrYySML4A6htwIQF5J/Usq9vBCs3hgiLKDkuFPvmld5kWJXm6AgB85 0m3gsWE3i/suIaONkRdYdH8W7W7tbdcp3clcJgrWVvPQWqA0kNpi+KB5uEaJ1kKcqZflMdvZLL42A rSM88GmJ5vSsMeP8ZeGZ+Y7w8MDl/Q9uzlA7HALYKQd2mob2E1jZDj1bhxMmPhWUM3A811ATl2Nys wSL3/LAA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mXho7-000EXp-Mq; Tue, 05 Oct 2021 10:36:31 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id E879C30003C; Tue, 5 Oct 2021 12:36:22 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A3A682038E20D; Tue, 5 Oct 2021 12:36:22 +0200 (CEST) Date: Tue, 5 Oct 2021 12:36:22 +0200 From: Peter Zijlstra To: Phil Auld Cc: Vincent Guittot , Mike Galbraith , Mel Gorman , Ingo Molnar , Valentin Schneider , Aubrey Li , Barry Song , Srikar Dronamraju , LKML Subject: Re: [PATCH 2/2] sched/fair: Scale wakeup granularity relative to nr_running Message-ID: References: <20210922132002.GX3959@techsingularity.net> <20210922150457.GA3959@techsingularity.net> <20210922173853.GB3959@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 23, 2021 at 08:24:03AM -0400, Phil Auld wrote: > It's capped at 8 cpus, which is pretty easy to reach these days, so the > values don't get too large. That scaling is almost a no-op these days. https://lkml.kernel.org/r/YVwdrh5pg0zSv2/b@hirez.programming.kicks-ass.net Ooh, hey, we already fixed that :-) So the reasoning there is that if the values get too big, interactiviy get *really* bad, but if you go from say 1 to 4 CPUs, interactivity can improve due to being able to run on other CPUs. At 8 CPUs we end up at 6ms*4=24ms, which is already pretty terrible.