Merge pull request #346 from DUNE-DAQ/asztuc/mlt_threadoccupancy_fix

Fixing TCProcessor's high mlt-dec thread occupancy

src/TCProcessor.cpp

@@ -68,6 +68,14 @@ TCProcessor::stop(const nlohmann::json& args)
 {
   inherited::stop(args);
   m_running_flag.store(false);
+
+  // Make sure condition_variable knows we flipped running flag
+  {
+    std::lock_guard<std::mutex> lock(m_td_vector_mutex);
+    m_cv.notify_all();
+  }
+
+  // Wait for the TD-sending thread to stop
   m_send_trigger_decisions_thread.join();
 
   // Drop all TDs in vectors at run stage change. Have to do this
@@ -113,7 +121,6 @@ TCProcessor::conf(const appmodel::DataHandlerModule* cfg)
         link->get_sid()});
   }
 
-
     // TODO: Group links!
   //m_group_links_data = conf->get_groups_links();
   parse_group_links(m_group_links_data);
@@ -233,6 +240,7 @@ TCProcessor::make_td(const TCWrapper* tcw)
   else {
     std::lock_guard<std::mutex> lock(m_td_vector_mutex);
     add_tc(tc);
+    m_cv.notify_one();
     TLOG_DEBUG(10) << "pending tds size: " << m_pending_tds.size();
   }
   return;
@@ -302,9 +310,15 @@ TCProcessor::create_decision(const PendingTD& pending_td)
 
 void
 TCProcessor::send_trigger_decisions() {
+ // A unique lock that can be locked and unlocked
+ std::unique_lock<std::mutex> lock(m_td_vector_mutex);
 
  while (m_running_flag) {
-    std::lock_guard<std::mutex> lock(m_td_vector_mutex);
+    // Either there are pending TDs, or wait for a bit
+    m_cv.wait(lock, [this] {
+        return !m_pending_tds.empty() || !m_running_flag;
+    });
+
     auto ready_tds = get_ready_tds(m_pending_tds);
     TLOG_DEBUG(10) << "ready tds: " << ready_tds.size() << ", updated pending tds: " << m_pending_tds.size();
 

src/trigger/TCProcessor.hpp

@@ -119,6 +119,7 @@ class TCProcessor : public datahandlinglibs::TaskRawDataProcessorModel<TCWrapper
   };
   std::vector<PendingTD> m_pending_tds;
   std::mutex m_td_vector_mutex;
+  std::condition_variable m_cv;
 
   void add_tc(const triggeralgs::TriggerCandidate tc);
   void add_tc_ignored(const triggeralgs::TriggerCandidate tc);