mac80211: Tx frame latency statistics

Measure TX latency and jitter statistics per station per TID.
These Measurements are disabled by default and can be enabled
via debugfs.

Features included for each station's TID:

1. Keep count of the maximum and average latency of Tx frames.
2. Keep track of many frames arrived in a specific time range
   (need to enable through debugfs and configure the bins ranges)

Signed-off-by: Matti Gottlieb <matti.gottlieb@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index e541856b4007..6d59e21cdb9f 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -19,6 +19,7 @@
 #include <linux/bitmap.h>
 #include <linux/rcupdate.h>
 #include <linux/export.h>
+#include <linux/time.h>
 #include <net/net_namespace.h>
 #include <net/ieee80211_radiotap.h>
 #include <net/cfg80211.h>
@@ -1741,6 +1742,26 @@ fail:
         return NETDEV_TX_OK; /* meaning, we dealt with the skb */
 }
 
+/*
+ * Measure Tx frame arrival time for Tx latency statistics calculation
+ * A single Tx frame latency should be measured from when it is entering the
+ * Kernel until we receive Tx complete confirmation indication and the skb is
+ * freed.
+ */
+static void ieee80211_tx_latency_start_msrmnt(struct ieee80211_local *local,
+                                              struct sk_buff *skb)
+{
+        struct timespec skb_arv;
+        struct ieee80211_tx_latency_bin_ranges *tx_latency;
+
+        tx_latency = rcu_dereference(local->tx_latency);
+        if (!tx_latency)
+                return;
+
+        ktime_get_ts(&skb_arv);
+        skb->tstamp = ktime_set(skb_arv.tv_sec, skb_arv.tv_nsec);
+}
+
 /**
  * ieee80211_subif_start_xmit - netif start_xmit function for Ethernet-type
  * subinterfaces (wlan#, WDS, and VLAN interfaces)
@@ -1791,6 +1812,9 @@ netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb,
 
         rcu_read_lock();
 
+        /* Measure frame arrival for Tx latency statistics calculation */
+        ieee80211_tx_latency_start_msrmnt(local, skb);
+
         switch (sdata->vif.type) {
         case NL80211_IFTYPE_AP_VLAN:
                 sta = rcu_dereference(sdata->u.vlan.sta);