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Fri, 23 May 2025 18:15:02 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5342D2004D; Fri, 23 May 2025 18:15:02 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D197020040; Fri, 23 May 2025 18:14:58 +0000 (GMT) Received: from li-7bb28a4c-2dab-11b2-a85c-887b5c60d769.ibm.com.com (unknown [9.124.221.90]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 23 May 2025 18:14:58 +0000 (GMT) From: Shrikanth Hegde To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, tglx@linutronix.de, yury.norov@gmail.com, maddy@linux.ibm.com Cc: sshegde@linux.ibm.com, vschneid@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, jstultz@google.com, kprateek.nayak@amd.com, huschle@linux.ibm.com, srikar@linux.ibm.com, linux-kernel@vger.kernel.org, linux@rasmusvillemoes.dk Subject: [RFC PATCH 1/5] cpumask: Introduce cpu parked mask Date: Fri, 23 May 2025 23:44:44 +0530 Message-ID: <20250523181448.3777233-2-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20250523181448.3777233-1-sshegde@linux.ibm.com> References: <20250523181448.3777233-1-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: quoted-printable X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=RrPFLDmK c=1 sm=1 tr=0 ts=6830bb2c cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=dt9VzEwgFbYA:10 a=VnNF1IyMAAAA:8 a=yoKQFJCjtn0IRW-TtgoA:9 X-Proofpoint-ORIG-GUID: pUONPhN9KHOsk5Q3d8nIq_trzcGGgKqW X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTIzMDE2NCBTYWx0ZWRfXworABcV5JF6p VB+MOYYXAuLyCl1ZSbN+jj/JlfDWi3dvfwrnX6/ozV4QgGMsCsLM7giuYeWaigMbWW7pPQwVFWF p+9ghOuW5pj8fA8NfemmabfguBPjrY6gyWdstwVaN158NFKydr9D2yDIJLtnHxLWYxhSDDh8ami ulrfaWxNOTbefYFe5to8CUtTJjYwMrSIJLBp0re6tuXXL7xw6k49/6ico961s6fAvbh3CRx0DdA Bub4mJqRabFo/TqBQFHfIYgJBdiRiewY1C0yUrHs3O+tHiwDYc4RFO8NNVpt1mT8uEmKTboUGLJ rAJmXfgYhzyT7ad2hn7ExsE6RFraOBD/2WqBJxv2HGGGRb+k12kuUK5arsVUFdDVDCi8kezYBiQ qyhUoRny1L07MQQjD1knChfJfS92pQ/7f7Rq5cVJUthwkCtclQUhTfYiKHsW5GsJDEFyeZVr X-Proofpoint-GUID: VZ_NEmXUshB2UHwK9Wi_Gs2rwAhtX7Ql X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-23_06,2025-05-22_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 malwarescore=0 impostorscore=0 mlxlogscore=999 suspectscore=0 bulkscore=0 lowpriorityscore=0 priorityscore=1501 mlxscore=0 spamscore=0 adultscore=0 clxscore=1015 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505160000 definitions=main-2505230164 Content-Type: text/plain; charset="utf-8" CPU is said to be parked, when underlying physical CPU is not=20 available. This happens when there is contention for CPU resource in para-virtualized case. One should avoid using these CPUs.=20 Build and maintain this state of parked CPUs. Scheduler will use this information and push the tasks out as soon as it can.=20 Signed-off-by: Shrikanth Hegde --- - Not sure if __read_mostly attribute suits for cpu_parked=20 since it can change often. Since often means a few mins, it is long time from scheduler perspective, hence kept it.=20 include/linux/cpumask.h | 14 ++++++++++++++ kernel/cpu.c | 3 +++ 2 files changed, 17 insertions(+) diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 6a569c7534db..501848303800 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -84,6 +84,7 @@ static __always_inline void set_nr_cpu_ids(unsigned int n= r) * cpu_enabled_mask - has bit 'cpu' set iff cpu can be brought online * cpu_online_mask - has bit 'cpu' set iff cpu available to scheduler * cpu_active_mask - has bit 'cpu' set iff cpu available to migration + * cpu_parked_mask - has bit 'cpu' set iff cpu is parked * * If !CONFIG_HOTPLUG_CPU, present =3D=3D possible, and active =3D=3D onl= ine. * @@ -93,6 +94,11 @@ static __always_inline void set_nr_cpu_ids(unsigned int = nr) * representing which CPUs are currently plugged in. And * cpu_online_mask is the dynamic subset of cpu_present_mask, * indicating those CPUs available for scheduling. + * + * A CPU is said to be parked when underlying physical CPU(pCPU) is not + * available at the moment. It is recommended not to run any workload on + * that CPU. + * * If HOTPLUG is enabled, then cpu_present_mask varies dynamically, * depending on what ACPI reports as currently plugged in, otherwise @@ -118,12 +124,14 @@ extern struct cpumask __cpu_enabled_mask; extern struct cpumask __cpu_present_mask; extern struct cpumask __cpu_active_mask; extern struct cpumask __cpu_dying_mask; +extern struct cpumask __cpu_parked_mask; #define cpu_possible_mask ((const struct cpumask *)&__cpu_possible_mask) #define cpu_online_mask ((const struct cpumask *)&__cpu_online_mask) #define cpu_enabled_mask ((const struct cpumask *)&__cpu_enabled_mask) #define cpu_present_mask ((const struct cpumask *)&__cpu_present_mask) #define cpu_active_mask ((const struct cpumask *)&__cpu_active_mask) #define cpu_dying_mask ((const struct cpumask *)&__cpu_dying_mask) +#define cpu_parked_mask ((const struct cpumask *)&__cpu_parked_mask) =20 extern atomic_t __num_online_cpus; =20 @@ -1146,6 +1154,7 @@ void init_cpu_possible(const struct cpumask *src); #define set_cpu_present(cpu, present) assign_cpu((cpu), &__cpu_present_mas= k, (present)) #define set_cpu_active(cpu, active) assign_cpu((cpu), &__cpu_active_mask, = (active)) #define set_cpu_dying(cpu, dying) assign_cpu((cpu), &__cpu_dying_mask, (dy= ing)) +#define set_cpu_parked(cpu, parked) assign_cpu((cpu), &__cpu_parked_mas= k, (parked)) =20 void set_cpu_online(unsigned int cpu, bool online); =20 @@ -1235,6 +1244,11 @@ static __always_inline bool cpu_dying(unsigned int c= pu) return cpumask_test_cpu(cpu, cpu_dying_mask); } =20 +static __always_inline bool cpu_parked(unsigned int cpu) +{ + return cpumask_test_cpu(cpu, cpu_parked_mask); +} + #else =20 #define num_online_cpus() 1U diff --git a/kernel/cpu.c b/kernel/cpu.c index a59e009e0be4..532fbfbe3226 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -3110,6 +3110,9 @@ EXPORT_SYMBOL(__cpu_dying_mask); atomic_t __num_online_cpus __read_mostly; EXPORT_SYMBOL(__num_online_cpus); =20 +struct cpumask __cpu_parked_mask __read_mostly; +EXPORT_SYMBOL(__cpu_parked_mask); + void init_cpu_present(const struct cpumask *src) { cpumask_copy(&__cpu_present_mask, src); --=20 2.39.3