memcg: oom wakeup filter

memcg's oom waitqueue is a system-wide wait_queue (for handling
hierarchy.) So, it's better to add custom wake function and do filtering
in wake up path.

This patch adds a filtering feature for waking up oom-waiters.  Hierarchy
is properly handled.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
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: 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 c8569bc..94ac208 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1293,14 +1293,56 @@ static void mem_cgroup_oom_unlock(struct mem_cgroup *mem)
 static DEFINE_MUTEX(memcg_oom_mutex);
 static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);
 
+struct oom_wait_info {
+       struct mem_cgroup *mem;
+       wait_queue_t    wait;
+};
+
+static int memcg_oom_wake_function(wait_queue_t *wait,
+       unsigned mode, int sync, void *arg)
+{
+       struct mem_cgroup *wake_mem = (struct mem_cgroup *)arg;
+       struct oom_wait_info *oom_wait_info;
+
+       oom_wait_info = container_of(wait, struct oom_wait_info, wait);
+
+       if (oom_wait_info->mem == wake_mem)
+               goto wakeup;
+       /* if no hierarchy, no match */
+       if (!oom_wait_info->mem->use_hierarchy || !wake_mem->use_hierarchy)
+               return 0;
+       /*
+        * Both of oom_wait_info->mem and wake_mem are stable under us.
+        * Then we can use css_is_ancestor without taking care of RCU.
+        */
+       if (!css_is_ancestor(&oom_wait_info->mem->css, &wake_mem->css) &&
+           !css_is_ancestor(&wake_mem->css, &oom_wait_info->mem->css))
+               return 0;
+
+wakeup:
+       return autoremove_wake_function(wait, mode, sync, arg);
+}
+
+static void memcg_wakeup_oom(struct mem_cgroup *mem)
+{
+       /* for filtering, pass "mem" as argument. */
+       __wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, mem);
+}
+
 /*
  * try to call OOM killer. returns false if we should exit memory-reclaim loop.
  */
 bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
 {
-       DEFINE_WAIT(wait);
+       struct oom_wait_info owait;
        bool locked;
 
+       owait.mem = mem;
+       owait.wait.flags = 0;
+       owait.wait.func = memcg_oom_wake_function;
+       owait.wait.private = current;
+       INIT_LIST_HEAD(&owait.wait.task_list);
+
        /* At first, try to OOM lock hierarchy under mem.*/
        mutex_lock(&memcg_oom_mutex);
        locked = mem_cgroup_oom_lock(mem);
@@ -1310,31 +1352,18 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
         * under OOM is always welcomed, use TASK_KILLABLE here.
         */
        if (!locked)
-               prepare_to_wait(&memcg_oom_waitq, &wait, TASK_KILLABLE);
+               prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
        mutex_unlock(&memcg_oom_mutex);
 
        if (locked)
                mem_cgroup_out_of_memory(mem, mask);
        else {
                schedule();
-               finish_wait(&memcg_oom_waitq, &wait);
+               finish_wait(&memcg_oom_waitq, &owait.wait);
        }
        mutex_lock(&memcg_oom_mutex);
        mem_cgroup_oom_unlock(mem);
-       /*
-        * Here, we use global waitq .....more fine grained waitq ?
-        * Assume following hierarchy.
-        * A/
-        *   01
-        *   02
-        * assume OOM happens both in A and 01 at the same time. Tthey are
-        * mutually exclusive by lock. (kill in 01 helps A.)
-        * When we use per memcg waitq, we have to wake up waiters on A and 02
-        * in addtion to waiters on 01. We use global waitq for avoiding mess.
-        * It will not be a big problem.
-        * (And a task may be moved to other groups while it's waiting for OOM.)
-        */
-       wake_up_all(&memcg_oom_waitq);
+       memcg_wakeup_oom(mem);
        mutex_unlock(&memcg_oom_mutex);
 
        if (test_thread_flag(TIF_MEMDIE) || fatal_signal_pending(current))