[Devel] Re: Unable to remove control groups on 2.6.23-rc8-mm1

Badari Pulavarty pbadari at us.ibm.com
Wed Sep 26 08:46:20 PDT 2007


On Wed, 2007-09-26 at 18:14 +0900, KAMEZAWA Hiroyuki wrote:
> This is an experimental patch for drop pages in empty cgroup.
> comments ?

Hmm.. Patch doesn't seems to help :(

elm3b155:/dev/cgroup/xxx # cat memory.usage_in_bytes
65536
elm3b155:/dev/cgroup/xxx # sync
elm3b155:/dev/cgroup/xxx # sync
elm3b155:/dev/cgroup/xxx # cat memory.usage_in_bytes
65536

Thanks,
Badari

> 
> ==
> An experimental patch.
> 
> Drop all pages in memcontrol cgroup if cgroup's task is empty.
> Please type "sync" before try to drop. Unless sync, maybe -EBUSY will return.
> 
> Problem: not handle mlocked pages now.
> 
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
> 
> ---
>  include/linux/memcontrol.h |   13 ++++-
>  mm/memcontrol.c            |  113 +++++++++++++++++++++++++++++++++++++++++++++
>  mm/vmscan.c                |   16 +++++-
>  3 files changed, 140 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6.23-rc8-mm1/mm/memcontrol.c
> ===================================================================
> --- linux-2.6.23-rc8-mm1.orig/mm/memcontrol.c
> +++ linux-2.6.23-rc8-mm1/mm/memcontrol.c
> @@ -63,6 +63,7 @@ struct mem_cgroup {
>  	 */
>  	spinlock_t lru_lock;
>  	unsigned long control_type;	/* control RSS or RSS+Pagecache */
> +	unsigned long force_drop;
>  };
> 
>  /*
> @@ -135,6 +136,31 @@ static inline int page_cgroup_locked(str
>  					&page->page_cgroup);
>  }
> 
> +static inline unsigned long long mem_cgroup_usage(struct mem_cgroup *mem)
> +{
> +	return mem->res.usage;
> +}
> +
> +int mem_cgroup_reclaim_end(struct mem_cgroup *mem)
> +{
> +	if (!mem)
> +		return 0;
> +	if (mem_cgroup_usage(mem) == 0)
> +		return 1;
> +	return 0;
> +}
> +
> +int mem_cgroup_force_reclaim(struct mem_cgroup *mem)
> +{
> +	if (!mem)
> +		return 0;
> +	/* Need more precise check if LRU is separated. */
> +	if (mem->force_drop)
> +		return 1;
> +	else
> +		return 0;
> +}
> +
>  void page_assign_page_cgroup(struct page *page, struct page_cgroup *pc)
>  {
>  	int locked;
> @@ -437,6 +463,52 @@ void mem_cgroup_uncharge(struct page_cgr
>  	}
>  }
> 
> +/*
> + * Drop all pages
> + * # of tasks in this cgroup must be 0 before call this.
> + */
> +int mem_cgroup_drop(struct mem_cgroup *mem)
> +{
> +
> +	unsigned long long before;
> +	struct cgroup *cg = mem->css.cgroup;
> +	int ret = -EBUSY;
> +	unsigned long expire = jiffies + 30 * HZ; /* just pseudo value */
> +
> +	css_get(&mem->css);
> +retry:
> +	/* disallow if there is the task. */
> +	if (atomic_read(&cg->count))
> +		goto end;
> +	/*
> +	 * We have to call try_to_free_mem_cgroup_pages() several times.
> +	 * Especially when there is write-back pages.
> +	 */
> +	if (time_after(jiffies, expire))
> +		goto end;
> +
> +	before = mem_cgroup_usage(mem);
> +
> +	if (before == 0) {
> +		ret = 0;
> +		goto end;
> +	}
> +	mem->force_drop = 1;
> +	if (try_to_free_mem_cgroup_pages(mem, GFP_HIGHUSER_MOVABLE) == 0)
> +		congestion_wait(WRITE, HZ/10);
> +	mem->force_drop = 0;
> +
> +	/* made some progress */
> +	if (mem_cgroup_usage(mem) <= before)
> +		goto retry;
> +
> +end:
> +	css_put(&mem->css);
> +	return ret;
> +}
> +
> +
> +
>  int mem_cgroup_write_strategy(char *buf, unsigned long long *tmp)
>  {
>  	*tmp = memparse(buf, &buf);
> @@ -522,6 +594,41 @@ static ssize_t mem_control_type_read(str
>  			ppos, buf, s - buf);
>  }
> 
> +static ssize_t mem_drop_type_write(struct cgroup *cont,
> +			struct cftype *cft, struct file *file,
> +			const char __user *userbuf,
> +			size_t nbytes, loff_t *pos)
> +{
> +	struct mem_cgroup *mem;
> +	int ret;
> +	char *buf, *end;
> +	unsigned long tmp;
> +
> +	mem = mem_cgroup_from_cont(cont);
> +	buf = kmalloc(nbytes + 1, GFP_KERNEL);
> +	ret = -ENOMEM;
> +	if (buf == NULL)
> +		goto out;
> +	buf[nbytes] = 0;
> +	ret = -EFAULT;
> +	if (copy_from_user(buf, userbuf, nbytes))
> +		goto out_free;
> +	ret = -EINVAL;
> +	tmp = simple_strtoul(buf, &end, 10);
> +
> +	if (*end != '\0')
> +		goto out_free;
> +	if (tmp) {
> +		ret = mem_cgroup_drop(mem);
> +		if (!ret)
> +			ret = nbytes;
> +	}
> +out_free:
> +	kfree(buf);
> +out:
> +	return ret;
> +}
> +
>  static struct cftype mem_cgroup_files[] = {
>  	{
>  		.name = "usage_in_bytes",
> @@ -544,6 +651,11 @@ static struct cftype mem_cgroup_files[] 
>  		.write = mem_control_type_write,
>  		.read = mem_control_type_read,
>  	},
> +	{
> +		.name = "drop_in_force",
> +		.write = mem_drop_type_write,
> +		.read = mem_cgroup_read,
> +	},
>  };
> 
>  static struct mem_cgroup init_mem_cgroup;
> @@ -567,6 +679,7 @@ mem_cgroup_create(struct cgroup_subsys *
>  	INIT_LIST_HEAD(&mem->inactive_list);
>  	spin_lock_init(&mem->lru_lock);
>  	mem->control_type = MEM_CGROUP_TYPE_ALL;
> +	mem->force_drop = 0;
>  	return &mem->css;
>  }
> 
> Index: linux-2.6.23-rc8-mm1/include/linux/memcontrol.h
> ===================================================================
> --- linux-2.6.23-rc8-mm1.orig/include/linux/memcontrol.h
> +++ linux-2.6.23-rc8-mm1/include/linux/memcontrol.h
> @@ -47,6 +47,10 @@ extern int mem_cgroup_cache_charge(struc
>  					gfp_t gfp_mask);
>  extern struct mem_cgroup *mm_cgroup(struct mm_struct *mm);
> 
> +/* called when page reclaim has no progress in mem cgroup */
> +extern int mem_cgroup_reclaim_end(struct mem_cgroup *mem);
> +extern int mem_cgroup_force_reclaim(struct mem_cgroup *mem);
> +
>  static inline void mem_cgroup_uncharge_page(struct page *page)
>  {
>  	mem_cgroup_uncharge(page_get_page_cgroup(page));
> @@ -102,7 +106,14 @@ static inline struct mem_cgroup *mm_cgro
>  {
>  	return NULL;
>  }
> -
> +static inline int mem_cgroup_force_reclaim(struct mem_cgroup *mem)
> +{
> +	return 0;
> +}
> +static inline int mem_cgroup_reclaim_end(struct mem_cgroup *mem)
> +{
> +	return 0;
> +}
>  #endif /* CONFIG_CGROUP_MEM_CONT */
> 
>  #endif /* _LINUX_MEMCONTROL_H */
> Index: linux-2.6.23-rc8-mm1/mm/vmscan.c
> ===================================================================
> --- linux-2.6.23-rc8-mm1.orig/mm/vmscan.c
> +++ linux-2.6.23-rc8-mm1/mm/vmscan.c
> @@ -1168,6 +1168,13 @@ static unsigned long shrink_zone(int pri
>  		zone->nr_scan_inactive = 0;
>  	else
>  		nr_inactive = 0;
> +	/* TODO: we need to know # of pages to be reclaimed per group */
> +	if (mem_cgroup_force_reclaim(sc->mem_cgroup)) {
> +		if (!nr_active)
> +			nr_active = sc->swap_cluster_max;
> +		if (!nr_inactive)
> +			nr_inactive = sc->swap_cluster_max;
> +	}
> 
>  	while (nr_active || nr_inactive) {
>  		if (nr_active) {
> @@ -1256,6 +1263,7 @@ static unsigned long do_try_to_free_page
>  	int ret = 0;
>  	unsigned long total_scanned = 0;
>  	unsigned long nr_reclaimed = 0;
> +	unsigned long progress;
>  	struct reclaim_state *reclaim_state = current->reclaim_state;
>  	unsigned long lru_pages = 0;
>  	int i;
> @@ -1276,7 +1284,8 @@ static unsigned long do_try_to_free_page
>  		sc->nr_scanned = 0;
>  		if (!priority)
>  			disable_swap_token();
> -		nr_reclaimed += shrink_zones(priority, zones, sc);
> +		progress = shrink_zones(priority, zones, sc);
> +		nr_reclaimed += progress;
>  		/*
>  		 * Don't shrink slabs when reclaiming memory from
>  		 * over limit cgroups
> @@ -1292,6 +1301,11 @@ static unsigned long do_try_to_free_page
>  			ret = 1;
>  			goto out;
>  		}
> +		if (progress == 0 &&
> +		    mem_cgroup_reclaim_end(sc->mem_cgroup)) {
> +			ret = 1;
> +			goto out;
> +		}
> 
>  		/*
>  		 * Try to write back as many pages as we just scanned.  This
> 

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