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Wed, 25 Oct 2023 17:56:33 -0400 (EDT) Message-ID: Date: Wed, 25 Oct 2023 17:56:48 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [POC][RFC][PATCH] sched: Extended Scheduler Time Slice Content-Language: en-US To: Steven Rostedt Cc: Mateusz Guzik , Peter Zijlstra , 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 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> <0d95385f-1be1-4dcf-93cb-8c5df3bc9d0c@efficios.com> <20231025151951.5f1a9ab1@gandalf.local.home> From: Mathieu Desnoyers In-Reply-To: <20231025151951.5f1a9ab1@gandalf.local.home> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 0A8B880008 X-Stat-Signature: izxdz5pbmbtj43yzh4wsd6afp87g3g3b X-Rspam-User: X-HE-Tag: 1698270994-62207 X-HE-Meta: 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 i+hvfVkT NaRzgs8St81WbbCikl5Jnf4Ium6Ypuont50JBZS1z7nVINE9CqdXFfUkUfX0R+pYqEKC4Y361Y6Nzx6bZEJN7Nja3Z2/OWnoFvGXTT4NgyKe73c4JOjvYtmkcz+tpQx6gsDkbZdXs4b7AEWIh0fREsZ+GtESb/+h2sLTnc8EDPlxrcDieyQeW1GekS6cTWtm1bMhCprNQqPcshbM4vBm9dS7VrCouhmOY7+cOs039tJXCz0mvw8XuYhK7ly8d4qC/G1FrtuhsDYYWEkJveCoHuh814UzyXoTONv8EZlSRhAznUA9AazODir+udJ26SvCY1gOc 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 2023-10-25 15:19, Steven Rostedt wrote: > On Wed, 25 Oct 2023 14:49:44 -0400 > Mathieu Desnoyers wrote: > >>> >>> No, I wouldn't say it's the same as priority inheritance, which is to help >>> with determinism and not performance. PI adds overhead but removes >>> unbounded latency. On average, a non PI mutex is faster than PI mutex, but >>> can suffer from unbounded priority inversion. >> >> AFAIU, this is because PI mutex as implemented by sys futex only boosts the >> priority of the lock owner. In my proposal here the owner would be able to >> borrow scheduler slices from the waiters as well. > > I would be worried that that could cause even more scheduling disruption. > Now we are taking time slices from other CPUs to run the current one? > AFAIU, as we look at the time slices of the waiting tasks, those have meaning in the context of the runqueue they are currently attached to. We first consume time slices from tasks sharing the same runqueue as the owner task. Else, I guess we'd need to migrate the owner task to the runqueue where the time slice is available so we can use it (but only if migration of the owner task is allowed to that target cpu). Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com