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Date:   Wed, 14 Apr 2021 23:28:20 -0400
From:   Masayoshi Mizuma <msys.mizuma@gmail.com>
To:     Waiman Long <longman@redhat.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Vlastimil Babka <vbabka@suse.cz>, Roman Gushchin <guro@fb.com>,
        linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        linux-mm@kvack.org, Shakeel Butt <shakeelb@google.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Alex Shi <alex.shi@linux.alibaba.com>,
        Chris Down <chris@chrisdown.name>,
        Yafang Shao <laoar.shao@gmail.com>,
        Wei Yang <richard.weiyang@gmail.com>,
        Xing Zhengjun <zhengjun.xing@linux.intel.com>
Subject: Re: [PATCH v3 4/5] mm/memcg: Separate out object stock data into its
 own struct
Message-ID: <20210415032820.coutviukiyieiysm@gabell>
References: <20210414012027.5352-1-longman@redhat.com>
 <20210414012027.5352-5-longman@redhat.com>
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In-Reply-To: <20210414012027.5352-5-longman@redhat.com>
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On Tue, Apr 13, 2021 at 09:20:26PM -0400, Waiman Long wrote:
> The object stock data stored in struct memcg_stock_pcp are independent
> of the other page based data stored there. Separating them out into
> their own struct to highlight the independency.
> 
> Signed-off-by: Waiman Long <longman@redhat.com>
> Acked-by: Roman Gushchin <guro@fb.com>
> Reviewed-by: Shakeel Butt <shakeelb@google.com>
> ---
>  mm/memcontrol.c | 41 ++++++++++++++++++++++++++---------------
>  1 file changed, 26 insertions(+), 15 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 539c3b632e47..69f728383efe 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2214,17 +2214,22 @@ void unlock_page_memcg(struct page *page)
>  }
>  EXPORT_SYMBOL(unlock_page_memcg);
>  
> -struct memcg_stock_pcp {
> -	struct mem_cgroup *cached; /* this never be root cgroup */
> -	unsigned int nr_pages;
> -
> +struct obj_stock {
>  #ifdef CONFIG_MEMCG_KMEM
>  	struct obj_cgroup *cached_objcg;
>  	struct pglist_data *cached_pgdat;
>  	unsigned int nr_bytes;
>  	int vmstat_idx;
>  	int vmstat_bytes;
> +#else
> +	int dummy[0];
>  #endif
> +};
> +
> +struct memcg_stock_pcp {
> +	struct mem_cgroup *cached; /* this never be root cgroup */
> +	unsigned int nr_pages;
> +	struct obj_stock obj;
>  
>  	struct work_struct work;
>  	unsigned long flags;
> @@ -2234,12 +2239,12 @@ static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
>  static DEFINE_MUTEX(percpu_charge_mutex);
>  
>  #ifdef CONFIG_MEMCG_KMEM
> -static void drain_obj_stock(struct memcg_stock_pcp *stock);
> +static void drain_obj_stock(struct obj_stock *stock);
>  static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
>  				     struct mem_cgroup *root_memcg);
>  
>  #else
> -static inline void drain_obj_stock(struct memcg_stock_pcp *stock)
> +static inline void drain_obj_stock(struct obj_stock *stock)
>  {
>  }
>  static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
> @@ -2249,6 +2254,13 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
>  }
>  #endif
>  
> +static inline struct obj_stock *current_obj_stock(void)
> +{
> +	struct memcg_stock_pcp *stock = this_cpu_ptr(&memcg_stock);
> +
> +	return &stock->obj;
> +}
> +
>  /**
>   * consume_stock: Try to consume stocked charge on this cpu.
>   * @memcg: memcg to consume from.
> @@ -2315,7 +2327,7 @@ static void drain_local_stock(struct work_struct *dummy)
>  	local_irq_save(flags);
>  
>  	stock = this_cpu_ptr(&memcg_stock);
> -	drain_obj_stock(stock);
> +	drain_obj_stock(&stock->obj);
>  	drain_stock(stock);
>  	clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
>  
> @@ -3177,13 +3189,13 @@ static inline void mod_objcg_state(struct obj_cgroup *objcg,
>  
>  static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
>  {
> -	struct memcg_stock_pcp *stock;
> +	struct obj_stock *stock;
>  	unsigned long flags;
>  	bool ret = false;
>  
>  	local_irq_save(flags);
>  
> -	stock = this_cpu_ptr(&memcg_stock);
> +	stock = current_obj_stock();
>  	if (objcg == stock->cached_objcg && stock->nr_bytes >= nr_bytes) {
>  		stock->nr_bytes -= nr_bytes;
>  		ret = true;
> @@ -3194,7 +3206,7 @@ static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
>  	return ret;
>  }
>  
> -static void drain_obj_stock(struct memcg_stock_pcp *stock)
> +static void drain_obj_stock(struct obj_stock *stock)
>  {
>  	struct obj_cgroup *old = stock->cached_objcg;
>  
> @@ -3242,8 +3254,8 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
>  {
>  	struct mem_cgroup *memcg;
>  
> -	if (stock->cached_objcg) {
> -		memcg = obj_cgroup_memcg(stock->cached_objcg);
> +	if (stock->obj.cached_objcg) {
> +		memcg = obj_cgroup_memcg(stock->obj.cached_objcg);
>  		if (memcg && mem_cgroup_is_descendant(memcg, root_memcg))
>  			return true;
>  	}
> @@ -3253,9 +3265,8 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
>  
>  static void __refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
>  {
> -	struct memcg_stock_pcp *stock;
> +	struct obj_stock *stock = current_obj_stock();
>  
> -	stock = this_cpu_ptr(&memcg_stock);
>  	if (stock->cached_objcg != objcg) { /* reset if necessary */
>  		drain_obj_stock(stock);
>  		obj_cgroup_get(objcg);
> @@ -3280,7 +3291,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
>  static void __mod_obj_stock_state(struct obj_cgroup *objcg,
>  				  struct pglist_data *pgdat, int idx, int nr)
>  {
> -	struct memcg_stock_pcp *stock = this_cpu_ptr(&memcg_stock);
> +	struct obj_stock *stock = current_obj_stock();
>  
>  	if (stock->cached_objcg != objcg) {
>  		/* Output the current data as is */
> -- 
> 2.18.1
> 
Please feel free to add:

Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>

Thanks!
Masa