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: <1a207072-8623-40ef-bf3c-0edc1c6304ea@linux.dev>
Date: Mon, 20 Oct 2025 23:32:17 +0800
From: Leon Hwang <leon.hwang@...ux.dev>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
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 2025/10/20 21:53, Lorenzo Stoakes wrote:
> 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>
> 

Thanks for the review, Lorenzo.

>> ---
>>  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);
> 

Indeed, your suggestion makes the code clearer.

I'll update both occurrences in the next revision.

Thanks,
Leon

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