net: activity_stats: Add statistics for network transmission activity

When enabled, tracks the frequency of network transmissions
(inbound and outbound) and buckets them accordingly.
Buckets are determined by time between network activity.

Each bucket represents the number of network transmisions that were
N sec or longer apart. Where N is defined as 1 << bucket index.

This network pattern tracking is particularly useful for wireless
networks (ie: 3G) where batching network activity closely together
is more power efficient than far apart.

New file: /proc/net/stat/activity

output:

Min Bucket(sec) Count
              1 7
              2 0
              4 1
              8 0
             16 0
             32 2
             64 1
            128 0

Change-Id: I4c4cd8627b872a55f326b1715c51bc3bdd6e8d92
Signed-off-by: Mike Chan <mike@android.com>

1 files changed, 115 insertions, 0 deletions

diff --git a/net/activity_stats.c b/net/activity_stats.c
new file mode 100644
index 00000000000..8a3e9347006
--- /dev/null
+++ b/net/activity_stats.c
@@ -0,0 +1,115 @@
+/* net/activity_stats.c
+ *
+ * Copyright (C) 2010 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Author: Mike Chan (mike@android.com)
+ */
+
+#include <linux/proc_fs.h>
+#include <linux/suspend.h>
+#include <net/net_namespace.h>
+
+/*
+ * Track transmission rates in buckets (power of 2).
+ * 1,2,4,8...512 seconds.
+ *
+ * Buckets represent the count of network transmissions at least
+ * N seconds apart, where N is 1 << bucket index.
+ */
+#define BUCKET_MAX 10
+
+/* Track network activity frequency */
+static unsigned long activity_stats[BUCKET_MAX];
+static ktime_t last_transmit;
+static ktime_t suspend_time;
+static DEFINE_SPINLOCK(activity_lock);
+
+void activity_stats_update(void)
+{
+	int i;
+	unsigned long flags;
+	ktime_t now;
+	s64 delta;
+
+	spin_lock_irqsave(&activity_lock, flags);
+	now = ktime_get();
+	delta = ktime_to_ns(ktime_sub(now, last_transmit));
+
+	for (i = BUCKET_MAX - 1; i >= 0; i--) {
+		/*
+		 * Check if the time delta between network activity is within the
+		 * minimum bucket range.
+		 */
+		if (delta < (1000000000ULL << i))
+			continue;
+
+		activity_stats[i]++;
+		last_transmit = now;
+		break;
+	}
+	spin_unlock_irqrestore(&activity_lock, flags);
+}
+
+static int activity_stats_read_proc(char *page, char **start, off_t off,
+					int count, int *eof, void *data)
+{
+	int i;
+	int len;
+	char *p = page;
+
+	/* Only print if offset is 0, or we have enough buffer space */
+	if (off || count < (30 * BUCKET_MAX + 22))
+		return -ENOMEM;
+
+	len = snprintf(p, count, "Min Bucket(sec) Count\n");
+	count -= len;
+	p += len;
+
+	for (i = 0; i < BUCKET_MAX; i++) {
+		len = snprintf(p, count, "%15d %lu\n", 1 << i, activity_stats[i]);
+		count -= len;
+		p += len;
+	}
+	*eof = 1;
+
+	return p - page;
+}
+
+static int activity_stats_notifier(struct notifier_block *nb,
+					unsigned long event, void *dummy)
+{
+	switch (event) {
+		case PM_SUSPEND_PREPARE:
+			suspend_time = ktime_get_real();
+			break;
+
+		case PM_POST_SUSPEND:
+			suspend_time = ktime_sub(ktime_get_real(), suspend_time);
+			last_transmit = ktime_sub(last_transmit, suspend_time);
+	}
+
+	return 0;
+}
+
+static struct notifier_block activity_stats_notifier_block = {
+	.notifier_call = activity_stats_notifier,
+};
+
+static int  __init activity_stats_init(void)
+{
+	create_proc_read_entry("activity", S_IRUGO,
+			init_net.proc_net_stat, activity_stats_read_proc, NULL);
+	return register_pm_notifier(&activity_stats_notifier_block);
+}
+
+subsys_initcall(activity_stats_init);
+