Re: [PATCH v9 4/7] mm: Change count_objcg_event() to count_objcg_events() for batch event updates.

[Yosry Ahmed <yosryahmed@google.com>]

On Mon, Sep 30, 2024 at 3:12 PM Kanchana P Sridhar
<kanchana.p.sridhar@intel.com> wrote:
>
> With the introduction of zswap_store() swapping out large folios,
> we need to efficiently update the objcg's memcg events once per
> successfully stored folio. For instance, the 'ZSWPOUT' event needs
> to be incremented by folio_nr_pages().
>
> To facilitate this, the existing count_objcg_event() API is modified
> to be count_objcg_events() that additionally accepts a count parameter.
> The only existing calls to count_objcg_event() are in zswap.c - these
> have been modified to call count_objcg_events() with a count of 1.
>
> Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>

Acked-by: Yosry Ahmed <yosryahmed@google.com>

> ---
>  include/linux/memcontrol.h | 12 +++++++-----
>  mm/zswap.c                 |  6 +++---
>  2 files changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 15c2716f9aa3..524006313b0d 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1764,8 +1764,9 @@ static inline int memcg_kmem_id(struct mem_cgroup *memcg)
>
>  struct mem_cgroup *mem_cgroup_from_slab_obj(void *p);
>
> -static inline void count_objcg_event(struct obj_cgroup *objcg,
> -                                    enum vm_event_item idx)
> +static inline void count_objcg_events(struct obj_cgroup *objcg,
> +                                     enum vm_event_item idx,
> +                                     unsigned long count)
>  {
>         struct mem_cgroup *memcg;
>
> @@ -1774,7 +1775,7 @@ static inline void count_objcg_event(struct obj_cgroup *objcg,
>
>         rcu_read_lock();
>         memcg = obj_cgroup_memcg(objcg);
> -       count_memcg_events(memcg, idx, 1);
> +       count_memcg_events(memcg, idx, count);
>         rcu_read_unlock();
>  }
>
> @@ -1829,8 +1830,9 @@ static inline struct mem_cgroup *mem_cgroup_from_slab_obj(void *p)
>         return NULL;
>  }
>
> -static inline void count_objcg_event(struct obj_cgroup *objcg,
> -                                    enum vm_event_item idx)
> +static inline void count_objcg_events(struct obj_cgroup *objcg,
> +                                     enum vm_event_item idx,
> +                                     unsigned long count)
>  {
>  }
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 0f281e50a034..69b9c025fd47 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -1053,7 +1053,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
>
>         count_vm_event(ZSWPWB);
>         if (entry->objcg)
> -               count_objcg_event(entry->objcg, ZSWPWB);
> +               count_objcg_events(entry->objcg, ZSWPWB, 1);
>
>         zswap_entry_free(entry);
>
> @@ -1482,7 +1482,7 @@ bool zswap_store(struct folio *folio)
>
>         if (objcg) {
>                 obj_cgroup_charge_zswap(objcg, entry->length);
> -               count_objcg_event(objcg, ZSWPOUT);
> +               count_objcg_events(objcg, ZSWPOUT, 1);
>         }
>
>         /*
> @@ -1576,7 +1576,7 @@ bool zswap_load(struct folio *folio)
>
>         count_vm_event(ZSWPIN);
>         if (entry->objcg)
> -               count_objcg_event(entry->objcg, ZSWPIN);
> +               count_objcg_events(entry->objcg, ZSWPIN, 1);
>
>         if (swapcache) {
>                 zswap_entry_free(entry);
> --
> 2.27.0
>