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Tue, 7 Apr 2026 19:21:15 +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, tglx@linutronix.de, yury.norov@gmail.com, gregkh@linuxfoundation.org Cc: sshegde@linux.ibm.com, pbonzini@redhat.com, seanjc@google.com, kprateek.nayak@amd.com, vschneid@redhat.com, iii@linux.ibm.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, joelagnelf@nvidia.com Subject: [PATCH v2 14/17] sched/core: Compute steal values at regular intervals Date: Wed, 8 Apr 2026 00:49:47 +0530 Message-ID: <20260407191950.643549-15-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260407191950.643549-1-sshegde@linux.ibm.com> References: <20260407191950.643549-1-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-Details-Enc: AW1haW4tMjYwNDA3MDE3NSBTYWx0ZWRfX3rb7q2yx5Ymn TwpYCV5rjESTH9ns/t29kIwTNPOFJIS36aPr1q7OJvmOgx3y73SHlVlX/E6Nnpq7qB+IsPVqmZW O0C/y8UzOj6sTBVE0+7zWYSixVQJvRY26rPH+ssj+9dmp458J3cbkfpOvQk//imqmUX8nNf1cyh OwZlqeFQfzrYS6xdaOek2hGmVL9/5yxJScq3345BiqWBEcjI7Q6IMOwIeRjDZAy9YCth1yOZX+b 6c4EBL9sp+i2UiM+LfpnfjHZu/IildQ4qHXGRtQp+0xfeWl+XiGsfO16xonPl1vSr/VtpCW1qWO cjHRtZVQYnQ3ZC14evUUSjKjjT5qe/BMoT270c5B6czaWrewtrwA+SW6laWUQZwugVRlgzSivRg f5LHF6bH6I9yPVezW4xY38+iAkHQ4rtJUm8kaHnOh9ji+egGPaIztjhLIgoHge6x2f0z2JLa+Iw 9WWYf+boOJRIHZEbQaQ== X-Proofpoint-ORIG-GUID: bJyLKEFO80FAoa284lmC9SAKEi3YYXWB X-Authority-Analysis: v=2.4 cv=e9k2j6p/ c=1 sm=1 tr=0 ts=69d55935 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=5Sjc-5nkPH-zHnvugUgA:9 X-Proofpoint-GUID: IsNuVmJHzGj1_-va0W8qdX9ZcQCeuogT X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-07_04,2026-04-07_05,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 impostorscore=0 malwarescore=0 suspectscore=0 spamscore=0 bulkscore=0 adultscore=0 priorityscore=1501 phishscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604010000 definitions=main-2604070175 Kick off the work to compute the steal time at regular interval. Gated with sched feature STEAL_MONITOR to avoid any overhead in systems that are not interested in it. The sampling period can configured at runtime using steal_mon_period. By default is 1000 milliseconds. i.e. 1 second This work is done by first online housekeeping CPU only. Hence it won't need any complicated synchronization. Signed-off-by: Shrikanth Hegde --- kernel/sched/core.c | 27 +++++++++++++++++++++++++++ kernel/sched/sched.h | 2 ++ 2 files changed, 29 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8c80600ddd28..1c6fcf1ae4fe 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5694,6 +5694,10 @@ void sched_tick(void) rq->idle_balance = idle_cpu(cpu); sched_balance_trigger(rq); } + + /* This feature works currently on SMT system */ + if (sched_feat(STEAL_MONITOR) && IS_ENABLED(CONFIG_SCHED_SMT)) + sched_trigger_steal_computation(cpu); } #ifdef CONFIG_NO_HZ_FULL @@ -11355,4 +11359,27 @@ void sched_steal_detection_work(struct work_struct *work) now = ktime_get(); sm->prev_time = now; } + +void sched_trigger_steal_computation(int cpu) +{ + int first_hk_cpu = cpumask_first_and(housekeeping_cpumask(HK_TYPE_KERNEL_NOISE), + cpu_online_mask); + ktime_t now; + + /* Done by first online housekeeping CPU only */ + if (likely(cpu != first_hk_cpu)) + return; + + /* + * Since everything is updated by first housekeeping CPU, + * There is no need for complex syncronization. + */ + now = ktime_get(); + + /* Default is once per second */ + if (likely((now - steal_mon.prev_time) < steal_mon.sampling_period_ms * NSEC_PER_MSEC)) + return; + + schedule_work_on(first_hk_cpu, &steal_mon.work); +} #endif diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index c0fbfb04eda3..337357e48a83 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -4157,6 +4157,7 @@ static inline bool task_can_run_on_preferred_cpu(struct task_struct *p) void sched_push_current_non_preferred_cpu(struct rq *rq); void sched_init_steal_monitor(void); void sched_steal_detection_work(struct work_struct *work); +void sched_trigger_steal_computation(int cpu); #else static inline bool task_can_run_on_preferred_cpu(struct task_struct *p) { @@ -4165,6 +4166,7 @@ static inline bool task_can_run_on_preferred_cpu(struct task_struct *p) static inline void sched_push_current_non_preferred_cpu(struct rq *rq) { } static inline void sched_init_steal_monitor(void) { } +static inline void sched_trigger_steal_computation(int cpu) { } #endif #endif /* _KERNEL_SCHED_SCHED_H */ -- 2.47.3