Re: [PATCH 06/11] memcg: kmem controller infrastructure

[Glauber Costa]

On 06/26/2012 01:12 PM, David Rientjes wrote:
> On Mon, 25 Jun 2012, Glauber Costa wrote:
>
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 83e7ba9..22479eb 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -21,6 +21,7 @@
> >   #define _LINUX_MEMCONTROL_H
> >   #include <linux/cgroup.h>
> >   #include <linux/vm_event_item.h>
> > +#include <linux/hardirq.h>
> >
> >   struct mem_cgroup;
> >   struct page_cgroup;
> > @@ -409,6 +410,12 @@ struct sock;
> >   #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> >   void sock_update_memcg(struct sock *sk);
> >   void sock_release_memcg(struct sock *sk);
> > +
> > +#define mem_cgroup_kmem_on 1
> > +bool __mem_cgroup_new_kmem_page(gfp_t gfp, void *handle, int order);
> > +void __mem_cgroup_commit_kmem_page(struct page *page, void *handle, int order);
> > +void __mem_cgroup_free_kmem_page(struct page *page, int order);
> > +#define is_kmem_tracked_alloc (gfp & __GFP_KMEMCG)
> >   #else
> >   static inline void sock_update_memcg(struct sock *sk)
> >   {
> > @@ -416,6 +423,43 @@ static inline void sock_update_memcg(struct sock *sk)
> >   static inline void sock_release_memcg(struct sock *sk)
> >   {
> >   }
> > +
> > +#define mem_cgroup_kmem_on 0
> > +#define __mem_cgroup_new_kmem_page(a, b, c) false
> > +#define __mem_cgroup_free_kmem_page(a,b )
> > +#define __mem_cgroup_commit_kmem_page(a, b, c)
> > +#define is_kmem_tracked_alloc (false)
> >   #endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
> > +
> > +static __always_inline
> > +bool mem_cgroup_new_kmem_page(gfp_t gfp, void *handle, int order)
> > +{
> > +	if (!mem_cgroup_kmem_on)
> > +		return true;
> > +	if (!is_kmem_tracked_alloc)
> > +		return true;
> > +	if (!current->mm)
> > +		return true;
> > +	if (in_interrupt())
> > +		return true;
>
> You can't test for current->mm in irq context, so you need to check for
> in_interrupt() first.
>
Right, thanks.

> Also, what prevents __mem_cgroup_new_kmem_page()
> from being called for a kthread that has called use_mm() before
> unuse_mm()?

Nothing, but I also don't see how to prevent that.
At a first glance, it seems fair to me to say that if a kernel thread 
uses the mm of a process, it poses as this process for any accounting 
purpose.

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