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Wed, 17 Jun 2026 17:44:09 +0000 (GMT) Received: from li-7bb28a4c-2dab-11b2-a85c-887b5c60d769.ibm.com.com (unknown [9.39.28.77]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 17 Jun 2026 17:44:08 +0000 (GMT) From: Shrikanth Hegde To: linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, yury.norov@gmail.com, kprateek.nayak@amd.com, iii@linux.ibm.com Cc: sshegde@linux.ibm.com, tglx@kernel.org, gregkh@linuxfoundation.org, pbonzini@redhat.com, seanjc@google.com, vschneid@redhat.com, huschle@linux.ibm.com, rostedt@goodmis.org, dietmar.eggemann@arm.com, mgorman@suse.de, bsegall@google.com, maddy@linux.ibm.com, srikar@linux.ibm.com, hdanton@sina.com, chleroy@kernel.org, vineeth@bitbyteword.org, frederic@kernel.org, arighi@nvidia.com, pauld@redhat.com, christian.loehle@arm.com, tj@kernel.org, tommaso.cucinotta@gmail.com, maz@kernel.org, rafael@kernel.org Subject: [PATCH v4 14/20] sched/core: Introduce a simple steal monitor Date: Wed, 17 Jun 2026 23:11:33 +0530 Message-ID: <20260617174139.155540-15-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260617174139.155540-1-sshegde@linux.ibm.com> References: <20260617174139.155540-1-sshegde@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Info: AW1haW4tMjYwNjE3MDE2NiBTYWx0ZWRfX/Yc9fs6pmX5n UQPE6LZSQ0bO5wtGAQyrrtgkuy9114R3wGEFc2+kzR2HwNXDgNlOlOfFzfPG/4hADWI7LM0vxgh GzgKm1UdsL6/02eVDmeECIeWsoAkWgo= X-Proofpoint-GUID: dbryGp5eaAjxOAUh6FWP7C7QJDjzI-nC X-Authority-Analysis: v=2.4 cv=bMgm5v+Z c=1 sm=1 tr=0 ts=6a32dcf5 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=OdSMrRaz63idaxcbYwMA:9 X-Proofpoint-ORIG-GUID: z-pB1IkLaBQFTF7d6qSFextfA1DELeo2 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjE3MDE2NiBTYWx0ZWRfXymiaiDClR9tj bYsbJLMJdpDVX/mASb5yZqzJf6CPUIsiXBWUiXzNIlO6dQPD4eAj9fxIPyMhmFviR3v2VitjLDp NMK4qi8oQQ5kxoYiSFwQvS7CJXQi3sE/vsQaeLG4Exmi/3HE1JOq6Lra7lI+8H/zEoLunY2g5EY wNab/ItNJ7Lg98Lj0pe6uWulJZYR+fIhf1IFzMb84BDD4NfpENshPJvlj3ZgwKarKVGqBUhx3QQ GGMc2bha5L87ATJau8/3tI9LBm0UlvVj0x+O/nIibSZIQcNZCJOJzo+kh6zqDmBsrPmyM17n07o gJJyhYorgDkINJSl12oaVJlw6wZNScKfgt4xWyQy5XUiuYl2bs6VlxHR7M1Y0gYO27ryF8Naiax 52OgckzJoBuuIbo1x+SMJ0oTYHYzUmYw9KluEEjSB/WCkV18rkUXaTG3UXCOA8qhiuZRcodzgK/ F9V021fDROPDae9EsDA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-17_02,2026-06-17_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 malwarescore=0 adultscore=0 spamscore=0 bulkscore=0 priorityscore=1501 phishscore=0 clxscore=1015 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606170166 Start with a simple steal monitor. It is meant to look at steal time and make the decision to reduce/increase the preferred CPUs. It has - work function to execute the steal time calculations and decision making periodically. - low and high thresholds for steal time. - sampling period to control the frequency of steal time calculations. - cache the previous decision to avoid oscillations Signed-off-by: Shrikanth Hegde --- v3->v4: - Drop tmp_mask include/linux/sched.h | 11 +++++++++++ kernel/sched/core.c | 23 +++++++++++++++++++++++ kernel/sched/sched.h | 3 +++ 3 files changed, 37 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index 5f523782ca28..ce6bc8a22eb1 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2517,4 +2517,15 @@ extern void migrate_enable(void); DEFINE_LOCK_GUARD_0(migrate, migrate_disable(), migrate_enable()) +#ifdef CONFIG_PREFERRED_CPU +struct steal_monitor_t { + struct work_struct work; + ktime_t prev_time; + u64 prev_steal; + int previous_decision; + unsigned int low_threshold; + unsigned int high_threshold; + unsigned int sampling_period_ms; +}; +#endif #endif diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 24d4abc74241..cc48632dd42d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -9138,6 +9138,8 @@ void __init sched_init(void) preempt_dynamic_init(); + sched_init_steal_monitor(); + scheduler_running = 1; } @@ -11384,4 +11386,25 @@ void sched_push_current_non_preferred_cpu(struct rq *rq) stop_one_cpu_nowait(rq->cpu, sched_non_preferred_cpu_push_stop, push_task, this_cpu_ptr(&npc_push_task_work)); } + +struct steal_monitor_t steal_mon; + +void sched_init_steal_monitor(void) +{ + INIT_WORK(&steal_mon.work, sched_steal_detection_work); + steal_mon.low_threshold = 200; /* 2% steal time */ + steal_mon.high_threshold = 500; /* 5% steal time */ + steal_mon.sampling_period_ms = 1000; /* once per second */ +} + +/* This is only a skeleton. Subsequent patches introduce more of it */ +void sched_steal_detection_work(struct work_struct *work) +{ + struct steal_monitor_t *sm = container_of(work, struct steal_monitor_t, work); + ktime_t now; + + /* Update the prev_time for next iteration*/ + now = ktime_get(); + sm->prev_time = now; +} #endif diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 9cb006c21090..984da3827f19 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -4240,8 +4240,11 @@ static inline bool task_has_preferred_cpus(struct task_struct *p) #ifdef CONFIG_PREFERRED_CPU DECLARE_STATIC_KEY_FALSE(__sched_sm_enable); +void sched_init_steal_monitor(void); +void sched_steal_detection_work(struct work_struct *work); void sched_push_current_non_preferred_cpu(struct rq *rq); #else /* !CONFIG_PREFERRED_CPU */ static inline void sched_push_current_non_preferred_cpu(struct rq *rq) { } +static inline void sched_init_steal_monitor(void) { } #endif #endif /* _KERNEL_SCHED_SCHED_H */ -- 2.47.3