From: Vladimir Davydov <vdavydov@virtuozzo.com>
Date: Fri, 25 Mar 2016 21:20:39 +0000 (-0700)
Subject: oom: make oom_reaper_list single linked
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=29c696e1c6eceb5db6b21f0c89495fcfcd40c0eb;p=openwrt%2Fstaging%2Fblogic.git

oom: make oom_reaper_list single linked

Entries are only added/removed from oom_reaper_list at head so we can
use a single linked list and hence save a word in task_struct.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.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/include/linux/sched.h b/include/linux/sched.h
index c2d2d7c5d463..49b1febcf7c3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1852,7 +1852,7 @@ struct task_struct {
 #endif
 	int pagefault_disabled;
 #ifdef CONFIG_MMU
-	struct list_head oom_reaper_list;
+	struct task_struct *oom_reaper_list;
 #endif
 /* CPU-specific state of this task */
 	struct thread_struct thread;
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 1a21819a8e5e..a49638f41e45 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -419,7 +419,7 @@ bool oom_killer_disabled __read_mostly;
  */
 static struct task_struct *oom_reaper_th;
 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
-static LIST_HEAD(oom_reaper_list);
+static struct task_struct *oom_reaper_list;
 static DEFINE_SPINLOCK(oom_reaper_lock);
 
 
@@ -528,13 +528,11 @@ static int oom_reaper(void *unused)
 	while (true) {
 		struct task_struct *tsk = NULL;
 
-		wait_event_freezable(oom_reaper_wait,
-				     (!list_empty(&oom_reaper_list)));
+		wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
 		spin_lock(&oom_reaper_lock);
-		if (!list_empty(&oom_reaper_list)) {
-			tsk = list_first_entry(&oom_reaper_list,
-					struct task_struct, oom_reaper_list);
-			list_del(&tsk->oom_reaper_list);
+		if (oom_reaper_list != NULL) {
+			tsk = oom_reaper_list;
+			oom_reaper_list = tsk->oom_reaper_list;
 		}
 		spin_unlock(&oom_reaper_lock);
 
@@ -553,7 +551,8 @@ static void wake_oom_reaper(struct task_struct *tsk)
 	get_task_struct(tsk);
 
 	spin_lock(&oom_reaper_lock);
-	list_add(&tsk->oom_reaper_list, &oom_reaper_list);
+	tsk->oom_reaper_list = oom_reaper_list;
+	oom_reaper_list = tsk;
 	spin_unlock(&oom_reaper_lock);
 	wake_up(&oom_reaper_wait);
 }