linux-kernel - [PATCH 1/6] smp: optimize smp_call_function_many

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Date: Mon, 13 May 2024 15:01:41 -0700
From: Yury Norov <yury.norov@...il.com>
To: linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Ben Segall <bsegall@...gle.com>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Imran Khan <imran.f.khan@...cle.com>,
	Ingo Molnar <mingo@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Leonardo Bras <leobras@...hat.com>,
	Mel Gorman <mgorman@...e.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Rik van Riel <riel@...riel.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Waiman Long <longman@...hat.com>,
	Yury Norov <yury.norov@...il.com>,
	Zefan Li <lizefan.x@...edance.com>,
	cgroups@...r.kernel.org
Subject: [PATCH 1/6] smp: optimize smp_call_function_many_cond()

The function may be called with mask == cpu_online_mask, and in this
case we can use a cheaper cpumask_cooy() instead of cpumask_and().

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 kernel/smp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index f085ebcdf9e7..6f41214a1b54 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -798,7 +798,10 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
 
 	if (run_remote) {
 		cfd = this_cpu_ptr(&cfd_data);
-		cpumask_and(cfd->cpumask, mask, cpu_online_mask);
+		if (mask == cpu_online_mask)
+			cpumask_copy(cfd->cpumask, mask);
+		else
+			cpumask_and(cfd->cpumask, mask, cpu_online_mask);
 		__cpumask_clear_cpu(this_cpu, cfd->cpumask);
 
 		cpumask_clear(cfd->cpumask_ipi);
-- 
2.40.1