[PATCH 13/22] x86: smp: move cpumask_weight() out of for-loop in remove_siblinginfo

From: Yury Norov <yury.norov@gmail.com>
To: "Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"David Laight" <David.Laight@ACULAB.COM>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Joe Perches" <joe@perches.com>,
	"Julia Lawall" <Julia.Lawall@inria.fr>,
	"Michał Mirosław" <mirq-linux@rere.qmqm.pl>,
	"Nicholas Piggin" <npiggin@gmail.com>,
	"Nicolas Palix" <nicolas.palix@imag.fr>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
	"Matti Vaittinen" <Matti.Vaittinen@fi.rohmeurope.com>,
	linux-kernel@vger.kernel.org
Cc: Yury Norov <yury.norov@gmail.com>,
	Balbir Singh <sblbir@amazon.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H . Peter Anvin" <hpa@zytor.com>, Huang Rui <ray.huang@amd.com>,
	Ingo Molnar <mingo@redhat.com>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Sean Christopherson <seanjc@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	x86@kernel.org
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	[thread overview]
Message-ID: <20220510154750.212913-14-yury.norov@gmail.com> (raw)
In-Reply-To: <20220510154750.212913-1-yury.norov@gmail.com>

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

