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Tue, 14 Apr 2026 17:17:29 -0700 (PDT) Date: Wed, 15 Apr 2026 01:17:28 +0100 From: Qais Yousef 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, kprateek.nayak@amd.com, linux-kernel@vger.kernel.org Subject: Re: [patch] sched/fair: delayed dequeued entity bias wakeup preempt short Message-ID: <20260415001728.2rt7ewnkshbcgjde@airbuntu> References: <20260410144808.2943278-1-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=utf-8 Content-Disposition: inline In-Reply-To: <20260410144808.2943278-1-vincent.guittot@linaro.org> On 04/10/26 16:48, Vincent Guittot wrote: > When checking if a shorter slice entity can preempt curr, we compare it with > the next entity to be picked but delayed dequeue entities can screw the > decision whereas they will be dequeued when picking next entity. > Dequeue them while checking for preemption as they will be dequeued anyway > when picking next entity. > > Test on snapdragon rb5: > hackbench -T -p -l 16000000 -g 2 1> /dev/null & > cyclictest -t 1 -i 2777 -D 63 --policy=fair --mlock -h 20000 -q > > tip/sched/core tip/sched/core +this patch > cyclictest slice (ms) (default)2.8 8 8 > hackbench slice (ms) (default)2.8 20 20 > Total Samples | 22559 22595 22683 > Average (us) | 157 64( 59%) 59( 8%) > Median (P50) (us) | 57 57( 0%) 58(- 2%) > 90th Percentile (us) | 64 60( 6%) 60( 0%) > 99th Percentile (us) | 2407 67( 97%) 67( 0%) > 99.9th Percentile (us) | 3400 2288( 33%) 727( 68%) > Maximum (us) | 5037 9252(-84%) 7461( 19%) Max is still high. The clear buddies patch reduces it though, I assume the combined effect of the two deals with that?