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Wed, 17 Jun 2026 17:44:39 +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 17:44:39 +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 18/20] sched/core: Mark the direction of steal values to avoid oscillations Date: Wed, 17 Jun 2026 23:11:37 +0530 Message-ID: <20260617174139.155540-19-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-Authority-Analysis: v=2.4 cv=OcSoyBTY c=1 sm=1 tr=0 ts=6a32dd13 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=tcntZ0dPoHREjsMmYjgA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjE3MDE2NiBTYWx0ZWRfXwcIu4fWji4Yl QAvsWeDwtJrwOWeP5QcslfdZD2AcA3F+M2c2F1+Pf6Od+uMojDO+s1zq4EGlOUDP4AjaYJvNi/p Xqz7D85ES35RX2FIbZ06OOF7LBu7a/RVkZ939bzfkcCAIRe6w1nX1az8321VXVpJcJcTqyHYaPy 5Tu0Ou/NKBwyc6igREuId+ZH5BIPiZ8IvPLxJYEWUU8JhmlKleau5mDAMKbyQApoPbzeko0PNri UQK6XcMVsE/5nOuyUEuszDntPVZoYUbBAK+E5EajXcRcll8Td88KaGWIb/1gVNM3i0LOOfhb19e Me7dgvCP6erzLtZRcUCYUO6eK31+4bHVcZdxWvJpD6dK1a0PbovFpfIGb++JfxHwwLr+PrXcmPy XfC5a/kK4iQqbJX4H2UQiOb4izYVLsyJawcFUwlJIuJARvXQgHPZ+tE63kzTgi2HHf2zb9SoP+L LoyyCuWUAh3wZBEXl9Q== X-Proofpoint-GUID: NOQgVtda707PJArFet4KrhDLsYa54u8E X-Proofpoint-Spam-Info: AW1haW4tMjYwNjE3MDE2NiBTYWx0ZWRfXz6Fft7WJqAos MupLuL1c4iuSGqfFQTPYdIz0NEDPSzwUWJTRc5TaI0QmbLgO+V8sV6uvtfHi8z6xD6dbfFavjvm EDR7gb1wyUmXSp+A+bOMw3pIDSvwiJs= X-Proofpoint-ORIG-GUID: i6UMNDee4EdH5d5PhI7cCC9ljGDYG3_L 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 priorityscore=1501 phishscore=0 bulkscore=0 suspectscore=0 lowpriorityscore=0 impostorscore=0 malwarescore=0 spamscore=0 adultscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606170166 Cache the previous decision on steal time. So consecutive values of high values or low values are taken for increase/decrease of preferred CPUs. Also make lower threhold equal to less than to handle one setting it to zero. Signed-off-by: Shrikanth Hegde --- v3->v4: - Consider equal or less than for low threshold. - reset the direction when disabling the feature. kernel/sched/core.c | 12 ++++++++++-- kernel/sched/debug.c | 1 + 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 657c36a0e7ca..57d52973ef0d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -11483,12 +11483,20 @@ void sched_steal_detection_work(struct work_struct *work) steal_ratio = (delta_steal * 100 * 100) / (delta_ns * num_active_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) arch_dec_preferred_cpus(sm, steal_ratio); /* 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) arch_inc_preferred_cpus(sm, steal_ratio); + + /* 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; } void sched_trigger_steal_computation(int cpu) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 55b8beb42574..ae7a641931d1 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -650,6 +650,7 @@ static ssize_t sched_sm_en_write(struct file *filp, const char __user *ubuf, } else if (!sched_sm_wr_enable && orig) { static_branch_disable(&__sched_sm_enable); cancel_work_sync(&steal_mon.work); + steal_mon.previous_decision = 0; cpumask_copy(&__cpu_preferred_mask, cpu_active_mask); } -- 2.47.3