Re: [mm] [PATCH 2/4] Add the soft limit interface v2

[Li Zefan <lizf@cn.fujitsu.com>]

Balbir Singh wrote:
> A new configuration file called soft_limit_in_bytes is added. The parsing
> and configuration rules remain the same as for the limit_in_bytes user
> interface.
> 
> A global list of all memory cgroups over their soft limit is maintained.
> This list is then used to reclaim memory on global pressure. A cgroup is
> removed from the list when the cgroup is deleted.
> 
> The global list is protected with a read-write spinlock.
> 

You are not using read-write spinlock..

> 
> Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
> ---
> 
>  mm/memcontrol.c |   33 ++++++++++++++++++++++++++++++++-
>  1 file changed, 32 insertions(+), 1 deletion(-)
> 
> diff -puN mm/memcontrol.c~memory-controller-add-soft-limit-interface mm/memcontrol.c
> --- linux-2.6.25-rc2/mm/memcontrol.c~memory-controller-add-soft-limit-interface	2008-02-19 12:31:49.000000000 +0530
> +++ linux-2.6.25-rc2-balbir/mm/memcontrol.c	2008-02-19 12:31:49.000000000 +0530
> @@ -35,6 +35,10 @@
>  
>  struct cgroup_subsys mem_cgroup_subsys;
>  static const int MEM_CGROUP_RECLAIM_RETRIES = 5;
> +static spinlock_t mem_cgroup_sl_list_lock;	/* spin lock that protects */
> +						/* the list of cgroups over*/
> +						/* their soft limit */
> +static struct list_head mem_cgroup_sl_exceeded_list;
>  
>  /*
>   * Statistics for memory cgroup.
> @@ -136,6 +140,10 @@ struct mem_cgroup {
>  	 * statistics.
>  	 */
>  	struct mem_cgroup_stat stat;
> +	/*
> +	 * List of all mem_cgroup's that exceed their soft limit
> +	 */
> +	struct list_head sl_exceeded_list;
>  };
>  
>  /*
> @@ -679,6 +687,18 @@ retry:
>  		goto retry;
>  	}
>  
> +	/*
> +	 * If we exceed our soft limit, we get added to the list of
> +	 * cgroups over their soft limit
> +	 */
> +	if (!res_counter_check_under_limit(&mem->res, RES_SOFT_LIMIT)) {
> +		spin_lock_irqsave(&mem_cgroup_sl_list_lock, flags);
> +		if (list_empty(&mem->sl_exceeded_list))
> +			list_add_tail(&mem->sl_exceeded_list,
> +						&mem_cgroup_sl_exceeded_list);
> +		spin_unlock_irqrestore(&mem_cgroup_sl_list_lock, flags);
> +	}
> +
>  	mz = page_cgroup_zoneinfo(pc);
>  	spin_lock_irqsave(&mz->lru_lock, flags);
>  	/* Update statistics vector */
> @@ -736,13 +756,14 @@ void mem_cgroup_uncharge(struct page_cgr
>  	if (atomic_dec_and_test(&pc->ref_cnt)) {
>  		page = pc->page;
>  		mz = page_cgroup_zoneinfo(pc);
> +		mem = pc->mem_cgroup;
>  		/*
>  		 * get page->cgroup and clear it under lock.
>  		 * force_empty can drop page->cgroup without checking refcnt.
>  		 */
>  		unlock_page_cgroup(page);
> +
>  		if (clear_page_cgroup(page, pc) == pc) {
> -			mem = pc->mem_cgroup;
>  			css_put(&mem->css);
>  			res_counter_uncharge(&mem->res, PAGE_SIZE);
>  			spin_lock_irqsave(&mz->lru_lock, flags);
> @@ -1046,6 +1067,12 @@ static struct cftype mem_cgroup_files[] 
>  		.name = "stat",
>  		.open = mem_control_stat_open,
>  	},
> +	{
> +		.name = "soft_limit_in_bytes",
> +		.private = RES_SOFT_LIMIT,
> +		.write = mem_cgroup_write,
> +		.read = mem_cgroup_read,
> +	},
>  };
>  
>  static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
> @@ -1097,6 +1124,9 @@ mem_cgroup_create(struct cgroup_subsys *
>  	if (unlikely((cont->parent) == NULL)) {
>  		mem = &init_mem_cgroup;
>  		init_mm.mem_cgroup = mem;
> +		INIT_LIST_HEAD(&mem->sl_exceeded_list);
> +		spin_lock_init(&mem_cgroup_sl_list_lock);
> +		INIT_LIST_HEAD(&mem_cgroup_sl_exceeded_list);
>  	} else
>  		mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);
>  
> @@ -1104,6 +1134,7 @@ mem_cgroup_create(struct cgroup_subsys *
>  		return NULL;
>  
>  	res_counter_init(&mem->res);
> +	INIT_LIST_HEAD(&mem->sl_exceeded_list);
>  

mem->sl_exceeded_list initialized twice ?

>  	memset(&mem->info, 0, sizeof(mem->info));
>  
> _
>