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Thu, 25 Jun 2026 12:50:00 +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 12:50:00 +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 22/24] virt/steal_monitor: Act on steal values at regular intervals Date: Thu, 25 Jun 2026 18:16:46 +0530 Message-ID: <20260625124648.802832-23-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-Proofpoint-ORIG-GUID: 6WvYsFH6SEFWoTJJJaoxu7yd6zALtNcl X-Proofpoint-GUID: I9NIemXf19NNtTB5J0LYndKLtfiIVcwc X-Authority-Analysis: v=2.4 cv=Y4XIdBeN c=1 sm=1 tr=0 ts=6a3d2405 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=FaF7mGpESULvgM3RsB4A:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjI1MDExMCBTYWx0ZWRfX5ylpFu0o/hVA KqOSfIYH6aVxqKORWS8glgVej18GszGgr6a0s8TyT/jVHW+AFjoTqGf4304f0zHge4W2IzSIX3g eO7g5RrgCgcf2sXFJtoVKnmPDSMhMF2rUmBycWpWDgCvY3i7gqwBu7XI7uWJ0IhOU+VYlJ4jIvc g6ZXlWz0Au5sX4XPRYWmaaji9ehYH6brMzvnm+cOYFKsqjJIZz3atPFPRitfhHe+kRkH0DqqdlJ RqDOYBuNK8tdQ3+G3F25+azV+Cgb1VL1IwxBnoH4Jt3zB/895JfV07EhiqzoaHYWWuFci15ycPB bnDZClHa2I1kvkKpY31QheecobNeAtjSMvd8jpx3lwF04zPcCEbtbY+H7IdfSjS02HO2hB+oLFs BIQ8w9TFca9wol+OdGyMFhjcUNjD1TDDXkhF+RtJ4ajWPZZvYdbiqddJuyGrBpIUwtMghMpZ6j9 3Mm8d15J0kECNWloVHA== X-Proofpoint-Spam-Info: AW1haW4tMjYwNjI1MDExMCBTYWx0ZWRfXw6LyVds0n8ob PVdLLu3EVVH69umL3WjxY6BhTb2SyfayPTGwCSJrbNq5Vav6zzf4XT3lRA6GAPbBpas/OHBPanH HyUpnjOwZh0IFW4GELrilxqsPYqaZ9U= 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 adultscore=0 priorityscore=1501 malwarescore=0 lowpriorityscore=0 spamscore=0 clxscore=1015 suspectscore=0 impostorscore=0 phishscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606250110 This is the steal_monitor core functionality done in periodic work - Calculate the steal_ratio. It is multiplied by 100 to consider the fractional values of steal time. I.e 10 means 0.1% steal time. - If steal value is higher than high threshold, call the method to reduce the preferred CPUs. - If steal value is lower or equal to low threshold, call the method to increase the preferred CPUs. - If the steal value is in between, no action is taken. - Save the values for next delta calculations. Signed-off-by: Shrikanth Hegde --- v4->v5: - Modified for steal_monitor drivers/virt/steal_monitor/sm_core.c | 29 ++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/drivers/virt/steal_monitor/sm_core.c b/drivers/virt/steal_monitor/sm_core.c index fac8f4d5dac7..641488a5a3b5 100644 --- a/drivers/virt/steal_monitor/sm_core.c +++ b/drivers/virt/steal_monitor/sm_core.c @@ -34,6 +34,33 @@ MODULE_PARM_DESC(low_threshold, static void compute_preferred_cpus_work(struct work_struct *work) { + u64 curr_steal, delta_steal, delta_ns, steal_ratio; + ktime_t now; + + curr_steal = get_system_steal_time(); + now = ktime_get(); + + /* get the deltas */ + delta_steal = curr_steal > sm_core_ctx.prev_steal ? + curr_steal - sm_core_ctx.prev_steal : 0; + delta_ns = max_t(u64, ktime_to_ns(ktime_sub(now, sm_core_ctx.prev_time)), 1); + + /* Update for next calculation */ + sm_core_ctx.prev_steal = curr_steal; + sm_core_ctx.prev_time = now; + + /* Multiply by 100 to consider the fractional values of steal time */ + steal_ratio = (delta_steal * 100 * 100) / + (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) + decrease_preferred_cpus(&sm_core_ctx); + + /* If the steal time values are low, increase preferred CPUs */ + if (steal_ratio <= sm_core_ctx.low_threshold) + increase_preferred_cpus(&sm_core_ctx); + /* At least one core is kept as preferred */ WARN_ON(cpumask_empty(cpu_preferred_mask)); @@ -54,6 +81,8 @@ static int __init steal_monitor_init(void) sm_core_ctx.interval_ms, sm_core_ctx.high_threshold, sm_core_ctx.low_threshold); INIT_DELAYED_WORK(&sm_core_ctx.work, compute_preferred_cpus_work); + sm_core_ctx.prev_steal = get_system_steal_time(); + sm_core_ctx.prev_time = ktime_get(); schedule_delayed_work(&sm_core_ctx.work, msecs_to_jiffies(sm_core_ctx.interval_ms)); -- 2.47.3