linux-kernel - Re: [External] Re: [PATCH 5/5] mm: memcontrol: Simplify the mem_cgroup_page

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Date:   Tue, 27 Oct 2020 22:15:16 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Roman Gushchin <guro@...com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, laoar.shao@...il.com,
        Chris Down <chris@...isdown.name>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>, esyr@...hat.com,
        Suren Baghdasaryan <surenb@...gle.com>, areber@...hat.com,
        Marco Elver <elver@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Cgroups <cgroups@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [External] Re: [PATCH 5/5] mm: memcontrol: Simplify the mem_cgroup_page_lruvec

On Tue, Oct 27, 2020 at 9:36 PM Michal Hocko <mhocko@...e.com> wrote:
>
> On Tue 27-10-20 16:02:56, Muchun Song wrote:
> > We can reuse the code of mem_cgroup_lruvec() to simplify the code
> > of the mem_cgroup_page_lruvec().
>
> yes, removing the code duplication is reasonable. But ...
>
> >
> > Signed-off-by: Muchun Song <songmuchun@...edance.com>
> > ---
> >  include/linux/memcontrol.h | 44 +++++++++++++++++++++++++++-----------
> >  mm/memcontrol.c            | 40 ----------------------------------
> >  2 files changed, 32 insertions(+), 52 deletions(-)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 95807bf6be64..5e8480e54cd8 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -451,16 +451,9 @@ mem_cgroup_nodeinfo(struct mem_cgroup *memcg, int nid)
> >       return memcg->nodeinfo[nid];
> >  }
> >
> > -/**
> > - * mem_cgroup_lruvec - get the lru list vector for a memcg & node
> > - * @memcg: memcg of the wanted lruvec
> > - *
> > - * Returns the lru list vector holding pages for a given @memcg &
> > - * @node combination. This can be the node lruvec, if the memory
> > - * controller is disabled.
> > - */
> > -static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg,
> > -                                            struct pglist_data *pgdat)
> > +static inline struct lruvec *mem_cgroup_node_lruvec(struct mem_cgroup *memcg,
> > +                                                 struct pglist_data *pgdat,
> > +                                                 int nid)
>
> This is just wrong interface. Either take nid or pgdat. You do not want
> both because that just begs for wrong usage.

If we want to avoid abuse of mem_cgroup_node_lruvec. We can move
those functions to the memcontrol.c. And add the "static" attribute to the
mem_cgroup_node_lruvec. Just export mem_cgroup_lruvec and
mem_cgroup_page_lruvec. Is this OK?

Thanks.

> --
> Michal Hocko
> SUSE Labs

-- 
Yours,
Muchun