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

[Li Zefan]

Li Zefan åé:
> 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..
> 

Ah, the spinlock is changed to r/w spinlock in [PATCH 3/4].

>> Signed-off-by: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
>> ---
>>
>>  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));
>>  
>> _
>>
> --
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