[PATCH 1/2] Resource usage threshold notification addition to res_counter (v3)

[Vladislav Buzov <vbuzov@embeddedalley.com>]

This patch updates the Resource Counter to add a configurable resource usage
threshold notification mechanism.

Signed-off-by: Vladislav Buzov <vbuzov@embeddedalley.com>
Signed-off-by: Dan Malek <dan@embeddedalley.com>
---
 Documentation/cgroups/resource_counter.txt |   21 ++++++++-
 include/linux/res_counter.h                |   69 ++++++++++++++++++++++++++++
 kernel/res_counter.c                       |    7 +++
 3 files changed, 95 insertions(+), 2 deletions(-)

diff --git a/Documentation/cgroups/resource_counter.txt b/Documentation/cgroups/resource_counter.txt
index 95b24d7..1369dff 100644
--- a/Documentation/cgroups/resource_counter.txt
+++ b/Documentation/cgroups/resource_counter.txt
@@ -39,7 +39,20 @@ to work with it.
  	The failcnt stands for "failures counter". This is the number of
 	resource allocation attempts that failed.
 
- c. spinlock_t lock
+ e. unsigned long long threshold
+
+ 	The resource usage threshold to notify the resouce controller. This is
+	the minimal difference between the resource limit and current usage
+	to fire a notification.
+
+ f. void (*threshold_notifier)(struct res_counter *counter)
+
+	The threshold notification callback installed by the resource
+	controller. Called when the usage reaches or exceeds the threshold.
+	Should be fast and not sleep because called when interrupts are
+	disabled.
+
+ g. spinlock_t lock
 
  	Protects changes of the above values.
 
@@ -140,6 +153,7 @@ counter fields. They are recommended to adhere to the following rules:
 	usage		usage_in_<unit_of_measurement>
 	max_usage	max_usage_in_<unit_of_measurement>
 	limit		limit_in_<unit_of_measurement>
+	threshold	notify_threshold_in_<unit_of_measurement>
 	failcnt		failcnt
 	lock		no file :)
 
@@ -153,9 +167,12 @@ counter fields. They are recommended to adhere to the following rules:
 	usage		prohibited
 	max_usage	reset to usage
 	limit		set the limit
+	threshold	set the threshold
 	failcnt		reset to zero
 
-
+ d. Notification is enabled by installing the threshold notifier callback. It
+    is up to the resouce controller to communicate the notification to user
+    space tasks.
 
 5. Usage example
 
diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index 511f42f..5ec98d7 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -9,6 +9,11 @@
  *
  * Author: Pavel Emelianov <xemul@openvz.org>
  *
+ * Resouce usage threshold notification update
+ * Copyright 2009 CE Linux Forum and Embedded Alley Solutions, Inc.
+ * Author: Dan Malek <dan@embeddedalley.com>
+ * Author: Vladislav Buzov <vbuzov@embeddedalley.com>
+ *
  * See Documentation/cgroups/resource_counter.txt for more
  * info about what this counter is.
  */
@@ -35,6 +40,19 @@ struct res_counter {
 	 */
 	unsigned long long limit;
 	/*
+	 * the resource usage threshold to notify the resouce controller. This
+	 * is the minimal difference between the resource limit and current
+	 * usage to fire a notification.
+	 */
+	unsigned long long threshold;
+	/*
+	 * the threshold notification callback installed by the resource
+	 * controller. Called when the usage reaches or exceeds the threshold.
+	 * Should be fast and not sleep because called when interrupts are
+	 * disabled.
+	 */
+	void (*threshold_notifier)(struct res_counter *counter);
+	/*
 	 * the number of unsuccessful attempts to consume the resource
 	 */
 	unsigned long long failcnt;
@@ -87,6 +105,7 @@ enum {
 	RES_MAX_USAGE,
 	RES_LIMIT,
 	RES_FAILCNT,
+	RES_THRESHOLD,
 };
 
 /*
@@ -132,6 +151,21 @@ static inline bool res_counter_limit_check_locked(struct res_counter *cnt)
 	return false;
 }
 
+static inline bool res_counter_threshold_check_locked(struct res_counter *cnt)
+{
+	if (cnt->usage + cnt->threshold < cnt->limit)
+		return true;
+
+	return false;
+}
+
+static inline void res_counter_threshold_notify_locked(struct res_counter *cnt)
+{
+	if (!res_counter_threshold_check_locked(cnt) &&
+	    cnt->threshold_notifier)
+		cnt->threshold_notifier(cnt);
+}
+
 /*
  * Helper function to detect if the cgroup is within it's limit or
  * not. It's currently called from cgroup_rss_prepare()
@@ -147,6 +181,21 @@ static inline bool res_counter_check_under_limit(struct res_counter *cnt)
 	return ret;
 }
 
+/*
+ * Helper function to detect if the cgroup usage is under it's threshold or
+ * not.
+ */
+static inline bool res_counter_check_under_threshold(struct res_counter *cnt)
+{
+	bool ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&cnt->lock, flags);
+	ret = res_counter_threshold_check_locked(cnt);
+	spin_unlock_irqrestore(&cnt->lock, flags);
+	return ret;
+}
+
 static inline void res_counter_reset_max(struct res_counter *cnt)
 {
 	unsigned long flags;
@@ -174,6 +223,26 @@ static inline int res_counter_set_limit(struct res_counter *cnt,
 	spin_lock_irqsave(&cnt->lock, flags);
 	if (cnt->usage <= limit) {
 		cnt->limit = limit;
+		if (limit <= cnt->threshold)
+			cnt->threshold = 0;
+		else
+			res_counter_threshold_notify_locked(cnt);
+		ret = 0;
+	}
+	spin_unlock_irqrestore(&cnt->lock, flags);
+	return ret;
+}
+
+static inline int res_counter_set_threshold(struct res_counter *cnt,
+		unsigned long long threshold)
+{
+	unsigned long flags;
+	int ret = -EINVAL;
+
+	spin_lock_irqsave(&cnt->lock, flags);
+	if (cnt->limit > threshold) {
+		cnt->threshold = threshold;
+		res_counter_threshold_notify_locked(cnt);
 		ret = 0;
 	}
 	spin_unlock_irqrestore(&cnt->lock, flags);
diff --git a/kernel/res_counter.c b/kernel/res_counter.c
index e1338f0..9b36748 100644
--- a/kernel/res_counter.c
+++ b/kernel/res_counter.c
@@ -5,6 +5,10 @@
  *
  * Author: Pavel Emelianov <xemul@openvz.org>
  *
+ * Resouce usage threshold notification update
+ * Copyright 2009 CE Linux Forum and Embedded Alley Solutions, Inc.
+ * Author: Dan Malek <dan@embeddedalley.com>
+ * Author: Vladislav Buzov <vbuzov@embeddedalley.com>
  */
 
 #include <linux/types.h>
@@ -32,6 +36,7 @@ int res_counter_charge_locked(struct res_counter *counter, unsigned long val)
 	counter->usage += val;
 	if (counter->usage > counter->max_usage)
 		counter->max_usage = counter->usage;
+	res_counter_threshold_notify_locked(counter);
 	return 0;
 }
 
@@ -101,6 +106,8 @@ res_counter_member(struct res_counter *counter, int member)
 		return &counter->limit;
 	case RES_FAILCNT:
 		return &counter->failcnt;
+	case RES_THRESHOLD:
+		return &counter->threshold;
 	};
 
 	BUG();
-- 
1.5.6.3

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