2021-05-05 10:59:45

by Zheng Yongjun

Subject: [PATCH -next v4] bcache: Use DEFINE_MUTEX() for mutex lock

Mutex lock can be initialized automatically with DEFINE_MUTEX() rather
than explicitly calling mutex_init().

This patch will reduce the size of bcache.ko about 16 bytes, the
reason as follows:

Though this patch will increase the size of .data segment about 32
bytes, it will also reduce the size of .init.text and
.rodata.str1.1(at x86_64), .rodata_str1.8(at arm64) total about 48
bytes which reduce the size more than .data segment;

Here is the statistics:
Sections: (arm64 platform)
Idx name size
-.init.text 00000240
+.init.text 00000228

-.rodata.str1.8 000012cd
+.rodata.str1.8 000012b5

-.data 00000c60
+.data 00000c80

Sections: (x86 platform)
Idx name size
-.init.text 000001d9
+.init.text 000001bf

-.rodata.str1.1 00000c80
+.rodata.str1.1 00000c6d

-.data 00000cc0
+.data 00000ce0

Reported-by: Hulk Robot <[email protected]>
Signed-off-by: Zheng Yongjun <[email protected]>
---

v4:
- change commit log, delete bss information at commit description.
v3:
- change commit log, delete statistic about .bss segment.
v2:
- add commit log about the reason why bcache.ko size reduced.
---
drivers/md/bcache/super.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 03e1fe4de53d..3635f454309e 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -40,7 +40,7 @@ static const char invalid_uuid[] = {
};

static struct kobject *bcache_kobj;
-struct mutex bch_register_lock;
+DEFINE_MUTEX(bch_register_lock);
bool bcache_is_reboot;
LIST_HEAD(bch_cache_sets);
static LIST_HEAD(uncached_devices);
@@ -2869,7 +2869,6 @@ static int __init bcache_init(void)

check_module_parameters();

- mutex_init(&bch_register_lock);
init_waitqueue_head(&unregister_wait);
register_reboot_notifier(&reboot);

--
2.25.1

2021-05-06 03:45:09

by Coly Li

Subject: Re: [PATCH -next v4] bcache: Use DEFINE_MUTEX() for mutex lock

On 5/5/21 7:06 PM, Zheng Yongjun wrote:
> Mutex lock can be initialized automatically with DEFINE_MUTEX() rather
> than explicitly calling mutex_init().
>
> This patch will reduce the size of bcache.ko about 16 bytes, the
> reason as follows:
>
> Though this patch will increase the size of .data segment about 32
> bytes, it will also reduce the size of .init.text and
> .rodata.str1.1(at x86_64), .rodata_str1.8(at arm64) total about 48
> bytes which reduce the size more than .data segment;
>
> Here is the statistics:
> Sections: (arm64 platform)
> Idx name size
> -.init.text 00000240
> +.init.text 00000228
>
> -.rodata.str1.8 000012cd
> +.rodata.str1.8 000012b5
>
> -.data 00000c60
> +.data 00000c80
>
> Sections: (x86 platform)
> Idx name size
> -.init.text 000001d9
> +.init.text 000001bf
>
> -.rodata.str1.1 00000c80
> +.rodata.str1.1 00000c6d
>
> -.data 00000cc0
> +.data 00000ce0
>
> Reported-by: Hulk Robot <[email protected]>
> Signed-off-by: Zheng Yongjun <[email protected]>

Added in my for-test queue.

Thanks.

Coly Li

[snipped]

2021-05-06 08:36:13

by Zheng Yongjun

Subject: 答复: [PATCH -next v4] bcache: Use DEFINE_M UTEX() for mutex lock

I've been on a business trip some time ago and didn't do upstream work. Thanks for your patience:)

-----邮件原件-----
发件人: Coly Li [mailto:[email protected]]
发送时间: 2021年5月6日 11:27
收件人: zhengyongjun <[email protected]>
抄送: pmail_hulkci <[email protected]>; [email protected]; [email protected]; [email protected]
主题: Re: [PATCH -next v4] bcache: Use DEFINE_MUTEX() for mutex lock

On 5/5/21 7:06 PM, Zheng Yongjun wrote:
> Mutex lock can be initialized automatically with DEFINE_MUTEX() rather
> than explicitly calling mutex_init().
>
> This patch will reduce the size of bcache.ko about 16 bytes, the
> reason as follows:
>
> Though this patch will increase the size of .data segment about 32
> bytes, it will also reduce the size of .init.text and
> .rodata.str1.1(at x86_64), .rodata_str1.8(at arm64) total about 48
> bytes which reduce the size more than .data segment;
>
> Here is the statistics:
> Sections: (arm64 platform)
> Idx name size
> -.init.text 00000240
> +.init.text 00000228
>
> -.rodata.str1.8 000012cd
> +.rodata.str1.8 000012b5
>
> -.data 00000c60
> +.data 00000c80
>
> Sections: (x86 platform)
> Idx name size
> -.init.text 000001d9
> +.init.text 000001bf
>
> -.rodata.str1.1 00000c80
> +.rodata.str1.1 00000c6d
>
> -.data 00000cc0
> +.data 00000ce0
>
> Reported-by: Hulk Robot <[email protected]>
> Signed-off-by: Zheng Yongjun <[email protected]>

Added in my for-test queue.

Thanks.

Coly Li

[snipped]