Re: [PATCH -mm 3/4] fork: charge threadinfo to memcg explicitly

[Vladimir Davydov]

On 03/27/2014 02:00 AM, Michal Hocko wrote:
> On Wed 26-03-14 19:28:06, Vladimir Davydov wrote:
>> We have only a few places where we actually want to charge kmem so
>> instead of intruding into the general page allocation path with
>> __GFP_KMEMCG it's better to explictly charge kmem there. All kmem
>> charges will be easier to follow that way.
>>
>> This is a step toward removing __GFP_KMEMCG. It makes fork charge task
>> threadinfo pages explicitly instead of passing __GFP_KMEMCG to
>> alloc_pages.
> Looks good from a quick glance. I would also remove
> THREADINFO_GFP_ACCOUNTED in this patch.

To do so,  I'd have to remove __GFP_KMEMCG check from
memcg_kmem_newpage_charge, which is better to do in the next patch,
which removes __GFP_KMEMCG everywhere, IMO.

Thanks.

>> Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
>> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxx>
>> Cc: Glauber Costa <glommer@xxxxxxxxx>
>> ---
>>  kernel/fork.c |   13 ++++++++++---
>>  1 file changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/fork.c b/kernel/fork.c
>> index f4b09bc15f3a..8209780cf732 100644
>> --- a/kernel/fork.c
>> +++ b/kernel/fork.c
>> @@ -150,15 +150,22 @@ void __weak arch_release_thread_info(struct thread_info *ti)
>>  static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
>>  						  int node)
>>  {
>> -	struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED,
>> -					     THREAD_SIZE_ORDER);
>> +	struct page *page;
>> +	struct mem_cgroup *memcg = NULL;
>>  
>> +	if (!memcg_kmem_newpage_charge(THREADINFO_GFP_ACCOUNTED, &memcg,
>> +				       THREAD_SIZE_ORDER))
>> +		return NULL;
>> +	page = alloc_pages_node(node, THREADINFO_GFP, THREAD_SIZE_ORDER);
>> +	memcg_kmem_commit_charge(page, memcg, THREAD_SIZE_ORDER);
>>  	return page ? page_address(page) : NULL;
>>  }
>>  
>>  static inline void free_thread_info(struct thread_info *ti)
>>  {
>> -	free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
>> +	if (ti)
>> +		memcg_kmem_uncharge_pages(virt_to_page(ti), THREAD_SIZE_ORDER);
>> +	free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
>>  }
>>  # else
>>  static struct kmem_cache *thread_info_cache;
>> -- 
>> 1.7.10.4
>>

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