Re: [RFC][-mm] Memory controller add mm->owner

[Li Zefan <lizf@cn.fujitsu.com>]

Balbir Singh wrote:
> This patch removes the mem_cgroup member from mm_struct and instead adds
> an owner. This approach was suggested by Paul Menage. The advantage of
> this approach is that, once the mm->owner is known, using the subsystem
> id, the cgroup can be determined. It also allows several control groups
> that are virtually grouped by mm_struct, to exist independent of the memory
> controller i.e., without adding mem_cgroup's for each controller,
> to mm_struct.
> 
> The code initially assigns mm->owner to the task and then after the
> thread group leader is identified. The mm->owner is changed to the thread
> group leader of the task later at the end of copy_process.
> 
> Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
> ---
> 
>  include/linux/memcontrol.h |   14 +++++++++++++-
>  include/linux/mm_types.h   |    5 ++++-
>  kernel/fork.c              |    4 ++++
>  mm/memcontrol.c            |   42 ++++++++++++++++++++++++++++++++++--------
>  4 files changed, 55 insertions(+), 10 deletions(-)
> 
> diff -puN include/linux/mm_types.h~memory-controller-add-mm-owner include/linux/mm_types.h
> --- linux-2.6.25-rc5/include/linux/mm_types.h~memory-controller-add-mm-owner	2008-03-20 13:35:09.000000000 +0530
> +++ linux-2.6.25-rc5-balbir/include/linux/mm_types.h	2008-03-20 15:11:05.000000000 +0530
> @@ -228,7 +228,10 @@ struct mm_struct {
>  	rwlock_t		ioctx_list_lock;
>  	struct kioctx		*ioctx_list;
>  #ifdef CONFIG_CGROUP_MEM_RES_CTLR
> -	struct mem_cgroup *mem_cgroup;
> +	struct task_struct *owner;	/* The thread group leader that */
> +					/* owns the mm_struct. This     */
> +					/* might be useful even outside */
> +					/* of the config option         */
>  #endif
>  
>  #ifdef CONFIG_PROC_FS
> diff -puN kernel/fork.c~memory-controller-add-mm-owner kernel/fork.c
> --- linux-2.6.25-rc5/kernel/fork.c~memory-controller-add-mm-owner	2008-03-20 13:35:09.000000000 +0530
> +++ linux-2.6.25-rc5-balbir/kernel/fork.c	2008-03-24 18:49:29.000000000 +0530
> @@ -1357,6 +1357,10 @@ static struct task_struct *copy_process(
>  	write_unlock_irq(&tasklist_lock);
>  	proc_fork_connector(p);
>  	cgroup_post_fork(p);
> +
> +	if (!(clone_flags & CLONE_VM))
> +		mem_cgroup_fork_init(p);
> +
>  	return p;
>  
>  bad_fork_free_pid:
> diff -puN include/linux/memcontrol.h~memory-controller-add-mm-owner include/linux/memcontrol.h
> --- linux-2.6.25-rc5/include/linux/memcontrol.h~memory-controller-add-mm-owner	2008-03-20 13:35:09.000000000 +0530
> +++ linux-2.6.25-rc5-balbir/include/linux/memcontrol.h	2008-03-24 18:49:52.000000000 +0530
> @@ -29,6 +29,7 @@ struct mm_struct;
>  
>  extern void mm_init_cgroup(struct mm_struct *mm, struct task_struct *p);
>  extern void mm_free_cgroup(struct mm_struct *mm);
> +extern void mem_cgroup_fork_init(struct task_struct *p);
>  
>  #define page_reset_bad_cgroup(page)	((page)->page_cgroup = 0)
>  
> @@ -49,7 +50,7 @@ extern void mem_cgroup_out_of_memory(str
>  int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem);
>  
>  #define mm_match_cgroup(mm, cgroup)	\
> -	((cgroup) == rcu_dereference((mm)->mem_cgroup))
> +	((cgroup) == mem_cgroup_from_task((mm)->owner))
>  
>  extern int mem_cgroup_prepare_migration(struct page *page);
>  extern void mem_cgroup_end_migration(struct page *page);
> @@ -72,6 +73,8 @@ extern long mem_cgroup_calc_reclaim_acti
>  extern long mem_cgroup_calc_reclaim_inactive(struct mem_cgroup *mem,
>  				struct zone *zone, int priority);
>  
> +extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
> +
>  #else /* CONFIG_CGROUP_MEM_RES_CTLR */
>  static inline void mm_init_cgroup(struct mm_struct *mm,
>  					struct task_struct *p)
> @@ -82,6 +85,10 @@ static inline void mm_free_cgroup(struct
>  {
>  }
>  
> +static inline void mem_cgroup_fork_init(struct task_struct *p)
> +{
> +}
> +
>  static inline void page_reset_bad_cgroup(struct page *page)
>  {
>  }
> @@ -172,6 +179,11 @@ static inline long mem_cgroup_calc_recla
>  {
>  	return 0;
>  }
> +
> +static void mm_free_fork_cgroup(struct task_struct *p)
> +{
> +}
> +

Where is this function used? I don't see the corresponding one
with CONFIG_CGROUP_MEM_RES_CTLR enabled?

>  #endif /* CONFIG_CGROUP_MEM_CONT */
>  
>  #endif /* _LINUX_MEMCONTROL_H */
> diff -puN mm/memcontrol.c~memory-controller-add-mm-owner mm/memcontrol.c
> --- linux-2.6.25-rc5/mm/memcontrol.c~memory-controller-add-mm-owner	2008-03-20 13:35:09.000000000 +0530
> +++ linux-2.6.25-rc5-balbir/mm/memcontrol.c	2008-03-24 19:04:32.000000000 +0530
> @@ -236,7 +236,7 @@ static struct mem_cgroup *mem_cgroup_fro
>  				css);
>  }
>  
> -static struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
> +struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
>  {
>  	return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
>  				struct mem_cgroup, css);
> @@ -248,12 +248,40 @@ void mm_init_cgroup(struct mm_struct *mm
>  
>  	mem = mem_cgroup_from_task(p);
>  	css_get(&mem->css);
> -	mm->mem_cgroup = mem;
> +	mm->owner = p;
> +}
> +
> +void mem_cgroup_fork_init(struct task_struct *p)
> +{
> +	struct mm_struct *mm = get_task_mm(p);
> +	struct mem_cgroup *mem, *oldmem;

Leave an empty line here.

> +	if (!mm)
> +		return;
> +
> +	/*
> +	 * Initial owner at mm_init_cgroup() time is the task itself.
> +	 * The thread group leader had not been setup then
> +	 */
> +	oldmem = mem_cgroup_from_task(mm->owner);
> +	/*
> +	 * Override the mm->owner after we know the thread group later
> +	 */
> +	mm->owner = p->group_leader;
> +	mem = mem_cgroup_from_task(mm->owner);
> +	css_get(&mem->css);
> +	css_put(&oldmem->css);
> +	mmput(mm);
>  }
>  
>  void mm_free_cgroup(struct mm_struct *mm)
>  {
> -	css_put(&mm->mem_cgroup->css);
> +	struct mem_cgroup *mem;
> +
> +	/*
> +	 * TODO: Should we assign mm->owner to NULL here?
> +	 */
> +	mem = mem_cgroup_from_task(mm->owner);
> +	css_put(&mem->css);
>  }
>  
>  static inline int page_cgroup_locked(struct page *page)
> @@ -476,6 +504,7 @@ unsigned long mem_cgroup_isolate_pages(u
>  	int zid = zone_idx(z);
>  	struct mem_cgroup_per_zone *mz;
>  
> +	BUG_ON(!mem_cont);
>  	mz = mem_cgroup_zoneinfo(mem_cont, nid, zid);
>  	if (active)
>  		src = &mz->active_list;
> @@ -573,13 +602,11 @@ retry:
>  	if (!mm)
>  		mm = &init_mm;
>  
> -	rcu_read_lock();
> -	mem = rcu_dereference(mm->mem_cgroup);
> +	mem = mem_cgroup_from_task(mm->owner);
>  	/*
>  	 * For every charge from the cgroup, increment reference count
>  	 */
>  	css_get(&mem->css);
> -	rcu_read_unlock();
>  
>  	while (res_counter_charge(&mem->res, PAGE_SIZE)) {
>  		if (!(gfp_mask & __GFP_WAIT))
> @@ -988,7 +1015,7 @@ mem_cgroup_create(struct cgroup_subsys *
>  
>  	if (unlikely((cont->parent) == NULL)) {
>  		mem = &init_mem_cgroup;
> -		init_mm.mem_cgroup = mem;
> +		init_mm.owner = &init_task;
>  	} else
>  		mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);
>  
> @@ -1069,7 +1096,6 @@ static void mem_cgroup_move_task(struct 
>  		goto out;
>  
>  	css_get(&mem->css);
> -	rcu_assign_pointer(mm->mem_cgroup, mem);
>  	css_put(&old_mem->css);
>  
>  out:
> _
>