Commit 0b7f569e authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds
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memcg: fix OOM killer under memcg 



This patch tries to fix OOM Killer problems caused by hierarchy.
Now, memcg itself has OOM KILL function (in oom_kill.c) and tries to
kill a task in memcg.

But, when hierarchy is used, it's broken and correct task cannot
be killed. For example, in following cgroup

	/groupA/	hierarchy=1, limit=1G,
		01	nolimit
		02	nolimit
All tasks' memory usage under /groupA, /groupA/01, groupA/02 is limited to
groupA's 1Gbytes but OOM Killer just kills tasks in groupA.

This patch provides makes the bad process be selected from all tasks
under hierarchy. BTW, currently, oom_jiffies is updated against groupA
in above case. oom_jiffies of tree should be updated.

To see how oom_jiffies is used, please check mem_cgroup_oom_called()
callers.

[akpm@linux-foundation.org: build fix]
[akpm@linux-foundation.org: const fix]
Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 81d39c20

Documentation/cgroups/memcg_test.txt

+19 −1
Original line number Diff line number Diff line 
Memory Resource Controller(Memcg)  Implementation Memo.

Last Updated: 2009/1/19

Last Updated: 2009/1/20

Base Kernel Version: based on 2.6.29-rc2.



Because VM is getting complex (one of reasons is memcg...), memcg's behavior
@@ -360,3 +360,21 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y. 
	# kill malloc task.



	Of course, tmpfs v.s. swapoff test should be tested, too.



 9.8 OOM-Killer

	Out-of-memory caused by memcg's limit will kill tasks under

	the memcg. When hierarchy is used, a task under hierarchy

	will be killed by the kernel.

	In this case, panic_on_oom shouldn't be invoked and tasks

	in other groups shouldn't be killed.



	It's not difficult to cause OOM under memcg as following.

	Case A) when you can swapoff

	#swapoff -a

	#echo 50M > /memory.limit_in_bytes

	run 51M of malloc



	Case B) when you use mem+swap limitation.

	#echo 50M > memory.limit_in_bytes

	#echo 50M > memory.memsw.limit_in_bytes

	run 51M of malloc

include/linux/cgroup.h

+1 −1
Original line number Diff line number Diff line
@@ -503,7 +503,7 @@ struct cgroup_subsys_state *css_get_next(struct cgroup_subsys *ss, int id, 


/* Returns true if root is ancestor of cg */

bool css_is_ancestor(struct cgroup_subsys_state *cg,

		     struct cgroup_subsys_state *root);

		     const struct cgroup_subsys_state *root);



/* Get id and depth of css */

unsigned short css_id(struct cgroup_subsys_state *css);

kernel/cgroup.c

+1 −1
Original line number Diff line number Diff line
@@ -3405,7 +3405,7 @@ unsigned short css_depth(struct cgroup_subsys_state *css) 
}



bool css_is_ancestor(struct cgroup_subsys_state *child,

		    struct cgroup_subsys_state *root)

		    const struct cgroup_subsys_state *root)

{

	struct css_id *child_id = rcu_dereference(child->id);

	struct css_id *root_id = rcu_dereference(root->id);

mm/memcontrol.c

+28 −2
Original line number Diff line number Diff line
@@ -295,6 +295,9 @@ struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p) 
static struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)

{

	struct mem_cgroup *mem = NULL;



	if (!mm)

		return NULL;

	/*

	 * Because we have no locks, mm->owner's may be being moved to other

	 * cgroup. We use css_tryget() here even if this looks
@@ -486,10 +489,20 @@ void mem_cgroup_move_lists(struct page *page, 
int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)

{

	int ret;

	struct mem_cgroup *curr = NULL;



	task_lock(task);

	ret = task->mm && mm_match_cgroup(task->mm, mem);

	rcu_read_lock();

	curr = try_get_mem_cgroup_from_mm(task->mm);

	rcu_read_unlock();

	task_unlock(task);

	if (!curr)

		return 0;

	if (curr->use_hierarchy)

		ret = css_is_ancestor(&curr->css, &mem->css);

	else

		ret = (curr == mem);

	css_put(&curr->css);

	return ret;

}
@@ -820,6 +833,19 @@ bool mem_cgroup_oom_called(struct task_struct *task) 
	rcu_read_unlock();

	return ret;

}



static int record_last_oom_cb(struct mem_cgroup *mem, void *data)

{

	mem->last_oom_jiffies = jiffies;

	return 0;

}



static void record_last_oom(struct mem_cgroup *mem)

{

	mem_cgroup_walk_tree(mem, NULL, record_last_oom_cb);

}





/*

 * Unlike exported interface, "oom" parameter is added. if oom==true,

 * oom-killer can be invoked.
@@ -902,7 +928,7 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, 
				mutex_lock(&memcg_tasklist);

				mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);

				mutex_unlock(&memcg_tasklist);

				mem_over_limit->last_oom_jiffies = jiffies;

				record_last_oom(mem_over_limit);

			}

			goto nomem;

		}

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