linux-kernel - Re: [v7 PATCH 04/12] mm: vmscan: remove memcg_shrinker_map

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Date:   Wed, 10 Feb 2021 19:14:49 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Roman Gushchin <guro@...com>, Yang Shi <shy828301@...il.com>
Cc:     ktkhai@...tuozzo.com, shakeelb@...gle.com, david@...morbit.com,
        hannes@...xchg.org, mhocko@...e.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [v7 PATCH 04/12] mm: vmscan: remove memcg_shrinker_map_size

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@...tuozzo.com>
>> Signed-off-by: Yang Shi <shy828301@...il.com>

Acked-by: Vlastimil Babka <vbabka@...e.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!
>