Statistics for data request latencies (ARMmbed#2629)

* Adaptation layer TX latency statistics

* MAC data request TX latency statistics

* Updated change log

Author: Jarkko Paso

CHANGELOG.md

@@ -8,7 +8,7 @@
 * Adaptation layer removes oldest packets first when stack needs to release memory or reduce traffic
 
 ### Changes
-* 
+* Statistics for MAC data request latencies. Separated to adaptation layer and MAC queueing delays.
 
 ### Bug fixes
 * Added ignoring of retry messages from RADIUS server when waiting EAP-TLS

nanostack/mac_api.h

@@ -325,6 +325,7 @@ typedef struct mac_statistics_s {
     uint32_t mac_retry_count;           /**< MAC TX retry count. */
     uint32_t mac_cca_attempts_count;    /**< MAC CCA attempts count. */
     uint32_t mac_failed_cca_count;      /**< MAC failed CCA count. */
+    uint32_t mac_tx_latency_max;        /**< MAC data request max latency. */
 } mac_statistics_t;
 
 #ifdef __cplusplus

nanostack/nwk_stats_api.h

@@ -74,6 +74,7 @@ typedef struct nwk_stats_t {
     uint16_t adapt_layer_tx_queue_size; /**< Adaptation layer direct TX queue size. */
     uint16_t adapt_layer_tx_queue_peak; /**< Adaptation layer direct TX queue size peak. */
     uint32_t adapt_layer_tx_congestion_drop; /**< Adaptation layer direct TX randon early detection drop packet. */
+    uint16_t adapt_layer_tx_latency_max; /**< Adaptation layer latency between TX request and TX ready in seconds (MAX). */
 } nwk_stats_t;
 
 /**

source/6LoWPAN/adaptation_interface.c

@@ -1309,7 +1309,13 @@ int8_t lowpan_adaptation_interface_tx(protocol_interface_info_entry_t *cur, buff
     if (!interface_ptr) {
         goto tx_error_handler;
     }
-
+    // Set TX start timestamp
+    if (!buf->adaptation_timestamp) {
+        buf->adaptation_timestamp = protocol_core_monotonic_time;
+        if (!buf->adaptation_timestamp) {
+            buf->adaptation_timestamp--;
+        }
+    }
     uint8_t traffic_class = buf->options.traffic_class >> IP_TCLASS_DSCP_SHIFT;
 
     if (traffic_class == IP_DSCP_EF) {
@@ -1549,9 +1555,13 @@ int8_t lowpan_adaptation_interface_tx_confirm(protocol_interface_info_entry_t *c
         tr_error("No data request for this confirmation %u", confirm->msduHandle);
         return -1;
     }
-    //Check status for
     buffer_t *buf = tx_ptr->buf;
 
+    // Update adaptation layer latency for unicast packets. Given as seconds.
+    if (buf->link_specific.ieee802_15_4.requestAck && buf->adaptation_timestamp) {
+        protocol_stats_update(STATS_AL_TX_LATENCY, ((protocol_core_monotonic_time - buf->adaptation_timestamp) + 5) / 10);
+    }
+
     //Indirect data expiration
     if (confirm->status == MLME_TRANSACTION_EXPIRED && !active_direct_confirm) {
         if (buf->link_specific.ieee802_15_4.indirectTTL > 7000) {

source/Core/include/ns_buffer.h

@@ -218,6 +218,7 @@ typedef struct buffer {
     bool                rpl_instance_known: 1;
     bool                ip_routed_up: 1;
     uint8_t             rpl_flag_error;
+    uint32_t            adaptation_timestamp;   /*!< Timestamp when buffer pushed to adaptation interface. Unit 100ms */
     //uint8_t             bc_sending_superframe;  /*FHSS uses this randomly chosen superframe to send this packet (if broadcast)*/
     //uint8_t             fhss_channel_retries_left;
     //uint8_t             ip_transmission_prev_seq;  /*!< XXX: this stores the data packet seq. number, which is needed for re-transmission. */

source/MAC/IEEE802_15_4/mac_data_buffer.h

@@ -100,6 +100,7 @@ typedef struct mac_pre_build_frame {
     uint16_t blacklist_period_ms;
     uint16_t initial_tx_channel;
     uint32_t tx_time;
+    uint32_t request_start_time_us;
     bool upper_layer_request: 1;
     bool mac_allocated_payload_ptr: 1;
     bool asynch_request: 1;

source/MAC/IEEE802_15_4/mac_mcps_sap.c

@@ -383,6 +383,8 @@ void mcps_sap_data_req_handler_ext(protocol_interface_rf_mac_setup_s *rf_mac_set
     buffer->tx_request_restart_cnt = rf_mac_setup->tx_failure_restart_max;
     //check that header + payload length is not bigger than MAC MTU
 
+    buffer->request_start_time_us = mac_mcps_sap_get_phy_timestamp(rf_mac_setup);
+
     if (data_req->InDirectTx) {
         mac_indirect_queue_write(rf_mac_setup, buffer);
     } else {
@@ -1630,6 +1632,11 @@ static void mcps_data_confirm_handle(protocol_interface_rf_mac_setup_s *rf_ptr,
         confirm.timestamp = 0;
     }
 
+    if (buffer->fcf_dsn.ackRequested) {
+        // Update latency for unicast packets. Given as milliseconds.
+        sw_mac_stats_update(rf_ptr, STAT_MAC_TX_LATENCY, ((mac_mcps_sap_get_phy_timestamp(rf_ptr) - buffer->request_start_time_us) + 500) / 1000);
+    }
+
     if (buffer->upper_layer_request) {
         //Check tunnel
         mcps_sap_prebuild_frame_buffer_free(buffer);

source/MAC/IEEE802_15_4/sw_mac.c

@@ -765,6 +765,11 @@ void sw_mac_stats_update(protocol_interface_rf_mac_setup_s *setup, mac_stats_typ
             case STAT_MAC_TX_CCA_FAIL:
                 setup->mac_statistics->mac_failed_cca_count++;
                 break;
+            case STAT_MAC_TX_LATENCY:
+                if (update_val > setup->mac_statistics->mac_tx_latency_max) {
+                    setup->mac_statistics->mac_tx_latency_max = update_val;
+                }
+                break;
         }
     }
 }

source/MAC/IEEE802_15_4/sw_mac_internal.h

@@ -35,6 +35,7 @@ typedef enum {
     STAT_MAC_TX_RETRY,
     STAT_MAC_TX_CCA_ATT,
     STAT_MAC_TX_CCA_FAIL,
+    STAT_MAC_TX_LATENCY
 } mac_stats_type_t;
 
 typedef enum arm_nwk_timer_id {

source/NWK_INTERFACE/Include/protocol_stats.h

@@ -45,7 +45,8 @@ typedef enum {
     STATS_ETX_1ST_PARENT,
     STATS_ETX_2ND_PARENT,
     STATS_AL_TX_QUEUE_SIZE,
-    STATS_AL_TX_CONGESTION_DROP
+    STATS_AL_TX_CONGESTION_DROP,
+    STATS_AL_TX_LATENCY
 
 } nwk_stats_type_t;
 

source/NWK_INTERFACE/protocol_stats.c

@@ -155,6 +155,11 @@ void protocol_stats_update(nwk_stats_type_t type, uint16_t update_val)
             case STATS_AL_TX_CONGESTION_DROP:
                 nwk_stats_ptr->adapt_layer_tx_congestion_drop++;
                 break;
+            case STATS_AL_TX_LATENCY:
+                if (update_val > nwk_stats_ptr->adapt_layer_tx_latency_max) {
+                    nwk_stats_ptr->adapt_layer_tx_latency_max = update_val;
+                }
+                break;
         }
     }
 }