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

[David Rientjes]

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

> +	if (gfp & __GFP_NOFAIL)
> +		return true;
> +	return __mem_cgroup_new_kmem_page(gfp, handle, order);
> +}
> +
> +static __always_inline
> +void mem_cgroup_free_kmem_page(struct page *page, int order)
> +{
> +	if (mem_cgroup_kmem_on)
> +		__mem_cgroup_free_kmem_page(page, order);
> +}
> +
> +static __always_inline
> +void mem_cgroup_commit_kmem_page(struct page *page, struct mem_cgroup *handle,
> +				 int order)
> +{
> +	if (mem_cgroup_kmem_on)
> +		__mem_cgroup_commit_kmem_page(page, handle, order);
> +}
>  #endif /* _LINUX_MEMCONTROL_H */
>