2023-10-29 10:30:27

by Christophe JAILLET

Subject: [PATCH] bcache: Optimize sysfs_hprint()

The size of what is in 'buf' is already computed by bch_hprint(), so skip
these bytes when calling strcat().

This easily saves a few cycles. (should it matter)

Signed-off-by: Christophe JAILLET <[email protected]>
---
drivers/md/bcache/sysfs.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/bcache/sysfs.h b/drivers/md/bcache/sysfs.h
index 65b8bd975ab1..798bcbeab0bb 100644
--- a/drivers/md/bcache/sysfs.h
+++ b/drivers/md/bcache/sysfs.h
@@ -78,7 +78,7 @@ do { \
do { \
if (attr == &sysfs_ ## file) { \
ssize_t ret = bch_hprint(buf, val); \
- strcat(buf, "\n"); \
+ strcat(buf + ret, "\n"); \
return ret + 1; \
} \
} while (0)
--
2.34.1

2023-10-30 07:38:43

by Coly Li

Subject: Re: [PATCH] bcache: Optimize sysfs_hprint()

> 2023年10月29日 18:30，Christophe JAILLET <[email protected]> 写道：
>
> The size of what is in 'buf' is already computed by bch_hprint(), so skip
> these bytes when calling strcat().
>
> This easily saves a few cycles. (should it matter)
>
> Signed-off-by: Christophe JAILLET <[email protected]>

Your change does save several cpu cycles, but hurts the readability. This is not hot code path, just let strcat to do what it was designed for.

Thanks.

Coly Li

> ---
> drivers/md/bcache/sysfs.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/bcache/sysfs.h b/drivers/md/bcache/sysfs.h
> index 65b8bd975ab1..798bcbeab0bb 100644
> --- a/drivers/md/bcache/sysfs.h
> +++ b/drivers/md/bcache/sysfs.h
> @@ -78,7 +78,7 @@ do { \
> do { \
> if (attr == &sysfs_ ## file) { \
> ssize_t ret = bch_hprint(buf, val); \
> - strcat(buf, "\n"); \
> + strcat(buf + ret, "\n"); \
> return ret + 1; \
> } \
> } while (0)
> --
> 2.34.1
>