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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 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 6707B14000B X-Stat-Signature: ubjofcgqw6kjxjcd15md9u7t185uzzyf X-Rspam-User: X-HE-Tag: 1698337928-297294 X-HE-Meta: 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 nHhiDy1x u/exBUy+0OHmnSK4+xnWF1aSgrqeVh4xsNYD9enFIMUFe1yojAe3T+Yejw1ujlYwaxEIQQapyPDskrSopvKpJXJ+w2j6zwAcjF6Fcr6q2+2uz0cpfVZrVQyN+wsDWnl9fHQmHWNgCD0gqpf94357GolLnLz3K6Wud7FJGhS7bPqSbn7cBdlOKC5Di5En3+YUvrododQDDdEUHowV2uWSGUQU2LGPKWDsodnor4Qc/OLmJTmLaP6l57oqlkk2AHIk7LHYZqh4E2ovaQXg+hTWCnKKLCSjVmjVvCfPS X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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