+ lib-group_cpus-drop-unneeded-cpumask_empty-call-in-__group_cpus_evenly.patch added to mm-nonmm-unstable branch

+ lib-group_cpus-drop-unneeded-cpumask_empty-call-in-__group_cpus_evenly.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: lib/group_cpus: drop unneeded cpumask_empty() call in __group_cpus_evenly()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     lib-group_cpus-drop-unneeded-cpumask_empty-call-in-__group_cpus_evenly.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-group_cpus-drop-unneeded-cpumask_empty-call-in-__group_cpus_evenly.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Yury Norov <yury.norov@gmail.com>
Subject: lib/group_cpus: drop unneeded cpumask_empty() call in __group_cpus_evenly()
Date: Thu, 28 Dec 2023 12:09:33 -0800

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 redundant cpumask_empty() call from the
__group_cpus_evenly() and save few cycles.

Link: https://lkml.kernel.org/r/20231228200936.2475595-7-yury.norov@gmail.com
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/group_cpus.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

--- a/lib/group_cpus.c~lib-group_cpus-drop-unneeded-cpumask_empty-call-in-__group_cpus_evenly
+++ a/lib/group_cpus.c
@@ -259,9 +259,6 @@ static int __group_cpus_evenly(unsigned
 	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);
 
 	/*
@@ -401,9 +398,14 @@ struct cpumask *group_cpus_evenly(unsign
 		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;
 
_

Patches currently in -mm which might be from yury.norov@gmail.com are

cpumask-introduce-for_each_cpu_and_from.patch
lib-group_cpus-optimize-inner-loop-in-grp_spread_init_one.patch
lib-group_cpus-relax-atomicity-requirement-in-grp_spread_init_one.patch
lib-group_cpus-optimize-outer-loop-in-grp_spread_init_one.patch
lib-group_cpus-dont-zero-cpumasks-in-group_cpus_evenly-on-allocation.patch
lib-group_cpus-drop-unneeded-cpumask_empty-call-in-__group_cpus_evenly.patch
cpumask-define-cleanup-function-for-cpumasks.patch
lib-group_cpus-rework-group_cpus_evenly.patch
lib-group_cpus-simplify-group_cpus_evenly-for-more.patch