Re: [PATCH 1/3] memcg/hugetlb: Introduce memcg_accounts_hugetlb

[Yosry Ahmed <yosryahmed@google.com>]

On Fri, Nov 8, 2024 at 2:21 PM Shakeel Butt <shakeel.butt@linux.dev> wrote:
>
> On Fri, Nov 08, 2024 at 01:29:44PM -0800, Joshua Hahn wrote:
> > This patch isolates the check for whether memcg accounts hugetlb.
> > This condition can only be true if the memcg mount option
> > memory_hugetlb_accounting is on, which includes hugetlb usage
> > in memory.current.
> >
> > Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> >
> > ---
> >  mm/memcontrol.c | 17 ++++++++++++++---
> >  1 file changed, 14 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index f3a9653cef0e..97f63ec9c9fb 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -1425,6 +1425,9 @@ unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item)
> >               memcg_page_state_output_unit(item);
> >  }
> >
> > +/* Forward declaration */
> > +bool memcg_accounts_hugetlb(void);
>
> No need for forward declaration. Just define it here and make it static.

Also please pull the #ifdef outside the function definition, e.g.

#ifdef CONFIG_HUGETLB_PAGE
static bool memcg_accounts_hugetlb(void)
{
     return cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
}
#else /* CONFIG_HUGETLB_PAGE */
static bool memcg_accounts_hugetlb(void) { return false; }
{
     return false;
}
#endif /* CONFIG_HUGETLB_PAGE */

>
> > +
> >  static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
> >  {
> >       int i;
> > @@ -1446,7 +1449,7 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
> >
> >  #ifdef CONFIG_HUGETLB_PAGE
> >               if (unlikely(memory_stats[i].idx == NR_HUGETLB) &&
> > -                 !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
> > +                     !memcg_accounts_hugetlb())
> >                       continue;
> >  #endif
> >               size = memcg_page_state_output(memcg, memory_stats[i].idx);
> > @@ -4483,6 +4486,15 @@ int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp)
> >       return ret;
> >  }
> >
> > +bool memcg_accounts_hugetlb(void)
> > +{
> > +#ifdef CONFIG_HUGETLB_PAGE
> > +     return cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
> > +#else
> > +     return false;
> > +#endif
> > +}
> > +
> >  /**
> >   * mem_cgroup_hugetlb_try_charge - try to charge the memcg for a hugetlb folio
> >   * @memcg: memcg to charge.
> > @@ -4508,8 +4520,7 @@ int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
> >        * but do not attempt to commit charge later (or cancel on error) either.
> >        */
> >       if (mem_cgroup_disabled() || !memcg ||
> > -             !cgroup_subsys_on_dfl(memory_cgrp_subsys) ||
> > -             !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
> > +             !cgroup_subsys_on_dfl(memory_cgrp_subsys) || !memcg_accounts_hugetlb())
> >               return -EOPNOTSUPP;
> >
> >       if (try_charge(memcg, gfp, nr_pages))
> > --
> > 2.43.5
> >
>