Messages in this thread Patch in this message | | | From | Yury Norov <> | Subject | [PATCH 13/22] x86: smp: move cpumask_weight() out of for-loop in remove_siblinginfo | Date | Tue, 10 May 2022 08:47:41 -0700 |
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Because argument of the function is constant inside for_each_cpu() loop, the cpumask_weight() does the same work O(NR_CPUS) times, while it may be calculated only once.
This patch moves cpumask_weight() out of the loop and replaces it with cpumask_weight_eq(). While here, fix comment format.
CC: Balbir Singh <sblbir@amazon.com> CC: Boris Ostrovsky <boris.ostrovsky@oracle.com> CC: Borislav Petkov <bp@alien8.de> CC: Dave Hansen <dave.hansen@linux.intel.com> CC: H. Peter Anvin <hpa@zytor.com> CC: Huang Rui <ray.huang@amd.com> CC: Ingo Molnar <mingo@redhat.com> CC: Paul E. McKenney <paulmck@kernel.org> CC: Peter Zijlstra <peterz@infradead.org> CC: Rafael J. Wysocki <rafael.j.wysocki@intel.com> CC: Sean Christopherson <seanjc@google.com> CC: Thomas Gleixner <tglx@linutronix.de> CC: Tim Chen <tim.c.chen@linux.intel.com> CC: x86@kernel.org CC: linux-kernel@vger.kernel.org Signed-off-by: Yury Norov <yury.norov@gmail.com> --- arch/x86/kernel/smpboot.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 5e7f9532a10d..7d948f79ef31 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1605,13 +1605,14 @@ static void remove_siblinginfo(int cpu) { int sibling; struct cpuinfo_x86 *c = &cpu_data(cpu); + bool last_thread_sibling = cpumask_weight_eq(topology_sibling_cpumask(cpu), 1); for_each_cpu(sibling, topology_core_cpumask(cpu)) { cpumask_clear_cpu(cpu, topology_core_cpumask(sibling)); - /*/ + /* * last thread sibling in this cpu core going down */ - if (cpumask_weight(topology_sibling_cpumask(cpu)) == 1) + if (last_thread_sibling) cpu_data(sibling).booted_cores--; } -- 2.32.0
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