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=-2.0 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 74707C3A5A5 for ; Thu, 5 Sep 2019 11:30:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 45DBF2070C for ; Thu, 5 Sep 2019 11:30:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="kST9Skas" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388460AbfIELaN (ORCPT ); Thu, 5 Sep 2019 07:30:13 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:41174 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725921AbfIELaN (ORCPT ); Thu, 5 Sep 2019 07:30:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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: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=3Z6GGxQtw6kGZ90rRUAsKRrfp8SLjkfWxpfQA5HECNQ=; b=kST9SkasBfRkvNAy3jwGSEqAx L5hV5CM0qO23/QJaoYSxUxpqMwhdekI9KbVAvA3Q3J+LOMm6kjJf0t+4RQP0yxfp/J1v1Irv7p20L JU15zzpLAoEiiP/7USl6oOLXMdnYwFAz2UsKeP/b8pvcQOW8izmbSYkTbk4DXe3sel3WoDhE8R0Of 9KXIolpsXvHQjfhOeCT9kvsEJEqaN8rMbZyADLjSJ2I2tlfzZ7qfgLEnGSG/HmzjHCs0aTguKxmOl dR7dQMuSw88uIJHMEOx2pLmtfHbKcN9xgJfpxa/gdCymyCSUGNtJkyr2sXlABmPKFWZghNOT5gcpp jIRvB213A==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1i5pxk-0006sr-BV; Thu, 05 Sep 2019 11:30:04 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 549A4305E47; Thu, 5 Sep 2019 13:29:25 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4B6E829CBE121; Thu, 5 Sep 2019 13:30:02 +0200 (CEST) Date: Thu, 5 Sep 2019 13:30:02 +0200 From: Peter Zijlstra To: Qais Yousef Cc: Patrick Bellasi , Subhra Mazumdar , linux-kernel@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de, steven.sistare@oracle.com, dhaval.giani@oracle.com, daniel.lezcano@linaro.org, vincent.guittot@linaro.org, viresh.kumar@linaro.org, tim.c.chen@linux.intel.com, mgorman@techsingularity.net, parth@linux.ibm.com Subject: Re: [RFC PATCH 1/9] sched,cgroup: Add interface for latency-nice Message-ID: <20190905113002.GK2349@hirez.programming.kicks-ass.net> References: <20190830174944.21741-1-subhra.mazumdar@oracle.com> <20190830174944.21741-2-subhra.mazumdar@oracle.com> <20190905083127.GA2332@hirez.programming.kicks-ass.net> <87r24v2i14.fsf@arm.com> <20190905104616.GD2332@hirez.programming.kicks-ass.net> <20190905111346.2w6kuqrdvaqvgilu@e107158-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190905111346.2w6kuqrdvaqvgilu@e107158-lin.cambridge.arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 05, 2019 at 12:13:47PM +0100, Qais Yousef wrote: > On 09/05/19 12:46, Peter Zijlstra wrote: > > This is important because we want to be able to bias towards less > > importance to (tail) latency as well as more importantance to (tail) > > latency. > > > > Specifically, Oracle wants to sacrifice (some) latency for throughput. > > Facebook OTOH seems to want to sacrifice (some) throughput for latency. > > Another use case I'm considering is using latency-nice to prefer an idle CPU if > latency-nice is set otherwise go for the most energy efficient CPU. > > Ie: sacrifice (some) energy for latency. > > The way I see interpreting latency-nice here as a binary switch. But > maybe we can use the range to select what (some) energy to sacrifice > mean here. Hmmm. It cannot be binary, per definition is must be ternary, that is, <0, ==0 and >0 (or middle value if you're of that persuasion). In your case, I'm thinking you mean >0, we want to lower the latency. Anyway; there were a number of things mentioned at OSPM that we could tie into this thing and finding sensible mappings is going to be a bit of trial and error I suppose. But as patrick said; we're very much exporting a BIAS knob, not a set of behaviours.