Re: [PATCH] Cgroup: Fix memory accounting scalability inshrink_page_list

[Johannes Weiner]

On Fri, Jul 20, 2012 at 03:53:29PM +0200, Michal Hocko wrote:
> On Thu 19-07-12 16:34:26, Tim Chen wrote:
> [...]
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 33dc256..aac5672 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -779,6 +779,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> >  
> >  	cond_resched();
> >  
> > +	mem_cgroup_uncharge_start();
> >  	while (!list_empty(page_list)) {
> >  		enum page_references references;
> >  		struct address_space *mapping;
> 
> Is this safe? We have a scheduling point few lines below. What prevents
> from task move while we are in the middle of the batch?

The batch is accounted in task_struct, so moving a batching task to
another CPU shouldn't be a problem.
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