Re: [PATCH] Unused check for thread group leader in mem_cgroup_move_task

[Balbir Singh <balbir-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org> [2008-12-01 13:30:30]:

> On Mon, 1 Dec 2008 09:51:35 +0530
> Nikanth Karthikesan <knikanth-l3A5Bk7waGM@public.gmane.org> wrote:
> 
> > Ok. Then should we remove the unused code which simply checks for thread group 
> > leader but does nothing?
> >  
> > Thanks
> > Nikanth
> > 
> Hmm, it seem that code is obsolete. thanks.
> Balbir, how do you think ?
> 
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
> 
> Anyway we have to visit here, again.

Sorry, I did not review this patch. The correct thing was nikanth did
at first, move this to can_attach(). Why would we allow threads to
exist in different groups, but still mark them as being accounted to
the thread group leader.

It can be a bit confusing for end users, it can be helpful when all
controllers are mounted together. I agree we did not do anything
useful in move_task(). The correct check now, should be for mm->owner.

If the common case is going to be that memory and cpu are mounted
together, then this patch is correct, but it can be confusing to users
who look at tasks/threads, but as the threads consume memory, the
accounting will happen with mm->owner.

-- 
	Balbir