MCOL-5044 This patch replaces PriorityThreadPool with FairThreadPool that uses a simple

operations + morsel size weight model to equally allocate CPU b/w parallel query morsels.
This patch delivers better parallel query timings distribution(timings graph resembles normal
distribution with a bigger left side thus more queries runs faster comparing with PrioThreadPool-based
single-node installation).
See changes in batchprimitiveprocessor-jl.h and comments in fair_threadpool.h for
important implementation details

dbcon/joblist/batchprimitiveprocessor-jl.cpp

@@ -1274,6 +1274,10 @@ void BatchPrimitiveProcessorJL::runBPP(ByteStream& bs, uint32_t pmNum)
   bs << uniqueID;
   bs << _priority;
 
+  // The weight is used by PrimProc thread pool algo
+  uint32_t weight = calculateBPPWeight();
+  bs << weight;
+
   bs << dbRoot;
   bs << count;
 

dbcon/joblist/batchprimitiveprocessor-jl.h

@@ -252,8 +252,27 @@ class BatchPrimitiveProcessorJL
   }
 
  private:
-  // void setLBIDForScan(uint64_t rid, uint32_t dbroot);
+  const size_t perColumnProjectWeight_ = 10;
+  const size_t perColumnFilteringWeight_ = 10;
+  const size_t fe1Weight_ = 10;
+  const size_t fe2Weight_ = 10;
+  const size_t joinWeight_ = 500;
+  const size_t aggregationWeight_ = 500;
 
+  // This is simple SQL operations-based model leveraged by
+  // FairThreadPool run by PP facility.
+  // Every operation mentioned in this calculation spends
+  // some CPU so the morsel uses this op weights more.
+  uint32_t calculateBPPWeight() const
+  {
+    uint32_t weight = perColumnProjectWeight_ * projectCount;
+    weight += filterCount * perColumnFilteringWeight_;
+    weight += tJoiners.size() * joinWeight_;
+    weight += (aggregatorPM) ? aggregationWeight_ : 0;
+    weight += (fe1) ? fe1Weight_ : 0;
+    weight += (fe2) ? fe2Weight_ : 0;
+    return weight;
+  }
   BPSOutputType ot;
 
   bool needToSetLBID;

dbcon/joblist/diskjoinstep.h

@@ -20,7 +20,6 @@
 #include "tuplehashjoin.h"
 #include "joinpartition.h"
 #include "threadnaming.h"
-#include "../../utils/threadpool/prioritythreadpool.h"
 
 #pragma once
 

primitives/primproc/batchprimitiveprocessor.cpp

@@ -140,6 +140,7 @@ BatchPrimitiveProcessor::BatchPrimitiveProcessor()
  , ptMask(0)
  , firstInstance(false)
  , valuesLBID(0)
+ , weight_(0)
 {
   pp.setLogicalBlockMode(true);
   pp.setBlockPtr((int*)blockData);
@@ -193,6 +194,7 @@ BatchPrimitiveProcessor::BatchPrimitiveProcessor(ByteStream& b, double prefetch,
  // ptMask(processorThreads - 1),
  , firstInstance(true)
  , valuesLBID(0)
+ , weight_(0)
 {
   // promote processorThreads to next power of 2.  also need to change the name to bucketCount or similar
   processorThreads = nextPowOf2(processorThreads);
@@ -542,6 +544,7 @@ void BatchPrimitiveProcessor::resetBPP(ByteStream& bs, const SP_UM_MUTEX& w, con
 
   // skip the header, sessionID, stepID, uniqueID, and priority
   bs.advance(sizeof(ISMPacketHeader) + 16);
+  bs >> weight_;
   bs >> dbRoot;
   bs >> count;
   bs >> ridCount;

primitives/primproc/batchprimitiveprocessor.h

@@ -137,6 +137,11 @@ class BatchPrimitiveProcessor
     fBusy = b;
   }
 
+  size_t getWeight() const
+  {
+    return weight_;
+  }
+
   uint16_t FilterCount() const
   {
     return filterCount;
@@ -433,6 +438,9 @@ class BatchPrimitiveProcessor
   uint ptMask;
   bool firstInstance;
   uint64_t valuesLBID;
+  uint32_t weight_;
+
+  static const uint64_t maxResultCount = 1048576;  // 2^20
 
   friend class Command;
   friend class ColumnCommand;

primitives/primproc/bppseeder.h

@@ -47,7 +47,7 @@
 
 namespace primitiveprocessor
 {
-class BPPSeeder : public threadpool::PriorityThreadPool::Functor
+class BPPSeeder : public threadpool::FairThreadPool::Functor
 {
  public:
   BPPSeeder(const messageqcpp::SBS&, const SP_UM_MUTEX& wLock, const SP_UM_IOSOCK& ios, const int pmThreads,
@@ -71,6 +71,11 @@ class BPPSeeder : public threadpool::PriorityThreadPool::Functor
   {
     return _priority;
   }
+  size_t getWeight() const
+  {
+    assert(bpp);
+    return bpp->getWeight();
+  }
 
  private:
   BPPSeeder();

primitives/primproc/primitiveserver.cpp

@@ -124,7 +124,7 @@ oam::OamCache* oamCache = oam::OamCache::makeOamCache();
 // FIXME: there is an anon ns burried later in between 2 named namespaces...
 namespace primitiveprocessor
 {
-boost::shared_ptr<threadpool::PriorityThreadPool> OOBPool;
+boost::shared_ptr<threadpool::FairThreadPool> OOBPool;
 
 BlockRequestProcessor** BRPp;
 #ifndef _MSC_VER
@@ -1050,7 +1050,7 @@ using namespace primitiveprocessor;
 /** @brief The job type to process a dictionary scan (pDictionaryScan class on the UM)
  * TODO: Move this & the impl into different files
  */
-class DictScanJob : public threadpool::PriorityThreadPool::Functor
+class DictScanJob : public threadpool::FairThreadPool::Functor
 {
  public:
   DictScanJob(SP_UM_IOSOCK ios, SBS bs, SP_UM_MUTEX writeLock);
@@ -1242,7 +1242,7 @@ struct BPPHandler
     scoped.unlock();
   }
 
-  struct BPPHandlerFunctor : public PriorityThreadPool::Functor
+  struct BPPHandlerFunctor : public FairThreadPool::Functor
   {
     BPPHandlerFunctor(boost::shared_ptr<BPPHandler> r, SBS b) : bs(b)
     {
@@ -1710,7 +1710,7 @@ return 0;
   PrimitiveServer* fPrimitiveServerPtr;
 };
 
-class DictionaryOp : public PriorityThreadPool::Functor
+class DictionaryOp : public FairThreadPool::Functor
 {
  public:
   DictionaryOp(SBS cmd) : bs(cmd)
@@ -1947,8 +1947,7 @@ struct ReadThread
   void operator()()
   {
     utils::setThreadName("PPReadThread");
-    boost::shared_ptr<threadpool::PriorityThreadPool> procPoolPtr =
+    threadpool::FairThreadPool* procPoolPtr = fPrimitiveServerPtr->getProcessorThreadPool();
-        fPrimitiveServerPtr->getProcessorThreadPool();
     SBS bs;
     UmSocketSelector* pUmSocketSelector = UmSocketSelector::instance();
 
@@ -2044,35 +2043,69 @@ struct ReadThread
           switch (ismHdr->Command)
           {
             case DICT_CREATE_EQUALITY_FILTER:
-            {
-              PriorityThreadPool::Job job;
-              const uint8_t* buf = bs->buf();
-              uint32_t pos = sizeof(ISMPacketHeader) - 2;
-              job.stepID = *((uint32_t*)&buf[pos + 6]);
-              job.uniqueID = *((uint32_t*)&buf[pos + 10]);
-              job.sock = outIos;
-              job.functor = boost::shared_ptr<PriorityThreadPool::Functor>(new CreateEqualityFilter(bs));
-              OOBPool->addJob(job);
-              break;
-            }
-
             case DICT_DESTROY_EQUALITY_FILTER:
+            case BATCH_PRIMITIVE_CREATE:
+            case BATCH_PRIMITIVE_ADD_JOINER:
+            case BATCH_PRIMITIVE_END_JOINER:
+            case BATCH_PRIMITIVE_DESTROY:
+            case BATCH_PRIMITIVE_ABORT:
             {
-              PriorityThreadPool::Job job;
               const uint8_t* buf = bs->buf();
               uint32_t pos = sizeof(ISMPacketHeader) - 2;
-              job.stepID = *((uint32_t*)&buf[pos + 6]);
+              const uint32_t txnId = *((uint32_t*)&buf[pos + 2]);
-              job.uniqueID = *((uint32_t*)&buf[pos + 10]);
+              const uint32_t stepID = *((uint32_t*)&buf[pos + 6]);
-              job.sock = outIos;
+              const uint32_t uniqueID = *((uint32_t*)&buf[pos + 10]);
-              job.functor = boost::shared_ptr<PriorityThreadPool::Functor>(new DestroyEqualityFilter(bs));
+              const uint32_t weight = 1;
+              const uint32_t priority = 0;
+              uint32_t id = 0;
+              boost::shared_ptr<FairThreadPool::Functor> functor;
+              if (ismHdr->Command == DICT_CREATE_EQUALITY_FILTER)
+              {
+                functor.reset(new CreateEqualityFilter(bs));
+              }
+              else if (ismHdr->Command == DICT_DESTROY_EQUALITY_FILTER)
+              {
+                functor.reset(new DestroyEqualityFilter(bs));
+              }
+              else if (ismHdr->Command == BATCH_PRIMITIVE_CREATE)
+              {
+                functor.reset(new BPPHandler::Create(fBPPHandler, bs));
+              }
+              else if (ismHdr->Command == BATCH_PRIMITIVE_ADD_JOINER)
+              {
+                functor.reset(new BPPHandler::AddJoiner(fBPPHandler, bs));
+              }
+              else if (ismHdr->Command == BATCH_PRIMITIVE_END_JOINER)
+              {
+                id = fBPPHandler->getUniqueID(bs, ismHdr->Command);
+                functor.reset(new BPPHandler::LastJoiner(fBPPHandler, bs));
+              }
+              else if (ismHdr->Command == BATCH_PRIMITIVE_DESTROY)
+              {
+                functor.reset(new BPPHandler::Destroy(fBPPHandler, bs));
+              }
+              else if (ismHdr->Command == BATCH_PRIMITIVE_ABORT)
+              {
+                id = fBPPHandler->getUniqueID(bs, ismHdr->Command);
+                functor.reset(new BPPHandler::Abort(fBPPHandler, bs));
+              }
+              FairThreadPool::Job job(uniqueID, stepID, txnId, functor, outIos, weight, priority, id);
               OOBPool->addJob(job);
               break;
             }
 
             case DICT_TOKEN_BY_SCAN_COMPARE:
+            case BATCH_PRIMITIVE_RUN:
             {
-              idbassert(bs->length() >= sizeof(TokenByScanRequestHeader));
+              TokenByScanRequestHeader* hdr = nullptr;
-              TokenByScanRequestHeader* hdr = (TokenByScanRequestHeader*)ismHdr;
+              boost::shared_ptr<FairThreadPool::Functor> functor;
+              uint32_t id = 0;
+              uint32_t weight = 0;
+              uint32_t priority = 0;
+              uint32_t txnId = 0;
+              uint32_t stepID = 0;
+              uint32_t uniqueID = 0;
+              bool isSyscat = false;
 
               if (bRotateDest)
               {
@@ -2090,23 +2123,41 @@ struct ReadThread
                 }
               }
 
-              PriorityThreadPool::Job job;
+              if (ismHdr->Command == DICT_TOKEN_BY_SCAN_COMPARE)
-              job.functor = boost::shared_ptr<DictScanJob>(new DictScanJob(outIos, bs, writeLock));
+              {
-              job.id = hdr->Hdr.UniqueID;
+                idbassert(bs->length() >= sizeof(TokenByScanRequestHeader));
-              job.weight = LOGICAL_BLOCK_RIDS;
+                hdr = (TokenByScanRequestHeader*)ismHdr;
-              job.priority = hdr->Hdr.Priority;
+                functor.reset(new DictScanJob(outIos, bs, writeLock));
-              const uint8_t* buf = bs->buf();
+                id = hdr->Hdr.UniqueID;
-              uint32_t pos = sizeof(ISMPacketHeader) - 2;
+                weight = LOGICAL_BLOCK_RIDS;
-              job.stepID = *((uint32_t*)&buf[pos + 6]);
+                priority = hdr->Hdr.Priority;
-              job.uniqueID = *((uint32_t*)&buf[pos + 10]);
+                const uint8_t* buf = bs->buf();
-              job.sock = outIos;
+                const uint32_t pos = sizeof(ISMPacketHeader) - 2;
-
+                txnId = *((uint32_t*)&buf[pos + 2]);
-              if (hdr->flags & IS_SYSCAT)
+                stepID = *((uint32_t*)&buf[pos + 6]);
+                uniqueID = *((uint32_t*)&buf[pos + 10]);
+                isSyscat = hdr->flags & IS_SYSCAT;
+              }
+              else if (ismHdr->Command == BATCH_PRIMITIVE_RUN)
+              {
+                functor.reset(new BPPSeeder(bs, writeLock, outIos,
+                  fPrimitiveServerPtr->ProcessorThreads(),
+                  fPrimitiveServerPtr->PTTrace()));
+                BPPSeeder* bpps = dynamic_cast<BPPSeeder*>(functor.get());
+                id = bpps->getID();
+                priority = bpps->priority();
+                const uint8_t* buf = bs->buf();
+                const uint32_t pos = sizeof(ISMPacketHeader) - 2;
+                txnId = *((uint32_t*)&buf[pos + 2]);
+                stepID = *((uint32_t*)&buf[pos + 6]);
+                uniqueID = *((uint32_t*)&buf[pos + 10]);
+                weight = ismHdr->Size + *((uint32_t*)&buf[pos + 18]);
+                isSyscat = bpps->isSysCat();
+              }
+              FairThreadPool::Job job(uniqueID, stepID, txnId, functor, outIos, weight, priority, id);
+
+              if (isSyscat)
               {
-                // boost::thread t(DictScanJob(outIos, bs, writeLock));
-                // using already-existing threads may cut latency
-                // if it's changed back to running in an independent thread
-                // change the issyscat() checks in BPPSeeder as well
                 OOBPool->addJob(job);
               }
               else
@@ -2117,146 +2168,11 @@ struct ReadThread
               break;
             }
 
-            case BATCH_PRIMITIVE_RUN:
-            {
-              if (bRotateDest)
-              {
-                if (!pUmSocketSelector->nextIOSocket(fIos, outIos, writeLock))
-                {
-                  // If we ever fall into this part of the
-                  // code we have a "bug" of some sort.
-                  // See handleUmSockSelErr() for more info.
-                  // We reset ios and mutex to defaults.
-                  handleUmSockSelErr(string("BPR cmd"));
-                  outIos = outIosDefault;
-                  writeLock = writeLockDefault;
-                  pUmSocketSelector->delConnection(fIos);
-                  bRotateDest = false;
-                }
-              }
-
-              /* Decide whether this is a syscat call and run
-              right away instead of queueing */
-              boost::shared_ptr<BPPSeeder> bpps(new BPPSeeder(bs, writeLock, outIos,
-                                                              fPrimitiveServerPtr->ProcessorThreads(),
-                                                              fPrimitiveServerPtr->PTTrace()));
-              PriorityThreadPool::Job job;
-              job.functor = bpps;
-              job.id = bpps->getID();
-              job.weight = ismHdr->Size;
-              job.priority = bpps->priority();
-              const uint8_t* buf = bs->buf();
-              uint32_t pos = sizeof(ISMPacketHeader) - 2;
-              job.stepID = *((uint32_t*)&buf[pos + 6]);
-              job.uniqueID = *((uint32_t*)&buf[pos + 10]);
-              job.sock = outIos;
-
-              if (bpps->isSysCat())
-              {
-                // boost::thread t(*bpps);
-                // using already-existing threads may cut latency
-                // if it's changed back to running in an independent thread
-                // change the issyscat() checks in BPPSeeder as well
-                OOBPool->addJob(job);
-              }
-              else
-              {
-                procPoolPtr->addJob(job);
-              }
-
-              break;
-            }
-
-            case BATCH_PRIMITIVE_CREATE:
-            {
-              PriorityThreadPool::Job job;
-              job.functor =
-                  boost::shared_ptr<PriorityThreadPool::Functor>(new BPPHandler::Create(fBPPHandler, bs));
-              const uint8_t* buf = bs->buf();
-              uint32_t pos = sizeof(ISMPacketHeader) - 2;
-              job.stepID = *((uint32_t*)&buf[pos + 6]);
-              job.uniqueID = *((uint32_t*)&buf[pos + 10]);
-              job.sock = outIos;
-              OOBPool->addJob(job);
-              // fBPPHandler->createBPP(*bs);
-              break;
-            }
-
-            case BATCH_PRIMITIVE_ADD_JOINER:
-            {
-              PriorityThreadPool::Job job;
-              job.functor =
-                  boost::shared_ptr<PriorityThreadPool::Functor>(new BPPHandler::AddJoiner(fBPPHandler, bs));
-              job.id = fBPPHandler->getUniqueID(bs, ismHdr->Command);
-              const uint8_t* buf = bs->buf();
-              uint32_t pos = sizeof(ISMPacketHeader) - 2;
-              job.stepID = *((uint32_t*)&buf[pos + 6]);
-              job.uniqueID = *((uint32_t*)&buf[pos + 10]);
-              job.sock = outIos;
-              OOBPool->addJob(job);
-              // fBPPHandler->addJoinerToBPP(*bs);
-              break;
-            }
-
-            case BATCH_PRIMITIVE_END_JOINER:
-            {
-              // lastJoinerMsg can block; must do this in a different thread
-              // OOBPool->invoke(BPPHandler::LastJoiner(fBPPHandler, bs));  // needs a threadpool that can
-              // resched boost::thread tmp(BPPHandler::LastJoiner(fBPPHandler, bs));
-              PriorityThreadPool::Job job;
-              job.functor =
-                  boost::shared_ptr<PriorityThreadPool::Functor>(new BPPHandler::LastJoiner(fBPPHandler, bs));
-              job.id = fBPPHandler->getUniqueID(bs, ismHdr->Command);
-              const uint8_t* buf = bs->buf();
-              uint32_t pos = sizeof(ISMPacketHeader) - 2;
-              job.stepID = *((uint32_t*)&buf[pos + 6]);
-              job.uniqueID = *((uint32_t*)&buf[pos + 10]);
-              job.sock = outIos;
-              OOBPool->addJob(job);
-              break;
-            }
-
-            case BATCH_PRIMITIVE_DESTROY:
-            {
-              // OOBPool->invoke(BPPHandler::Destroy(fBPPHandler, bs));  // needs a threadpool that can
-              // resched boost::thread tmp(BPPHandler::Destroy(fBPPHandler, bs));
-              PriorityThreadPool::Job job;
-              job.functor =
-                  boost::shared_ptr<PriorityThreadPool::Functor>(new BPPHandler::Destroy(fBPPHandler, bs));
-              job.id = fBPPHandler->getUniqueID(bs, ismHdr->Command);
-              const uint8_t* buf = bs->buf();
-              uint32_t pos = sizeof(ISMPacketHeader) - 2;
-              job.stepID = *((uint32_t*)&buf[pos + 6]);
-              job.uniqueID = *((uint32_t*)&buf[pos + 10]);
-              job.sock = outIos;
-              OOBPool->addJob(job);
-              // fBPPHandler->destroyBPP(*bs);
-              break;
-            }
-
             case BATCH_PRIMITIVE_ACK:
             {
               fBPPHandler->doAck(*bs);
               break;
             }
-
-            case BATCH_PRIMITIVE_ABORT:
-            {
-              // OBPool->invoke(BPPHandler::Abort(fBPPHandler, bs));
-              // fBPPHandler->doAbort(*bs);
-              PriorityThreadPool::Job job;
-              job.functor =
-                  boost::shared_ptr<PriorityThreadPool::Functor>(new BPPHandler::Abort(fBPPHandler, bs));
-              job.id = fBPPHandler->getUniqueID(bs, ismHdr->Command);
-              const uint8_t* buf = bs->buf();
-              uint32_t pos = sizeof(ISMPacketHeader) - 2;
-              job.stepID = *((uint32_t*)&buf[pos + 6]);
-              job.uniqueID = *((uint32_t*)&buf[pos + 10]);
-              job.sock = outIos;
-              OOBPool->addJob(job);
-              break;
-            }
-
             default:
             {
               std::ostringstream os;
@@ -2406,12 +2322,12 @@ PrimitiveServer::PrimitiveServer(int serverThreads, int serverQueueSize, int pro
   fServerpool.setQueueSize(fServerQueueSize);
   fServerpool.setName("PrimitiveServer");
 
-  fProcessorPool.reset(new threadpool::PriorityThreadPool(fProcessorWeight, highPriorityThreads,
+  fProcessorPool = new threadpool::FairThreadPool(fProcessorWeight, highPriorityThreads,
-                                                          medPriorityThreads, lowPriorityThreads, 0));
+                                                      medPriorityThreads, lowPriorityThreads, 0);
 
   // We're not using either the priority or the job-clustering features, just need a threadpool
   // that can reschedule jobs, and an unlimited non-blocking queue
-  OOBPool.reset(new threadpool::PriorityThreadPool(1, 5, 0, 0, 1));
+  OOBPool.reset(new threadpool::FairThreadPool(1, 5, 0, 0, 1));
 
   asyncCounter = 0;
 

primitives/primproc/primitiveserver.h

@@ -37,6 +37,7 @@
 
 #include "threadpool.h"
 #include "../../utils/threadpool/prioritythreadpool.h"
+#include "fair_threadpool.h"
 #include "messagequeue.h"
 #include "blockrequestprocessor.h"
 #include "batchprimitiveprocessor.h"
@@ -48,7 +49,7 @@ extern oam::OamCache* oamCache;
 
 namespace primitiveprocessor
 {
-extern boost::shared_ptr<threadpool::PriorityThreadPool> OOBPool;
+extern boost::shared_ptr<threadpool::FairThreadPool> OOBPool;
 extern dbbc::BlockRequestProcessor** BRPp;
 extern BRM::DBRM* brm;
 extern boost::mutex bppLock;
@@ -128,7 +129,7 @@ class PrimitiveServer
 
   /** @brief get a pointer the shared processor thread pool
    */
-  inline boost::shared_ptr<threadpool::PriorityThreadPool> getProcessorThreadPool() const
+  inline threadpool::FairThreadPool* getProcessorThreadPool() const
   {
     return fProcessorPool;
   }
@@ -165,7 +166,7 @@ class PrimitiveServer
   /** @brief the thread pool used to process
    * primitive commands
    */
-  boost::shared_ptr<threadpool::PriorityThreadPool> fProcessorPool;
+  threadpool::FairThreadPool* fProcessorPool;
 
   int fServerThreads;
   int fServerQueueSize;

tests/CMakeLists.txt

@@ -51,11 +51,10 @@ if (WITH_UNITTESTS)
     target_link_libraries(simd_processors ${ENGINE_LDFLAGS} ${MARIADB_CLIENT_LIBS} ${ENGINE_WRITE_LIBS} ${GTEST_LIBRARIES} processor dbbc)
     gtest_discover_tests(simd_processors TEST_PREFIX columnstore:)
 
-    # Comment this out b/c FairThreadPoolRemove segfaults in containers. Moreover this code isn't
+    add_executable(fair_threadpool_test fair_threadpool.cpp)
-    # in production yet.
+    add_dependencies(fair_threadpool_test googletest)
-    # add_executable(fair_threadpool_test fair_threadpool.cpp)
+    target_link_libraries(fair_threadpool_test ${ENGINE_LDFLAGS} ${MARIADB_CLIENT_LIBS} ${ENGINE_WRITE_LIBS} ${GTEST_LIBRARIES} processor dbbc)
-    # target_link_libraries(fair_threadpool_test ${ENGINE_LDFLAGS} ${MARIADB_CLIENT_LIBS} ${ENGINE_WRITE_LIBS} ${GTEST_LIBRARIES} processor dbbc)
+    gtest_discover_tests(fair_threadpool_test TEST_PREFIX columnstore:)
-    # gtest_discover_tests(fair_threadpool_test TEST_PREFIX columnstore:)
 
     # CPPUNIT TESTS
     add_executable(we_shared_components_tests shared_components_tests.cpp)

tests/fair_threadpool.cpp

@@ -111,12 +111,11 @@ TEST_F(FairThreadPoolTest, FairThreadPoolAdd)
 
   while (threadPool->queueSize())
   {
-    usleep(2500000);
+    usleep(250000);
   }
-  usleep(2500000);
 
-  EXPECT_EQ(threadPool->queueSize(), 0);
+  EXPECT_EQ(threadPool->queueSize(), 0ULL);
-  EXPECT_EQ(results.size(), 3);
+  EXPECT_EQ(results.size(), 3ULL);
   EXPECT_EQ(results[0], 1);
   EXPECT_EQ(results[1], 3);
   EXPECT_EQ(results[2], 2);
@@ -139,11 +138,11 @@ TEST_F(FairThreadPoolTest, FairThreadPoolRemove)
 
   while (threadPool->queueSize())
   {
-    usleep(1500000);
+    usleep(250000);
   }
 
-  EXPECT_EQ(threadPool->queueSize(), 0);
+  EXPECT_EQ(threadPool->queueSize(), 0ULL);
-  EXPECT_EQ(results.size(), 2);
+  EXPECT_EQ(results.size(), 2ULL);
   EXPECT_EQ(results[0], 1);
   EXPECT_EQ(results[1], 3);
 }
@@ -164,11 +163,11 @@ TEST_F(FairThreadPoolTest, FairThreadPoolReschedule)
 
   while (threadPool->queueSize())
   {
-    usleep(1500000);
+    usleep(250000);
   }
 
-  EXPECT_EQ(threadPool->queueSize(), 0);
+  EXPECT_EQ(threadPool->queueSize(), 0ULL);
-  EXPECT_EQ(results.size(), 3);
+  EXPECT_EQ(results.size(), 3ULL);
   EXPECT_EQ(results[0], 1);
   EXPECT_TRUE(isThisOrThat(results, 1, 2, 2, 3));
 }

utils/threadpool/fair_threadpool.cpp

@@ -34,7 +34,7 @@ namespace threadpool
 {
 FairThreadPool::FairThreadPool(uint targetWeightPerRun, uint highThreads, uint midThreads, uint lowThreads,
                                uint ID)
- : _stop(false), weightPerRun(targetWeightPerRun), id(ID), blockedThreads(0), extraThreads(0), stopExtra(true)
+ : _stop(false), weightPerRun(targetWeightPerRun), id(ID)
 {
   boost::thread* newThread;
   size_t numberOfThreads = highThreads + midThreads + lowThreads;
@@ -73,32 +73,20 @@ void FairThreadPool::addJob_(const Job& job, bool useLock)
     ++threadCounts;
   }
 
-  // If some threads have blocked (because of output queue full)
-  // Temporarily add some extra worker threads to make up for the blocked threads.
-  if (blockedThreads > extraThreads)
-  {
-    stopExtra = false;
-    newThread = threads.create_thread(ThreadHelper(this, PriorityThreadPool::Priority::EXTRA));
-    newThread->detach();
-    extraThreads++;
-  }
-  else if (blockedThreads == 0)
-  {
-    // Release the temporary threads -- some threads have become unblocked.
-    stopExtra = true;
-  }
-
   auto jobsListMapIter = txn2JobsListMap_.find(job.txnIdx_);
-  if (jobsListMapIter == txn2JobsListMap_.end())
+  if (jobsListMapIter == txn2JobsListMap_.end()) // there is no txn in the map
   {
     ThreadPoolJobsList* jobsList = new ThreadPoolJobsList;
     jobsList->push_back(job);
     txn2JobsListMap_[job.txnIdx_] = jobsList;
-    WeightT currentTopWeight = weightedTxnsQueue_.empty() ? 0 : weightedTxnsQueue_.top().first;
+    weightedTxnsQueue_.push({job.weight_, job.txnIdx_});
-    weightedTxnsQueue_.push({currentTopWeight, job.txnIdx_});
   }
-  else
+  else // txn is in the map
   {
+    if (jobsListMapIter->second->empty()) // there are no jobs for the txn
+    {
+      weightedTxnsQueue_.push({job.weight_, job.txnIdx_});
+    }
     jobsListMapIter->second->push_back(job);
   }
 
@@ -135,11 +123,8 @@ void FairThreadPool::removeJobs(uint32_t id)
 
 void FairThreadPool::threadFcn(const PriorityThreadPool::Priority preferredQueue)
 {
-  if (preferredQueue == PriorityThreadPool::Priority::EXTRA)
+  utils::setThreadName("Idle");
-    utils::setThreadName("Extra");
+  RunListT runList(1); // This is a vector to allow to grab multiple jobs
-  else
-    utils::setThreadName("Idle");
-  RunListT runList; // This is a vector to allow to grab multiple jobs
   RescheduleVecType reschedule;
   bool running = false;
   bool rescheduleJob = false;
@@ -151,12 +136,6 @@ void FairThreadPool::threadFcn(const PriorityThreadPool::Priority preferredQueue
       runList.clear(); // remove the job
       std::unique_lock<std::mutex> lk(mutex);
 
-      if (preferredQueue == PriorityThreadPool::Priority::EXTRA && stopExtra)
-      {
-        --extraThreads;
-        return;
-      }
-
       if (weightedTxnsQueue_.empty())
       {
         newJob.wait(lk);
@@ -166,7 +145,7 @@ void FairThreadPool::threadFcn(const PriorityThreadPool::Priority preferredQueue
       WeightedTxnT weightedTxn = weightedTxnsQueue_.top();
       auto txnAndJobListPair = txn2JobsListMap_.find(weightedTxn.second);
       // Looking for non-empty jobsList in a loop
-      // Waiting on cond_var if PQ is empty(no jobs in this thread pool)
+      // The loop waits on newJob cond_var if PQ is empty(no jobs in this thread pool)
       while (txnAndJobListPair == txn2JobsListMap_.end() || txnAndJobListPair->second->empty())
       {
         // JobList is empty. This can happen when this method pops the last Job.
@@ -196,7 +175,6 @@ void FairThreadPool::threadFcn(const PriorityThreadPool::Priority preferredQueue
       weightedTxnsQueue_.pop();
       TransactionIdxT txnIdx = txnAndJobListPair->first;
       ThreadPoolJobsList* jobsList = txnAndJobListPair->second;
-      // Job& job = jobsList->front();
       runList.push_back(jobsList->front());
 
       jobsList->pop_front();
@@ -210,13 +188,15 @@ void FairThreadPool::threadFcn(const PriorityThreadPool::Priority preferredQueue
       lk.unlock();
 
       running = true;
-      rescheduleJob = (*(runList[0].functor_))();
+      rescheduleJob = (*(runList[0].functor_))(); // run the functor
       running = false;
 
       utils::setThreadName("Idle");
 
       if (rescheduleJob)
       {
+        // to avoid excessive CPU usage waiting for data from storage
+        usleep(500);
         lk.lock();
         addJob_(runList[0], false);
         newJob.notify_one();

utils/threadpool/fair_threadpool.h

@@ -39,6 +39,12 @@
 
 namespace threadpool
 {
+// The idea of this thread pool is to run morsel jobs(primitive job) is to equaly distribute CPU time
+// b/w multiple parallel queries(thread maps morsel to query using txnId). Query(txnId) has its weight
+// stored in PriorityQueue that thread increases before run another morsel for the query. When query is
+// done(ThreadPoolJobsList is empty) it is removed from PQ and the Map(txn to ThreadPoolJobsList).
+// I tested multiple morsels per one loop iteration in ::threadFcn. This approach reduces CPU consumption
+// and increases query timings.
 class FairThreadPool
 {
  public:
@@ -92,23 +98,6 @@ class FairThreadPool
    */
   void dump();
 
-  // If a job is blocked, we want to temporarily increase the number of threads managed by the pool
-  // A problem can occur if all threads are running long or blocked for a single query. Other
-  // queries won't get serviced, even though there are cpu cycles available.
-  // These calls are currently protected by respondLock in sendThread(). If you call from other
-  // places, you need to consider atomicity.
-  void incBlockedThreads()
-  {
-    blockedThreads++;
-  }
-  void decBlockedThreads()
-  {
-    blockedThreads--;
-  }
-  uint32_t blockedThreadCount() const
-  {
-    return blockedThreads;
-  }
   size_t queueSize() const
   {
     return weightedTxnsQueue_.size();
@@ -165,9 +154,6 @@ class FairThreadPool
   using Txn2ThreadPoolJobsListMap = std::unordered_map<TransactionIdxT, ThreadPoolJobsList*>;
   Txn2ThreadPoolJobsListMap txn2JobsListMap_;
   WeightedTxnPrioQueue weightedTxnsQueue_;
-  std::atomic<uint32_t> blockedThreads;
-  std::atomic<uint32_t> extraThreads;
-  bool stopExtra;
 };
 
 }  // namespace threadpool