Safeguard against empty buffer & bypass low memory intensity request

# Explain what has been changed

# Explain why this change is being made

# Provide links to any relevant tickets, articles or other resources

DRAMSys/simulator/src/controller/scheduler/SMS.cpp

@@ -50,19 +50,22 @@ unsigned int SMS::totalMemoryRequests()
   return totalSize;
 }
 
-void SMS::batchFormation()
+bool SMS::batchFormation()
 {
   if (existReadyBatch())
   {
+    return false;
     SC_REPORT_FATAL("SMS", "Form ready batches when exist at least a ready batch");
   }
   else
   {
+    bool isBatchForm = false;
     unsigned int totalNumThreads = Configuration::getInstance().NumberOfTracePlayers;
     for (unsigned int threadID = 1; threadID <= totalNumThreads; threadID++)
     {
-      batchFormation(Thread(threadID));
+      isBatchForm = isBatchForm || batchFormation(Thread(threadID));
     }
+    return isBatchForm;
   }
 }
 
@@ -77,33 +80,31 @@ void SMS::batchScheduler()
     bool isSJF = (rand() % 100) < SJFprobability;
     if (!existReadyBatch())
     {
-      // bypass low memory intensity thread
-      
-      // bypass if system is lightly load
-      if (totalMemoryRequests() <= 16 && totalMemoryRequests() > 0) //TODO how about buffer empty?
+      if (totalMemoryRequests() == 0)
       {
+        continue;
+      }
+      else if (totalMemoryRequests() <= 16 && totalMemoryRequests() > 0)
+      {
+        // bypass if system is lightly load
         bypassRequests();
       }
-      else
+      else if (totalMemoryRequests() > 16)
       {
-        batchFormation();
-        if (isSJF)
+        // bypass low memory intensity thread
+        bypassLowMemoryIntensity();
+
+        // pick & drain a ready batch
+        if (batchFormation())
         {
-          selectSJF();
-        }
-        else
-        {
-          selectRR();
+          isSJF ? selectSJF() : selectRR();
         }
       }
     }
-    else if (isSJF)
-    {
-      selectSJF();
-    }
     else
     {
-      selectRR();
+      // pick & drain a ready batch
+      isSJF ? selectSJF() : selectRR();
     }
   }
 }
@@ -115,7 +116,7 @@ void SMS::selectSJF()
   unsigned int totalNumThreads = Configuration::getInstance().NumberOfTracePlayers;
   for (unsigned int threadID = 2; threadID <= totalNumThreads; threadID++)
   {
-    if (memrequestcounter[Thread(threadID)] <= memrequestcounter[Thread(minThread)])
+    if (inFlightMemRequestCounter[Thread(threadID)] <= inFlightMemRequestCounter[Thread(minThread)])
     {
       minThread = threadID;
     }
@@ -123,12 +124,15 @@ void SMS::selectSJF()
 
   // drain to bank buffers
   std::deque<gp*> requestPtrs = readybatches[Thread(minThread)]->getTransactions();
-  for (auto intr = requestPtrs.begin(); intr != requestPtrs.end(); intr++)
+  if (!requestPtrs.empty())
   {
-    Bank bank = DramExtension::getExtension(*intr).getBank();
-    bankbuffer[bank].emplace_back(*intr);
+    for (auto intr = requestPtrs.begin(); intr != requestPtrs.end(); intr++)
+    {
+      Bank bank = DramExtension::getExtension(*intr).getBank();
+      bankbuffer[bank].emplace_back(*intr);
+    }
+    requestPtrs.clear();
   }
-  requestPtrs.clear();
 
   // reform the drained ready batch
   // batchFormation(Thread(minThread));
@@ -140,25 +144,38 @@ void SMS::selectRR()
 
   // drain to bank buffers
   std::deque<gp*> requestPtrs = (*next).second->getTransactions();
-  for (auto intr = requestPtrs.begin(); intr != requestPtrs.end(); intr++)
+  if (!requestPtrs.empty())
   {
-    Bank bank = DramExtension::getExtension(*intr).getBank();
-    bankbuffer[bank].emplace_back(*intr);
+    for (auto intr = requestPtrs.begin(); intr != requestPtrs.end(); intr++)
+    {
+      Bank bank = DramExtension::getExtension(*intr).getBank();
+      bankbuffer[bank].emplace_back(*intr);
+    }
+    requestPtrs.clear();
   }
-  requestPtrs.clear();
 
   // reform the drained ready batch
   // batchFormation((*next).first);
 
   // point to next pair
-  do
+  if (existReadyBatch())
   {
-    next++;
-    if (next == readybatches.end())
+    do
     {
-      next = readybatches.begin();
-    }
-  } while ((*next).second->isEmpty());
+      next++;
+      if (next == readybatches.end())
+      {
+        next = readybatches.begin();
+      }
+    } while ((*next).second->isEmpty());
+  }
+  else
+  {
+    // point to next empty ready batch, later call to batchScheduler() will call batchFormation()
+    // this next empty ready batch will be refilled
+    next++;
+  }
+
 }
 
 bool SMS::existReadyBatch()
@@ -173,10 +190,11 @@ bool SMS::existReadyBatch()
   return false;
 }
 
-void SMS::batchFormation(Thread thread)
+bool SMS::batchFormation(Thread thread)
 {
   if (!readybatches[thread]->isEmpty())
   {
+    return false;
     SC_REPORT_FATAL("SMS", "Ready batch formation for non empty ready batch");
   }
   else
@@ -185,14 +203,15 @@ void SMS::batchFormation(Thread thread)
     {
       buffer[thread].pop_front();
     }
+    return !readybatches[thread]->isEmpty();
   }
 }
 
 void SMS::bypassRequests()
 {
-  for(auto& thread_requests : buffer)
+  for (auto& thread_requests : buffer)
   {
-    for(auto request = thread_requests.second.begin(); request != thread_requests.second.end(); request++)
+    for (auto request = thread_requests.second.begin(); request != thread_requests.second.end(); request++)
     {
       Bank bank = DramExtension::getExtension(*request).getBank();
       bankbuffer[bank].emplace_back(*request);
@@ -200,3 +219,21 @@ void SMS::bypassRequests()
     }
   }
 }
+
+void SMS::bypassLowMemoryIntensity()
+{
+  unsigned int totalNumThreads = Configuration::getInstance().NumberOfTracePlayers;
+  for (unsigned int threadID = 1; threadID <= totalNumThreads; threadID++)
+  {
+    if (memoryIntensity[Thread(threadID)] < 1 && memoryIntensity[Thread(threadID)] > 0)
+    {
+      for (auto request = buffer[Thread(threadID)].begin();
+          request != buffer[Thread(threadID)].end(); request++)
+      {
+        Bank bank = DramExtension::getExtension(*request).getBank();
+        bankbuffer[bank].emplace_back(*request);
+        buffer[Thread(threadID)].erase(request);
+      }
+    }
+  }
+}

DRAMSys/simulator/src/controller/scheduler/SMS.h

@@ -44,12 +44,13 @@ private:
     unsigned int SJFprobability;
 
     unsigned int totalMemoryRequests();
-    void batchFormation();
+    bool batchFormation();
     void selectSJF();
     void selectRR();
     bool existReadyBatch();
-    void batchFormation(Thread thread);
+    bool batchFormation(Thread thread);
     void bypassRequests();
+    void bypassLowMemoryIntensity();
 };
 
 #endif // SMS_H