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Thu, 25 Jun 2026 12:50:08 +0000 (GMT) Received: from li-7bb28a4c-2dab-11b2-a85c-887b5c60d769.ibm.com.com (unknown [9.39.20.6]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 25 Jun 2026 12:50:08 +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, corbet@lwn.net 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, 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, rdunlap@infradead.org, kernellwp@gmail.com, linux-doc@vger.kernel.org Subject: [PATCH v5 23/24] virt/steal_monitor: Add direction control Date: Thu, 25 Jun 2026 18:16:47 +0530 Message-ID: <20260625124648.802832-24-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260625124648.802832-1-sshegde@linux.ibm.com> References: <20260625124648.802832-1-sshegde@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-doc@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=I4VVgtgg c=1 sm=1 tr=0 ts=6a3d240d cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=_v5trmpiMvKuf-VRmTkA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjI1MDExMCBTYWx0ZWRfX88UP6UZBA3ac pW4fQSAQQEDw0O5eL7aoqznPDvnsQ8Qq2d7B6iovcR4RddtQHgYWAiO2a66QbeXfKYSqbA8qvKU RFRLJjzzDycHuQMviQuHZumJpEEn0SJULhTpgM1Zsicm1xHeo9WBuMlJWDeFcD55ubFg+X2npGj NOb5C7sr6HfNizfga5scW3yw7MkFelCA8NDHZIZTex3/VjVZQhfVhRkLjIofCWIfq1vZMtL9J2U DAZQdslH92PbPucA4ddIE0LjHUVaKsQpg/sb07esgHNZP6OgF/OXbPlaFA11PbrhppE0rLeU1eR awphWaPM3QcCDxj8pscdBGTg0irRGZIls1h9nyS9fA8AU1gH+cvJ9wKXUPIrNf2Dd487xOulSq3 SPDYtjD7pMojWSwncMRswqjX5C44IyjwTRgv4HhHgqzSWOOFqQPmNEo6eTBjiH7FLV2qHFhWBUU w0hF0nMWSnXbm8eUphw== X-Proofpoint-GUID: 6J1t5O95YluinG2Wov_cFclKF4qPH1X2 X-Proofpoint-ORIG-GUID: b6hq1s2QPDsWr-SSas7qRvhw9MyTb31j X-Proofpoint-Spam-Info: AW1haW4tMjYwNjI1MDExMCBTYWx0ZWRfX4yI+FcRMbvL5 lnc++kJspZlQckoOQXLPoTbqWHhdjgcBGXmAQU3eQtUGmuQ6lv9WzU78FX+R4d7t53SulZyeSxF kopf1irtSxNs90+SJyKR8/kYDx8I398= 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=2026-06-25_01,2026-06-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 malwarescore=0 clxscore=1015 impostorscore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 priorityscore=1501 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606250110 Cache the previous direction on steal time. So two consecutive values of high values or low values are taken for decrease/increase of preferred CPUs. This helps to avoid oscillations. Signed-off-by: Shrikanth Hegde --- v4->v5: - Modified for steal_monitor drivers/virt/steal_monitor/sm_core.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/drivers/virt/steal_monitor/sm_core.c b/drivers/virt/steal_monitor/sm_core.c index 641488a5a3b5..f5b0e568eb32 100644 --- a/drivers/virt/steal_monitor/sm_core.c +++ b/drivers/virt/steal_monitor/sm_core.c @@ -20,6 +20,12 @@ struct steal_monitor sm_core_ctx = { .low_threshold = 200, /* 2% */ }; +enum sm_direction { + SM_DIR_INCREASE = -1, + SM_DIR_NONE = 0, + SM_DIR_DECREASE = 1, +}; + module_param_named(interval_ms, sm_core_ctx.interval_ms, uint, 0644); MODULE_PARM_DESC(interval_ms, "Sampling frequency for steal values in milliseconds (default: 1000)"); @@ -54,13 +60,23 @@ static void compute_preferred_cpus_work(struct work_struct *work) (delta_ns * get_num_cpus_steal_ratio()); /* If the steal time values are high, reduce preferred CPUs */ - if (steal_ratio > sm_core_ctx.high_threshold) + if (sm_core_ctx.prev_direction == SM_DIR_DECREASE && + steal_ratio > sm_core_ctx.high_threshold) decrease_preferred_cpus(&sm_core_ctx); /* If the steal time values are low, increase preferred CPUs */ - if (steal_ratio <= sm_core_ctx.low_threshold) + if (sm_core_ctx.prev_direction == SM_DIR_INCREASE && + steal_ratio <= sm_core_ctx.low_threshold) increase_preferred_cpus(&sm_core_ctx); + /* mark the direction. This helps to avoid ping-pongs */ + if (steal_ratio > sm_core_ctx.high_threshold) + sm_core_ctx.prev_direction = SM_DIR_DECREASE; + else if (steal_ratio <= sm_core_ctx.low_threshold) + sm_core_ctx.prev_direction = SM_DIR_INCREASE; + else + sm_core_ctx.prev_direction = SM_DIR_NONE; + /* At least one core is kept as preferred */ WARN_ON(cpumask_empty(cpu_preferred_mask)); -- 2.47.3