Subject: [RFC PATCH v4 2/3] mac80211: add periodic monitor for channel busy time

From: Baligh Gasmi <[email-masked]>
Date: Wed, 1 Jun 2022 13:29:02 +0200

Add a worker scheduled periodicaly to calculate the busy time average of
the current channel.

This will be used in the estimation for expected throughput.

Signed-off-by: Baligh Gasmi <[email-masked]>
---
 net/mac80211/ieee80211_i.h |  6 ++++
 net/mac80211/iface.c       | 65 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 86ef0a46a68c..2cb388335ce8 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -901,6 +901,7 @@ struct ieee80211_if_nan {
 	struct idr function_inst_ids;
 };
 
+DECLARE_EWMA(avg_busy, 8, 4)
 struct ieee80211_sub_if_data {
 	struct list_head list;
 
@@ -1024,6 +1025,11 @@ struct ieee80211_sub_if_data {
 	} debugfs;
 #endif
 
+	struct delayed_work monitor_work;
+	u64 last_time;
+	u64 last_time_busy;
+	struct ewma_avg_busy avg_busy;
+
 	/* must be last, dynamically sized area in this! */
 	struct ieee80211_vif vif;
 };
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 41531478437c..45b860c59d79 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -1970,6 +1970,64 @@ static void ieee80211_assign_perm_addr(struct ieee80211_local *local,
 	mutex_unlock(&local->iflist_mtx);
 }
 
+#define DEFAULT_MONITOR_INTERVAL_MS 1000
+
+static void ieee80211_if_monitor_work(struct work_struct *work)
+{
+	struct delayed_work *delayed_work = to_delayed_work(work);
+	struct ieee80211_sub_if_data *sdata =
+		container_of(delayed_work, struct ieee80211_sub_if_data,
+			     monitor_work);
+	struct survey_info survey;
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_chanctx_conf *chanctx_conf;
+	struct ieee80211_channel *channel = NULL;
+	int q = 0;
+	u64 interval = DEFAULT_MONITOR_INTERVAL_MS;
+
+	rcu_read_lock();
+	chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf);
+	if (chanctx_conf)
+		channel = chanctx_conf->def.chan;
+	rcu_read_unlock();
+
+	if (!channel)
+		goto end;
+
+	if (!local->started)
+		goto end;
+
+	do {
+		survey.filled = 0;
+		if (drv_get_survey(local, q++, &survey) != 0) {
+			survey.filled = 0;
+			break;
+		}
+	} while (channel != survey.channel);
+
+	if (survey.filled & SURVEY_INFO_TIME) {
+		/* real interval */
+		interval = survey.time - sdata->last_time;
+		/* store last time */
+		sdata->last_time = survey.time;
+	}
+
+	if (survey.filled & SURVEY_INFO_TIME_BUSY) {
+		/* busy */
+		u64 busy = survey.time_busy < sdata->last_time_busy ? 0 :
+			survey.time_busy - sdata->last_time_busy;
+		/* average percent busy time */
+		ewma_avg_busy_add(&sdata->avg_busy,
+				  (busy * 100) / interval);
+		/* store last busy time */
+		sdata->last_time_busy = survey.time_busy;
+	}
+
+end:
+	schedule_delayed_work(&sdata->monitor_work,
+			      msecs_to_jiffies(DEFAULT_MONITOR_INTERVAL_MS));
+}
+
 int ieee80211_if_add(struct ieee80211_local *local, const char *name,
 		     unsigned char name_assign_type,
 		     struct wireless_dev **new_wdev, enum nl80211_iftype type,
@@ -2083,6 +2141,8 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
 			  ieee80211_dfs_cac_timer_work);
 	INIT_DELAYED_WORK(&sdata->dec_tailroom_needed_wk,
 			  ieee80211_delayed_tailroom_dec);
+	INIT_DELAYED_WORK(&sdata->monitor_work,
+			  ieee80211_if_monitor_work);
 
 	for (i = 0; i < NUM_NL80211_BANDS; i++) {
 		struct ieee80211_supported_band *sband;
@@ -2154,6 +2214,9 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
 	list_add_tail_rcu(&sdata->list, &local->interfaces);
 	mutex_unlock(&local->iflist_mtx);
 
+	schedule_delayed_work(&sdata->monitor_work,
+			      msecs_to_jiffies(DEFAULT_MONITOR_INTERVAL_MS));
+
 	if (new_wdev)
 		*new_wdev = &sdata->wdev;
 
@@ -2164,6 +2227,8 @@ void ieee80211_if_remove(struct ieee80211_sub_if_data *sdata)
 {
 	ASSERT_RTNL();
 
+	cancel_delayed_work_sync(&sdata->monitor_work);
+
 	mutex_lock(&sdata->local->iflist_mtx);
 	list_del_rcu(&sdata->list);
 	mutex_unlock(&sdata->local->iflist_mtx);
-- 
2.36.1