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Tue, 7 Apr 2026 19:21:25 +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 16/17] sched/core: Mark the direction of steal values to avoid oscillations Date: Wed, 8 Apr 2026 00:49:49 +0530 Message-ID: <20260407191950.643549-17-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: AW1haW4tMjYwNDA3MDE3NSBTYWx0ZWRfX/mNrmKdcZzjc sP3xVxswId1zbqQxq7pmDzlecqI20l6u6NI0g80kg6xSJr5ne0LrNwbgBZUl2C48XWFaECJss/E pha3fPdKibwRYxGxVlvMrweBdj6nkQMQ/NK2EhxphjwaaVi//KEocwRUmcRiluGMaed06f8gMAD XkpAxm159FUwju+zcUlriF8x8Cd8xnRAp7Cq/WdR8KyaBiyS/ZlrV8NEPRByIySpnL6OaxoGlH9 vjjROIMyYutQ0SLrJCmGTGOpWjqraXA+GHV5psNPYCNoe2j3SfXmrkro/ctpU+sqC4LrW9s0/QN PCAxsfTrrMFzEkxhxxiB8okfJGpGxZdUgw1LgJK7eyZ8fmFbub5UC8qhVSmK9TLjkCkyWtThfL/ JOzqAa9VuPH0BNU6Qaovq49x9/pwOndI1kuUve+ldap76n8UOMyG4MDTNfz5jIjODBpLO5idwgG qS0l4FqjsD7ei+mChNw== X-Proofpoint-GUID: pNDiS4HV3w36aUIesUVNM57KMbGjfEPs X-Authority-Analysis: v=2.4 cv=a/wAM0SF c=1 sm=1 tr=0 ts=69d5593f cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=NVR8b6ZH4u3ztrVwBTQA:9 X-Proofpoint-ORIG-GUID: IftFx8kLcBlbywHXlocQMyKqsKpdO0is 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 bulkscore=0 clxscore=1015 spamscore=0 impostorscore=0 priorityscore=1501 phishscore=0 lowpriorityscore=0 adultscore=0 malwarescore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604010000 definitions=main-2604070175 Cache the previous decision on steal time. So consecutive values of high values or low values are taken for increase/decrease of preferred CPUs. Signed-off-by: Shrikanth Hegde --- kernel/sched/core.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 6e2b733adf45..cb9110f95ebf 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -11374,7 +11374,7 @@ void sched_steal_detection_work(struct work_struct *work) steal_ratio = (delta_steal * 100 * 100) / (delta_ns * num_online_cpus()); /* If the steal time values are high, reduce one core from preferred CPUs */ - if (steal_ratio > sm->high_threshold) { + if (sm->previous_decision == 1 && steal_ratio > sm->high_threshold) { int last_cpu; cpumask_and(sm->tmp_mask, cpu_online_mask, cpu_preferred_mask); @@ -11396,7 +11396,7 @@ void sched_steal_detection_work(struct work_struct *work) } /* If the steal time values are low, increase one core as preferred CPUs */ - if (steal_ratio < sm->low_threshold) { + if (sm->previous_decision == -1 && steal_ratio < sm->low_threshold) { int first_cpu; first_cpu = cpumask_first_andnot(cpu_online_mask, cpu_preferred_mask); @@ -11407,6 +11407,14 @@ void sched_steal_detection_work(struct work_struct *work) for_each_cpu(tmp_cpu, cpu_smt_mask(first_cpu)) set_cpu_preferred(tmp_cpu, true); } + + /* mark the direction. This helps to avoid ping-pongs */ + if (steal_ratio > sm->high_threshold) + sm->previous_decision = 1; + else if (steal_ratio < sm->low_threshold) + sm->previous_decision = -1; + else + sm->previous_decision = 0; #endif } -- 2.47.3