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([2a01:e0a:f:6020:d339:889f:6b52:541d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d63de3499sm7047744f8f.1.2026.04.10.06.23.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Apr 2026 06:23:26 -0700 (PDT) From: Vincent Guittot To: 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, qyousef@layalina.io Cc: Vincent Guittot Subject: [PATCH] sched/eevdf: clear buddies for preempt_short Date: Fri, 10 Apr 2026 15:23:21 +0200 Message-ID: <20260410132321.2897789-1-vincent.guittot@linaro.org> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" next buddy should not prevent shorter slice preemption. Don't take buddy into account when checking if shorter slice entity can preempt and clear it if the entity with a shorter slice can preempt current. Test on snapdragon rb5: hackbench -T -p -l 16000000 -g 2 1> /dev/null & hackbench runs in cgroup /test-A cyclictest -t 1 -i 2777 -D 63 --policy=3Dfair --mlock -h 20000 -q cyclictest runs in cgroup /test-B 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 | 22679 22595 22686 Average (us) | 84 94(-12%) 59( 37%) Median (P50) (us) | 56 56( 0%) 56( 0%) 90th Percentile (us) | 64 65(- 2%) 63( 3%) 99th Percentile (us) | 1047 1273(-22%) 74( 94%) 99.9th Percentile (us) | 2431 4751(-95%) 663( 86%) Maximum (us) | 4694 8655(-84%) 3934( 55%) Signed-off-by: Vincent Guittot --- kernel/sched/fair.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 597ce5b718d2..0c6b9541d864 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1116,7 +1116,7 @@ static struct sched_entity *__pick_eevdf(struct cfs_r= q *cfs_rq, bool protect) /* * Picking the ->next buddy will affect latency but not fairness. */ - if (sched_feat(PICK_BUDDY) && + if (sched_feat(PICK_BUDDY) && protect && cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next)) { /* ->next will never be delayed */ WARN_ON_ONCE(cfs_rq->next->sched_delayed); @@ -9110,8 +9110,10 @@ static void wakeup_preempt_fair(struct rq *rq, struc= t task_struct *p, int wake_f return; =20 preempt: - if (preempt_action =3D=3D PREEMPT_WAKEUP_SHORT) + if (preempt_action =3D=3D PREEMPT_WAKEUP_SHORT) { cancel_protect_slice(se); + clear_buddies(cfs_rq, se); + } =20 resched_curr_lazy(rq); } --=20 2.43.0