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Wed, 25 Jun 2025 17:12:10 -0700 (PDT) Date: Wed, 25 Jun 2025 20:12:08 -0400 From: Yury Norov To: Shrikanth Hegde Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, tglx@linutronix.de, maddy@linux.ibm.com, vschneid@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, kprateek.nayak@amd.com, huschle@linux.ibm.com, srikar@linux.ibm.com, linux-kernel@vger.kernel.org, christophe.leroy@csgroup.eu, linuxppc-dev@lists.ozlabs.org, gregkh@linuxfoundation.org Subject: Re: [RFC v2 7/9] sched: Add static key check for cpu_avoid Message-ID: References: <20250625191108.1646208-1-sshegde@linux.ibm.com> <20250625191108.1646208-8-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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250625191108.1646208-8-sshegde@linux.ibm.com> On Thu, Jun 26, 2025 at 12:41:06AM +0530, Shrikanth Hegde wrote: > Checking if a CPU is avoid can add a slight overhead and should be > done only when necessary. > > Add a static key check which makes it almost nop when key is false. > Arch needs to set the key when it decides to. Refer to debug patch > for example. > > Signed-off-by: Shrikanth Hegde > --- > This method avoids additional ifdefs. So kept it that way instead of > CONFIG_PARAVIRT. > > Added a helper function for cpu_avoid, since including sched.h fails in > cpumask.h > > kernel/sched/core.c | 8 ++++---- > kernel/sched/fair.c | 5 +++-- > kernel/sched/rt.c | 8 ++++---- > kernel/sched/sched.h | 9 +++++++++ > 4 files changed, 20 insertions(+), 10 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index aea4232e3ec4..51426b17ef55 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -148,9 +148,9 @@ __read_mostly int sysctl_resched_latency_warn_once = 1; > * Limited because this is done with IRQs disabled. > */ > __read_mostly unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK; > - > __read_mostly int scheduler_running; > > +DEFINE_STATIC_KEY_FALSE(paravirt_cpu_avoid_enabled); > #ifdef CONFIG_SCHED_CORE > > DEFINE_STATIC_KEY_FALSE(__sched_core_enabled); > @@ -2438,7 +2438,7 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) > return false; > > /* CPU marked as avoid, shouldn't chosen to run any task*/ > - if (cpu_avoid(cpu)) > + if (cpu_avoid_check(cpu)) > return false; Here you're patching the code that you've just added. Can you simply add it in a proper way?..