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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01555C25B67 for ; Thu, 26 Oct 2023 16:32:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231584AbjJZQcK (ORCPT ); Thu, 26 Oct 2023 12:32:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229815AbjJZQcH (ORCPT ); Thu, 26 Oct 2023 12:32:07 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EEE8718A for ; Thu, 26 Oct 2023 09:32:05 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 36AB0C433C7; Thu, 26 Oct 2023 16:31:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1698337925; bh=mwOuEWH5+kQn0ZBjzsAnPRyYaTf4kTB3yErog2f8nnk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ardJItnQr+bpEXzfybRI8oLpMn09c6VJ5rc3lWM7jRXcltZIdHuj5WaDQ9pDlXvol AwyMZSVYqbpwh9m7EMtfQHuVxQUQyvKaIXUIq2OKaqyrfP+12DzqvAuk0tIUrDY34g K+UTIKYePblDV5zZ5u20q+nhswtzfBXUGmvMKq3eHckDOozvmkVi4ZtlMj9NIOdWK+ szQD9ZbVVh48pUgKT5nNWDYCWs7zyhPV7PDtpNLbDOw5K/7yuizJxPoN0L9cutuUWw VuhSn1RsL47kk3SudhXOE7UK7558E6fCkObhiRasVCbqoZV/ukiZ/Ir+xjPbZbldj0 P5aXco3Z1R/BQ== Message-ID: <82b0104f-1f05-44b0-9e95-57beecd541c8@kernel.org> Date: Thu, 26 Oct 2023 18:31:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [POC][RFC][PATCH] sched: Extended Scheduler Time Slice To: Steven Rostedt , 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 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> <20231026114927.46145fe6@gandalf.local.home> Content-Language: en-US, pt-BR, it-IT From: Daniel Bristot de Oliveira In-Reply-To: <20231026114927.46145fe6@gandalf.local.home> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/26/23 17:49, Steven Rostedt wrote: > 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. terminologies, terminologies.... those academic people :-) I think that this can also be seen as an extension of the non-preemptive mode to the user space, but... not entirely, it is a ceiling to the [ higher than fair/lower than RT ] prior? and it is not global. It is partitioned: once the section starts, it stays there, being preempted by RT/DL? [ trying to understand the implications of it ] > > This is why I do not want to associate this as another form of PI or > ceiling. > > -- Steve