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[35.204.162.40]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9910285a85sm62300966b.39.2024.10.03.02.52.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Oct 2024 02:52:13 -0700 (PDT) Date: Thu, 3 Oct 2024 09:52:09 +0000 From: Quentin Perret To: Vincent Guittot Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, lukasz.luba@arm.com, rafael.j.wysocki@intel.com, linux-kernel@vger.kernel.org, qyousef@layalina.io, hongyan.xia2@arm.com Subject: Re: [RFC PATCH 4/5] sched/fair: Use EAS also when overutilized Message-ID: References: <20240830130309.2141697-1-vincent.guittot@linaro.org> <20240830130309.2141697-5-vincent.guittot@linaro.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thursday 03 Oct 2024 at 10:57:55 (+0200), Vincent Guittot wrote: > The current pelt algorithm track actual cpu utilization and can go > above cpu capacity (but not above 1024) so a task utilization can > become bigger than a little cpu capacity Right, the time invariance thing. So yes, I still think that a mix of co-scheduling and task migrations (which is likely common in the overcommitted state) will cause some CPUs to appear lightly utilized at least transiently, hence tricking feec() into thinking it can help when it really can't. > As replied to Lukasz, if you want to discard utilization of a trask > you need to check the previous cpu Please help me out here because I'm still not quite sure what we're talking about. Could you please expand a bit? Thanks, Quentin