linux-kernel - Re: [PATCH] mm: Use unsigned types for fragmentation score

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Date:   Thu, 18 Jun 2020 07:24:57 -0700
From:   Nitin Gupta <ngupta@...ingupta.dev>
To:     Baoquan He <bhe@...hat.com>, Nitin Gupta <nigupta@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:PROC SYSCTL" <linux-fsdevel@...r.kernel.org>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: Use unsigned types for fragmentation score

On 6/18/20 6:41 AM, Baoquan He wrote:
> On 06/17/20 at 06:03pm, Nitin Gupta wrote:
>> Proactive compaction uses per-node/zone "fragmentation score" which
>> is always in range [0, 100], so use unsigned type of these scores
>> as well as for related constants.
>>
>> Signed-off-by: Nitin Gupta <nigupta@...dia.com>
>> ---
>>  include/linux/compaction.h |  4 ++--
>>  kernel/sysctl.c            |  2 +-
>>  mm/compaction.c            | 18 +++++++++---------
>>  mm/vmstat.c                |  2 +-
>>  4 files changed, 13 insertions(+), 13 deletions(-)
>>
>> diff --git a/include/linux/compaction.h b/include/linux/compaction.h
>> index 7a242d46454e..25a521d299c1 100644
>> --- a/include/linux/compaction.h
>> +++ b/include/linux/compaction.h
>> @@ -85,13 +85,13 @@ static inline unsigned long compact_gap(unsigned int order)
>>  
>>  #ifdef CONFIG_COMPACTION
>>  extern int sysctl_compact_memory;
>> -extern int sysctl_compaction_proactiveness;
>> +extern unsigned int sysctl_compaction_proactiveness;
>>  extern int sysctl_compaction_handler(struct ctl_table *table, int write,
>>  			void *buffer, size_t *length, loff_t *ppos);
>>  extern int sysctl_extfrag_threshold;
>>  extern int sysctl_compact_unevictable_allowed;
>>  
>> -extern int extfrag_for_order(struct zone *zone, unsigned int order);
>> +extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order);
>>  extern int fragmentation_index(struct zone *zone, unsigned int order);
>>  extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
>>  		unsigned int order, unsigned int alloc_flags,
>> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
>> index 58b0a59c9769..40180cdde486 100644
>> --- a/kernel/sysctl.c
>> +++ b/kernel/sysctl.c
>> @@ -2833,7 +2833,7 @@ static struct ctl_table vm_table[] = {
>>  	{
>>  		.procname	= "compaction_proactiveness",
>>  		.data		= &sysctl_compaction_proactiveness,
>> -		.maxlen		= sizeof(int),
>> +		.maxlen		= sizeof(sysctl_compaction_proactiveness),
> 
> Patch looks good to me. Wondering why not using 'unsigned int' here,
> just curious.
> 


It's just coding style preference. I see the same style used for many
other sysctls too (min_free_kbytes etc.).

Thanks,
Nitin