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

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Message-ID: <20210209204314.GG524633@carbon.DHCP.thefacebook.com>
Date:   Tue, 9 Feb 2021 12:43:14 -0800
From:   Roman Gushchin <guro@...com>
To:     Yang Shi <shy828301@...il.com>
CC:     <ktkhai@...tuozzo.com>, <vbabka@...e.cz>, <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 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>
> ---
>  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.

The rest of the patch looks good to me.

Thanks!