Re: [PATCH v3 3/7] mm: introduce __memcg_kmem_uncharge_memcg()

[Shakeel Butt]

From: Roman Gushchin <guro@xxxxxx>
Date: Wed, May 8, 2019 at 1:30 PM
To: Andrew Morton, Shakeel Butt
Cc: <linux-mm@xxxxxxxxx>, <linux-kernel@xxxxxxxxxxxxxxx>,
<kernel-team@xxxxxx>, Johannes Weiner, Michal Hocko, Rik van Riel,
Christoph Lameter, Vladimir Davydov, <cgroups@xxxxxxxxxxxxxxx>, Roman
Gushchin

> Let's separate the page counter modification code out of
> __memcg_kmem_uncharge() in a way similar to what
> __memcg_kmem_charge() and __memcg_kmem_charge_memcg() work.
>
> This will allow to reuse this code later using a new
> memcg_kmem_uncharge_memcg() wrapper, which calls
> __memcg_kmem_unchare_memcg() if memcg_kmem_enabled()

__memcg_kmem_uncharge_memcg()

> check is passed.
>
> Signed-off-by: Roman Gushchin <guro@xxxxxx>

Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>


> ---
>  include/linux/memcontrol.h | 10 ++++++++++
>  mm/memcontrol.c            | 25 +++++++++++++++++--------
>  2 files changed, 27 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 36bdfe8e5965..deb209510902 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1298,6 +1298,8 @@ int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order);
>  void __memcg_kmem_uncharge(struct page *page, int order);
>  int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
>                               struct mem_cgroup *memcg);
> +void __memcg_kmem_uncharge_memcg(struct mem_cgroup *memcg,
> +                                unsigned int nr_pages);
>
>  extern struct static_key_false memcg_kmem_enabled_key;
>  extern struct workqueue_struct *memcg_kmem_cache_wq;
> @@ -1339,6 +1341,14 @@ static inline int memcg_kmem_charge_memcg(struct page *page, gfp_t gfp,
>                 return __memcg_kmem_charge_memcg(page, gfp, order, memcg);
>         return 0;
>  }
> +
> +static inline void memcg_kmem_uncharge_memcg(struct page *page, int order,
> +                                            struct mem_cgroup *memcg)
> +{
> +       if (memcg_kmem_enabled())
> +               __memcg_kmem_uncharge_memcg(memcg, 1 << order);
> +}
> +
>  /*
>   * helper for accessing a memcg's index. It will be used as an index in the
>   * child cache array in kmem_cache, and also to derive its name. This function
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 48a8f1c35176..b2c39f187cbb 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2750,6 +2750,22 @@ int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
>         css_put(&memcg->css);
>         return ret;
>  }
> +
> +/**
> + * __memcg_kmem_uncharge_memcg: uncharge a kmem page
> + * @memcg: memcg to uncharge
> + * @nr_pages: number of pages to uncharge
> + */
> +void __memcg_kmem_uncharge_memcg(struct mem_cgroup *memcg,
> +                                unsigned int nr_pages)
> +{
> +       if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
> +               page_counter_uncharge(&memcg->kmem, nr_pages);
> +
> +       page_counter_uncharge(&memcg->memory, nr_pages);
> +       if (do_memsw_account())
> +               page_counter_uncharge(&memcg->memsw, nr_pages);
> +}
>  /**
>   * __memcg_kmem_uncharge: uncharge a kmem page
>   * @page: page to uncharge
> @@ -2764,14 +2780,7 @@ void __memcg_kmem_uncharge(struct page *page, int order)
>                 return;
>
>         VM_BUG_ON_PAGE(mem_cgroup_is_root(memcg), page);
> -
> -       if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
> -               page_counter_uncharge(&memcg->kmem, nr_pages);
> -
> -       page_counter_uncharge(&memcg->memory, nr_pages);
> -       if (do_memsw_account())
> -               page_counter_uncharge(&memcg->memsw, nr_pages);
> -
> +       __memcg_kmem_uncharge_memcg(memcg, nr_pages);
>         page->mem_cgroup = NULL;
>
>         /* slab pages do not have PageKmemcg flag set */
> --
> 2.20.1
>