1 files changed, 144 insertions, 0 deletions

diff --git a/lib/find_bit_benchmark.c b/lib/find_bit_benchmark.c
new file mode 100644
index 000000000000..f4394a36f9aa
--- /dev/null
+++ b/lib/find_bit_benchmark.c
@@ -0,0 +1,144 @@
+/*
+ * Test for find_*_bit functions.
+ *
+ * Copyright (c) 2017 Cavium.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+
+/*
+ * find_bit functions are widely used in kernel, so the successful boot
+ * is good enough test for correctness.
+ *
+ * This test is focused on performance of traversing bitmaps. Two typical
+ * scenarios are reproduced:
+ * - randomly filled bitmap with approximately equal number of set and
+ *   cleared bits;
+ * - sparse bitmap with few set bits at random positions.
+ */
+
+#include <linux/bitops.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/random.h>
+
+#define BITMAP_LEN      (4096UL * 8 * 10)
+#define SPARSE          500
+
+static DECLARE_BITMAP(bitmap, BITMAP_LEN) __initdata;
+
+/*
+ * This is Schlemiel the Painter's algorithm. It should be called after
+ * all other tests for the same bitmap because it sets all bits of bitmap to 1.
+ */
+static int __init test_find_first_bit(void *bitmap, unsigned long len)
+{
+        unsigned long i, cnt;
+        cycles_t cycles;
+
+        cycles = get_cycles();
+        for (cnt = i = 0; i < len; cnt++) {
+                i = find_first_bit(bitmap, len);
+                __clear_bit(i, bitmap);
+        }
+        cycles = get_cycles() - cycles;
+        pr_err("find_first_bit:\t\t%llu cycles,\t%ld iterations\n",
+               (u64)cycles, cnt);
+
+        return 0;
+}
+
+static int __init test_find_next_bit(const void *bitmap, unsigned long len)
+{
+        unsigned long i, cnt;
+        cycles_t cycles;
+
+        cycles = get_cycles();
+        for (cnt = i = 0; i < BITMAP_LEN; cnt++)
+                i = find_next_bit(bitmap, BITMAP_LEN, i) + 1;
+        cycles = get_cycles() - cycles;
+        pr_err("find_next_bit:\t\t%llu cycles,\t%ld iterations\n",
+               (u64)cycles, cnt);
+
+        return 0;
+}
+
+static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len)
+{
+        unsigned long i, cnt;
+        cycles_t cycles;
+
+        cycles = get_cycles();
+        for (cnt = i = 0; i < BITMAP_LEN; cnt++)
+                i = find_next_zero_bit(bitmap, len, i) + 1;
+        cycles = get_cycles() - cycles;
+        pr_err("find_next_zero_bit:\t%llu cycles,\t%ld iterations\n",
+               (u64)cycles, cnt);
+
+        return 0;
+}
+
+static int __init test_find_last_bit(const void *bitmap, unsigned long len)
+{
+        unsigned long l, cnt = 0;
+        cycles_t cycles;
+
+        cycles = get_cycles();
+        do {
+                cnt++;
+                l = find_last_bit(bitmap, len);
+                if (l >= len)
+                        break;
+                len = l;
+        } while (len);
+        cycles = get_cycles() - cycles;
+        pr_err("find_last_bit:\t\t%llu cycles,\t%ld iterations\n",
+               (u64)cycles, cnt);
+
+        return 0;
+}
+
+static int __init find_bit_test(void)
+{
+        unsigned long nbits = BITMAP_LEN / SPARSE;
+
+        pr_err("\nStart testing find_bit() with random-filled bitmap\n");
+
+        get_random_bytes(bitmap, sizeof(bitmap));
+
+        test_find_next_bit(bitmap, BITMAP_LEN);
+        test_find_next_zero_bit(bitmap, BITMAP_LEN);
+        test_find_last_bit(bitmap, BITMAP_LEN);
+        test_find_first_bit(bitmap, BITMAP_LEN);
+
+        pr_err("\nStart testing find_bit() with sparse bitmap\n");
+
+        bitmap_zero(bitmap, BITMAP_LEN);
+
+        while (nbits--)
+                __set_bit(prandom_u32() % BITMAP_LEN, bitmap);
+
+        test_find_next_bit(bitmap, BITMAP_LEN);
+        test_find_next_zero_bit(bitmap, BITMAP_LEN);
+        test_find_last_bit(bitmap, BITMAP_LEN);
+        test_find_first_bit(bitmap, BITMAP_LEN);
+
+        return 0;
+}
+module_init(find_bit_test);
+
+static void __exit test_find_bit_cleanup(void)
+{
+}
+module_exit(test_find_bit_cleanup);
+
+MODULE_LICENSE("GPL");