[Devel] Re: [PATCH v3 16/28] memcg: kmem controller charge/uncharge infrastructure

[Glauber Costa]

On 05/30/2012 04:34 PM, Frederic Weisbecker wrote:
> On Fri, May 25, 2012 at 05:03:36PM +0400, Glauber Costa wrote:
>> +bool __mem_cgroup_new_kmem_page(struct page *page, gfp_t gfp)
>> +{
>> +	struct mem_cgroup *memcg;
>> +	struct page_cgroup *pc;
>> +	bool ret = true;
>> +	size_t size;
>> +	struct task_struct *p;
>> +
>> +	if (!current->mm || in_interrupt())
>> +		return true;
>> +
>> +	rcu_read_lock();
>> +	p = rcu_dereference(current->mm->owner);
>> +	memcg = mem_cgroup_from_task(p);
>
> So this takes the memcg of the group owner rather than the
> task? I understand why we want this for user memory, but for
> kernel?

That was already discussed when this first came up in my last submission
If I recall correctly, Kame pointed out that this would be needed for 
proper OOM-scoring and killing.

Now of course we won't oom kernel threads or anything like that. But 
since this is also accounted towards memcg, it should at least be 
consistent with each memcg it accounts to.

We can't account kmem for the thread's memcg, and mem to the process'.