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Date:   Sun, 6 Dec 2020 15:49:05 +0900
From:   Levi Yun <ppbuk5246@...il.com>
To:     akpm@...ux-foundation.org, yury.norov@...il.com,
        andriy.shevchenko@...ux.intel.com,
        richard.weiyang@...ux.alibaba.com, christian.brauner@...ntu.com,
        arnd@...db.de, jpoimboe@...hat.com, changbin.du@...el.com,
        rdunlap@...radead.org, masahiroy@...nel.org,
        gregkh@...uxfoundation.org, peterz@...radead.org,
        peter.enderborg@...y.com, krzk@...nel.org,
        brendanhiggins@...gle.com, keescook@...omium.org,
        broonie@...nel.org, matti.vaittinen@...rohmeurope.com,
        mhiramat@...nel.org, jpa@....mail.kapsi.fi, nivedita@...m.mit.edu,
        glider@...gle.com, orson.zhai@...soc.com,
        takahiro.akashi@...aro.org, clm@...com, josef@...icpanda.com,
        dsterba@...e.com, dushistov@...l.ru
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-btrfs@...r.kernel.org
Subject: [PATCH v2 5/8] lib/find_bit_bench.c: Add find_last_zero_bit.

Add bench test of find_last_zero_bit.

Also, this patch fix the unmatched iterations value with
find_next_bit and find_last_bit which happen when
the last bit set or not,
Let suppose, 4096 bitmap size and 4095 bit is set only.
In this case former find_next_bit returns iterations count as 0.
But find_last_bit returns it as 1.
This unmatched return value makes some confusion.
So we fix it.

Signed-off-by: Levi Yun <ppbuk5246@...il.com>
---
 lib/find_bit_benchmark.c | 51 +++++++++++++++++++++++++++++-----------
 1 file changed, 37 insertions(+), 14 deletions(-)

diff --git a/lib/find_bit_benchmark.c b/lib/find_bit_benchmark.c
index 5637c5711db9..007371169008 100644
--- a/lib/find_bit_benchmark.c
+++ b/lib/find_bit_benchmark.c
@@ -35,14 +35,14 @@ static DECLARE_BITMAP(bitmap2, BITMAP_LEN) __initdata;
  */
 static int __init test_find_first_bit(void *bitmap, unsigned long len)
 {
-	unsigned long i, cnt;
+	unsigned long i = 0, cnt = 0;
 	ktime_t time;
 
 	time = ktime_get();
-	for (cnt = i = 0; i < len; cnt++) {
+	do {
 		i = find_first_bit(bitmap, len);
 		__clear_bit(i, bitmap);
-	}
+	} while (i++ < len && ++cnt);
 	time = ktime_get() - time;
 	pr_err("find_first_bit:     %18llu ns, %6ld iterations\n", time, cnt);
 
@@ -51,12 +51,13 @@ static int __init test_find_first_bit(void *bitmap, unsigned long len)
 
 static int __init test_find_next_bit(const void *bitmap, unsigned long len)
 {
-	unsigned long i, cnt;
+	unsigned long i = 0, cnt = 0;
 	ktime_t time;
 
 	time = ktime_get();
-	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
-		i = find_next_bit(bitmap, BITMAP_LEN, i) + 1;
+	do {
+		i = find_next_bit(bitmap, BITMAP_LEN, i);
+	} while (i++ < BITMAP_LEN && ++cnt);
 	time = ktime_get() - time;
 	pr_err("find_next_bit:      %18llu ns, %6ld iterations\n", time, cnt);
 
@@ -65,12 +66,13 @@ static int __init test_find_next_bit(const void *bitmap, unsigned long len)
 
 static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len)
 {
-	unsigned long i, cnt;
+	unsigned long i = 0, cnt = 0;
 	ktime_t time;
 
 	time = ktime_get();
-	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
-		i = find_next_zero_bit(bitmap, len, i) + 1;
+	do {
+		i = find_next_zero_bit(bitmap, len, i);
+	} while (i++ < BITMAP_LEN && ++cnt);
 	time = ktime_get() - time;
 	pr_err("find_next_zero_bit: %18llu ns, %6ld iterations\n", time, cnt);
 
@@ -84,27 +86,46 @@ static int __init test_find_last_bit(const void *bitmap, unsigned long len)
 
 	time = ktime_get();
 	do {
-		cnt++;
 		l = find_last_bit(bitmap, len);
 		if (l >= len)
 			break;
 		len = l;
-	} while (len);
+	} while (len >= 0 && ++cnt); /**< to find real 0 bit set. */
 	time = ktime_get() - time;
 	pr_err("find_last_bit:      %18llu ns, %6ld iterations\n", time, cnt);
 
 	return 0;
 }
 
+static int __init test_find_last_zero_bit(const void *bitmap, unsigned long len)
+{
+	unsigned long l, cnt = 0;
+	ktime_t time;
+
+	time = ktime_get();
+	do {
+		l = find_last_zero_bit(bitmap, len);
+		if (l >= len)
+			break;
+		len = l;
+	} while (len >= 0 && ++cnt); /**< to find real 0 bit set. */
+	time = ktime_get() - time;
+	pr_err("find_last_zero_bit:      %18llu ns, %6ld iterations\n", time, cnt);
+
+	return 0;
+}
+
+
 static int __init test_find_next_and_bit(const void *bitmap,
 		const void *bitmap2, unsigned long len)
 {
-	unsigned long i, cnt;
+	unsigned long i, cnt = 0;
 	ktime_t time;
 
 	time = ktime_get();
-	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
-		i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i + 1);
+	do {
+		i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i);
+	} while (i++ < BITMAP_LEN && ++cnt);
 	time = ktime_get() - time;
 	pr_err("find_next_and_bit:  %18llu ns, %6ld iterations\n", time, cnt);
 
@@ -123,6 +144,7 @@ static int __init find_bit_test(void)
 	test_find_next_bit(bitmap, BITMAP_LEN);
 	test_find_next_zero_bit(bitmap, BITMAP_LEN);
 	test_find_last_bit(bitmap, BITMAP_LEN);
+	test_find_last_zero_bit(bitmap, BITMAP_LEN);
 
 	/*
 	 * test_find_first_bit() may take some time, so
@@ -144,6 +166,7 @@ static int __init find_bit_test(void)
 	test_find_next_bit(bitmap, BITMAP_LEN);
 	test_find_next_zero_bit(bitmap, BITMAP_LEN);
 	test_find_last_bit(bitmap, BITMAP_LEN);
+	test_find_last_zero_bit(bitmap, BITMAP_LEN);
 	test_find_first_bit(bitmap, BITMAP_LEN);
 	test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);
 
-- 
2.27.0

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