linux-kernel - Re: [PATCH mm-new v2] mm/khugepaged: Factor out common logic in [scan,alloc]_sleep_millisecs

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Message-ID: <CAA1CXcAgjZ2o44ifY_Ay9MjgGT6q0vfrRBy=vxyecH68YcMYtQ@mail.gmail.com>
Date: Tue, 21 Oct 2025 11:42:16 -0600
From: Nico Pache <npache@...hat.com>
To: Leon Hwang <leon.hwang@...ux.dev>
Cc: akpm@...ux-foundation.org, david@...hat.com, lorenzo.stoakes@...cle.com, 
	ziy@...dia.com, baolin.wang@...ux.alibaba.com, Liam.Howlett@...cle.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 v2] mm/khugepaged: Factor out common logic in [scan,alloc]_sleep_millisecs_store()

On Tue, Oct 21, 2025 at 7:45 AM Leon Hwang <leon.hwang@...ux.dev> 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.
>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Reviewed-by: Zi Yan <ziy@...dia.com>
> Reviewed-by: Lance Yang <lance.yang@...ux.dev>
> Signed-off-by: Leon Hwang <leon.hwang@...ux.dev>

Nice cleanup!

Acked-by: Nico Pache <npache@...hat.com>

> ---
> v1 -> v2:
>   - Simplify callsites of __sleep_millisecs_store() (per Lorenzo).
>   - Collect Reviewed-by from Lorenzo, Zi and Lance - thanks!
>   - https://lore.kernel.org/linux-mm/20251020115350.8175-1-leon.hwang@linux.dev/
>
>  mm/khugepaged.c | 27 +++++++++++----------------
>  1 file changed, 11 insertions(+), 16 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 6f2ae2238b5b..5b7276bc14b1 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 +139,19 @@ 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)
> +{
> +       return __sleep_millisecs_store(buf, count, &khugepaged_scan_sleep_millisecs);
> +}
>  static struct kobj_attribute scan_sleep_millisecs_attr =
>         __ATTR_RW(scan_sleep_millisecs);
>
> @@ -160,18 +166,7 @@ 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;
> -
> -       khugepaged_alloc_sleep_millisecs = msecs;
> -       khugepaged_sleep_expire = 0;
> -       wake_up_interruptible(&khugepaged_wait);
> -
> -       return count;
> +       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
>