linux-kernel - Re: [PATCH mm-new 1/1] mm/khugepaged: Factor out common logic in [scan,alloc]_sleep_millisecs

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Message-ID: <7d9b4ac6-b0c2-4a0e-bee1-23f7a82eea72@lucifer.local>
Date: Mon, 20 Oct 2025 14:53:28 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Leon Hwang <leon.hwang@...ux.dev>
Cc: akpm@...ux-foundation.org, david@...hat.com, ziy@...dia.com,
        baolin.wang@...ux.alibaba.com, Liam.Howlett@...cle.com,
        npache@...hat.com, ryan.roberts@....com, dev.jain@....com,
        baohua@...nel.org, lance.yang@...ux.dev, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH mm-new 1/1] mm/khugepaged: Factor out common logic in
 [scan,alloc]_sleep_millisecs_store()

On Mon, Oct 20, 2025 at 07:53:50PM +0800, Leon Hwang wrote:
> Both scan_sleep_millisecs_store() and alloc_sleep_millisecs_store()
> perform the same operations: parse the input value, update their
> respective sleep interval, reset khugepaged_sleep_expire, and wake up
> the khugepaged thread.
>
> Factor out this duplicated logic into a helper function
> __sleep_millisecs_store(), and simplify both store functions.
>
> No functional change intended.
>
> Signed-off-by: Leon Hwang <leon.hwang@...ux.dev>

Thanks this is a decent cleanup, with the nit(s0 below addressed LGTM, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  mm/khugepaged.c | 29 ++++++++++++++---------------
>  1 file changed, 14 insertions(+), 15 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 0341c3d13e9e..0b7915015e9e 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -129,9 +129,8 @@ static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
>  	return sysfs_emit(buf, "%u\n", khugepaged_scan_sleep_millisecs);
>  }
>
> -static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
> -					  struct kobj_attribute *attr,
> -					  const char *buf, size_t count)
> +static ssize_t __sleep_millisecs_store(const char *buf, size_t count,
> +				       unsigned int *millisecs)
>  {
>  	unsigned int msecs;
>  	int err;
> @@ -140,12 +139,21 @@ static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
>  	if (err)
>  		return -EINVAL;
>
> -	khugepaged_scan_sleep_millisecs = msecs;
> +	*millisecs = msecs;
>  	khugepaged_sleep_expire = 0;
>  	wake_up_interruptible(&khugepaged_wait);
>
>  	return count;
>  }
> +
> +static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
> +					  struct kobj_attribute *attr,
> +					  const char *buf, size_t count)
> +{
> +	unsigned int *millisecs = &khugepaged_scan_sleep_millisecs;
> +
> +	return __sleep_millisecs_store(buf, count, millisecs);

I think this'd be much clearer as:

return __sleep_millisecs_store(buf, count, &khugepaged_alloc_scan_millisecs);

> +}
>  static struct kobj_attribute scan_sleep_millisecs_attr =
>  	__ATTR_RW(scan_sleep_millisecs);
>
> @@ -160,18 +168,9 @@ static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
>  					   struct kobj_attribute *attr,
>  					   const char *buf, size_t count)
>  {
> -	unsigned int msecs;
> -	int err;
> -
> -	err = kstrtouint(buf, 10, &msecs);
> -	if (err)
> -		return -EINVAL;
> +	unsigned int *millisecs = &khugepaged_alloc_sleep_millisecs;
>
> -	khugepaged_alloc_sleep_millisecs = msecs;
> -	khugepaged_sleep_expire = 0;
> -	wake_up_interruptible(&khugepaged_wait);
> -
> -	return count;
> +	return __sleep_millisecs_store(buf, count, millisecs);
>  }

I think this'd be much clearer as:

return __sleep_millisecs_store(buf, count, &khugepaged_alloc_sleep_millisecs);

>  static struct kobj_attribute alloc_sleep_millisecs_attr =
>  	__ATTR_RW(alloc_sleep_millisecs);
> --
> 2.51.0
>