Re: [RFC 3/5] mm/memcontrol: do not scan anon pages if memsw limit is hit

[jingxiang zeng <jingxiangzeng.cas@gmail.com>]

On Thu, 20 Mar 2025 at 03:36, Shakeel Butt <shakeel.butt@linux.dev> wrote:
>
> On Wed, Mar 19, 2025 at 02:41:46PM +0800, Jingxiang Zeng wrote:
> > From: Zeng Jingxiang <linuszeng@tencent.com>
> >
> > When memory recycling is triggered by the hard watermark of
>
> What is hard watermark?

memory.memsw.limit_in_bytes.
>
> > memsw, anonymous pages do not want to be recycled any further.
> > This is consistent with the processing method of cgroup v2.
> >
> > Signed-off-by: Zeng Jingxiang <linuszeng@tencent.com>
>
> Is this patch orthogonal to the series or is it needed for v1 as well?

Yes, it is needed for cgroupv1 as well
>
> > ---
> >  mm/memcontrol.c | 15 +++++++++++----
> >  1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index c1171fb2bfd6..623ebf610946 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -5072,14 +5072,21 @@ void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
> >
> >  long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
> >  {
> > +     struct page_counter *pg_counter;
> >       long nr_swap_pages = get_nr_swap_pages();
> >
> > -     if (mem_cgroup_disabled() || do_memsw_account())
> > +     if (mem_cgroup_disabled())
> >               return nr_swap_pages;
> > -     for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg))
> > +     for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) {
> > +             if (do_memsw_account())
> > +                     pg_counter = &memcg->memsw;
> > +             else
> > +                     pg_counter = &memcg->swap;
> > +
> >               nr_swap_pages = min_t(long, nr_swap_pages,
> > -                                   READ_ONCE(memcg->swap.max) -
> > -                                   page_counter_read(&memcg->swap));
> > +                                   READ_ONCE(pg_counter->max) -
> > +                                   page_counter_read(pg_counter));
> > +     }
> >       return nr_swap_pages;
> >  }
> >
> > --
> > 2.41.1
> >
>