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Subject: Re: [v7 PATCH 04/12] mm: vmscan: remove memcg_shrinker_map_size
To:     Roman Gushchin <guro@fb.com>, Yang Shi <shy828301@gmail.com>
Cc:     ktkhai@virtuozzo.com, shakeelb@google.com, david@fromorbit.com,
        hannes@cmpxchg.org, mhocko@suse.com, akpm@linux-foundation.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20210209174646.1310591-1-shy828301@gmail.com>
 <20210209174646.1310591-5-shy828301@gmail.com>
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From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <d27223a8-0a00-b670-da5b-205d4c16a2e4@suse.cz>
Date:   Wed, 10 Feb 2021 19:14:49 +0100
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On 2/9/21 9:43 PM, Roman Gushchin wrote:
> On Tue, Feb 09, 2021 at 09:46:38AM -0800, Yang Shi wrote:
>> Both memcg_shrinker_map_size and shrinker_nr_max is maintained, but actually the
>> map size can be calculated via shrinker_nr_max, so it seems unnecessary to keep both.
>> Remove memcg_shrinker_map_size since shrinker_nr_max is also used by iterating the
>> bit map.
>> 
>> Acked-by: Kirill Tkhai <ktkhai@virtuozzo.com>
>> Signed-off-by: Yang Shi <shy828301@gmail.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

>> ---
>>  mm/vmscan.c | 18 +++++++++---------
>>  1 file changed, 9 insertions(+), 9 deletions(-)
>> 
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index e4ddaaaeffe2..641077b09e5d 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -185,8 +185,10 @@ static LIST_HEAD(shrinker_list);
>>  static DECLARE_RWSEM(shrinker_rwsem);
>>  
>>  #ifdef CONFIG_MEMCG
>> +static int shrinker_nr_max;
>>  
>> -static int memcg_shrinker_map_size;
>> +#define NR_MAX_TO_SHR_MAP_SIZE(nr_max) \
>> +	(DIV_ROUND_UP(nr_max, BITS_PER_LONG) * sizeof(unsigned long))
> 
> How about something like this?
> 
> static inline int shrinker_map_size(int nr_items)
> {
> 	return DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long);
> }
> 
> I think it look less cryptic.

Yeah that looks nicer so I'm fine with that potential change.

> The rest of the patch looks good to me.
> 
> Thanks!
>