Re: [PATCH 13/14] mm: memcontrol: account socket memory in unified hierarchy memory controller

[Michal Hocko <mhocko@kernel.org>]

On Thu 12-11-15 18:41:32, Johannes Weiner wrote:
> Socket memory can be a significant share of overall memory consumed by
> common workloads. In order to provide reasonable resource isolation in
> the unified hierarchy, this type of memory needs to be included in the
> tracking/accounting of a cgroup under active memory resource control.
> 
> Overhead is only incurred when a non-root control group is created AND
> the memory controller is instructed to track and account the memory
> footprint of that group. cgroup.memory=nosocket can be specified on
> the boot commandline to override any runtime configuration and
> forcibly exclude socket memory from active memory resource control.

Do you have any numbers about the overhead?

> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

With a way to disable this feature I am OK with it.
cgroup.memory=nosocket should be documented (at least in
Documentation/kernel-parameters.txt)

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

> ---
>  include/linux/memcontrol.h |  12 ++++-
>  mm/memcontrol.c            | 131 +++++++++++++++++++++++++++++++++++++--------
>  2 files changed, 118 insertions(+), 25 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 4cf5afa..809d6de 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -256,6 +256,10 @@ struct mem_cgroup {
>  	struct wb_domain cgwb_domain;
>  #endif
>  
> +#ifdef CONFIG_INET
> +	struct work_struct	socket_work;
> +#endif
> +
>  	/* List of events which userspace want to receive */
>  	struct list_head event_list;
>  	spinlock_t event_list_lock;
> @@ -691,7 +695,7 @@ static inline void mem_cgroup_wb_stats(struct bdi_writeback *wb,
>  
>  #endif	/* CONFIG_CGROUP_WRITEBACK */
>  
> -#if defined(CONFIG_INET) && defined(CONFIG_MEMCG_KMEM)
> +#ifdef CONFIG_INET
>  struct sock;
>  extern struct static_key memcg_sockets_enabled_key;
>  #define mem_cgroup_sockets_enabled static_key_false(&memcg_sockets_enabled_key)
> @@ -701,11 +705,15 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
>  void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
>  static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
>  {
> +#ifdef CONFIG_MEMCG_KMEM
>  	return memcg->tcp_mem.memory_pressure;
> +#else
> +	return false;
> +#endif
>  }
>  #else
>  #define mem_cgroup_sockets_enabled 0
> -#endif /* CONFIG_INET && CONFIG_MEMCG_KMEM */
> +#endif /* CONFIG_INET */
>  
>  #ifdef CONFIG_MEMCG_KMEM
>  extern struct static_key memcg_kmem_enabled_key;
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 408fb04..cad9525 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -80,6 +80,9 @@ struct mem_cgroup *root_mem_cgroup __read_mostly;
>  
>  #define MEM_CGROUP_RECLAIM_RETRIES	5
>  
> +/* Socket memory accounting disabled? */
> +static bool cgroup_memory_nosocket;
> +
>  /* Whether the swap controller is active */
>  #ifdef CONFIG_MEMCG_SWAP
>  int do_swap_account __read_mostly;
> @@ -1923,6 +1926,18 @@ static int memcg_cpu_hotplug_callback(struct notifier_block *nb,
>  	return NOTIFY_OK;
>  }
>  
> +static void reclaim_high(struct mem_cgroup *memcg,
> +			 unsigned int nr_pages,
> +			 gfp_t gfp_mask)
> +{
> +	do {
> +		if (page_counter_read(&memcg->memory) <= memcg->high)
> +			continue;
> +		mem_cgroup_events(memcg, MEMCG_HIGH, 1);
> +		try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, true);
> +	} while ((memcg = parent_mem_cgroup(memcg)));
> +}
> +
>  /*
>   * Scheduled by try_charge() to be executed from the userland return path
>   * and reclaims memory over the high limit.
> @@ -1930,20 +1945,13 @@ static int memcg_cpu_hotplug_callback(struct notifier_block *nb,
>  void mem_cgroup_handle_over_high(void)
>  {
>  	unsigned int nr_pages = current->memcg_nr_pages_over_high;
> -	struct mem_cgroup *memcg, *pos;
> +	struct mem_cgroup *memcg;
>  
>  	if (likely(!nr_pages))
>  		return;
>  
> -	pos = memcg = get_mem_cgroup_from_mm(current->mm);
> -
> -	do {
> -		if (page_counter_read(&pos->memory) <= pos->high)
> -			continue;
> -		mem_cgroup_events(pos, MEMCG_HIGH, 1);
> -		try_to_free_mem_cgroup_pages(pos, nr_pages, GFP_KERNEL, true);
> -	} while ((pos = parent_mem_cgroup(pos)));
> -
> +	memcg = get_mem_cgroup_from_mm(current->mm);
> +	reclaim_high(memcg, nr_pages, GFP_KERNEL);
>  	css_put(&memcg->css);
>  	current->memcg_nr_pages_over_high = 0;
>  }
> @@ -4141,6 +4149,8 @@ struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
>  }
>  EXPORT_SYMBOL(parent_mem_cgroup);
>  
> +static void socket_work_func(struct work_struct *work);
> +
>  static struct cgroup_subsys_state * __ref
>  mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
>  {
> @@ -4180,6 +4190,9 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
>  #ifdef CONFIG_CGROUP_WRITEBACK
>  	INIT_LIST_HEAD(&memcg->cgwb_list);
>  #endif
> +#ifdef CONFIG_INET
> +	INIT_WORK(&memcg->socket_work, socket_work_func);
> +#endif
>  	return &memcg->css;
>  
>  free_out:
> @@ -4237,6 +4250,11 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
>  	if (ret)
>  		return ret;
>  
> +#ifdef CONFIG_INET
> +	if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
> +		static_key_slow_inc(&memcg_sockets_enabled_key);
> +#endif
> +
>  	/*
>  	 * Make sure the memcg is initialized: mem_cgroup_iter()
>  	 * orders reading memcg->initialized against its callers
> @@ -4276,6 +4294,11 @@ static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
>  	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
>  
>  	memcg_destroy_kmem(memcg);
> +#ifdef CONFIG_INET
> +	if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
> +		static_key_slow_dec(&memcg_sockets_enabled_key);
> +	cancel_work_sync(&memcg->socket_work);
> +#endif
>  	__mem_cgroup_free(memcg);
>  }
>  
> @@ -5464,8 +5487,7 @@ void mem_cgroup_replace_page(struct page *oldpage, struct page *newpage)
>  	commit_charge(newpage, memcg, true);
>  }
>  
> -/* Writing them here to avoid exposing memcg's inner layout */
> -#if defined(CONFIG_INET) && defined(CONFIG_MEMCG_KMEM)
> +#ifdef CONFIG_INET
>  
>  struct static_key memcg_sockets_enabled_key;
>  EXPORT_SYMBOL(memcg_sockets_enabled_key);
> @@ -5490,10 +5512,16 @@ void sock_update_memcg(struct sock *sk)
>  
>  	rcu_read_lock();
>  	memcg = mem_cgroup_from_task(current);
> -	if (memcg != root_mem_cgroup &&
> -	    test_bit(MEMCG_SOCK_ACTIVE, &memcg->tcp_mem.flags) &&
> -	    css_tryget_online(&memcg->css))
> +	if (memcg == root_mem_cgroup)
> +		goto out;
> +#ifdef CONFIG_MEMCG_KMEM
> +	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
> +	    !test_bit(MEMCG_SOCK_ACTIVE, &memcg->tcp_mem.flags))
> +		goto out;
> +#endif
> +	if (css_tryget_online(&memcg->css))
>  		sk->sk_memcg = memcg;
> +out:
>  	rcu_read_unlock();
>  }
>  EXPORT_SYMBOL(sock_update_memcg);
> @@ -5504,6 +5532,14 @@ void sock_release_memcg(struct sock *sk)
>  	css_put(&sk->sk_memcg->css);
>  }
>  
> +static void socket_work_func(struct work_struct *work)
> +{
> +	struct mem_cgroup *memcg;
> +
> +	memcg = container_of(work, struct mem_cgroup, socket_work);
> +	reclaim_high(memcg, CHARGE_BATCH, GFP_KERNEL);
> +}
> +
>  /**
>   * mem_cgroup_charge_skmem - charge socket memory
>   * @memcg: memcg to charge
> @@ -5514,16 +5550,43 @@ void sock_release_memcg(struct sock *sk)
>   */
>  bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
>  {
> +	unsigned int batch = max(CHARGE_BATCH, nr_pages);
>  	struct page_counter *counter;
> +	bool force = false;
>  
> -	if (page_counter_try_charge(&memcg->tcp_mem.memory_allocated,
> -				    nr_pages, &counter)) {
> -		memcg->tcp_mem.memory_pressure = 0;
> +#ifdef CONFIG_MEMCG_KMEM
> +	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
> +		if (page_counter_try_charge(&memcg->tcp_mem.memory_allocated,
> +					    nr_pages, &counter)) {
> +			memcg->tcp_mem.memory_pressure = 0;
> +			return true;
> +		}
> +		page_counter_charge(&memcg->tcp_mem.memory_allocated, nr_pages);
> +		memcg->tcp_mem.memory_pressure = 1;
> +		return false;
> +	}
> +#endif
> +	if (consume_stock(memcg, nr_pages))
>  		return true;
> +retry:
> +	if (page_counter_try_charge(&memcg->memory, batch, &counter))
> +		goto done;
> +
> +	if (batch > nr_pages) {
> +		batch = nr_pages;
> +		goto retry;
>  	}
> -	page_counter_charge(&memcg->tcp_mem.memory_allocated, nr_pages);
> -	memcg->tcp_mem.memory_pressure = 1;
> -	return false;
> +
> +	page_counter_charge(&memcg->memory, batch);
> +	force = true;
> +done:
> +	css_get_many(&memcg->css, batch);
> +	if (batch > nr_pages)
> +		refill_stock(memcg, batch - nr_pages);
> +
> +	schedule_work(&memcg->socket_work);
> +
> +	return !force;
>  }
>  
>  /**
> @@ -5533,10 +5596,32 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
>   */
>  void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
>  {
> -	page_counter_uncharge(&memcg->tcp_mem.memory_allocated, nr_pages);
> +#ifdef CONFIG_MEMCG_KMEM
> +	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
> +		page_counter_uncharge(&memcg->tcp_mem.memory_allocated,
> +				      nr_pages);
> +		return;
> +	}
> +#endif
> +	page_counter_uncharge(&memcg->memory, nr_pages);
> +	css_put_many(&memcg->css, nr_pages);
>  }
>  
> -#endif
> +#endif /* CONFIG_INET */
> +
> +static int __init cgroup_memory(char *s)
> +{
> +	char *token;
> +
> +	while ((token = strsep(&s, ",")) != NULL) {
> +		if (!*token)
> +			continue;
> +		if (!strcmp(token, "nosocket"))
> +			cgroup_memory_nosocket = true;
> +	}
> +	return 0;
> +}
> +__setup("cgroup.memory=", cgroup_memory);
>  
>  /*
>   * subsys_initcall() for memory controller.
> -- 
> 2.6.2

-- 
Michal Hocko
SUSE Labs