From: Levi Yun <ppbuk5246@gmail.com>
To: dushistov@mail.ru, arnd@arndb.de, akpm@linux-foundation.org,
gustavo@embeddedor.com, vilhelm.gray@gmail.com,
richard.weiyang@linux.alibaba.com,
andriy.shevchenko@linux.intel.com, joseph.qi@linux.alibaba.com,
skalluru@marvell.com, yury.norov@gmail.com, jpoimboe@redhat.com
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH] lib/find_bit_bench: fix the unmatched iterations cnt
Date: Fri, 11 Dec 2020 17:50:39 +0900 [thread overview]
Message-ID: <20201211085039.GA7619@ubuntu> (raw)
We should have same iteration count when we walk the same bitmap
regardless of using find_next_bit or find_last_bit.
When we run the find_bit_benchmark.ko, we sometime get
unmatched iterations count below:
Start testing find_bit() with random-filled bitmap
[+...] find_next_bit: 875085 ns, 163755 iterations <
[+...] find_next_zero_bit: 865319 ns, 163926 iterations
[+...] find_last_bit: 611807 ns, 163756 iterations <
[+...] find_first_bit: 1601016 ns, 16335 iterations
[+...] find_next_and_bit: 400645 ns, 74040 iterations
[+...]
Start testing find_bit() with sparse bitmap
[+...] find_next_bit: 9942 ns, 654 iterations
[+...] find_next_zero_bit: 1678445 ns, 327027 iterations
[+...] find_last_bit: 7131 ns, 654 iterations
[+...] find_first_bit: 551383 ns, 654 iterations
[+...] find_next_and_bit: 3027 ns, 1 iterations
Normally, this is happen when the last bit of bitmap was set.
This patch fix the unmatched iterations count between
test_find_next_bit and test_find_last_bit.
Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
---
lib/find_bit_benchmark.c | 30 ++++++++++++++++--------------
1 file changed, 16 insertions(+), 14 deletions(-)
diff --git a/lib/find_bit_benchmark.c b/lib/find_bit_benchmark.c
index 5637c5711db9..766e0487852b 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);
@@ -84,12 +86,11 @@ 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);
time = ktime_get() - time;
pr_err("find_last_bit: %18llu ns, %6ld iterations\n", time, cnt);
@@ -99,12 +100,13 @@ static int __init test_find_last_bit(const void *bitmap, unsigned long len)
static int __init test_find_next_and_bit(const void *bitmap,
const void *bitmap2, 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_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);
--
2.27.0
next reply other threads:[~2020-12-11 8:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-11 8:50 Levi Yun [this message]
2020-12-11 16:11 ` [PATCH] lib/find_bit_bench: fix the unmatched iterations cnt Andy Shevchenko
2020-12-11 17:20 ` Yury Norov
2020-12-12 0:09 ` Yun Levi
2020-12-12 18:55 ` Yury Norov
2020-12-13 0:12 ` Yun Levi
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