Re: [PATCH -mm] memcg: cleanup static keys decrement

[Michal Hocko <mhocko@suse.cz>]

On Mon 02-02-15 14:45:27, Vladimir Davydov wrote:
> Move memcg_socket_limit_enabled decrement to tcp_destroy_cgroup (called
> from memcg_destroy_kmem -> mem_cgroup_sockets_destroy) and zap a bunch
> of wrapper functions.
> 
> Although this patch moves static keys decrement from __mem_cgroup_free
> to mem_cgroup_css_free, it does not introduce any functional changes,
> because the keys are incremented on setting the limit (tcp or kmem),
> which can only happen after successful mem_cgroup_css_online.

Looks good to me and code reduce looks nice as well.

> Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>

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

> ---
>  include/net/sock.h        |    5 -----
>  mm/memcontrol.c           |   38 +++++---------------------------------
>  net/ipv4/tcp_memcontrol.c |    4 ++++
>  3 files changed, 9 insertions(+), 38 deletions(-)
> 
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 2210fec65669..28bdf874da4a 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -1099,11 +1099,6 @@ static inline bool memcg_proto_active(struct cg_proto *cg_proto)
>  	return test_bit(MEMCG_SOCK_ACTIVE, &cg_proto->flags);
>  }
>  
> -static inline bool memcg_proto_activated(struct cg_proto *cg_proto)
> -{
> -	return test_bit(MEMCG_SOCK_ACTIVATED, &cg_proto->flags);
> -}
> -
>  #ifdef SOCK_REFCNT_DEBUG
>  static inline void sk_refcnt_debug_inc(struct sock *sk)
>  {
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 3b2cc3a5413a..f1ab93daa1b7 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -519,16 +519,6 @@ struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg)
>  }
>  EXPORT_SYMBOL(tcp_proto_cgroup);
>  
> -static void disarm_sock_keys(struct mem_cgroup *memcg)
> -{
> -	if (!memcg_proto_activated(&memcg->tcp_mem))
> -		return;
> -	static_key_slow_dec(&memcg_socket_limit_enabled);
> -}
> -#else
> -static void disarm_sock_keys(struct mem_cgroup *memcg)
> -{
> -}
>  #endif
>  
>  #ifdef CONFIG_MEMCG_KMEM
> @@ -583,28 +573,8 @@ void memcg_put_cache_ids(void)
>  struct static_key memcg_kmem_enabled_key;
>  EXPORT_SYMBOL(memcg_kmem_enabled_key);
>  
> -static void disarm_kmem_keys(struct mem_cgroup *memcg)
> -{
> -	if (memcg->kmem_acct_activated)
> -		static_key_slow_dec(&memcg_kmem_enabled_key);
> -	/*
> -	 * This check can't live in kmem destruction function,
> -	 * since the charges will outlive the cgroup
> -	 */
> -	WARN_ON(page_counter_read(&memcg->kmem));
> -}
> -#else
> -static void disarm_kmem_keys(struct mem_cgroup *memcg)
> -{
> -}
>  #endif /* CONFIG_MEMCG_KMEM */
>  
> -static void disarm_static_keys(struct mem_cgroup *memcg)
> -{
> -	disarm_sock_keys(memcg);
> -	disarm_kmem_keys(memcg);
> -}
> -
>  static struct mem_cgroup_per_zone *
>  mem_cgroup_zone_zoneinfo(struct mem_cgroup *memcg, struct zone *zone)
>  {
> @@ -4092,7 +4062,11 @@ static void memcg_deactivate_kmem(struct mem_cgroup *memcg)
>  
>  static void memcg_destroy_kmem(struct mem_cgroup *memcg)
>  {
> -	memcg_destroy_kmem_caches(memcg);
> +	if (memcg->kmem_acct_activated) {
> +		memcg_destroy_kmem_caches(memcg);
> +		static_key_slow_dec(&memcg_kmem_enabled_key);
> +		WARN_ON(page_counter_read(&memcg->kmem));
> +	}
>  	mem_cgroup_sockets_destroy(memcg);
>  }
>  #else
> @@ -4523,8 +4497,6 @@ static void __mem_cgroup_free(struct mem_cgroup *memcg)
>  		free_mem_cgroup_per_zone_info(memcg, node);
>  
>  	free_percpu(memcg->stat);
> -
> -	disarm_static_keys(memcg);
>  	kfree(memcg);
>  }
>  
> diff --git a/net/ipv4/tcp_memcontrol.c b/net/ipv4/tcp_memcontrol.c
> index c2a75c6957a1..2379c1b4efb2 100644
> --- a/net/ipv4/tcp_memcontrol.c
> +++ b/net/ipv4/tcp_memcontrol.c
> @@ -47,6 +47,10 @@ void tcp_destroy_cgroup(struct mem_cgroup *memcg)
>  		return;
>  
>  	percpu_counter_destroy(&cg_proto->sockets_allocated);
> +
> +	if (test_bit(MEMCG_SOCK_ACTIVATED, &cg_proto->flags))
> +		static_key_slow_dec(&memcg_socket_limit_enabled);
> +
>  }
>  EXPORT_SYMBOL(tcp_destroy_cgroup);
>  
> -- 
> 1.7.10.4
> 

-- 
Michal Hocko
SUSE Labs

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