simplify RLC buffer status query procedures

- add a simple and low-overhead has_data() method to check whether
  an RLC entity has data to transmit or not
- use this method for all calls that are actually not interested
  in the amount of data to send
- use the more expensive get_buffer_state() for all cases where
  the actual size of the buffer is of importance

lib/include/srslte/interfaces/ue_interfaces.h

@@ -300,11 +300,12 @@ public:
 class rlc_interface_mac : public srslte::read_pdu_interface
 {
 public:
-  /* MAC calls RLC to get buffer state for a logical channel.
-   * This function should return quickly. */
-  virtual uint32_t get_buffer_state(uint32_t lcid) = 0;
-  virtual uint32_t get_total_buffer_state(uint32_t lcid) = 0; 
+  /* MAC calls has_data() to query whether a logical channel has data to transmit (without
+   * knowing how much. This function should return quickly. */
+  virtual bool has_data(const uint32_t lcid) = 0;
 
+  /* MAC calls RLC to get the buffer state for a logical channel. */
+  virtual uint32_t get_buffer_state(const uint32_t lcid) = 0;
 
   const static int MAX_PDU_SEGMENTS = 20;
 

lib/include/srslte/upper/rlc.h

@@ -67,8 +67,8 @@ public:
   bool rb_is_um(uint32_t lcid);
 
   // MAC interface
-  uint32_t get_buffer_state(uint32_t lcid);
-  uint32_t get_total_buffer_state(uint32_t lcid);
+  bool     has_data(const uint32_t lcid);
+  uint32_t get_buffer_state(const uint32_t lcid);
   uint32_t get_total_mch_buffer_state(uint32_t lcid);
   int      read_pdu(uint32_t lcid, uint8_t *payload, uint32_t nof_bytes);
   int      read_pdu_mch(uint32_t lcid, uint8_t *payload, uint32_t nof_bytes);

lib/include/srslte/upper/rlc_am.h

@@ -89,8 +89,8 @@ public:
   void write_sdu(byte_buffer_t *sdu, bool blocking = true);
 
   // MAC interface
+  bool     has_data();
   uint32_t get_buffer_state();
-  uint32_t get_total_buffer_state(); 
   int      read_pdu(uint8_t *payload, uint32_t nof_bytes);
   void     write_pdu(uint8_t *payload, uint32_t nof_bytes);
 
@@ -117,8 +117,8 @@ private:
     void write_sdu(byte_buffer_t *sdu, bool blocking);
     int read_pdu(uint8_t *payload, uint32_t nof_bytes);
 
+    bool     has_data();
     uint32_t get_buffer_state();
-    uint32_t get_total_buffer_state();
     uint32_t get_num_tx_bytes();
     void reset_metrics();
 

lib/include/srslte/upper/rlc_common.h

@@ -169,8 +169,8 @@ public:
   virtual void write_sdu(byte_buffer_t *sdu, bool blocking) = 0;
 
   // MAC interface
+  virtual bool     has_data() = 0;
   virtual uint32_t get_buffer_state() = 0;
-  virtual uint32_t get_total_buffer_state() = 0;
   virtual int      read_pdu(uint8_t *payload, uint32_t nof_bytes) = 0;
   virtual void     write_pdu(uint8_t *payload, uint32_t nof_bytes) = 0;
 };

lib/include/srslte/upper/rlc_tm.h

@@ -62,8 +62,8 @@ public:
   void write_sdu(byte_buffer_t *sdu, bool blocking);
 
   // MAC interface
+  bool     has_data();
   uint32_t get_buffer_state();
-  uint32_t get_total_buffer_state();
   int      read_pdu(uint8_t *payload, uint32_t nof_bytes);
   void     write_pdu(uint8_t *payload, uint32_t nof_bytes);
 

lib/include/srslte/upper/rlc_tx_queue.h

@@ -110,8 +110,11 @@ public:
     unread_bytes = 0;
   }
 
+  bool is_empty() {
+    return queue.empty();
+  }
+
 private:
-  bool                        is_empty() { return queue.empty(); }
 
   block_queue<byte_buffer_t*> queue;
   uint32_t                    unread_bytes;

lib/include/srslte/upper/rlc_um.h

@@ -68,8 +68,8 @@ public:
   void write_sdu(byte_buffer_t *sdu, bool blocking = true);
 
   // MAC interface
+  bool     has_data();
   uint32_t get_buffer_state();
-  uint32_t get_total_buffer_state();
   int      read_pdu(uint8_t *payload, uint32_t nof_bytes);
   void     write_pdu(uint8_t *payload, uint32_t nof_bytes);
   int get_increment_sequence_num();
@@ -96,7 +96,8 @@ private:
     void try_write_sdu(byte_buffer_t *sdu);
     uint32_t get_num_tx_bytes();
     void reset_metrics();
-    uint32_t get_buffer_size_bytes();
+    bool has_data();
+    uint32_t get_buffer_state();
 
   private:
     byte_buffer_pool        *pool;

lib/src/upper/rlc.cc

@@ -256,26 +256,26 @@ bool rlc::rb_is_um(uint32_t lcid)
 /*******************************************************************************
   MAC interface
 *******************************************************************************/
-uint32_t rlc::get_buffer_state(uint32_t lcid)
+bool rlc::has_data(uint32_t lcid)
 {
-  uint32_t ret = 0;
+  bool has_data = false;
 
   pthread_rwlock_rdlock(&rwlock);
   if (valid_lcid(lcid)) {
-    ret = rlc_array.at(lcid)->get_buffer_state();
+    has_data = rlc_array.at(lcid)->has_data();
   }
   pthread_rwlock_unlock(&rwlock);
 
-  return ret;
+  return has_data;
 }
 
-uint32_t rlc::get_total_buffer_state(uint32_t lcid)
+uint32_t rlc::get_buffer_state(uint32_t lcid)
 {
   uint32_t ret = 0;
 
   pthread_rwlock_rdlock(&rwlock);
   if (valid_lcid(lcid)) {
-    ret = rlc_array.at(lcid)->get_total_buffer_state();
+    ret = rlc_array.at(lcid)->get_buffer_state();
   }
   pthread_rwlock_unlock(&rwlock);
 
@@ -288,7 +288,7 @@ uint32_t rlc::get_total_mch_buffer_state(uint32_t lcid)
 
   pthread_rwlock_rdlock(&rwlock);
   if (valid_lcid_mrb(lcid)) {
-    ret = rlc_array_mrb.at(lcid)->get_total_buffer_state();
+    ret = rlc_array_mrb.at(lcid)->get_buffer_state();
   }
   pthread_rwlock_unlock(&rwlock);
 

lib/src/upper/rlc_am.cc

@@ -152,14 +152,14 @@ void rlc_am::write_sdu(byte_buffer_t *sdu, bool blocking)
  * MAC interface
  ***************************************************************************/
 
-uint32_t rlc_am::get_buffer_state()
+bool rlc_am::has_data()
 {
-  return tx.get_buffer_state();
+  return tx.has_data();
 }
 
-uint32_t rlc_am::get_total_buffer_state()
+uint32_t rlc_am::get_buffer_state()
 {
-  return tx.get_total_buffer_state();
+  return tx.get_buffer_state();
 }
 
 int rlc_am::read_pdu(uint8_t *payload, uint32_t nof_bytes)
@@ -314,63 +314,16 @@ bool rlc_am::rlc_am_tx::do_status()
   return parent->rx.get_do_status();
 }
 
-uint32_t rlc_am::rlc_am_tx::get_buffer_state()
+// Function is supposed to return as fast as possible
+bool rlc_am::rlc_am_tx::has_data()
 {
-  pthread_mutex_lock(&mutex);
-  uint32_t n_bytes = 0;
-  uint32_t n_sdus  = 0;
-
-  // Bytes needed for status report
-  if (do_status() && not status_prohibited) {
-    n_bytes = parent->rx.get_status_pdu_length();
-    log->debug("%s Buffer state - status report: %d bytes\n", RB_NAME, n_bytes);
-    goto unlock_and_return;
-  }
-
-  // Bytes needed for retx
-  if (not retx_queue.empty()) {
-    rlc_amd_retx_t retx = retx_queue.front();
-    log->debug("Buffer state - retx - SN: %d, Segment: %s, %d:%d\n", retx.sn, retx.is_segment ? "true" : "false", retx.so_start, retx.so_end);
-    if(tx_window.end() != tx_window.find(retx.sn)) {
-      int req_bytes = required_buffer_size(retx);
-      if (req_bytes < 0) {
-        log->error("In get_buffer_state(): Removing retx.sn=%d from queue\n", retx.sn);
-        retx_queue.pop_front();
-        goto unlock_and_return;
-      }
-      n_bytes = static_cast<uint32_t>(req_bytes);
-      log->debug("Buffer state - retx: %d bytes\n", n_bytes);
-      goto unlock_and_return;
-    }
-  }
-
-  // Bytes needed for tx SDUs
-  if (tx_window.size() < 1024) {
-    n_sdus  = tx_sdu_queue.size();
-    n_bytes = tx_sdu_queue.size_bytes();
-    if (tx_sdu != NULL) {
-      n_sdus++;
-      n_bytes += tx_sdu->N_bytes;
-    }
-  }
-
-  // Room needed for header extensions? (integer rounding)
-  if (n_sdus > 1) {
-    n_bytes += ((n_sdus-1)*1.5)+0.5;
-  }
-
-  // Room needed for fixed header?
-  if (n_bytes > 0) {
-    n_bytes += 3;
-    log->debug("Buffer state - tx SDUs: %d bytes\n", n_bytes);
-  }
-
-unlock_and_return:
-  pthread_mutex_unlock(&mutex);
-  return n_bytes;
+  return (((do_status() && not status_prohibited)) ||        // if we have a status PDU to transmit
+           (not retx_queue.empty()) ||                       // if we have a retransmission
+           (tx_sdu != NULL) ||                               // if we are currently transmitting a SDU
+           (not tx_sdu_queue.is_empty()));                   // or if there is a SDU queued up for transmission
 }
 
-uint32_t rlc_am::rlc_am_tx::get_total_buffer_state()
+uint32_t rlc_am::rlc_am_tx::get_buffer_state()
 {
   pthread_mutex_lock(&mutex);
   uint32_t n_bytes = 0;
@@ -385,11 +338,11 @@ uint32_t rlc_am::rlc_am_tx::get_total_buffer_state()
   // Bytes needed for retx
   if(not retx_queue.empty()) {
     rlc_amd_retx_t retx = retx_queue.front();
-    log->debug("Buffer state - retx - SN: %d, Segment: %s, %d:%d\n", retx.sn, retx.is_segment ? "true" : "false", retx.so_start, retx.so_end);
+    log->debug("%s Buffer state - retx - SN: %d, Segment: %s, %d:%d\n", RB_NAME, retx.sn, retx.is_segment ? "true" : "false", retx.so_start, retx.so_end);
     if(tx_window.end() != tx_window.find(retx.sn)) {
       int req_bytes = required_buffer_size(retx);
       if (req_bytes < 0) {
-        log->error("In get_total_buffer_state(): Removing retx.sn=%d from queue\n", retx.sn);
+        log->error("In get_buffer_state(): Removing retx.sn=%d from queue\n", retx.sn);
         retx_queue.pop_front();
       } else {
         n_bytes += req_bytes;
@@ -413,10 +366,10 @@ uint32_t rlc_am::rlc_am_tx::get_total_buffer_state()
     n_bytes += ((n_sdus-1)*1.5)+0.5;
   }
 
-  // Room needed for fixed header?
-  if (n_bytes > 0) {
+  // Room needed for fixed header of data PDUs
+  if (n_bytes > 0 && n_sdus > 0) {
     n_bytes += 3;
-    log->debug("Buffer state - tx SDUs: %d bytes\n", n_bytes);
+    log->debug("%s Total buffer state - %d SDUs (%d B)\n", RB_NAME, n_sdus, n_bytes);
   }
 
   pthread_mutex_unlock(&mutex);

lib/src/upper/rlc_tm.cc

@@ -123,14 +123,14 @@ void rlc_tm::write_sdu(byte_buffer_t *sdu, bool blocking)
 }
 
 // MAC interface
-uint32_t rlc_tm::get_buffer_state()
+bool rlc_tm::has_data()
 {
-  return ul_queue.size_bytes();
+  return not ul_queue.is_empty();
 }
 
-uint32_t rlc_tm::get_total_buffer_state()
+uint32_t rlc_tm::get_buffer_state()
 {
-  return get_buffer_state();
+  return ul_queue.size_bytes();
 }
 
 uint32_t rlc_tm::get_num_tx_bytes()

lib/src/upper/rlc_um.cc

@@ -162,14 +162,14 @@ void rlc_um::write_sdu(byte_buffer_t *sdu, bool blocking)
  * MAC interface
  ***************************************************************************/
 
-uint32_t rlc_um::get_buffer_state()
+bool rlc_um::has_data()
 {
-  return tx.get_buffer_size_bytes();
+  return tx.has_data();
 }
 
-uint32_t rlc_um::get_total_buffer_state()
+uint32_t rlc_um::get_buffer_state()
 {
-  return get_buffer_state();
+  return tx.get_buffer_state();
 }
 
 int rlc_um::read_pdu(uint8_t *payload, uint32_t nof_bytes)
@@ -313,7 +313,13 @@ void rlc_um::rlc_um_tx::reset_metrics()
 }
 
 
-uint32_t rlc_um::rlc_um_tx::get_buffer_size_bytes()
+bool rlc_um::rlc_um_tx::has_data()
+{
+  return (tx_sdu != NULL || !tx_sdu_queue.is_empty());
+}
+
+
+uint32_t rlc_um::rlc_um_tx::get_buffer_state()
 {
   // Bytes needed for tx SDUs
   uint32_t n_sdus  = tx_sdu_queue.size();

srsenb/src/upper/rlc.cc

@@ -142,7 +142,7 @@ int rlc::read_pdu(uint16_t rnti, uint32_t lcid, uint8_t* payload, uint32_t nof_b
   if(users.count(rnti)) {
     if(rnti != SRSLTE_MRNTI) {
       ret = users[rnti].rlc->read_pdu(lcid, payload, nof_bytes);
-      tx_queue = users[rnti].rlc->get_total_buffer_state(lcid);
+      tx_queue = users[rnti].rlc->get_buffer_state(lcid);
     } else {
       ret = users[rnti].rlc->read_pdu_mch(lcid, payload, nof_bytes);
       tx_queue = users[rnti].rlc->get_total_mch_buffer_state(lcid);
@@ -168,7 +168,7 @@ void rlc::write_pdu(uint16_t rnti, uint32_t lcid, uint8_t* payload, uint32_t nof
     
     // In the eNodeB, there is no polling for buffer state from the scheduler, thus 
     // communicate buffer state every time a new PDU is written
-    uint32_t tx_queue   = users[rnti].rlc->get_total_buffer_state(lcid);
+    uint32_t tx_queue   = users[rnti].rlc->get_buffer_state(lcid);
     uint32_t retx_queue = 0; 
     log_h->debug("Buffer state PDCP: rnti=0x%x, lcid=%d, tx_queue=%d\n", rnti, lcid, tx_queue);
     mac->rlc_buffer_state(rnti, lcid, tx_queue, retx_queue);
@@ -191,7 +191,7 @@ void rlc::write_sdu(uint16_t rnti, uint32_t lcid, srslte::byte_buffer_t* sdu)
   if (users.count(rnti)) {
     if(rnti != SRSLTE_MRNTI){
       users[rnti].rlc->write_sdu(lcid, sdu, false);
-      tx_queue   = users[rnti].rlc->get_total_buffer_state(lcid);
+      tx_queue   = users[rnti].rlc->get_buffer_state(lcid);
     }else {
       users[rnti].rlc->write_sdu_mch(lcid, sdu);
       tx_queue   = users[rnti].rlc->get_total_mch_buffer_state(lcid);

srsue/src/mac/mux.cc

@@ -73,7 +73,7 @@ void mux::reset()
 bool mux::is_pending_any_sdu()
 {
   for (uint32_t i=0;i<lch.size();i++) {
-    if (rlc->get_buffer_state(lch[i].id)) {
+    if (rlc->has_data(lch[i].id)) {
       return true; 
     }
   }
@@ -81,7 +81,7 @@ bool mux::is_pending_any_sdu()
 }
 
 bool mux::is_pending_sdu(uint32_t lch_id) {
-  return rlc->get_buffer_state(lch_id)>0;  
+  return rlc->has_data(lch_id);
 }
 
 int mux::find_lchid(uint32_t lcid) 

srsue/src/mac/proc_bsr.cc

@@ -104,10 +104,10 @@ bool bsr_proc::check_highest_channel() {
   
   for (int i=0;i<MAX_LCID && pending_data_lcid == -1;i++) {
     if (lcg[i] >= 0) {
-      if (rlc->get_buffer_state(i) > 0) {
+      if (rlc->has_data(i)) {
         pending_data_lcid = i; 
         for (int j=0;j<MAX_LCID;j++) {
-          if (rlc->get_buffer_state(j) > 0) {
+          if (rlc->has_data(j)) {
             if (priorities[j] > priorities[i]) {
               pending_data_lcid = -1; 
             }
@@ -148,7 +148,7 @@ bool bsr_proc::check_single_channel() {
   
   for (int i=0;i<MAX_LCID;i++) {
     if (lcg[i] >= 0) {
-      if (rlc->get_buffer_state(i) > 0) {
+      if (rlc->has_data(i)) {
         pending_data_lcid = i;
         nof_nonzero_lcid++; 
       }

srsue/src/ue.cc

@@ -312,11 +312,11 @@ bool ue::switch_off() {
   // wait for max. 5s for it to be sent (according to TS 24.301 Sec 25.5.2.2)
   const uint32_t RB_ID_SRB1 = 1;
   int cnt = 0, timeout = 5;
-  while (rlc.get_buffer_state(RB_ID_SRB1) && ++cnt <= timeout) {
+  while (rlc.has_data(RB_ID_SRB1) && ++cnt <= timeout) {
     sleep(1);
   }
   bool detach_sent = true;
-  if (rlc.get_buffer_state(RB_ID_SRB1)) {
+  if (rlc.has_data(RB_ID_SRB1)) {
     nas_log.warning("Detach couldn't be sent after %ds.\n", timeout);
     detach_sent = false;
   }

srsue/test/mac/mac_test.cc

@@ -282,7 +282,7 @@ public:
     sib2_period = 0; 
     send_ack = 0; 
   }
-  uint32_t get_total_buffer_state(uint32_t lcid) {
+  bool has_data(uint32_t lcid) {
     return get_buffer_state(lcid); 
   }
   uint32_t get_buffer_state(uint32_t lcid) {