linux-kernel - [PATCH 36/54] lib/cpumask: add cpumask_weight

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Date:   Sun, 23 Jan 2022 10:39:07 -0800
From:   Yury Norov <yury.norov@...il.com>
To:     Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        David Laight <David.Laight@...lab.com>,
        Joe Perches <joe@...ches.com>, Dennis Zhou <dennis@...nel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Nicholas Piggin <npiggin@...il.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Alexey Klimov <aklimov@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 36/54] lib/cpumask: add cpumask_weight_{eq,gt,ge,lt,le}

In many cases people use cpumask_weight() to compare the result against
some number or expression:

	if (cpumask_weight(...) > 1)
		do_something();

It may be significantly improved for large cpumasks: if first few words
count set bits to a number greater than given, we can stop counting and
immediately return.

The same idea would work in other direction: if we know that the number
of set bits that we counted so far is small enough, so that it would be
smaller than required number even if all bits of the rest of the cpumask
are set, we can stop counting earlier.

This patch adds cpumask_weight_{eq, gt, ge, lt, le} helpers based on
corresponding bitmap functions. The following patches apply new functions
where appropriate.

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 include/linux/cpumask.h | 50 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 64dae70d31f5..1906e3225737 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -575,6 +575,56 @@ static inline unsigned int cpumask_weight(const struct cpumask *srcp)
 	return bitmap_weight(cpumask_bits(srcp), nr_cpumask_bits);
 }
 
+/**
+ * cpumask_weight_eq - Check if # of bits in *srcp is equal to a given number
+ * @srcp: the cpumask to count bits (< nr_cpu_ids) in.
+ * @num: the number to check.
+ */
+static inline bool cpumask_weight_eq(const struct cpumask *srcp, unsigned int num)
+{
+	return bitmap_weight_eq(cpumask_bits(srcp), nr_cpumask_bits, num);
+}
+
+/**
+ * cpumask_weight_gt - Check if # of bits in *srcp is greater than a given number
+ * @srcp: the cpumask to count bits (< nr_cpu_ids) in.
+ * @num: the number to check.
+ */
+static inline bool cpumask_weight_gt(const struct cpumask *srcp, int num)
+{
+	return bitmap_weight_gt(cpumask_bits(srcp), nr_cpumask_bits, num);
+}
+
+/**
+ * cpumask_weight_ge - Check if # of bits in *srcp is greater than or equal to a given number
+ * @srcp: the cpumask to count bits (< nr_cpu_ids) in.
+ * @num: the number to check.
+ */
+static inline bool cpumask_weight_ge(const struct cpumask *srcp, int num)
+{
+	return bitmap_weight_ge(cpumask_bits(srcp), nr_cpumask_bits, num);
+}
+
+/**
+ * cpumask_weight_lt - Check if # of bits in *srcp is less than a given number
+ * @srcp: the cpumask to count bits (< nr_cpu_ids) in.
+ * @num: the number to check.
+ */
+static inline bool cpumask_weight_lt(const struct cpumask *srcp, int num)
+{
+	return bitmap_weight_lt(cpumask_bits(srcp), nr_cpumask_bits, num);
+}
+
+/**
+ * cpumask_weight_le - Check if # of bits in *srcp is less than or equal to a given number
+ * @srcp: the cpumask to count bits (< nr_cpu_ids) in.
+ * @num: the number to check.
+ */
+static inline bool cpumask_weight_le(const struct cpumask *srcp, int num)
+{
+	return bitmap_weight_le(cpumask_bits(srcp), nr_cpumask_bits, num);
+}
+
 /**
  * cpumask_shift_right - *dstp = *srcp >> n
  * @dstp: the cpumask result
-- 
2.30.2