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

Balbir Singh
2008-02-19T08:40:48Z

Li Zefan wrote:
> Li Zefan 写道:
>> 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@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 ?
>>

Good catch, yes for the root, it can be initialized twice. I'll fix it in v3.

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