LMK: Import RB Tree optimization from Motorola

Signed-off-by: Paul Reioux <[email protected]>

drivers/staging/android/Kconfig

@@ -76,6 +76,14 @@ config ANDROID_LOW_MEMORY_KILLER_AUTODETECT_OOM_ADJ_VALUES
 	  /sys/module/lowmemorykiller/parameters/adj and convert them
 	  to oom_score_adj values.
 
+config ANDROID_LMK_ADJ_RBTREE
+	bool "Android Low Memory Killer: Red-Black Tree search"
+	depends on ANDROID_LOW_MEMORY_KILLER
+	default y
+	---help---
+	  Utilize RB Tree for walking the tasklist.. O(log n) vs O(n)
+	  much speedier for long task list!
+
 source "drivers/staging/android/switch/Kconfig"
 
 config ANDROID_INTF_ALARM_DEV

drivers/staging/android/lowmemorykiller.c

@@ -250,6 +250,12 @@ void tune_lmk_param(int *other_free, int *other_file, struct shrink_control *sc)
 	}
 }
 
+#ifdef CONFIG_ANDROID_LMK_ADJ_RBTREE
+static struct task_struct *pick_next_from_adj_tree(struct task_struct *task);
+static struct task_struct *pick_first_task(void);
+static struct task_struct *pick_last_task(void);
+#endif
+
 static DEFINE_MUTEX(scan_mutex);
 
 static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
@@ -310,7 +316,13 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
 	selected_oom_score_adj = min_score_adj;
 
 	rcu_read_lock();
+#ifdef CONFIG_ANDROID_LMK_ADJ_RBTREE
+	for (tsk = pick_first_task();
+		tsk != pick_last_task();
+		tsk = pick_next_from_adj_tree(tsk)) {
+#else
 	for_each_process(tsk) {
+#endif
 		struct task_struct *p;
 		int oom_score_adj;
 
@@ -338,15 +350,23 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc)
 		oom_score_adj = p->signal->oom_score_adj;
 		if (oom_score_adj < min_score_adj) {
 			task_unlock(p);
+#ifdef CONFIG_ANDROID_LMK_ADJ_RBTREE
+			break;
+#else
 			continue;
+#endif
 		}
 		tasksize = get_mm_rss(p->mm);
 		task_unlock(p);
 		if (tasksize <= 0)
 			continue;
 		if (selected) {
 			if (oom_score_adj < selected_oom_score_adj)
+#ifdef CONFIG_ANDROID_LMK_ADJ_RBTREE
+				break;
+#else
 				continue;
+#endif
 			if (oom_score_adj == selected_oom_score_adj &&
 			    tasksize <= selected_tasksize)
 				continue;
@@ -498,6 +518,85 @@ static const struct kparam_array __param_arr_adj = {
 };
 #endif
 
+#ifdef CONFIG_ANDROID_LMK_ADJ_RBTREE
+DEFINE_SPINLOCK(lmk_lock);
+struct rb_root tasks_scoreadj = RB_ROOT;
+void add_2_adj_tree(struct task_struct *task)
+{
+	struct rb_node **link = &tasks_scoreadj.rb_node;
+	struct rb_node *parent = NULL;
+	struct task_struct *task_entry;
+	s64 key = task->signal->oom_score_adj;
+	/*
+ * 	 * Find the right place in the rbtree:
+ * 	 	 */
+	spin_lock(&lmk_lock);
+	while (*link) {
+		parent = *link;
+		task_entry = rb_entry(parent, struct task_struct, adj_node);
+
+		if (key < task_entry->signal->oom_score_adj)
+			link = &parent->rb_right;
+		else
+			link = &parent->rb_left;
+	}
+
+	rb_link_node(&task->adj_node, parent, link);
+	rb_insert_color(&task->adj_node, &tasks_scoreadj);
+	spin_unlock(&lmk_lock);
+}
+
+void delete_from_adj_tree(struct task_struct *task)
+{
+	spin_lock(&lmk_lock);
+	rb_erase(&task->adj_node, &tasks_scoreadj);
+	spin_unlock(&lmk_lock);
+}
+
+
+static struct task_struct *pick_next_from_adj_tree(struct task_struct *task)
+{
+	struct rb_node *next;
+
+	spin_lock(&lmk_lock);
+	next = rb_next(&task->adj_node);
+	spin_unlock(&lmk_lock);
+
+	if (!next)
+		return NULL;
+
+	 return rb_entry(next, struct task_struct, adj_node);
+}
+
+static struct task_struct *pick_first_task(void)
+{
+	struct rb_node *left;
+
+	spin_lock(&lmk_lock);
+	left = rb_first(&tasks_scoreadj);
+	spin_unlock(&lmk_lock);
+
+	if (!left)
+		return NULL;
+
+	return rb_entry(left, struct task_struct, adj_node);
+}
+
+static struct task_struct *pick_last_task(void)
+{
+	struct rb_node *right;
+
+	spin_lock(&lmk_lock);
+	right = rb_last(&tasks_scoreadj);
+	spin_unlock(&lmk_lock);
+
+	if (!right)
+		return NULL;
+
+	return rb_entry(right, struct task_struct, adj_node);
+}
+#endif
+
 module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
 #ifdef CONFIG_ANDROID_LOW_MEMORY_KILLER_AUTODETECT_OOM_ADJ_VALUES
 __module_param_call(MODULE_PARAM_PREFIX, adj,

include/linux/sched.h

@@ -1324,6 +1324,9 @@ struct task_struct {
 #endif
 
 	struct list_head tasks;
+#ifdef CONFIG_ANDROID_LMK_ADJ_RBTREE
+	struct rb_node adj_node;
+#endif
 #ifdef CONFIG_SMP
 	struct plist_node pushable_tasks;
 #endif
@@ -1671,6 +1674,14 @@ static inline struct pid *task_tgid(struct task_struct *task)
 	return task->group_leader->pids[PIDTYPE_PID].pid;
 }
 
+#ifdef CONFIG_ANDROID_LMK_ADJ_RBTREE
+extern void add_2_adj_tree(struct task_struct *task);
+extern void delete_from_adj_tree(struct task_struct *task);
+#else
+static inline void add_2_adj_tree(struct task_struct *task) { }
+static inline void delete_from_adj_tree(struct task_struct *task) { }
+#endif
+
 /*
  * Without tasklist or rcu lock it is not safe to dereference
  * the result of task_pgrp/task_session even if task == current,