diff --git a/common/thorhelper/thorcommon.hpp b/common/thorhelper/thorcommon.hpp
index f85244be7b5..aad74478a3e 100644
--- a/common/thorhelper/thorcommon.hpp
+++ b/common/thorhelper/thorcommon.hpp
@@ -682,7 +682,10 @@ class CStatsContextLogger : public CSimpleInterfaceOf<IContextLogger>
     mutable CRuntimeStatisticCollection stats;
 public:
     CStatsContextLogger(const CRuntimeStatisticCollection  &_mapping, const LogMsgJobInfo & _job=unknownJob) : job(_job), stats(_mapping) {}
-
+    void reset()
+    {
+        stats.reset();
+    }
     virtual void CTXLOGva(const LogMsgCategory & cat, const LogMsgJobInfo & job, LogMsgCode code, const char *format, va_list args) const override  __attribute__((format(printf,5,0)))
     {
         VALOG(cat, job, code, format, args);
diff --git a/system/jhtree/jhtree.cpp b/system/jhtree/jhtree.cpp
index 53265d82167..4a245bb24a7 100644
--- a/system/jhtree/jhtree.cpp
+++ b/system/jhtree/jhtree.cpp
@@ -573,10 +573,13 @@ class jhtree_decl CKeyLevelManager : implements IKeyManager, public CInterface
         filter->describe(out);
     }
 
-    virtual void mergeStats(CRuntimeStatisticCollection & stats) const
+    virtual void mergeStats(CRuntimeStatisticCollection & targetStats) const
     {
+        // IO Stats comming from the keyCursor and jhtree cache stats coming from this class's stats
         if (keyCursor)
-            keyCursor->mergeStats(stats);
+            keyCursor->mergeStats(targetStats); // merge IO stats
+        if (stats.ctx)
+            targetStats.merge(stats.ctx->queryStats()); // merge jhtree cache stats
     }
 };
 
diff --git a/system/jlib/jstats.cpp b/system/jlib/jstats.cpp
index 1ca005cb6aa..9830a2dba9f 100644
--- a/system/jlib/jstats.cpp
+++ b/system/jlib/jstats.cpp
@@ -1322,8 +1322,8 @@ const StatisticsMapping noStatistics({});
 const StatisticsMapping jhtreeCacheStatistics({ StNumIndexSeeks, StNumIndexScans, StNumPostFiltered, StNumIndexWildSeeks,
                                                 StNumNodeCacheAdds, StNumLeafCacheAdds, StNumBlobCacheAdds, StNumNodeCacheHits, StNumLeafCacheHits, StNumBlobCacheHits, StCycleNodeLoadCycles, StCycleLeafLoadCycles,
                                                 StCycleBlobLoadCycles, StCycleNodeReadCycles, StCycleLeafReadCycles, StCycleBlobReadCycles, StNumNodeDiskFetches, StNumLeafDiskFetches, StNumBlobDiskFetches,
-                                                StCycleNodeFetchCycles, StCycleLeafFetchCycles, StCycleBlobFetchCycles, StCycleIndexCacheBlockedCycles, StNumIndexMergeCompares, StNumIndexMerges, StNumIndexSkips, StNumIndexNullSkips,
-                                                StTimeLeafLoad, StTimeLeafRead, StTimeLeafFetch, StTimeIndexCacheBlocked, StTimeNodeFetch});
+                                                StCycleNodeFetchCycles, StCycleLeafFetchCycles, StCycleBlobFetchCycles, StCycleIndexCacheBlockedCycles, StNumIndexMergeCompares, StNumIndexMerges, StNumIndexSkips,
+                                                StNumIndexNullSkips, StTimeLeafLoad, StTimeLeafRead, StTimeLeafFetch, StTimeIndexCacheBlocked, StTimeNodeFetch, StTimeNodeLoad, StTimeNodeRead});
 
 const StatisticsMapping allStatistics(StKindAll);
 const StatisticsMapping heapStatistics({StNumAllocations, StNumAllocationScans});
diff --git a/thorlcr/activities/keyedjoin/thkeyedjoin.cpp b/thorlcr/activities/keyedjoin/thkeyedjoin.cpp
index 9b43086248d..920fa8e61bf 100644
--- a/thorlcr/activities/keyedjoin/thkeyedjoin.cpp
+++ b/thorlcr/activities/keyedjoin/thkeyedjoin.cpp
@@ -310,7 +310,7 @@ class CKeyedJoinMaster : public CMasterActivity
         totalIndexParts = 0;
 
         Owned<IDistributedFile> dataFile;
-        Owned<IDistributedFile> indexFile = lookupReadFile(indexFileName, AccessMode::readRandom, false, false, 0 != (helper->getJoinFlags() & JFindexoptional), true, indexReadActivityStatistics, &indexFileStatsTableEntry);
+        Owned<IDistributedFile> indexFile = lookupReadFile(indexFileName, AccessMode::readRandom, false, false, 0 != (helper->getJoinFlags() & JFindexoptional), true, indexReadFileStatistics, &indexFileStatsTableEntry);
         if (indexFile)
         {
             if (!isFileKey(indexFile))
diff --git a/thorlcr/activities/keyedjoin/thkeyedjoinslave.cpp b/thorlcr/activities/keyedjoin/thkeyedjoinslave.cpp
index e072e6cc814..3edc40700b1 100644
--- a/thorlcr/activities/keyedjoin/thkeyedjoinslave.cpp
+++ b/thorlcr/activities/keyedjoin/thkeyedjoinslave.cpp
@@ -1248,7 +1248,7 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
             if (limiter)
                 limiter->dec(); // unblocks any requests to start lookup threads
         }
-        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) = 0;
+        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) const = 0;
     };
 
     class CKeyLookupLocalBase : public CLookupHandler
@@ -1284,7 +1284,6 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
         }
         void processRows(CThorExpandingRowArray &processing, unsigned partNo, IKeyManager *keyManager)
         {
-            CStatsScopedThresholdDeltaUpdater scoped(activity.statsUpdater);
             for (unsigned r=0; r<processing.ordinality() && !stopped; r++)
             {
                 OwnedConstThorRow row = processing.getClear(r);
@@ -1309,7 +1308,7 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
                         joinGroup->setAtMostLimitHit(); // also clears existing rows
                         break;
                     }
-                    KLBlobProviderAdapter adapter(keyManager, &activity.contextLogger);
+                    KLBlobProviderAdapter adapter(keyManager, nullptr);
                     byte const * keyRow = keyManager->queryKeyBuffer();
                     size_t fposOffset = keyManager->queryRowSize() - sizeof(offset_t);
                     offset_t fpos = rtlReadBigUInt8(keyRow + fposOffset);
@@ -1350,6 +1349,8 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
 
         //Need ptr to std::vector as std::atomic's are not constructable(doesn't have copy constructor)
         std::unique_ptr<std::vector<std::atomic<IKeyManager *>>> keyManagers;
+        // One context logger per part. (Extract stats for logical file by mapping part to logical file/subfile)
+        std::vector<Owned<CStatsContextLogger>> contextLoggers;
     public:
         CKeyLookupLocalHandler(CKeyedJoinSlave &_activity) : CKeyLookupLocalBase(_activity)
         {
@@ -1368,6 +1369,16 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
             keyManagers.reset(new std::vector<std::atomic<IKeyManager *>>(parts.size()));
             for (auto & k: *keyManagers)
                 k = nullptr;
+            if (contextLoggers.size() > 0)
+            {
+                for (auto contextLogger: contextLoggers)
+                    contextLogger->reset();
+            }
+            else
+            {
+                for (unsigned i=0; i<parts.size(); i++)
+                    contextLoggers.push_back(new CStatsContextLogger(jhtreeCacheStatistics, thorJob));
+            }
         }
         virtual void addPartNum(unsigned partNum) override
         {
@@ -1382,13 +1393,13 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
             std::atomic<IKeyManager *> & keyManager = (*keyManagers)[selected];
             if (!keyManager) // delayed until actually needed
             {
-                keyManager = activity.createPartKeyManager(partNo, copy);
+                keyManager = activity.createPartKeyManager(partNo, copy, contextLoggers[selected]);
                 // NB: potentially translation per part could be different if dealing with superkeys
                 setupTranslation(partNo, selected, *keyManager);
             }
             processRows(processing, partNo, keyManager);
         }
-        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) override
+        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) const override
         {
             for (size_t i=0; i<parts.size(); i++)
             {
@@ -1408,10 +1419,10 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
     class CKeyLookupMergeHandler : public CKeyLookupLocalBase
     {
         typedef CKeyLookupLocalBase PARENT;
-
+        CStatsContextLogger contextLogger;
         std::atomic<IKeyManager *> keyManager{nullptr};
     public:
-        CKeyLookupMergeHandler(CKeyedJoinSlave &_activity) : CKeyLookupLocalBase(_activity)
+        CKeyLookupMergeHandler(CKeyedJoinSlave &_activity) : CKeyLookupLocalBase(_activity), contextLogger(jhtreeCacheStatistics, thorJob)
         {
             limiter = &activity.lookupThreadLimiter;
             translators.push_back(nullptr);
@@ -1433,33 +1444,22 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
                     Owned<IKeyIndex> keyIndex = activity.createPartKeyIndex(partNo, copy, false);
                     partKeySet->addIndex(keyIndex.getClear());
                 }
-                keyManager = createKeyMerger(helper->queryIndexRecordSize()->queryRecordAccessor(true), partKeySet, 0, nullptr, helper->hasNewSegmentMonitors(), false);
+                keyManager = createKeyMerger(helper->queryIndexRecordSize()->queryRecordAccessor(true), partKeySet, 0, &contextLogger, helper->hasNewSegmentMonitors(), false);
                 setupTranslation(0, 0, *keyManager);
             }
             processRows(processing, 0, keyManager);
         }
-        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) override
+        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) const override
         {
-            if (keyManager)
-            {
-                for (size_t i=0; i<parts.size(); i++)
-                {
-                    if (isSuper)
-                    {
-                        unsigned subfile = subFileNum[i];
-                        (*keyManager).mergeStats(*fileStats[startOffset+subfile]);
-                    }
-                    else
-                        (*keyManager).mergeStats(*fileStats[startOffset]);
-                }
-            }
+            // CKeyLookupMergeHandler is not tracking the stats at the part level and that means it is not possible to associate the stats with a  logical file level.
+            // Superfile: all stats will be associated with the first sub index file.  For non-super, it makes no difference (there is only one index file).
+            // (Future: make necessary changes to createKeyMerger to track stats at the part level/logical level.)
+            fileStats[startOffset]->merge(contextLogger.queryStats());
         }
-
     };
     class CRemoteLookupHandler : public CLookupHandler
     {
         typedef CLookupHandler PARENT;
-
     protected:
         rank_t lookupSlave = RANK_NULL;
         mptag_t replyTag = TAG_NULL;
@@ -1543,14 +1543,12 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
             for (auto &h: handles)
                 h = 0;
         }
-        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) override
-        {
-            /* Note: currently, stats from remote file not tracked */
-        }
     };
     class CKeyLookupRemoteHandler : public CRemoteLookupHandler
     {
         typedef CRemoteLookupHandler PARENT;
+        // One context logger per part. (Extract stats for logical file by mapping part to logical file/subfile)
+        std::vector<Owned<CStatsContextLogger>> contextLoggers;
 
         void initRead(CMessageBuffer &msg, unsigned selected, unsigned partNo, unsigned copy)
         {
@@ -1633,6 +1631,20 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
             limiter = &activity.lookupThreadLimiter;
             allParts = &activity.allIndexParts;
         }
+        virtual void init() override
+        {
+            PARENT::init();
+            if (contextLoggers.size() > 0)
+            {
+                for (auto contextLogger: contextLoggers)
+                    contextLogger->reset();
+            }
+            else
+            {
+                for (unsigned i=0; i<parts.size(); i++)
+                    contextLoggers.push_back(new CStatsContextLogger(jhtreeCacheStatistics, thorJob));
+            }
+        }
         virtual StringBuffer &getInfo(StringBuffer &info) const override
         {
             return PARENT::getInfo(info).append(", lookupSlave=").append(lookupSlave);
@@ -1750,10 +1762,16 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
                     joinGroup->decPending(); // Every queued lookup row triggered an inc., this is the corresponding dec.
                 }
                 unsigned __int64 seeks, scans, wildseeks;
+                unsigned __int64 nodeDiskFetches, leafDiskFetches, blobDiskFetches;
                 mb.read(seeks).read(scans).read(wildseeks);
-                activity.inactiveStats.sumStatistic(StNumIndexSeeks, seeks);
-                activity.inactiveStats.sumStatistic(StNumIndexScans, scans);
-                activity.inactiveStats.sumStatistic(StNumIndexWildSeeks, wildseeks);
+                mb.read(nodeDiskFetches).read(leafDiskFetches).read(blobDiskFetches);
+                CStatsContextLogger * contextLogger(contextLoggers[selected]);
+                contextLogger->noteStatistic(StNumIndexSeeks, seeks);
+                contextLogger->noteStatistic(StNumIndexScans, scans);
+                contextLogger->noteStatistic(StNumIndexWildSeeks, wildseeks);
+                contextLogger->noteStatistic(StNumNodeDiskFetches, nodeDiskFetches);
+                contextLogger->noteStatistic(StNumLeafDiskFetches, leafDiskFetches);
+                contextLogger->noteStatistic(StNumBlobDiskFetches, blobDiskFetches);
                 if (received == numRows)
                     break;
             }
@@ -1763,6 +1781,19 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
             PARENT::end();
             doClose(kjs_keyclose);
         }
+        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) const override
+        {
+            assertex(parts.size()==contextLoggers.size());
+            for (size_t i=0; i<parts.size(); i++)
+            {
+                CStatsContextLogger * contextLogger = contextLoggers[i];
+                // Superfile: entry is StartOffset + subfileNum
+                // Otherwise, use 'startOffset' entry for the stats
+                unsigned fileEntry = isSuper ? (startOffset+subFileNum[i]) : startOffset;
+                assertex(fileEntry < fileStats.size());
+                fileStats[fileEntry]->merge(contextLogger->queryStats());
+            }
+        }
     };
     class CFetchLocalLookupHandler : public CLookupHandler
     {
@@ -1863,13 +1894,13 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
                 diskSeeks++;
             }
         }
-        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) override
+        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) const override
         {
             for (size_t i=0; i<parts.size(); i++)
             {
                 if ((*partIOCreated)[i])
                 {
-                    PartIO & partIO = partIOs[i];
+                    const PartIO & partIO = partIOs[i];
                     if (isSuper)
                     {
                         unsigned subfile = subFileNum[i];
@@ -2077,6 +2108,8 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
             PARENT::end();
             doClose(kjs_fetchclose);
         }
+        // Not tracking remote fetch file stats.  Future: may be something to consider.
+        virtual void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) const override {}
     };
     class CReadAheadThread : implements IThreaded
     {
@@ -2189,7 +2222,7 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
                     lookupHandler->end();
             }
         }
-        void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset)
+        void getFileStats(std::vector<OwnedPtr<CRuntimeStatisticCollection>> & fileStats, unsigned startOffset) const
         {
             ForEachItemIn(h, handlers)
                 handlers.item(h)->getFileStats(fileStats, startOffset);
@@ -2223,8 +2256,6 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
     CPartDescriptorArray allIndexParts;
     std::vector<unsigned> localIndexParts, localFetchPartMap;
     IArrayOf<IKeyIndex> tlkKeyIndexes;
-    CStatsContextLogger contextLogger;
-    CStatsCtxLoggerDeltaUpdater statsUpdater;
     Owned<IEngineRowAllocator> joinFieldsAllocator;
     OwnedConstThorRow defaultRight;
     unsigned joinFlags = 0;
@@ -2420,7 +2451,7 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
         {
             IKeyIndex *tlkKeyIndex = &tlkKeyIndexes.item(i);
             const RtlRecord &keyRecInfo = helper->queryIndexRecordSize()->queryRecordAccessor(true);
-            Owned<IKeyManager> tlkManager = createLocalKeyManager(keyRecInfo, nullptr, &contextLogger, helper->hasNewSegmentMonitors(), false);
+            Owned<IKeyManager> tlkManager = createLocalKeyManager(keyRecInfo, nullptr, nullptr, helper->hasNewSegmentMonitors(), false);
             tlkManager->setKey(tlkKeyIndex);
             keyManagers.append(*tlkManager.getClear());
         }
@@ -2452,10 +2483,10 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
             return createKeyIndex(filename, crc, *lazyIFileIO, (unsigned) -1, false);
         }
     }
-    IKeyManager *createPartKeyManager(unsigned partNo, unsigned copy)
+    IKeyManager *createPartKeyManager(unsigned partNo, unsigned copy, IContextLogger *ctx)
     {
         Owned<IKeyIndex> keyIndex = createPartKeyIndex(partNo, copy, false);
-        return createLocalKeyManager(helper->queryIndexRecordSize()->queryRecordAccessor(true), keyIndex, &contextLogger, helper->hasNewSegmentMonitors(), false);
+        return createLocalKeyManager(helper->queryIndexRecordSize()->queryRecordAccessor(true), keyIndex, ctx, helper->hasNewSegmentMonitors(), false);
     }
     const void *preparePendingLookupRow(void *row, size32_t maxSz, const void *lhsRow, size32_t keySz)
     {
@@ -2617,7 +2648,6 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
     }
     void stopReadAhead()
     {
-        CStatsScopedThresholdDeltaUpdater scoped(statsUpdater);
         keyLookupHandlers.flush();
         keyLookupHandlers.join(); // wait for pending handling, there may be more fetch items as a result
         fetchLookupHandlers.flushTS();
@@ -2938,7 +2968,7 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
 public:
     IMPLEMENT_IINTERFACE_USING(PARENT);
 
-    CKeyedJoinSlave(CGraphElementBase *_container) : PARENT(_container, keyedJoinActivityStatistics), readAheadThread(*this), contextLogger(jhtreeCacheStatistics, thorJob), statsUpdater(jhtreeCacheStatistics, *this, contextLogger)
+    CKeyedJoinSlave(CGraphElementBase *_container) : PARENT(_container, keyedJoinActivityStatistics), readAheadThread(*this)
     {
         helper = static_cast <IHThorKeyedJoinArg *> (queryHelper());
         reInit = 0 != (helper->getFetchFlags() & (FFvarfilename|FFdynamicfilename)) || (helper->getJoinFlags() & JFvarindexfilename);
@@ -3112,7 +3142,7 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
             }
             ISuperFileDescriptor *superFdesc = numIndexParts?allIndexParts.item(0).queryOwner().querySuperFileDescriptor():nullptr;
             unsigned numIndexSubFiles = superFdesc?superFdesc->querySubFiles():0;
-            setupSpace4FileStats(indexFileStatsTableEntry, true, superFdesc!=nullptr, numIndexSubFiles, indexReadActivityStatistics);
+            setupSpace4FileStats(indexFileStatsTableEntry, true, superFdesc!=nullptr, numIndexSubFiles, indexReadFileStatistics);
             setupLookupHandlers(keyLookupHandlers, totalIndexParts, superFdesc, localIndexParts, indexPartToSlaveMap, localKey, forceRemoteKeyedLookup ? ht_remotekeylookup : ht_localkeylookup, ht_remotekeylookup);
             data.read(totalDataParts);
             if (totalDataParts)
@@ -3368,7 +3398,6 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
     }
     virtual void stop() override
     {
-        CStatsScopedDeltaUpdater scoped(statsUpdater);
         endOfInput = true; // signals to readAhead which is reading input, that is should stop asap.
 
         // could be blocked in readAhead(), because CJoinGroup's are no longer being processed
@@ -3784,11 +3813,22 @@ class CKeyedJoinSlave : public CSlaveActivity, implements IJoinProcessor, implem
     {
         return container.queryId();
     }
-    virtual void serializeStats(MemoryBuffer &mb) override
+    virtual void gatherActiveStats(CRuntimeStatisticCollection &activeStats) const
     {
+        PARENT::gatherActiveStats(activeStats);
+        // fileStats gather per logical file.  Handlers track stats per part. Multiple handlers could be updating the same logical file.
+        // To allow each handler to update the same logical file without overwriting the other handlers updates, the fileStats are 'merged' into fileStats[]
+        // So, reset required because the handlers merge stats rather than sets them
+        for (auto & fileStatItem: fileStats)
+            fileStatItem->reset();
+
         keyLookupHandlers.getFileStats(fileStats, indexFileStatsTableEntry);
         fetchLookupHandlers.getFileStats(fileStats, dataFileStatsTableEntry);
-
+        for (auto & fileStatItem: fileStats)
+            activeStats.merge(*fileStatItem);
+    }
+    virtual void serializeStats(MemoryBuffer &mb) override
+    {
         PARENT::serializeStats(mb);
         mb.append((unsigned)fileStats.size());
         for (auto &stats: fileStats)
diff --git a/thorlcr/graph/thgraphmaster.cpp b/thorlcr/graph/thgraphmaster.cpp
index 0634b4291cc..b37ccfda83e 100644
--- a/thorlcr/graph/thgraphmaster.cpp
+++ b/thorlcr/graph/thgraphmaster.cpp
@@ -649,13 +649,30 @@ void CMasterActivity::done()
 
 void CMasterActivity::updateFileReadCostStats()
 {
-    // Updates numDiskReads & readCost in the file attributes and returns the readCost
-    auto updateReadCosts = [](IDistributedFile *file, CThorStatsCollection &stats)
+    // Update numDiskReads & readCost in the file attributes and return readCost
+    auto updateReadCosts = [](bool useJhtreeCacheStats, IDistributedFile *file, CThorStatsCollection &stats)
     {
-        stat_type curDiskReads = stats.getStatisticSum(StNumDiskReads);
+        StringBuffer clusterName;
+        file->getClusterName(0, clusterName);
         IPropertyTree & fileAttr = file->queryAttributes();
-        cost_type legacyReadCost = getLegacyReadCost(fileAttr, file);
-        cost_type curReadCost = money2cost_type(calcFileAccessCost(file, 0, curDiskReads));
+        cost_type legacyReadCost = 0, curReadCost = 0;
+        // Legacy files will not have the readCost stored as an attribute
+        if (!hasReadWriteCostFields(fileAttr) && fileAttr.hasProp(getDFUQResultFieldName(DFUQRFnumDiskReads)))
+        {
+            // Legacy file: calculate readCost using prev disk reads and new disk reads
+            stat_type prevDiskReads = fileAttr.getPropInt64(getDFUQResultFieldName(DFUQRFnumDiskReads), 0);
+            legacyReadCost = money2cost_type(calcFileAccessCost(clusterName, 0, prevDiskReads));
+        }
+        stat_type curDiskReads = stats.getStatisticSum(StNumDiskReads);
+        if(useJhtreeCacheStats)
+        {
+            stat_type numActualReads = stats.getStatisticSum(StNumNodeDiskFetches)
+                                    + stats.getStatisticSum(StNumLeafDiskFetches)
+                                    + stats.getStatisticSum(StNumBlobDiskFetches);
+            curReadCost = money2cost_type(calcFileAccessCost(clusterName, 0, numActualReads));
+        }
+        else
+            curReadCost = money2cost_type(calcFileAccessCost(clusterName, 0, curDiskReads));
         file->addAttrValue(getDFUQResultFieldName(DFUQRFreadCost), legacyReadCost + curReadCost);
         file->addAttrValue(getDFUQResultFieldName(DFUQRFnumDiskReads), curDiskReads);
         return curReadCost;
@@ -663,11 +680,17 @@ void CMasterActivity::updateFileReadCostStats()
 
     if (fileStats.size()>0)
     {
+        ThorActivityKind activityKind = container.getKind();
         unsigned fileIndex = 0;
         diskAccessCost = 0;
-        for (unsigned i=0; i<readFiles.size();i++)
+        for (unsigned i=0; i<readFiles.size(); i++)
         {
             IDistributedFile *file = queryReadFile(i);
+            bool useJhtreeCache = false;
+            // Index uses jhtree caches, so use actual fetches to calculate cost
+            // To determine entry is an index file entry, use the test (i==0) because index file is always the first file
+            if ((TAKindexread == activityKind) || ((TAKkeyedjoin == activityKind) && (0 == i)))
+                useJhtreeCache = true;
             if (file)
             {
                 IDistributedSuperFile *super = file->querySuperFile();
@@ -677,13 +700,13 @@ void CMasterActivity::updateFileReadCostStats()
                     for (unsigned i=0; i<numSubFiles; i++)
                     {
                         IDistributedFile &subFile = super->querySubFile(i, true);
-                        diskAccessCost += updateReadCosts(&subFile, *fileStats[fileIndex]);
+                        diskAccessCost += updateReadCosts(useJhtreeCache, &subFile, *fileStats[fileIndex]);
                         fileIndex++;
                     }
                 }
                 else
                 {
-                    diskAccessCost += updateReadCosts(file, *fileStats[fileIndex]);
+                    diskAccessCost += updateReadCosts(useJhtreeCache, file, *fileStats[fileIndex]);
                     fileIndex++;
                 }
             }
@@ -693,7 +716,7 @@ void CMasterActivity::updateFileReadCostStats()
     {
         IDistributedFile *file = queryReadFile(0);
         if (file)
-            diskAccessCost = updateReadCosts(file, statsCollection);
+            diskAccessCost += updateReadCosts(true, file, statsCollection);
     }
 }
 
diff --git a/thorlcr/graph/thgraphslave.hpp b/thorlcr/graph/thgraphslave.hpp
index 5540b72c032..7b43999dbab 100644
--- a/thorlcr/graph/thgraphslave.hpp
+++ b/thorlcr/graph/thgraphslave.hpp
@@ -210,7 +210,10 @@ class graphslave_decl CSlaveActivity : public CActivityBase, public CEdgeProgres
     bool optUnordered = false; // is the output specified as unordered?
     CriticalSection statsCs; // to be used to protect objects refernce during stat. collection
     CRuntimeStatisticCollection inactiveStats; // stats collected from previous iteration, to be combined with current 'stats'
-    std::vector<OwnedPtr<CRuntimeStatisticCollection>> fileStats;
+    // fileStats is mutable as it is updated by gatherActiveStats (const member func)
+    // fileStats is in this base class as it used by multiple derived classes (both slave and master) but not all.
+    // (Having it in the base class aids setup and resizing.)
+    mutable std::vector<OwnedPtr<CRuntimeStatisticCollection>> fileStats;
 
 protected:
     unsigned __int64 queryLocalCycles() const;
diff --git a/thorlcr/slave/slavmain.cpp b/thorlcr/slave/slavmain.cpp
index 80ab3d47800..be79a186514 100644
--- a/thorlcr/slave/slavmain.cpp
+++ b/thorlcr/slave/slavmain.cpp
@@ -115,7 +115,6 @@ class CKJService : public CSimpleInterfaceOf<IKJService>, implements IThreaded,
     unsigned maxCachedKJManagers = defaultMaxCachedKJManagers;
     unsigned maxCachedFetchContexts = defaultMaxCachedFetchContexts;
     unsigned keyLookupMaxProcessThreads = defaultKeyLookupMaxProcessThreads;
-    CStatsContextLogger contextLogger;
     class CLookupKey
     {
         unsigned hashv = 0;
@@ -447,11 +446,13 @@ class CKJService : public CSimpleInterfaceOf<IKJService>, implements IThreaded,
         Owned<IKeyManager> keyManager;
         unsigned handle = 0;
         Owned<IHThorKeyedJoinArg> helper;
+        CStatsContextLogger contextLogger;
+
     public:
         CKMContainer(CKJService &_service, CKeyLookupContext *_ctx)
-            : service(_service), ctx(_ctx)
+            : service(_service), ctx(_ctx), contextLogger(jhtreeCacheStatistics, thorJob)
         {
-            keyManager.setown(ctx->createKeyManager(&service.contextLogger));
+            keyManager.setown(ctx->createKeyManager(&contextLogger));
             StringBuffer tracing;
             const IDynamicTransform *translator = ctx->queryTranslator(ctx->queryKey().getTracing(tracing));
             if (translator)
@@ -475,6 +476,7 @@ class CKJService : public CSimpleInterfaceOf<IKJService>, implements IThreaded,
         }
         inline IHThorKeyedJoinArg *queryHelper() const { return helper; }
         inline CKJService & queryService() const { return service; }
+        inline CStatsContextLogger & queryContextLogger() { return contextLogger; }
     };
     template<class KEY, class ITEM>
     class CKeyedCacheEntry : public CInterface
@@ -757,10 +759,8 @@ class CKJService : public CSimpleInterfaceOf<IKJService>, implements IThreaded,
                 unsigned rowCount = getRowCount();
                 unsigned rowNum = 0;
                 unsigned rowStart = 0;
-                const CRuntimeStatisticCollection & stats = kmc->queryService().contextLogger.queryStats();
-                unsigned __int64 startSeeks = stats.getStatisticValue(StNumIndexSeeks);
-                unsigned __int64 startScans = stats.getStatisticValue(StNumIndexScans);
-                unsigned __int64 startWildSeeks = stats.getStatisticValue(StNumIndexWildSeeks);
+                CStatsContextLogger & contextLogger = kmc->queryContextLogger();
+                CRuntimeStatisticCollection startStats(contextLogger.queryStats());
                 while (!abortSoon)
                 {
                     OwnedConstThorRow row = getRowClear(rowNum++);
@@ -770,9 +770,15 @@ class CKJService : public CSimpleInterfaceOf<IKJService>, implements IThreaded,
                     if (last || (replyMb.length() >= DEFAULT_KEYLOOKUP_MAXREPLYSZ))
                     {
                         countMarker.write(rowNum-rowStart);
-                        replyMb.append(stats.getStatisticValue(StNumIndexSeeks)-startSeeks);
-                        replyMb.append(stats.getStatisticValue(StNumIndexScans)-startScans);
-                        replyMb.append(stats.getStatisticValue(StNumIndexWildSeeks)-startWildSeeks);
+
+                        CRuntimeStatisticCollection deltaStats(startStats.queryMapping());
+                        contextLogger.updateStatsDeltaTo(deltaStats, startStats);
+                        replyMb.append(deltaStats.getStatisticValue(StNumIndexSeeks));
+                        replyMb.append(deltaStats.getStatisticValue(StNumIndexScans));
+                        replyMb.append(deltaStats.getStatisticValue(StNumIndexWildSeeks));
+                        replyMb.append(deltaStats.getStatisticValue(StNumNodeDiskFetches));
+                        replyMb.append(deltaStats.getStatisticValue(StNumLeafDiskFetches));
+                        replyMb.append(deltaStats.getStatisticValue(StNumBlobDiskFetches));
                         if (activityCtx->useMessageCompression())
                         {
                             fastLZCompressToBuffer(replyMsg, tmpMB.length(), tmpMB.toByteArray());
@@ -1189,7 +1195,7 @@ class CKJService : public CSimpleInterfaceOf<IKJService>, implements IThreaded,
 public:
     IMPLEMENT_IINTERFACE_USING(CSimpleInterfaceOf<IKJService>);
 
-    CKJService(mptag_t _mpTag) : threaded("CKJService", this), keyLookupMpTag(_mpTag), contextLogger(jhtreeCacheStatistics, thorJob)
+    CKJService(mptag_t _mpTag) : threaded("CKJService", this), keyLookupMpTag(_mpTag)
     {
         setupProcessorPool();
     }
diff --git a/thorlcr/thorutil/thormisc.cpp b/thorlcr/thorutil/thormisc.cpp
index 9eb7d43f8bf..207d2a4b0cd 100644
--- a/thorlcr/thorutil/thormisc.cpp
+++ b/thorlcr/thorutil/thormisc.cpp
@@ -78,9 +78,10 @@ const StatisticsMapping soapcallStatistics({StTimeSoapcall});
 const StatisticsMapping basicActivityStatistics({StTimeTotalExecute, StTimeLocalExecute, StTimeBlocked});
 const StatisticsMapping groupActivityStatistics({StNumGroups, StNumGroupMax}, basicActivityStatistics);
 const StatisticsMapping hashJoinActivityStatistics({StNumLeftRows, StNumRightRows}, basicActivityStatistics);
-const StatisticsMapping indexReadActivityStatistics({StNumRowsProcessed}, diskReadRemoteStatistics, basicActivityStatistics, jhtreeCacheStatistics);
+const StatisticsMapping indexReadFileStatistics({}, diskReadRemoteStatistics, jhtreeCacheStatistics);
+const StatisticsMapping indexReadActivityStatistics({StNumRowsProcessed}, indexReadFileStatistics, basicActivityStatistics);
 const StatisticsMapping indexWriteActivityStatistics({StPerReplicated, StNumLeafCacheAdds, StNumNodeCacheAdds, StNumBlobCacheAdds }, basicActivityStatistics, diskWriteRemoteStatistics);
-const StatisticsMapping keyedJoinActivityStatistics({ StNumIndexAccepted, StNumPreFiltered, StNumDiskSeeks, StNumDiskAccepted, StNumDiskRejected}, basicActivityStatistics, jhtreeCacheStatistics);
+const StatisticsMapping keyedJoinActivityStatistics({ StNumIndexAccepted, StNumPreFiltered, StNumDiskSeeks, StNumDiskAccepted, StNumDiskRejected}, basicActivityStatistics, indexReadFileStatistics);
 const StatisticsMapping loopActivityStatistics({StNumIterations}, basicActivityStatistics);
 const StatisticsMapping lookupJoinActivityStatistics({StNumSmartJoinSlavesDegradedToStd, StNumSmartJoinDegradedToLocal}, basicActivityStatistics);
 const StatisticsMapping joinActivityStatistics({StNumLeftRows, StNumRightRows}, basicActivityStatistics, spillStatistics);
diff --git a/thorlcr/thorutil/thormisc.hpp b/thorlcr/thorutil/thormisc.hpp
index ee667d4246c..5801109bf7c 100644
--- a/thorlcr/thorutil/thormisc.hpp
+++ b/thorlcr/thorutil/thormisc.hpp
@@ -154,6 +154,7 @@ extern graph_decl const StatisticsMapping graphStatistics;
 extern graph_decl const StatisticsMapping indexDistribActivityStatistics;
 extern graph_decl const StatisticsMapping soapcallActivityStatistics;
 
+extern graph_decl const StatisticsMapping indexReadFileStatistics;
 class BooleanOnOff
 {
     bool &tf;