rlc: switching latency measurments to use steady_clock

Author: yagoda

lib/rlc/rlc_rx_am_entity.cpp

@@ -208,7 +208,7 @@ void rlc_rx_am_entity::handle_data_pdu(byte_buffer_slice buf)
     } else {
       logger.log_info("RX SDU. sn={} sdu_len={}", header.sn, sdu.value().length());
       metrics.metrics_add_sdus(1, sdu.value().length());
-      auto latency = std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::high_resolution_clock::now() -
+      auto latency = std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::steady_clock::now() -
                                                                           sdu_info.time_of_arrival);
       metrics.metrics_add_sdu_latency(latency.count() / 1000);
       upper_dn.on_new_sdu(std::move(sdu.value()));
@@ -333,7 +333,7 @@ bool rlc_rx_am_entity::handle_full_data_sdu(const rlc_am_pdu_header& header, byt
   // Add new SN to RX window if no segments have been received yet
   rlc_rx_am_sdu_info& rx_sdu = rx_window->has_sn(header.sn) ? (*rx_window)[header.sn] : ([&]() -> rlc_rx_am_sdu_info& {
     rlc_rx_am_sdu_info& sdu = rx_window->add_sn(header.sn);
-    sdu.time_of_arrival     = std::chrono::high_resolution_clock::now();
+    sdu.time_of_arrival     = std::chrono::steady_clock::now();
     return sdu;
   })();
 
@@ -357,7 +357,7 @@ bool rlc_rx_am_entity::handle_segment_data_sdu(const rlc_am_pdu_header& header,
   // Add new SN to RX window if no segments have been received yet
   rlc_rx_am_sdu_info& rx_sdu = rx_window->has_sn(header.sn) ? (*rx_window)[header.sn] : ([&]() -> rlc_rx_am_sdu_info& {
     rlc_rx_am_sdu_info& sdu = rx_window->add_sn(header.sn);
-    sdu.time_of_arrival     = std::chrono::high_resolution_clock::now();
+    sdu.time_of_arrival     = std::chrono::steady_clock::now();
     return sdu;
   })();
 

lib/rlc/rlc_rx_am_entity.h

@@ -45,7 +45,7 @@ struct rlc_rx_am_sdu_info {
   /// Buffer for either a full SDU or a set of SDU segments.
   std::variant<byte_buffer_slice, segment_set_t> sdu_data;
   /// Time of arrival of the first segment of the SDU.
-  std::chrono::system_clock::time_point time_of_arrival;
+  std::chrono::steady_clock::time_point time_of_arrival;
 };
 
 /// \brief Rx state variables

lib/rlc/rlc_rx_um_entity.cpp

@@ -47,7 +47,7 @@ rlc_rx_um_entity::rlc_rx_um_entity(gnb_du_id_t                       gnb_du_id,
 void rlc_rx_um_entity::handle_pdu(byte_buffer_slice buf)
 {
   metrics.metrics_add_pdus(1, buf.length());
-  auto start = std::chrono::high_resolution_clock::now();
+  auto start = std::chrono::steady_clock::now();
   pcap.push_pdu(pcap_context, buf);
 
   rlc_um_pdu_header header = {};
@@ -81,8 +81,7 @@ void rlc_rx_um_entity::handle_pdu(byte_buffer_slice buf)
     // deliver to upper layer
     logger.log_info("RX SDU. sdu_len={}", sdu.value().length());
     metrics.metrics_add_sdus(1, sdu.value().length());
-    auto latency =
-        std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::high_resolution_clock::now() - start);
+    auto latency = std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::steady_clock::now() - start);
     metrics.metrics_add_sdu_latency(latency.count() / 1000);
     upper_dn.on_new_sdu(std::move(sdu.value()));
     // Nothing else to do here ...
@@ -118,7 +117,7 @@ void rlc_rx_um_entity::handle_pdu(byte_buffer_slice buf)
       // Do not pass empty SDU to upper layers and continue as normal to maintain state
     } else {
       logger.log_info("RX SDU. sn={} sdu_len={}", header.sn, sdu.value().length());
-      auto latency = std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::high_resolution_clock::now() -
+      auto latency = std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::steady_clock::now() -
                                                                           sdu_info.time_of_arrival);
       metrics.metrics_add_sdu_latency(latency.count() / 1000);
       metrics.metrics_add_sdus(1, sdu.value().length());
@@ -282,7 +281,7 @@ bool rlc_rx_um_entity::handle_segment_data_sdu(const rlc_um_pdu_header& header,
   // Add new SN to RX window if no segments have been received yet
   rlc_rx_um_sdu_info& rx_sdu = rx_window->has_sn(header.sn) ? (*rx_window)[header.sn] : ([&]() -> rlc_rx_um_sdu_info& {
     rlc_rx_um_sdu_info& sdu = rx_window->add_sn(header.sn);
-    sdu.time_of_arrival     = std::chrono::high_resolution_clock::now();
+    sdu.time_of_arrival     = std::chrono::steady_clock::now();
     return sdu;
   })();
   // Create SDU segment, to be stored later

lib/rlc/rlc_rx_um_entity.h

@@ -44,7 +44,7 @@ struct rlc_rx_um_sdu_info {
   /// Buffer for set of SDU segments.
   segment_set_t segments;
   /// Time of arrival of the first segment of the SDU.
-  std::chrono::system_clock::time_point time_of_arrival;
+  std::chrono::steady_clock::time_point time_of_arrival;
 };
 
 /// \brief Rx state variables