Re: [PATCH v2] memcg: localize memcg_kmem_enabled() check

[Michal Hocko <mhocko@kernel.org>]

On Thu 03-01-19 08:12:03, Shakeel Butt wrote:
> Move the memcg_kmem_enabled() checks into memcg kmem charge/uncharge
> functions, so, the users don't have to explicitly check that condition.
> This is purely code cleanup patch without any functional change. Only
> the order of checks in memcg_charge_slab() can potentially be changed
> but the functionally it will be same. This should not matter as
> memcg_charge_slab() is not in the hot path.

Looks good to me

> 
> Signed-off-by: Shakeel Butt <shakeelb@google.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> Changelog since v1:
> - Fixed the build when CONFIG_MEMCG is not set
> 
>  fs/pipe.c                  |  3 +--
>  include/linux/memcontrol.h | 37 +++++++++++++++++++++++++++++++++----
>  mm/memcontrol.c            | 16 ++++++++--------
>  mm/page_alloc.c            |  4 ++--
>  mm/slab.h                  |  4 ----
>  5 files changed, 44 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/pipe.c b/fs/pipe.c
> index bdc5d3c0977d..51d5fd8840ab 100644
> --- a/fs/pipe.c
> +++ b/fs/pipe.c
> @@ -140,8 +140,7 @@ static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
>  	struct page *page = buf->page;
>  
>  	if (page_count(page) == 1) {
> -		if (memcg_kmem_enabled())
> -			memcg_kmem_uncharge(page, 0);
> +		memcg_kmem_uncharge(page, 0);
>  		__SetPageLocked(page);
>  		return 0;
>  	}
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 83ae11cbd12c..b0eb29ea0d9c 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1273,12 +1273,12 @@ static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
>  
>  struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep);
>  void memcg_kmem_put_cache(struct kmem_cache *cachep);
> -int memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
> -			    struct mem_cgroup *memcg);
>  
>  #ifdef CONFIG_MEMCG_KMEM
> -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(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);
>  
>  extern struct static_key_false memcg_kmem_enabled_key;
>  extern struct workqueue_struct *memcg_kmem_cache_wq;
> @@ -1300,6 +1300,26 @@ static inline bool memcg_kmem_enabled(void)
>  	return static_branch_unlikely(&memcg_kmem_enabled_key);
>  }
>  
> +static inline int memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
> +{
> +	if (memcg_kmem_enabled())
> +		return __memcg_kmem_charge(page, gfp, order);
> +	return 0;
> +}
> +
> +static inline void memcg_kmem_uncharge(struct page *page, int order)
> +{
> +	if (memcg_kmem_enabled())
> +		__memcg_kmem_uncharge(page, order);
> +}
> +
> +static inline int memcg_kmem_charge_memcg(struct page *page, gfp_t gfp,
> +					  int order, struct mem_cgroup *memcg)
> +{
> +	if (memcg_kmem_enabled())
> +		return __memcg_kmem_charge_memcg(page, gfp, order, memcg);
> +	return 0;
> +}
>  /*
>   * 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
> @@ -1325,6 +1345,15 @@ static inline void memcg_kmem_uncharge(struct page *page, int order)
>  {
>  }
>  
> +static inline int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
> +{
> +	return 0;
> +}
> +
> +static inline void __memcg_kmem_uncharge(struct page *page, int order)
> +{
> +}
> +
>  #define for_each_memcg_cache_index(_idx)	\
>  	for (; NULL; )
>  
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 4afd5971f2d4..e8ca09920d71 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2557,7 +2557,7 @@ void memcg_kmem_put_cache(struct kmem_cache *cachep)
>  }
>  
>  /**
> - * memcg_kmem_charge_memcg: charge a kmem page
> + * __memcg_kmem_charge_memcg: charge a kmem page
>   * @page: page to charge
>   * @gfp: reclaim mode
>   * @order: allocation order
> @@ -2565,7 +2565,7 @@ void memcg_kmem_put_cache(struct kmem_cache *cachep)
>   *
>   * Returns 0 on success, an error code on failure.
>   */
> -int memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
> +int __memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
>  			    struct mem_cgroup *memcg)
>  {
>  	unsigned int nr_pages = 1 << order;
> @@ -2588,24 +2588,24 @@ int memcg_kmem_charge_memcg(struct page *page, gfp_t gfp, int order,
>  }
>  
>  /**
> - * memcg_kmem_charge: charge a kmem page to the current memory cgroup
> + * __memcg_kmem_charge: charge a kmem page to the current memory cgroup
>   * @page: page to charge
>   * @gfp: reclaim mode
>   * @order: allocation order
>   *
>   * Returns 0 on success, an error code on failure.
>   */
> -int memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
> +int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
>  {
>  	struct mem_cgroup *memcg;
>  	int ret = 0;
>  
> -	if (mem_cgroup_disabled() || memcg_kmem_bypass())
> +	if (memcg_kmem_bypass())
>  		return 0;
>  
>  	memcg = get_mem_cgroup_from_current();
>  	if (!mem_cgroup_is_root(memcg)) {
> -		ret = memcg_kmem_charge_memcg(page, gfp, order, memcg);
> +		ret = __memcg_kmem_charge_memcg(page, gfp, order, memcg);
>  		if (!ret)
>  			__SetPageKmemcg(page);
>  	}
> @@ -2613,11 +2613,11 @@ int memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
>  	return ret;
>  }
>  /**
> - * memcg_kmem_uncharge: uncharge a kmem page
> + * __memcg_kmem_uncharge: uncharge a kmem page
>   * @page: page to uncharge
>   * @order: allocation order
>   */
> -void memcg_kmem_uncharge(struct page *page, int order)
> +void __memcg_kmem_uncharge(struct page *page, int order)
>  {
>  	struct mem_cgroup *memcg = page->mem_cgroup;
>  	unsigned int nr_pages = 1 << order;
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 0634fbdef078..d65c337d2257 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1053,7 +1053,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
>  	if (PageMappingFlags(page))
>  		page->mapping = NULL;
>  	if (memcg_kmem_enabled() && PageKmemcg(page))
> -		memcg_kmem_uncharge(page, order);
> +		__memcg_kmem_uncharge(page, order);
>  	if (check_free)
>  		bad += free_pages_check(page);
>  	if (bad)
> @@ -4667,7 +4667,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
>  
>  out:
>  	if (memcg_kmem_enabled() && (gfp_mask & __GFP_ACCOUNT) && page &&
> -	    unlikely(memcg_kmem_charge(page, gfp_mask, order) != 0)) {
> +	    unlikely(__memcg_kmem_charge(page, gfp_mask, order) != 0)) {
>  		__free_pages(page, order);
>  		page = NULL;
>  	}
> diff --git a/mm/slab.h b/mm/slab.h
> index 4190c24ef0e9..cde51d7f631f 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -276,8 +276,6 @@ static __always_inline int memcg_charge_slab(struct page *page,
>  					     gfp_t gfp, int order,
>  					     struct kmem_cache *s)
>  {
> -	if (!memcg_kmem_enabled())
> -		return 0;
>  	if (is_root_cache(s))
>  		return 0;
>  	return memcg_kmem_charge_memcg(page, gfp, order, s->memcg_params.memcg);
> @@ -286,8 +284,6 @@ static __always_inline int memcg_charge_slab(struct page *page,
>  static __always_inline void memcg_uncharge_slab(struct page *page, int order,
>  						struct kmem_cache *s)
>  {
> -	if (!memcg_kmem_enabled())
> -		return;
>  	memcg_kmem_uncharge(page, order);
>  }
>  
> -- 
> 2.20.1.415.g653613c723-goog

-- 
Michal Hocko
SUSE Labs