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Commit 8033b97c authored by Daisuke Nishimura's avatar Daisuke Nishimura Committed by Linus Torvalds
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memcg: avoid oom during moving charge 



This move-charge-at-task-migration feature has extra charges on
"to"(pre-charges) and "from"(left-over charges) during moving charge.
This means unnecessary oom can happen.

This patch tries to avoid such oom.

Signed-off-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 854ffa8d

mm/memcontrol.c

+51 −2
Original line number Diff line number Diff line
@@ -254,7 +254,11 @@ static struct move_charge_struct { 
	struct mem_cgroup *to;

	unsigned long precharge;

	unsigned long moved_charge;

} mc;

	struct task_struct *moving_task;	/* a task moving charges */

	wait_queue_head_t waitq;		/* a waitq for other context */

} mc = {

	.waitq = __WAIT_QUEUE_HEAD_INITIALIZER(mc.waitq),

};



/*

 * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
@@ -1508,6 +1512,48 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, 
		if (mem_cgroup_check_under_limit(mem_over_limit))

			continue;



		/* try to avoid oom while someone is moving charge */

		if (mc.moving_task && current != mc.moving_task) {

			struct mem_cgroup *from, *to;

			bool do_continue = false;

			/*

			 * There is a small race that "from" or "to" can be

			 * freed by rmdir, so we use css_tryget().

			 */

			rcu_read_lock();

			from = mc.from;

			to = mc.to;

			if (from && css_tryget(&from->css)) {

				if (mem_over_limit->use_hierarchy)

					do_continue = css_is_ancestor(

							&from->css,

							&mem_over_limit->css);

				else

					do_continue = (from == mem_over_limit);

				css_put(&from->css);

			}

			if (!do_continue && to && css_tryget(&to->css)) {

				if (mem_over_limit->use_hierarchy)

					do_continue = css_is_ancestor(

							&to->css,

							&mem_over_limit->css);

				else

					do_continue = (to == mem_over_limit);

				css_put(&to->css);

			}

			rcu_read_unlock();

			if (do_continue) {

				DEFINE_WAIT(wait);

				prepare_to_wait(&mc.waitq, &wait,

							TASK_INTERRUPTIBLE);

				/* moving charge context might have finished. */

				if (mc.moving_task)

					schedule();

				finish_wait(&mc.waitq, &wait);

				continue;

			}

		}



		if (!nr_retries--) {

			if (oom) {

				mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
@@ -3381,7 +3427,6 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont) 
			INIT_WORK(&stock->work, drain_local_stock);

		}

		hotcpu_notifier(memcg_stock_cpu_callback, 0);



	} else {

		parent = mem_cgroup_from_cont(cont->parent);

		mem->use_hierarchy = parent->use_hierarchy;
@@ -3641,6 +3686,8 @@ static void mem_cgroup_clear_mc(void) 
	}

	mc.from = NULL;

	mc.to = NULL;

	mc.moving_task = NULL;

	wake_up_all(&mc.waitq);

}



static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
@@ -3666,10 +3713,12 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss, 
			VM_BUG_ON(mc.to);

			VM_BUG_ON(mc.precharge);

			VM_BUG_ON(mc.moved_charge);

			VM_BUG_ON(mc.moving_task);

			mc.from = from;

			mc.to = mem;

			mc.precharge = 0;

			mc.moved_charge = 0;

			mc.moving_task = current;



			ret = mem_cgroup_precharge_mc(mm);

			if (ret)