Remove concept of AppDomains from the GC (#24536)

* Remove concept of AppDomains from the GC
- Leave constructs allowing for multiple handle tables, as scenarios for that have been proposed
- Remove FEATURE_APPDOMAIN_RESOURCE_MONITORING

19 files changed, 13 insertions, 555 deletions

diff --git a/src/vm/appdomain.cpp b/src/vm/appdomain.cpp
index ed6d05fc87..2d92d3f952 100644
--- a/src/vm/appdomain.cpp
+++ b/src/vm/appdomain.cpp
@@ -115,10 +115,6 @@ GlobalStringLiteralMap* SystemDomain::m_pGlobalStringLiteralMap = NULL;
 DECLSPEC_ALIGN(16) 
 static BYTE         g_pSystemDomainMemory[sizeof(SystemDomain)];
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-size_t              SystemDomain::m_totalSurvivedBytes = 0;
-#endif //FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
 CrstStatic          SystemDomain::m_SystemDomainCrst;
 CrstStatic          SystemDomain::m_DelayedUnloadCrst;
 
@@ -1949,12 +1945,6 @@ void SystemDomain::LazyInitGlobalStringLiteralMap()
         AppDomain* pAppDomain = ::GetAppDomain();
         if (pAppDomain && pAppDomain->IsActive())
         {
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-            if (g_fEnableARM)
-            {
-                sc->pCurrentDomain = pAppDomain;
-            }
-#endif //FEATURE_APPDOMAIN_RESOURCE_MONITORING
             pAppDomain->EnumStaticGCRefs(fn, sc);
         }
     }
@@ -1962,83 +1952,6 @@ void SystemDomain::LazyInitGlobalStringLiteralMap()
     RETURN;
 }
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-void SystemDomain::ResetADSurvivedBytes()
-{
-    CONTRACT_VOID
-    {
-        NOTHROW;
-        GC_NOTRIGGER;
-        MODE_ANY;
-    }
-    CONTRACT_END;
-
-    _ASSERTE(GCHeapUtilities::IsGCInProgress());
-
-    SystemDomain* sysDomain = SystemDomain::System();
-    if (sysDomain)
-    {
-        AppDomain* pAppDomain = ::GetAppDomain();
-        if (pAppDomain && pAppDomain->IsUserActive())
-        {
-            pAppDomain->ResetSurvivedBytes();
-        }
-    }
-
-    RETURN;
-}
-
-ULONGLONG SystemDomain::GetADSurvivedBytes()
-{
-    CONTRACTL
-    {
-        NOTHROW;
-        GC_NOTRIGGER;
-        MODE_ANY;
-    }
-    CONTRACTL_END;
-
-    SystemDomain* sysDomain = SystemDomain::System();
-    ULONGLONG ullTotalADSurvived = 0;
-    if (sysDomain)
-    {
-        AppDomain* pAppDomain = ::GetAppDomain();
-        if (pAppDomain && pAppDomain->IsUserActive())
-        {
-            ULONGLONG ullSurvived = pAppDomain->GetSurvivedBytes();
-            ullTotalADSurvived += ullSurvived;
-        }
-    }
-
-    return ullTotalADSurvived;
-}
-
-void SystemDomain::RecordTotalSurvivedBytes(size_t totalSurvivedBytes)
-{
-    CONTRACT_VOID
-    {
-        NOTHROW;
-        GC_NOTRIGGER;
-        MODE_ANY;
-    }
-    CONTRACT_END;
-
-    m_totalSurvivedBytes = totalSurvivedBytes;
-
-    SystemDomain* sysDomain = SystemDomain::System();
-    if (sysDomain)
-    {
-        AppDomain* pAppDomain = ::GetAppDomain();
-        if (pAppDomain && pAppDomain->IsUserActive())
-        {
-            FireEtwAppDomainMemSurvived((ULONGLONG)pAppDomain, pAppDomain->GetSurvivedBytes(), totalSurvivedBytes, GetClrInstanceId());
-        }
-    }
-
-    RETURN;
-}
-#endif //FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
 // Only called when EE is suspended.
 DWORD SystemDomain::GetTotalNumSizedRefHandles()
 {
@@ -2977,12 +2890,6 @@ AppDomain::AppDomain()
     m_dwCreationHolders=0;
 #endif
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    m_ullTotalProcessorUsage = 0;
-    m_pullAllocBytes = NULL;
-    m_pullSurvivedBytes = NULL;
-#endif //FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
 #ifdef FEATURE_TYPEEQUIVALENCE
     m_pTypeEquivalenceTable = NULL;
 #endif // FEATURE_TYPEEQUIVALENCE
@@ -3080,27 +2987,6 @@ void AppDomain::Init()
 
 #ifndef CROSSGEN_COMPILE
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    // NOTE: it's important that we initialize ARM data structures before calling
-    // IGCHandleManager::CreateHandleStore, this is because AD::Init() can race with GC
-    // and once we add ourselves to the handle table map the GC can start walking
-    // our handles and calling AD::RecordSurvivedBytes() which touches ARM data.
-    if (GCHeapUtilities::IsServerHeap())
-        m_dwNumHeaps = CPUGroupInfo::CanEnableGCCPUGroups() ?
-                           CPUGroupInfo::GetNumActiveProcessors() :
-                           GetCurrentProcessCpuCount();
-    else
-        m_dwNumHeaps = 1;
-    m_pullAllocBytes = new ULONGLONG [m_dwNumHeaps * ARM_CACHE_LINE_SIZE_ULL];
-    m_pullSurvivedBytes = new ULONGLONG [m_dwNumHeaps * ARM_CACHE_LINE_SIZE_ULL];
-    for (DWORD i = 0; i < m_dwNumHeaps; i++)
-    {
-        m_pullAllocBytes[i * ARM_CACHE_LINE_SIZE_ULL] = 0;
-        m_pullSurvivedBytes[i * ARM_CACHE_LINE_SIZE_ULL] = 0;
-    }
-    m_ullLastEtwAllocBytes = 0;
-#endif //FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
     // Default domain reuses the handletablemap that was created during EEStartup
     m_handleStore = GCHandleUtilities::GetGCHandleManager()->GetGlobalHandleStore();
 
@@ -7070,66 +6956,6 @@ PTR_LoaderAllocator SystemDomain::GetGlobalLoaderAllocator()
     return PTR_LoaderAllocator(PTR_HOST_MEMBER_TADDR(SystemDomain,System(),m_GlobalAllocator));
 }
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
-#ifndef CROSSGEN_COMPILE
-// Return the total processor time (user and kernel) used by threads executing in this AppDomain so far. The
-// result is in 100ns units.
-ULONGLONG AppDomain::QueryProcessorUsage()
-{
-    CONTRACTL
-    {
-        NOTHROW;
-        GC_TRIGGERS;
-        MODE_ANY;
-    }
-    CONTRACTL_END;
-
-#ifndef DACCESS_COMPILE
-    Thread *pThread = NULL;
-
-    // Need to update our accumulated processor time count with current values from each thread that is
-    // currently executing in this domain.
-
-    // Take the thread store lock while we enumerate threads.
-    ThreadStoreLockHolder tsl;
-    while ((pThread = ThreadStore::GetThreadList(pThread)) != NULL)
-    {
-        // Skip unstarted and dead threads and those that are currently executing in a different AppDomain.
-        if (pThread->IsUnstarted() || pThread->IsDead() || pThread->GetDomain(INDEBUG(TRUE)) != this)
-            continue;
-
-        // Add the amount of time spent by the thread in the AppDomain since the last time we asked (calling
-        // Thread::QueryThreadProcessorUsage() will reset the thread's counter).
-        UpdateProcessorUsage(pThread->QueryThreadProcessorUsage());
-    }
-#endif // !DACCESS_COMPILE
-
-    // Return the updated total.
-    return m_ullTotalProcessorUsage;
-}
-
-// Add to the current count of processor time used by threads within this AppDomain. This API is called by
-// threads transitioning between AppDomains.
-void AppDomain::UpdateProcessorUsage(ULONGLONG ullAdditionalUsage)
-{
-    LIMITED_METHOD_CONTRACT;
-
-    // Need to be careful to synchronize here, multiple threads could be racing to update this count.
-    ULONGLONG ullOldValue;
-    ULONGLONG ullNewValue;
-    do
-    {
-        ullOldValue = m_ullTotalProcessorUsage;
-        ullNewValue = ullOldValue + ullAdditionalUsage;
-    } while (InterlockedCompareExchange64((LONGLONG*)&m_ullTotalProcessorUsage,
-                                          (LONGLONG)ullNewValue,
-                                          (LONGLONG)ullOldValue) != (LONGLONG)ullOldValue);
-}
-#endif // CROSSGEN_COMPILE
-
-#endif // FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
 #if defined(FEATURE_TYPEEQUIVALENCE)
 
 #ifndef DACCESS_COMPILE
diff --git a/src/vm/appdomain.hpp b/src/vm/appdomain.hpp
index 5bc45d7943..b2f2269771 100644
--- a/src/vm/appdomain.hpp
+++ b/src/vm/appdomain.hpp
@@ -2512,103 +2512,6 @@ public:
     PTR_LoaderHeap GetLowFrequencyHeap();
     PTR_LoaderHeap GetHighFrequencyHeap();
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    #define ARM_ETW_ALLOC_THRESHOLD (4 * 1024 * 1024)
-    // cache line size in ULONGLONG - 128 bytes which are 16 ULONGLONG's
-    #define ARM_CACHE_LINE_SIZE_ULL 16
-
-    inline ULONGLONG GetAllocBytes()
-    {
-        LIMITED_METHOD_CONTRACT;
-        ULONGLONG ullTotalAllocBytes = 0;
-
-        // Ensure that m_pullAllocBytes is non-null to avoid an AV in a race between GC and AD unload.
-        // A race can occur when a new appdomain is created, but an OOM is thrown when allocating for m_pullAllocBytes, causing the AD unload.
-        if(NULL != m_pullAllocBytes)
-        {
-            for (DWORD i = 0; i < m_dwNumHeaps; i++)
-            {
-                ullTotalAllocBytes += m_pullAllocBytes[i * ARM_CACHE_LINE_SIZE_ULL];
-            }
-        }
-        return ullTotalAllocBytes;
-    }
-
-    void RecordAllocBytes(size_t allocatedBytes, DWORD dwHeapNumber)
-    {
-        LIMITED_METHOD_CONTRACT;
-        _ASSERTE(dwHeapNumber < m_dwNumHeaps);
-        
-        // Ensure that m_pullAllocBytes is non-null to avoid an AV in a race between GC and AD unload.
-        // A race can occur when a new appdomain is created, but an OOM is thrown when allocating for m_pullAllocBytes, causing the AD unload.
-        if(NULL != m_pullAllocBytes)
-        {
-            m_pullAllocBytes[dwHeapNumber * ARM_CACHE_LINE_SIZE_ULL] += allocatedBytes;
-        }
-
-        ULONGLONG ullTotalAllocBytes = GetAllocBytes();
-
-        if ((ullTotalAllocBytes - m_ullLastEtwAllocBytes) >= ARM_ETW_ALLOC_THRESHOLD)
-        {
-            m_ullLastEtwAllocBytes = ullTotalAllocBytes;
-            FireEtwAppDomainMemAllocated((ULONGLONG)this, ullTotalAllocBytes, GetClrInstanceId());
-        }
-    }
-
-    inline ULONGLONG GetSurvivedBytes()
-    {
-        LIMITED_METHOD_CONTRACT;
-        ULONGLONG ullTotalSurvivedBytes = 0;
-
-        // Ensure that m_pullSurvivedBytes is non-null to avoid an AV in a race between GC and AD unload.
-        // A race can occur when a new appdomain is created, but an OOM is thrown when allocating for m_pullSurvivedBytes, causing the AD unload.
-        if(NULL != m_pullSurvivedBytes)
-        {
-            for (DWORD i = 0; i < m_dwNumHeaps; i++)
-            {
-                ullTotalSurvivedBytes += m_pullSurvivedBytes[i * ARM_CACHE_LINE_SIZE_ULL];
-            }
-        }
-        return ullTotalSurvivedBytes;
-    }
-
-    void RecordSurvivedBytes(size_t promotedBytes, DWORD dwHeapNumber)
-    {
-        WRAPPER_NO_CONTRACT;
-        _ASSERTE(dwHeapNumber < m_dwNumHeaps);
-   
-        // Ensure that m_pullSurvivedBytes is non-null to avoid an AV in a race between GC and AD unload.
-        // A race can occur when a new appdomain is created, but an OOM is thrown when allocating for m_pullSurvivedBytes, causing the AD unload.
-        if(NULL != m_pullSurvivedBytes)
-        {
-            m_pullSurvivedBytes[dwHeapNumber * ARM_CACHE_LINE_SIZE_ULL] += promotedBytes;
-        }
-    }
-
-    inline void ResetSurvivedBytes()
-    {
-        LIMITED_METHOD_CONTRACT;
-        
-        // Ensure that m_pullSurvivedBytes is non-null to avoid an AV in a race between GC and AD unload.
-        // A race can occur when a new appdomain is created, but an OOM is thrown when allocating for m_pullSurvivedBytes, causing the AD unload.
-        if(NULL != m_pullSurvivedBytes)
-        {
-            for (DWORD i = 0; i < m_dwNumHeaps; i++)
-            {
-                m_pullSurvivedBytes[i * ARM_CACHE_LINE_SIZE_ULL] = 0;
-            }
-        }
-    }
-
-    // Return the total processor time (user and kernel) used by threads executing in this AppDomain so far.
-    // The result is in 100ns units.
-    ULONGLONG QueryProcessorUsage();
-
-    // Add to the current count of processor time used by threads within this AppDomain. This API is called by
-    // threads transitioning between AppDomains.
-    void UpdateProcessorUsage(ULONGLONG ullAdditionalUsage);
-#endif //FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
 private:
     size_t EstimateSize();
     EEClassFactoryInfoHashTable* SetupClassFactHash();
@@ -2749,17 +2652,6 @@ private:
     // The thread-pool index of this app domain among existing app domains (starting from 1)
     TPIndex m_tpIndex;
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    ULONGLONG* m_pullAllocBytes;
-    ULONGLONG* m_pullSurvivedBytes;
-    DWORD m_dwNumHeaps;
-    ULONGLONG m_ullLastEtwAllocBytes;
-    // Total processor time (user and kernel) utilized by threads running in this AppDomain so far. May not
-    // account for threads currently executing in the AppDomain until a call to QueryProcessorUsage() is
-    // made.
-    Volatile<ULONGLONG> m_ullTotalProcessorUsage;
-#endif //FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
     Volatile<Stage> m_Stage;
 
     ArrayList        m_failedAssemblies;
@@ -3220,19 +3112,6 @@ public:
 
 #endif // DACCESS_COMPILE
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    // The *AD* methods are what we got from tracing through EE roots.
-    // RecordTotalSurvivedBytes is the total promoted from a GC.
-    static void ResetADSurvivedBytes();
-    static ULONGLONG GetADSurvivedBytes();
-    static void RecordTotalSurvivedBytes(size_t totalSurvivedBytes);
-    static ULONGLONG GetTotalSurvivedBytes()
-    {
-        LIMITED_METHOD_CONTRACT;
-        return m_totalSurvivedBytes;
-    }
-#endif //FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
     //****************************************************************************************
     // Routines to deal with the base library (currently mscorlib.dll)
     LPCWSTR BaseLibrary()
@@ -3341,11 +3220,6 @@ private:
 
     LoaderAllocator * m_pDelayedUnloadListOfLoaderAllocators;
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    // This is what gets promoted for the whole GC heap.
-    static size_t m_totalSurvivedBytes;
-#endif //FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
 #ifndef DACCESS_COMPILE
     static CrstStatic m_DelayedUnloadCrst;
     static CrstStatic       m_SystemDomainCrst;
diff --git a/src/vm/eeconfig.cpp b/src/vm/eeconfig.cpp
index a4b8e1d196..87e7467f23 100644
--- a/src/vm/eeconfig.cpp
+++ b/src/vm/eeconfig.cpp
@@ -712,11 +712,6 @@ HRESULT EEConfig::sync()
     iGCLatencyMode = GetConfigDWORD_DontUse_(CLRConfig::INTERNAL_GCLatencyMode, iGCLatencyMode);
 #endif
 
-    if (CLRConfig::GetConfigValue(CLRConfig::UNSUPPORTED_ARMEnabled))
-    {
-        g_fEnableARM = TRUE;
-    }
-
     bool gcConcurrentWasForced = false;
     // The CLRConfig value for UNSUPPORTED_gcConcurrent defaults to -1, and treats any
     // positive value as 'forcing' concurrent GC to be on. Because the standard logic
diff --git a/src/vm/eepolicy.cpp b/src/vm/eepolicy.cpp
index 2da1c70f70..66ec5c6be2 100644
--- a/src/vm/eepolicy.cpp
+++ b/src/vm/eepolicy.cpp
@@ -1249,7 +1249,6 @@ void EEPolicy::HandleCodeContractFailure(LPCWSTR pMessage, LPCWSTR pCondition, L
     // GetActionOnFailure will notify the host for us.
     EPolicyAction action = pPolicy->GetActionOnFailure(FAIL_CodeContract);
     Thread* pThread = GetThread();
-    AppDomain* pCurrentDomain = ::GetAppDomain();
 
     switch(action) {
     case eThrowException:
diff --git a/src/vm/eventtrace.cpp b/src/vm/eventtrace.cpp
index a4e7d6ffe4..25f5273a05 100644
--- a/src/vm/eventtrace.cpp
+++ b/src/vm/eventtrace.cpp
@@ -3844,9 +3844,6 @@ VOID ETW::EnumerationLog::StartRundown()
 
     EX_TRY
     {
-        BOOL bIsArmRundownEnabled = ETW_TRACING_CATEGORY_ENABLED(MICROSOFT_WINDOWS_DOTNETRUNTIME_RUNDOWN_PROVIDER_Context,
-                                                                 TRACE_LEVEL_INFORMATION,
-                                                                 CLR_RUNDOWNAPPDOMAINRESOURCEMANAGEMENT_KEYWORD);
         BOOL bIsPerfTrackRundownEnabled = ETW_TRACING_CATEGORY_ENABLED(MICROSOFT_WINDOWS_DOTNETRUNTIME_RUNDOWN_PROVIDER_Context,
                                                                  TRACE_LEVEL_INFORMATION,
                                                                  CLR_RUNDOWNPERFTRACK_KEYWORD);
@@ -3869,8 +3866,6 @@ VOID ETW::EnumerationLog::StartRundown()
                                         TRACE_LEVEL_INFORMATION, 
                                         CLR_RUNDOWNJITTEDMETHODILTONATIVEMAP_KEYWORD)
            ||
-           bIsArmRundownEnabled
-           ||
            bIsPerfTrackRundownEnabled
            ||
            bIsThreadingRundownEnabled)
@@ -3909,17 +3904,7 @@ VOID ETW::EnumerationLog::StartRundown()
 
             ETW::EnumerationLog::EnumerationHelper(NULL, NULL, enumerationOptions);
             
-            if (bIsArmRundownEnabled)
-            {
-                // When an ETW event consumer asks for ARM rundown, that not only enables
-                // the ETW events, but also causes some minor behavioral changes in the
-                // CLR, such as gathering CPU usage baselines for each thread right now,
-                // and also gathering resource usage information later on (keyed off of
-                // g_fEnableARM, which we'll set right now).
-                EnableARM();
-            }
-
-            if (bIsArmRundownEnabled || bIsThreadingRundownEnabled)
+            if (bIsThreadingRundownEnabled)
             {
                 SendThreadRundownEvent();
             }
diff --git a/src/vm/frames.cpp b/src/vm/frames.cpp
index 312efe9f3b..8d49702cef 100644
--- a/src/vm/frames.cpp
+++ b/src/vm/frames.cpp
@@ -1111,7 +1111,7 @@ void HijackFrame::GcScanRoots(promote_func *fn, ScanContext* sc)
         case RT_ByRef:
             LOG((LF_GC, INFO3, "Hijack Frame Carefully Promoting pointer" FMT_ADDR "to",
                 DBG_ADDR(OBJECTREF_TO_UNCHECKED_OBJECTREF(*objPtr))));
-            PromoteCarefully(fn, objPtr, sc, GC_CALL_INTERIOR | GC_CALL_CHECK_APP_DOMAIN);
+            PromoteCarefully(fn, objPtr, sc, GC_CALL_INTERIOR);
             LOG((LF_GC, INFO3, FMT_ADDR "\n", DBG_ADDR(OBJECTREF_TO_UNCHECKED_OBJECTREF(*objPtr))));
             break;
 
@@ -1340,7 +1340,7 @@ void TransitionFrame::PromoteCallerStackUsingGCRefMap(promote_func* fn, ScanCont
             fn(dac_cast<PTR_PTR_Object>(ppObj), sc, CHECK_APP_DOMAIN);
             break;
         case GCREFMAP_INTERIOR:
-            PromoteCarefully(fn, dac_cast<PTR_PTR_Object>(ppObj), sc, GC_CALL_INTERIOR | GC_CALL_CHECK_APP_DOMAIN);
+            PromoteCarefully(fn, dac_cast<PTR_PTR_Object>(ppObj), sc, GC_CALL_INTERIOR);
             break;
         case GCREFMAP_METHOD_PARAM:
             if (sc->promotion)
diff --git a/src/vm/gcenv.ee.common.cpp b/src/vm/gcenv.ee.common.cpp
index 6915ec8bda..1411853218 100644
--- a/src/vm/gcenv.ee.common.cpp
+++ b/src/vm/gcenv.ee.common.cpp
@@ -158,7 +158,7 @@ void GcEnumObject(LPVOID pData, OBJECTREF *pObj, uint32_t flags)
     //
     // Sanity check that the flags contain only these three values
     //
-    assert((flags & ~(GC_CALL_INTERIOR|GC_CALL_PINNED|GC_CALL_CHECK_APP_DOMAIN)) == 0);
+    assert((flags & ~(GC_CALL_INTERIOR|GC_CALL_PINNED)) == 0);
 
     // for interior pointers, we optimize the case in which
     //  it points into the current threads stack area
@@ -205,13 +205,6 @@ StackWalkAction GcStackCrawlCallBack(CrawlFrame* pCF, VOID* pData)
 
     GCCONTEXT   *gcctx = (GCCONTEXT*) pData;
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    if (g_fEnableARM)
-    {
-        gcctx->sc->pCurrentDomain = pCF->GetAppDomain();
-    }
-#endif //FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
     MethodDesc *pMD = pCF->GetFunction();
 
 #ifdef GC_PROFILING
diff --git a/src/vm/gcenv.ee.cpp b/src/vm/gcenv.ee.cpp
index 8e47caee94..ebbc7929a6 100644
--- a/src/vm/gcenv.ee.cpp
+++ b/src/vm/gcenv.ee.cpp
@@ -1013,15 +1013,6 @@ void GCToEEInterface::HandleFatalError(unsigned int exitCode)
     EEPOLICY_HANDLE_FATAL_ERROR(exitCode);
 }
 
-bool GCToEEInterface::ShouldFinalizeObjectForUnload(void* pDomain, Object* obj)
-{
-    // CoreCLR does not have appdomains, so this code path is dead. Other runtimes may
-    // choose to inspect the object being finalized here.
-    // [DESKTOP TODO] Desktop looks for "agile and finalizable" objects and may choose
-    // to move them to a new app domain instead of finalizing them here.
-    return true;
-}
-
 bool GCToEEInterface::EagerFinalized(Object* obj)
 {
     MethodTable* pMT = obj->GetGCSafeMethodTable();
@@ -1486,34 +1477,6 @@ IGCToCLREventSink* GCToEEInterface::EventSink()
     return &g_gcToClrEventSink;
 }
 
-uint32_t GCToEEInterface::GetDefaultDomainIndex()
-{
-    LIMITED_METHOD_CONTRACT;
-
-    return DefaultADID;
-}
-
-void *GCToEEInterface::GetAppDomainAtIndex(uint32_t appDomainIndex)
-{
-    LIMITED_METHOD_CONTRACT;
-
-    return ::GetAppDomain();
-}
-
-bool GCToEEInterface::AppDomainCanAccessHandleTable(uint32_t appDomainID)
-{
-    LIMITED_METHOD_CONTRACT;
-
-    return appDomainID == DefaultADID;
-}
-
-uint32_t GCToEEInterface::GetIndexOfAppDomainBeingUnloaded()
-{
-    LIMITED_METHOD_CONTRACT;
-
-    return 0xFFFFFFFF;
-}
-
 uint32_t GCToEEInterface::GetTotalNumSizedRefHandles()
 {
     LIMITED_METHOD_CONTRACT;
@@ -1522,13 +1485,6 @@ uint32_t GCToEEInterface::GetTotalNumSizedRefHandles()
 }
 
 
-bool GCToEEInterface::AppDomainIsRudeUnload(void *appDomain)
-{
-    LIMITED_METHOD_CONTRACT;
-
-    return false;
-}
-
 bool GCToEEInterface::AnalyzeSurvivorsRequested(int condemnedGeneration)
 {
     LIMITED_METHOD_CONTRACT;
diff --git a/src/vm/gcenv.ee.h b/src/vm/gcenv.ee.h
index 383c0796f6..de6ad5a542 100644
--- a/src/vm/gcenv.ee.h
+++ b/src/vm/gcenv.ee.h
@@ -62,7 +62,6 @@ public:
 
     void EnableFinalization(bool foundFinalizers);
     void HandleFatalError(unsigned int exitCode);
-    bool ShouldFinalizeObjectForUnload(void* pDomain, Object* obj);
     bool EagerFinalized(Object* obj);
     MethodTable* GetFreeObjectMethodTable();
     bool GetBooleanConfigValue(const char* key, bool* value);
@@ -76,12 +75,7 @@ public:
     void WalkAsyncPinned(Object* object, void* context, void(*callback)(Object*, Object*, void*));
     IGCToCLREventSink* EventSink();
 
-    uint32_t GetDefaultDomainIndex();
-    void *GetAppDomainAtIndex(uint32_t appDomainIndex);
-    bool AppDomainCanAccessHandleTable(uint32_t appDomainID);
-    uint32_t GetIndexOfAppDomainBeingUnloaded();
     uint32_t GetTotalNumSizedRefHandles();
-    bool AppDomainIsRudeUnload(void *appDomain);
 
     bool AnalyzeSurvivorsRequested(int condemnedGeneration);
     void AnalyzeSurvivorsFinished(int condemnedGeneration);
diff --git a/src/vm/gcenv.h b/src/vm/gcenv.h
index 162c14557e..767adb892c 100644
--- a/src/vm/gcenv.h
+++ b/src/vm/gcenv.h
@@ -68,22 +68,4 @@ namespace ETW
 #define _tfopen _wfopen
 #endif
 
-// -----------------------------------------------------------------------------------------------------------
-//
-// AppDomain emulation. We don't have these in the CLR anymore so instead we emulate the bare minimum of the API
-// touched by the GC/HandleTable and pretend we have precisely one (default) appdomain.
-//
-
-#define RH_DEFAULT_DOMAIN_ID 1
-
-struct ADIndex
-{
-    DWORD m_dwIndex;
-
-    ADIndex () : m_dwIndex(RH_DEFAULT_DOMAIN_ID) {}
-    explicit ADIndex (DWORD id) : m_dwIndex(id) {}
-    BOOL operator==(const ADIndex& ad) const { return m_dwIndex == ad.m_dwIndex; }
-    BOOL operator!=(const ADIndex& ad) const { return m_dwIndex != ad.m_dwIndex; }
-};
-
 #endif // GCENV_H_
diff --git a/src/vm/gctoclreventsink.cpp b/src/vm/gctoclreventsink.cpp
index d95a187c1d..4d64a49555 100644
--- a/src/vm/gctoclreventsink.cpp
+++ b/src/vm/gctoclreventsink.cpp
@@ -319,14 +319,14 @@ void GCToCLREventSink::FireGCFullNotify_V1(uint32_t genNumber, uint32_t isAlloc)
     FireEtwGCFullNotify_V1(genNumber, isAlloc, GetClrInstanceId());
 }
 
-void GCToCLREventSink::FireSetGCHandle(void *handleID, void *objectID, uint32_t kind, uint32_t generation, uint64_t appDomainID)
+void GCToCLREventSink::FireSetGCHandle(void *handleID, void *objectID, uint32_t kind, uint32_t generation)
 {
-    FireEtwSetGCHandle(handleID, objectID, kind, generation, appDomainID, GetClrInstanceId());
+    FireEtwSetGCHandle(handleID, objectID, kind, generation, (uint64_t)dac_cast<TADDR>(AppDomain::GetCurrentDomain()), GetClrInstanceId());
 }
 
-void GCToCLREventSink::FirePrvSetGCHandle(void *handleID, void *objectID, uint32_t kind, uint32_t generation, uint64_t appDomainID)
+void GCToCLREventSink::FirePrvSetGCHandle(void *handleID, void *objectID, uint32_t kind, uint32_t generation)
 {
-    FireEtwPrvSetGCHandle(handleID, objectID, kind, generation, appDomainID, GetClrInstanceId());
+    FireEtwPrvSetGCHandle(handleID, objectID, kind, generation, (uint64_t)dac_cast<TADDR>(AppDomain::GetCurrentDomain()), GetClrInstanceId());
 }
 
 void GCToCLREventSink::FireDestroyGCHandle(void *handleID)
diff --git a/src/vm/gctoclreventsink.h b/src/vm/gctoclreventsink.h
index 1e2edfccc2..12f5ae3cc5 100644
--- a/src/vm/gctoclreventsink.h
+++ b/src/vm/gctoclreventsink.h
@@ -76,8 +76,8 @@ public:
     void FireBGCAllocWaitBegin(uint32_t reason);
     void FireBGCAllocWaitEnd(uint32_t reason);
     void FireGCFullNotify_V1(uint32_t genNumber, uint32_t isAlloc);
-    void FireSetGCHandle(void *handleID, void *objectID, uint32_t kind, uint32_t generation, uint64_t appDomainID);
-    void FirePrvSetGCHandle(void *handleID, void *objectID, uint32_t kind, uint32_t generation, uint64_t appDomainID);
+    void FireSetGCHandle(void *handleID, void *objectID, uint32_t kind, uint32_t generation);
+    void FirePrvSetGCHandle(void *handleID, void *objectID, uint32_t kind, uint32_t generation);
     void FireDestroyGCHandle(void *handleID);
     void FirePrvDestroyGCHandle(void *handleID);
 };
diff --git a/src/vm/siginfo.cpp b/src/vm/siginfo.cpp
index 353abf48cb..0397b5aa8b 100644
--- a/src/vm/siginfo.cpp
+++ b/src/vm/siginfo.cpp
@@ -4871,7 +4871,7 @@ void PromoteCarefully(promote_func   fn,
     //
     // Sanity check that the flags contain only these three values
     //
-    assert((flags & ~(GC_CALL_INTERIOR|GC_CALL_PINNED|GC_CALL_CHECK_APP_DOMAIN)) == 0);
+    assert((flags & ~(GC_CALL_INTERIOR|GC_CALL_PINNED)) == 0);
 
     //
     // Sanity check that GC_CALL_INTERIOR FLAG is set
@@ -5010,7 +5010,7 @@ VOID MetaSig::GcScanRoots(ArgDestination *pValue,
 #ifdef _DEBUG
             pOldLocation = *pArgPtr;
 #endif
-            (*fn)(pArgPtr, sc, GC_CALL_CHECK_APP_DOMAIN );
+            (*fn)(pArgPtr, sc, 0 );
 
             // !!! Do not cast to (OBJECTREF*)
             // !!! If we are in the relocate phase, we may have updated root,
@@ -5038,7 +5038,7 @@ VOID MetaSig::GcScanRoots(ArgDestination *pValue,
             pOldLocation = *pArgPtr;
 #endif
 
-            (*fnc)(fn, pArgPtr, sc, GC_CALL_INTERIOR|GC_CALL_CHECK_APP_DOMAIN);
+            (*fnc)(fn, pArgPtr, sc, GC_CALL_INTERIOR);
 
             // !!! Do not cast to (OBJECTREF*)
             // !!! If we are in the relocate phase, we may have updated root,
diff --git a/src/vm/threads.cpp b/src/vm/threads.cpp
index 020f318684..07ea78f8a0 100644
--- a/src/vm/threads.cpp
+++ b/src/vm/threads.cpp
@@ -808,13 +808,6 @@ Thread* SetupThread(BOOL fInternal)
         FastInterlockOr((ULONG *) &pThread->m_State, Thread::TS_TPWorkerThread);
     }
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    if (g_fEnableARM)
-    {
-        pThread->QueryThreadProcessorUsage();
-    }
-#endif // FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
 #ifdef FEATURE_EVENT_TRACE
     ETW::ThreadLog::FireThreadCreated(pThread);
 #endif // FEATURE_EVENT_TRACE
@@ -865,15 +858,6 @@ void DestroyThread(Thread *th)
 
     _ASSERTE(g_fEEShutDown || th->m_dwLockCount == 0 || th->m_fRudeAborted);
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    if (g_fEnableARM)
-    {
-        AppDomain* pDomain = th->GetDomain();
-        pDomain->UpdateProcessorUsage(th->QueryThreadProcessorUsage());
-        FireEtwThreadTerminated((ULONGLONG)th, (ULONGLONG)pDomain, GetClrInstanceId());
-    }
-#endif // FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
     th->FinishSOWork();
 
     GCX_PREEMP_NO_DTOR();
@@ -966,14 +950,6 @@ HRESULT Thread::DetachThread(BOOL fDLLThreadDetach)
 
     _ASSERTE (this == GetThread());
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    if (g_fEnableARM && m_pDomain)
-    {
-        m_pDomain->UpdateProcessorUsage(QueryThreadProcessorUsage());
-        FireEtwThreadTerminated((ULONGLONG)this, (ULONGLONG)m_pDomain, GetClrInstanceId());
-    }
-#endif // FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
     FinishSOWork();
 
     FastInterlockIncrement(&Thread::m_DetachCount);
@@ -1555,10 +1531,6 @@ Thread::Thread()
     contextHolder.SuppressRelease();
     savedRedirectContextHolder.SuppressRelease();
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    m_ullProcessorUsageBaseline = 0;
-#endif // FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
 #ifdef FEATURE_COMINTEROP
     m_uliInitializeSpyCookie.QuadPart = 0ul;
     m_fInitializeSpyRegistered = false;
@@ -1825,12 +1797,6 @@ BOOL Thread::HasStarted(BOOL bRequiresTSL)
 
         ThreadStore::TransferStartedThread(this, bRequiresTSL);
 
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-        if (g_fEnableARM)
-        {
-            QueryThreadProcessorUsage();
-        }
-#endif // FEATURE_APPDOMAIN_RESOURCE_MONITORING
 #ifdef FEATURE_EVENT_TRACE
         ETW::ThreadLog::FireThreadCreated(this);
 #endif // FEATURE_EVENT_TRACE
@@ -8918,56 +8884,6 @@ ThreadStore::EnumMemoryRegions(CLRDataEnumMemoryFlags flags)
 
 #endif // #ifdef DACCESS_COMPILE
 
-
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-// For the purposes of tracking resource usage we implement a simple cpu resource usage counter on each
-// thread. Every time QueryThreadProcessorUsage() is invoked it returns the amount of cpu time (a combination
-// of user and kernel mode time) used since the last call to QueryThreadProcessorUsage(). The result is in 100
-// nanosecond units.
-ULONGLONG Thread::QueryThreadProcessorUsage()
-{
-    LIMITED_METHOD_CONTRACT;
-
-    // Get current values for the amount of kernel and user time used by this thread over its entire lifetime.
-    FILETIME sCreationTime, sExitTime, sKernelTime, sUserTime;
-    HANDLE hThread = GetThreadHandle();
-    BOOL fResult = GetThreadTimes(hThread,
-                                  &sCreationTime,
-                                  &sExitTime,
-                                  &sKernelTime,
-                                  &sUserTime);
-    if (!fResult)
-    {
-#ifdef _DEBUG
-        ULONG error = GetLastError();
-        printf("GetThreadTimes failed: %d; handle is %p\n", error, hThread);
-        _ASSERTE(FALSE);
-#endif
-        return 0;
-    }
-
-    // Combine the user and kernel times into a single value (FILETIME is just a structure representing an
-    // unsigned int64 in two 32-bit pieces).
-    _ASSERTE(sizeof(FILETIME) == sizeof(UINT64));
-    ULONGLONG ullCurrentUsage = *(ULONGLONG*)&sKernelTime + *(ULONGLONG*)&sUserTime;
-
-    // Store the current processor usage as the new baseline, and retrieve the previous usage.
-    ULONGLONG ullPreviousUsage = VolatileLoad(&m_ullProcessorUsageBaseline);
-    if (ullPreviousUsage >= ullCurrentUsage ||
-        ullPreviousUsage != (ULONGLONG)InterlockedCompareExchange64(
-            (LONGLONG*)&m_ullProcessorUsageBaseline, 
-            (LONGLONG)ullCurrentUsage, 
-            (LONGLONG)ullPreviousUsage))
-    {
-        // another thread beat us to it, and already reported this usage.  
-        return 0; 
-    }
-
-    // The result is the difference between this value and the previous usage value.
-    return ullCurrentUsage - ullPreviousUsage;
-}
-#endif // FEATURE_APPDOMAIN_RESOURCE_MONITORING
-
 OBJECTHANDLE Thread::GetOrCreateDeserializationTracker()
 {
     CONTRACTL
diff --git a/src/vm/threads.h b/src/vm/threads.h
index 68a66c3284..6b7fe45368 100644
--- a/src/vm/threads.h
+++ b/src/vm/threads.h
@@ -4835,18 +4835,8 @@ public:
     // Holds per-thread information the debugger uses to expose locking information
     // See ThreadDebugBlockingInfo.h for more details
     ThreadDebugBlockingInfo DebugBlockingInfo;
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    // For the purposes of tracking resource usage we implement a simple cpu resource usage counter on each
-    // thread. Every time QueryThreadProcessorUsage() is invoked it returns the amount of cpu time (a
-    // combination of user and kernel mode time) used since the last call to QueryThreadProcessorUsage(). The
-    // result is in 100 nanosecond units.
-    ULONGLONG QueryThreadProcessorUsage();
 
 private:
-    // The amount of processor time (both user and kernel) in 100ns units used by this thread at the time of
-    // the last call to QueryThreadProcessorUsage().
-    ULONGLONG m_ullProcessorUsageBaseline;
-#endif // FEATURE_APPDOMAIN_RESOURCE_MONITORING
 
     // Disables pumping and thread join in RCW creation
     bool m_fDisableComObjectEagerCleanup;
@@ -4854,7 +4844,6 @@ private:
     // See ThreadStore::TriggerGCForDeadThreadsIfNecessary()
     bool m_fHasDeadThreadBeenConsideredForGCTrigger;
 
-private:
     CLRRandom m_random;
 
 public:
diff --git a/src/vm/util.cpp b/src/vm/util.cpp
index fafbf5bbb2..0a21d3da6d 100644
--- a/src/vm/util.cpp
+++ b/src/vm/util.cpp
@@ -3148,49 +3148,6 @@ BOOL DelayLoadOleaut32CheckDisabled()
 }
 #endif
 
-BOOL EnableARM()
-{
-#ifdef FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    CONTRACTL
-    {
-        NOTHROW;
-        // TODO: this should really be GC_TRIGGERS so we wouldn't need the 
-        // CONTRACT_VIOLATION below but the hosting API that calls this
-        // can be called on a COOP thread and it has a GC_NOTRIGGER contract. 
-        // We should use the AD unload thread to call this function on.
-        GC_NOTRIGGER;
-    }
-    CONTRACTL_END;
-
-    BOOL fARMEnabled = g_fEnableARM;
-
-    if (!fARMEnabled)
-    {
-        if (ThreadStore::s_pThreadStore)
-        {
-            // We need to establish the baselines for the CPU usage counting.
-            Thread *pThread = NULL;
-            CONTRACT_VIOLATION(GCViolation);
-
-            // Take the thread store lock while we enumerate threads.
-            ThreadStoreLockHolder tsl ;
-
-            while ((pThread = ThreadStore::GetThreadList(pThread)) != NULL)
-            {
-                if (pThread->IsUnstarted() || pThread->IsDead())
-                    continue;
-                pThread->QueryThreadProcessorUsage();
-            }
-        }
-        g_fEnableARM = TRUE;
-    }
-
-    return fARMEnabled;
-#else // FEATURE_APPDOMAIN_RESOURCE_MONITORING
-    return FALSE;
-#endif // FEATURE_APPDOMAIN_RESOURCE_MONITORING
-}
-
 #endif // !DACCESS_COMPILE && !CROSSGEN_COMPILE
 
 
diff --git a/src/vm/util.hpp b/src/vm/util.hpp
index 512f09f87b..d1086a9337 100644
--- a/src/vm/util.hpp
+++ b/src/vm/util.hpp
@@ -1114,11 +1114,6 @@ extern LONG g_OLEAUT32_Loaded;
 
 BOOL DbgIsExecutable(LPVOID lpMem, SIZE_T length);
 
-#ifndef DACCESS_COMPILE
-// returns if ARM was already enabled or not.
-BOOL EnableARM();
-#endif // !DACCESS_COMPILE
-
 int GetRandomInt(int maxVal);
 
 //
diff --git a/src/vm/vars.cpp b/src/vm/vars.cpp
index 8b329d4c2e..0887f2e0f1 100644
--- a/src/vm/vars.cpp
+++ b/src/vm/vars.cpp
@@ -185,8 +185,6 @@ int g_IGCTrimCommit = 0;
 
 BOOL g_fEnableETW = FALSE;
 
-BOOL g_fEnableARM = FALSE;
-
 //
 // Global state variable indicating if the EE is in its init phase.
 //
diff --git a/src/vm/vars.hpp b/src/vm/vars.hpp
index e4b790836e..25d46c2cc0 100644
--- a/src/vm/vars.hpp
+++ b/src/vm/vars.hpp
@@ -482,7 +482,6 @@ extern int g_IGCTrimCommit;
 #endif
 
 extern BOOL g_fEnableETW;
-extern BOOL g_fEnableARM;
 
 // Returns a BOOL to indicate if the runtime is active or not
 BOOL IsRuntimeActive();