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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 3AA5DC48BE8 for ; Fri, 18 Jun 2021 08:36:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 094E36121D for ; Fri, 18 Jun 2021 08:36:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231437AbhFRIiW (ORCPT ); Fri, 18 Jun 2021 04:38:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50166 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229877AbhFRIiV (ORCPT ); Fri, 18 Jun 2021 04:38:21 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DBA14C061574 for ; Fri, 18 Jun 2021 01:36:12 -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=S/IRAbCRQfCl9L4QO1dDDFQ88Il9eqaq4QycQk5S0ss=; b=VwAjv5wBo63+YwdKB9+bI4qNO1 DJ1YJtoOtd4Q1f/9NGEF1PxIWViV6nWoaONw1/5FlGLeN73aLDdWDkIOrL0/GD/GfA+1Dklc6ltWj Zg4F9FgqEdtV4rQWmUdOZWfZWqHy88hrKxDj0J4QKQwbQ3ra7zgItdDofYGIoHJpXHns6JpmRMCYG zpLwxQ0x3knI96f1E8qVYWGQOmZeomN96tz3yshtrQQwgi6Yy8tuijvymk+DSJxAv35YfBBMl0xrM qFwBRnBGYxfTXxf/06dcxjXG3q74plfPCzx//nxL9S6gn2KqbEFc0/g8Su8CjA9HmuBREOFBjkPLh FIcfIDfA==; 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 1lu9x4-00A4JB-N4; Fri, 18 Jun 2021 08:34:28 +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 D4AD0300268; Fri, 18 Jun 2021 10:34:09 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B0DD5200F8627; Fri, 18 Jun 2021 10:34:09 +0200 (CEST) Date: Fri, 18 Jun 2021 10:34:09 +0200 From: Peter Zijlstra To: "Joel Fernandes (Google)" Cc: linux-kernel@vger.kernel.org, Dietmar Eggemann , Ingo Molnar , Josh Don , Juri Lelli , Luis Chamberlain , Mel Gorman , Qais Yousef , "Rafael J. Wysocki" , Vincent Guittot , Viresh Kumar , rostedt@goodmis.org Subject: Re: [RFC] schedutil: Fix iowait boost issues for slow I/O devices Message-ID: References: <20210618040639.3113489-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210618040639.3113489-1-joel@joelfernandes.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Aside from everything else: On Fri, Jun 18, 2021 at 12:06:39AM -0400, Joel Fernandes (Google) wrote: > +unsigned int sysctl_iowait_reset_ticks = 20; > +unsigned int sysctl_iowait_apply_ticks = 10; Never expose HZ to userspace. we even have USER_HZ (no new usage please) that fixed existing problems with that. If you expose a knob, make it in sane time units and convert internally to whatever you need. That said; less is more with knobs.