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: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f5fb991..589084f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -254,7 +254,11 @@
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 @@
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 @@
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 @@
}
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 @@
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)
