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Wed, 13 May 2026 06:39:59 +0000 (GMT) Received: from [9.39.28.2] (unknown [9.39.28.2]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 13 May 2026 06:39:58 +0000 (GMT) Message-ID: <0b3d8b79-6743-4f35-abc8-da4f2a6a2d80@linux.ibm.com> Date: Wed, 13 May 2026 12:09:58 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/3] sched/fair: Add compile time check in fastpaths for CONFIG_SCHED_SMT=n To: K Prateek Nayak , mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org Cc: juri.lelli@redhat.com, vschneid@redhat.com, dietmar.eggemann@arm.com, tj@kernel.org, rostedt@goodmis.org, mgorman@suse.de, bsegall@google.com, arighi@nvidia.com References: <20260512152125.308280-1-sshegde@linux.ibm.com> <20260512152125.308280-4-sshegde@linux.ibm.com> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: Content-Type: text/plain; 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I think the if() above can simply check for sched_smt_active() > before calling is_core_idle() like: > > if (sched_smt_active() && > !(env->sd->flags & SD_SHARE_CPUCAPACITY) && > !is_core_idle(cpu)) { > ... > } > > That way, we ensure we don't call is_core_idle() and the cpumask_and() > unnecessarily on topologies that don't have SMT domain similar to how > sched_use_asym_prio() guards the call to is_core_idle(). > > Thoughts? > In addition, Do you think it makes sense to consolidate use of sched_smt_present always using sched_smt_active() ? static __always_inline bool sched_smt_active(void) { return static_branch_likely(&sched_smt_present); } kernel/sched/core_sched.c: if (!static_branch_likely(&sched_smt_present)) kernel/sched/fair.c: if (!static_branch_likely(&sched_smt_present) || kernel/sched/sched.h: if (static_branch_unlikely(&sched_smt_present)) The last being differing with unlikely in update_idle_core. Does it make sense to call sched_smt_active there as well?