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

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Date:   Tue, 9 Feb 2021 15:31:17 -0800
From:   Yang Shi <shy828301@...il.com>
To:     Roman Gushchin <guro@...com>
Cc:     Kirill Tkhai <ktkhai@...tuozzo.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Shakeel Butt <shakeelb@...gle.com>,
        Dave Chinner <david@...morbit.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [v7 PATCH 04/12] mm: vmscan: remove memcg_shrinker_map_size

On Tue, Feb 9, 2021 at 12:43 PM Roman Gushchin <guro@...com> 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>
> > ---
> >  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.

OK, I don't have a strong opinion for either one (inline function or
macro). If no one objects this I could do it in the new version.

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