linux-kernel - [PATCH 6/6] lib/group_cpus.c: drop unneeded cpumask_empty() call in __group_cpus

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Message-Id: <20231207203900.859776-7-yury.norov@gmail.com>
Date:   Thu,  7 Dec 2023 12:39:00 -0800
From:   Yury Norov <yury.norov@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Cc:     Yury Norov <yury.norov@...il.com>, Ming Lei <ming.lei@...hat.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH 6/6] lib/group_cpus.c: drop unneeded cpumask_empty() call in __group_cpus_evenly()

The function is called twice. First time it's called with
cpumask_present as a parameter, which can't be empty. Second time it's
called with a mask created with cpumask_andnot(), which returns false if
the result is an empty mask.

We can safely drop redundand cpumask_empty() call from the
__group_cpus_evenly() and save few cycles.

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 lib/group_cpus.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/lib/group_cpus.c b/lib/group_cpus.c
index c7fcd04c87bf..664a56171a1b 100644
--- a/lib/group_cpus.c
+++ b/lib/group_cpus.c
@@ -252,9 +252,6 @@ static int __group_cpus_evenly(unsigned int startgrp, unsigned int numgrps,
 	nodemask_t nodemsk = NODE_MASK_NONE;
 	struct node_groups *node_groups;
 
-	if (cpumask_empty(cpu_mask))
-		return 0;
-
 	nodes = get_nodes_in_cpumask(node_to_cpumask, cpu_mask, &nodemsk);
 
 	/*
@@ -394,9 +391,14 @@ struct cpumask *group_cpus_evenly(unsigned int numgrps)
 		curgrp = 0;
 	else
 		curgrp = nr_present;
-	cpumask_andnot(npresmsk, cpu_possible_mask, npresmsk);
-	ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask,
-				  npresmsk, nmsk, masks);
+
+	if (cpumask_andnot(npresmsk, cpu_possible_mask, npresmsk))
+		/* If npresmsk is not empty */
+		ret = __group_cpus_evenly(curgrp, numgrps, node_to_cpumask,
+					  npresmsk, nmsk, masks);
+	else
+		ret = 0;
+
 	if (ret >= 0)
 		nr_others = ret;
 
-- 
2.40.1