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Wed, 1 Jul 2026 14:21:28 +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 v6 19/23] virt/steal_monitor: Provide default method to get num of CPUs for steal ratio Date: Wed, 1 Jul 2026 19:46:50 +0530 Message-ID: <20260701141654.500125-20-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260701141654.500125-1-sshegde@linux.ibm.com> References: <20260701141654.500125-1-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-Spam-Details-Enc: AW1haW4tMjYwNzAxMDE1MCBTYWx0ZWRfX5o0hyZ55J5Ld Fwy1dH/PbGgZotRyJUCrm+Z3mb/nKySO7fEYFwRKMh0wKX+vYh65BlWKcU3N5OWTA65SQY+ehhR APJtmQ8iKDuEO2Fvhvmf+LKRFraQpHsdpRRgqyH3oRUp4XqcdvOAHkWnqJ4Fnk6OFT/epUaBYrU zjafZYKaRV7KaKp80KDA/RxVVh/cP3uNazPW8FFQvt0RdML6gR+eFu+9e3ZYBqlaXc7gTwJq1x4 eK7AGJ5OkXQGWCFGhr8sEdHaGvfcndKjkuOx0ZMBbmW4yRk2crYzxZlCjP/PViyX/Jqowt/purN YvfHO+0xc1PreWI68BJlJPr5lsDVplTWRf+OmxEDv/QDzm3y/R8FCT6ObaTZHapaanwrBY6HTWz lZVb1z2r9yvhRtOkNFd/E0liZbzV8Rpa+t+At/taRt67AuAapchCZ5452nj5LgkSghCE5iO22ae ngRO0Qw4+pt4BB1teYA== X-Authority-Analysis: v=2.4 cv=V45NF+ni c=1 sm=1 tr=0 ts=6a45227b cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=drlZgsKemknilDNKuT0A:9 X-Proofpoint-ORIG-GUID: Z2G0-62jx_N8ns8K9jnTjIhQDWEoEXM1 X-Proofpoint-GUID: _RE0bLI3_bsQI0VH4R1DcXb70KwjsT5R X-Proofpoint-Spam-Info: AW1haW4tMjYwNzAxMDE1MCBTYWx0ZWRfX69hMb7fvwi2o 3OCJW5RivW2Ap4wfoBNzkWCMUtx1PlFjxmL3WOIWv3llI15CVnyZSaHV6M7caatZ3lYht0WZaxH pMhKtjV1MurZ7/5QusZhfFOfspkYGEs= 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=2026-07-01_03,2026-06-26_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 spamscore=0 suspectscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 clxscore=1015 impostorscore=0 malwarescore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607010150 This method informs the steal_monitor core, how many CPUs it needs to consider for steal ratio calculations. steal_ratio = (delta_steal * 100 * 100) / (delta_ns * number_of_cpus); Default method returns number of Active CPUs since it calculates steal time across active CPUs. Signed-off-by: Shrikanth Hegde --- v5->v6: - Add cpus_read_lock() for hotplug safety. drivers/virt/steal_monitor/defaults.c | 11 +++++++++++ drivers/virt/steal_monitor/sm_core.h | 1 + 2 files changed, 12 insertions(+) diff --git a/drivers/virt/steal_monitor/defaults.c b/drivers/virt/steal_monitor/defaults.c index 4e2e5b233948..70dcfb1ce4cb 100644 --- a/drivers/virt/steal_monitor/defaults.c +++ b/drivers/virt/steal_monitor/defaults.c @@ -27,6 +27,17 @@ u64 __weak get_system_steal_time(void) return total_steal; } +/* + * Return number of CPUs to consider for steal ratio calculation + * + * Default returns number of active CPUs. + */ +unsigned int __weak get_num_cpus_steal_ratio(void) +{ + guard(cpus_read_lock)(); + return num_active_cpus(); +} + /* * Default implementation of decrementing the preferred CPUs based on steal * time. This is simple logic and decrease the preferred CPUs by 1 core. diff --git a/drivers/virt/steal_monitor/sm_core.h b/drivers/virt/steal_monitor/sm_core.h index 030f6236c38e..794d3be04248 100644 --- a/drivers/virt/steal_monitor/sm_core.h +++ b/drivers/virt/steal_monitor/sm_core.h @@ -26,6 +26,7 @@ struct steal_monitor { extern struct steal_monitor sm_core_ctx; u64 get_system_steal_time(void); +unsigned int get_num_cpus_steal_ratio(void); void increase_preferred_cpus(struct steal_monitor *ctx); void decrease_preferred_cpus(struct steal_monitor *ctx); -- 2.47.3