On Wed, May 30, 2012 at 04:38:39PM +0400, Glauber Costa wrote:
> 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.
Can we have at least a comment in the code that explain the reasons of taking the
owner rather than the task? It's not going to be very obvious to future reviewers.
> Now of course we won't oom kernel threads or anything like that.
Seems we are not even accounting them anyway.
> 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'.
Don't know. This goes a bit against cgroups semantics which group at the task
level and not process. But I personally don't mind much, as long as it's
documented.
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