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Tue, 7 Apr 2026 19:20:21 +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, tglx@linutronix.de, yury.norov@gmail.com, gregkh@linuxfoundation.org Cc: sshegde@linux.ibm.com, pbonzini@redhat.com, seanjc@google.com, kprateek.nayak@amd.com, vschneid@redhat.com, iii@linux.ibm.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, joelagnelf@nvidia.com Subject: [PATCH v2 03/17] cpumask: Introduce cpu_preferred_mask Date: Wed, 8 Apr 2026 00:49:36 +0530 Message-ID: <20260407191950.643549-4-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260407191950.643549-1-sshegde@linux.ibm.com> References: <20260407191950.643549-1-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-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDA3MDE3NSBTYWx0ZWRfXyLQX0oxzK+E9 6mNgKhUH2Q3UsYEQVeNBCijjqXoNDx/ITgZZhYR4H+OzC8wbhGg3mrBqDEJ6OLn09SHxFX13NFs KHsCfY98kZsvNNJPPrY25OgTnVsiADdhGaHQHhcxhyp8qlEVsBYyhCC4urFOEebJRizUmlxO75y kr4EatAwtRkJnYJrexwgqL8VFrjneA4PJ1C95xKM984rZIyLolGDvn8UnVappX7fpieyO4AsXsv lOes2cU9k4oX95pHqqJCu/QeY/0AgneBpPzFQktOkIZJ7F8t+VElNz5PA4f5xFyHfihnvnh8/oi u67tF0//q/AM29W/dUkLWqcGPmkyMBvm2OxQ4S2p/4lBRbYeERcJXrS97XDAyLMoWJFV2ujjRcU b77Il8zV6zhEYQOwwDY6zB2olros5MG2tKb1mhhbyLR9WQuzVgTHjg54o2DRgKUekN3sBKwzqAy 1c3z+qM3+U+HWBzyJfQ== X-Authority-Analysis: v=2.4 cv=FsY1OWrq c=1 sm=1 tr=0 ts=69d55900 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=blX9kqOrpvjOr1fgGLAA:9 X-Proofpoint-ORIG-GUID: sEJ4GWpTB0NQmvGeNZL4-MJhaR5yUNoS X-Proofpoint-GUID: bQjtNmz3rzF7nCteueeJWLaUrk5nA8ST X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-07_04,2026-04-07_05,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 priorityscore=1501 impostorscore=0 spamscore=0 phishscore=0 lowpriorityscore=0 clxscore=1015 adultscore=0 malwarescore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604010000 definitions=main-2604070175 This patch does - Declare and Define cpu_preferred_mask. - Get/Set helpers for it. Values are set/clear by the scheduler by detecting the steal time values. A CPU is set to preferred when it comes online. Later it may be marked as non-preferred depending on steal time values with STEAL_MONITOR enabled. Signed-off-by: Shrikanth Hegde --- include/linux/cpumask.h | 22 ++++++++++++++++++++++ kernel/cpu.c | 6 ++++++ kernel/sched/core.c | 5 +++++ 3 files changed, 33 insertions(+) diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 80211900f373..80c5cc13b8ad 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -1296,6 +1296,28 @@ static __always_inline bool cpu_dying(unsigned int cpu) #endif /* NR_CPUS > 1 */ +/* + * All related wrappers kept together to avoid too many ifdefs + * See Documentation/scheduler/sched-arch.rst for details + */ +#ifdef CONFIG_PARAVIRT +extern struct cpumask __cpu_preferred_mask; +#define cpu_preferred_mask ((const struct cpumask *)&__cpu_preferred_mask) +#define set_cpu_preferred(cpu, preferred) assign_cpu((cpu), &__cpu_preferred_mask, (preferred)) + +static __always_inline bool cpu_preferred(unsigned int cpu) +{ + return cpumask_test_cpu(cpu, cpu_preferred_mask); +} +#else +static __always_inline bool cpu_preferred(unsigned int cpu) +{ + return true; +} + +static __always_inline void set_cpu_preferred(unsigned int cpu, bool preferred) { } +#endif + #define cpu_is_offline(cpu) unlikely(!cpu_online(cpu)) #if NR_CPUS <= BITS_PER_LONG diff --git a/kernel/cpu.c b/kernel/cpu.c index bc4f7a9ba64e..2d4d037680d4 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -3137,6 +3137,12 @@ void set_cpu_online(unsigned int cpu, bool online) if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask)) atomic_dec(&__num_online_cpus); } + + /* + * An online CPU is by default assumed to be preferred + * Unitl STEAL_MONITOR changes it + */ + set_cpu_preferred(cpu, online); } /* diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f351296922ac..7ea05a7a717b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -11228,3 +11228,8 @@ void sched_change_end(struct sched_change_ctx *ctx) p->sched_class->prio_changed(rq, p, ctx->prio); } } + +#ifdef CONFIG_PARAVIRT +struct cpumask __cpu_preferred_mask __read_mostly; +EXPORT_SYMBOL(__cpu_preferred_mask); +#endif -- 2.47.3