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[2620:137:e000::3:7]) by mx.google.com with ESMTPS id q129-20020a0de787000000b0059eae2bc317si14936772ywe.217.2023.10.26.08.49.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Oct 2023 08:49:38 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by snail.vger.email (Postfix) with ESMTP id 24EBE8217ED3; Thu, 26 Oct 2023 08:49:37 -0700 (PDT) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.10 at snail.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345480AbjJZPtg (ORCPT + 99 others); Thu, 26 Oct 2023 11:49:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345476AbjJZPte (ORCPT ); Thu, 26 Oct 2023 11:49:34 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C3F1196 for ; Thu, 26 Oct 2023 08:49:32 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E632CC433C8; Thu, 26 Oct 2023 15:49:28 +0000 (UTC) Date: Thu, 26 Oct 2023 11:49:27 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: Mateusz Guzik , Mathieu Desnoyers , LKML , Thomas Gleixner , Ankur Arora , Linus Torvalds , linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, willy@infradead.org, mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, jgross@suse.com, andrew.cooper3@citrix.com, Joel Fernandes , Youssef Esmat , Vineeth Pillai , Suleiman Souhlal , Ingo Molnar , Daniel Bristot de Oliveira Subject: Re: [POC][RFC][PATCH] sched: Extended Scheduler Time Slice Message-ID: <20231026114927.46145fe6@gandalf.local.home> In-Reply-To: <20231026094035.213e3744@gandalf.local.home> References: <20231025054219.1acaa3dd@gandalf.local.home> <20231025102952.GG37471@noisy.programming.kicks-ass.net> <20231025085434.35d5f9e0@gandalf.local.home> <20231025135545.GG31201@noisy.programming.kicks-ass.net> <20231025103105.5ec64b89@gandalf.local.home> <884e4603-4d29-41ae-8715-a070c43482c4@efficios.com> <20231025162435.ibhdktcshhzltr3r@f> <20231025131731.48461873@gandalf.local.home> <20231026085414.GL31411@noisy.programming.kicks-ass.net> <20231026094035.213e3744@gandalf.local.home> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-4.0 required=5.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Thu, 26 Oct 2023 08:49:37 -0700 (PDT) On Thu, 26 Oct 2023 09:40:35 -0400 Steven Rostedt wrote: > Hence, why I don't want to associate this with priority inheritance. The > time constraint is a fundamental difference. Let me add one more fundamental difference here that makes this solution different than priority inheritance and ceiling. PI and ceiling define the correctness of the system. If you get it wrong or remove it, the system can be incorrect and lock up, fail deadlines, etc. There's hundreds, if not thousands of papers mathematically defining the correctness of PI, ceiling and proxy execution, as they are complex and critical for the system to behave properly. This feature is a performance boost only, and has nothing to do with "correctness". That's because it has that arbitrary time where it can run a little more. It's more like the difference between having something in cache and a cache miss. This would cause many academics to quit and find a job in sales if they had to prove the correctness of an algorithm that gave you a boost for some random amount of time. The idea here is to help with performance. If it exists, great, your application will likely perform better. If it doesn't, no big deal, you may just have to deal with longer wait times on critical sections. This is why I do not want to associate this as another form of PI or ceiling. -- Steve