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callcounting.cpp
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
#include "common.h"
#ifdef FEATURE_TIERED_COMPILATION
#include "callcounting.h"
#include "threadsuspend.h"
#ifndef DACCESS_COMPILE
extern "C" void STDCALL OnCallCountThresholdReachedStub();
#endif
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// CallCountingStub
#ifndef DACCESS_COMPILE
const PCODE CallCountingStub::TargetForThresholdReached = (PCODE)GetEEFuncEntryPoint(OnCallCountThresholdReachedStub);
#endif
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// CallCountingManager::CallCountingInfo
#ifndef DACCESS_COMPILE
CallCountingManager::CallCountingInfo::CallCountingInfo(NativeCodeVersion codeVersion)
: m_codeVersion(codeVersion),
m_callCountingStub(nullptr),
m_remainingCallCount(0),
m_stage(Stage::Disabled)
{
WRAPPER_NO_CONTRACT;
_ASSERTE(!codeVersion.IsNull());
}
CallCountingManager::CallCountingInfo *
CallCountingManager::CallCountingInfo::CreateWithCallCountingDisabled(NativeCodeVersion codeVersion)
{
CONTRACTL
{
THROWS;
GC_NOTRIGGER;
MODE_ANY;
}
CONTRACTL_END;
return new CallCountingInfo(codeVersion);
}
CallCountingManager::CallCountingInfo::CallCountingInfo(NativeCodeVersion codeVersion, CallCount callCountThreshold)
: m_codeVersion(codeVersion),
m_callCountingStub(nullptr),
m_remainingCallCount(callCountThreshold),
m_stage(Stage::StubIsNotActive)
{
WRAPPER_NO_CONTRACT;
_ASSERTE(!codeVersion.IsNull());
_ASSERTE(callCountThreshold != 0);
}
CallCountingManager::CallCountingInfo::~CallCountingInfo()
{
WRAPPER_NO_CONTRACT;
_ASSERTE(m_stage == Stage::Complete);
_ASSERTE(m_callCountingStub == nullptr);
}
#endif // !DACCESS_COMPILE
CallCountingManager::PTR_CallCountingInfo CallCountingManager::CallCountingInfo::From(PTR_CallCount remainingCallCountCell)
{
WRAPPER_NO_CONTRACT;
_ASSERTE(remainingCallCountCell != nullptr);
return PTR_CallCountingInfo(dac_cast<TADDR>(remainingCallCountCell) - offsetof(CallCountingInfo, m_remainingCallCount));
}
NativeCodeVersion CallCountingManager::CallCountingInfo::GetCodeVersion() const
{
WRAPPER_NO_CONTRACT;
return m_codeVersion;
}
#ifndef DACCESS_COMPILE
const CallCountingStub *CallCountingManager::CallCountingInfo::GetCallCountingStub() const
{
WRAPPER_NO_CONTRACT;
_ASSERTE(m_stage != Stage::Disabled);
return m_callCountingStub;
}
void CallCountingManager::CallCountingInfo::SetCallCountingStub(const CallCountingStub *callCountingStub)
{
WRAPPER_NO_CONTRACT;
_ASSERTE(g_pConfig->TieredCompilation_UseCallCountingStubs());
_ASSERTE(m_stage == Stage::StubIsNotActive);
_ASSERTE(m_callCountingStub == nullptr);
_ASSERTE(callCountingStub != nullptr);
++s_callCountingStubCount;
m_callCountingStub = callCountingStub;
}
void CallCountingManager::CallCountingInfo::ClearCallCountingStub()
{
WRAPPER_NO_CONTRACT;
_ASSERTE(m_stage == Stage::StubIsNotActive || m_stage == Stage::Complete);
_ASSERTE(m_callCountingStub != nullptr);
m_callCountingStub = nullptr;
// The total and completed stub counts are updated along with deleting stubs
}
PTR_CallCount CallCountingManager::CallCountingInfo::GetRemainingCallCountCell()
{
WRAPPER_NO_CONTRACT;
_ASSERTE(m_stage != Stage::Disabled);
//_ASSERTE(m_callCountingStub != nullptr);
return &m_remainingCallCount;
}
#endif // !DACCESS_COMPILE
CallCountingManager::CallCountingInfo::Stage CallCountingManager::CallCountingInfo::GetStage() const
{
WRAPPER_NO_CONTRACT;
return m_stage;
}
#ifndef DACCESS_COMPILE
FORCEINLINE void CallCountingManager::CallCountingInfo::SetStage(Stage stage)
{
WRAPPER_NO_CONTRACT;
_ASSERTE(m_stage != Stage::Disabled);
_ASSERTE(stage <= Stage::Complete);
switch (stage)
{
case Stage::StubIsNotActive:
_ASSERTE(m_stage == Stage::StubMayBeActive);
_ASSERTE(m_callCountingStub != nullptr);
_ASSERTE(s_activeCallCountingStubCount != 0);
--s_activeCallCountingStubCount;
break;
case Stage::StubMayBeActive:
_ASSERTE(m_callCountingStub != nullptr);
FALLTHROUGH;
case Stage::PendingCompletion:
_ASSERTE(m_stage == Stage::StubIsNotActive || m_stage == Stage::StubMayBeActive);
if (m_stage == Stage::StubIsNotActive && m_callCountingStub != nullptr)
{
++s_activeCallCountingStubCount;
}
break;
case Stage::Complete:
_ASSERTE(m_stage != Stage::Complete);
if (m_callCountingStub != nullptr)
{
if (m_stage != Stage::StubIsNotActive)
{
_ASSERTE(s_activeCallCountingStubCount != 0);
--s_activeCallCountingStubCount;
}
++s_completedCallCountingStubCount;
}
break;
default:
UNREACHABLE();
}
m_stage = stage;
}
#endif
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// CallCountingManager::CallCountingInfo::CodeVersionHashTraits
CallCountingManager::CallCountingInfo::CodeVersionHashTraits::key_t
CallCountingManager::CallCountingInfo::CodeVersionHashTraits::GetKey(const element_t &e)
{
WRAPPER_NO_CONTRACT;
return e->GetCodeVersion();
}
BOOL CallCountingManager::CallCountingInfo::CodeVersionHashTraits::Equals(const key_t &k1, const key_t &k2)
{
WRAPPER_NO_CONTRACT;
return k1 == k2;
}
CallCountingManager::CallCountingInfo::CodeVersionHashTraits::count_t
CallCountingManager::CallCountingInfo::CodeVersionHashTraits::Hash(const key_t &k)
{
WRAPPER_NO_CONTRACT;
return (count_t)dac_cast<TADDR>(k.GetMethodDesc()) + k.GetVersionId();
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// CallCountingManager::CallCountingStubAllocator
CallCountingManager::CallCountingStubAllocator::CallCountingStubAllocator() : m_heap(nullptr)
{
WRAPPER_NO_CONTRACT;
}
CallCountingManager::CallCountingStubAllocator::~CallCountingStubAllocator()
{
CONTRACTL
{
NOTHROW;
GC_NOTRIGGER;
MODE_ANY;
}
CONTRACTL_END;
#ifndef DACCESS_COMPILE
LoaderHeap *heap = m_heap;
if (heap != nullptr)
{
delete m_heap;
}
#endif
}
#ifndef DACCESS_COMPILE
void CallCountingManager::CallCountingStubAllocator::Reset()
{
WRAPPER_NO_CONTRACT;
this->~CallCountingStubAllocator();
new(this) CallCountingStubAllocator();
}
const CallCountingStub *CallCountingManager::CallCountingStubAllocator::AllocateStub(
CallCount *remainingCallCountCell,
PCODE targetForMethod)
{
CONTRACTL
{
THROWS;
GC_NOTRIGGER;
MODE_ANY;
}
CONTRACTL_END;
LoaderHeap *heap = m_heap;
if (heap == nullptr)
{
heap = AllocateHeap();
}
SIZE_T sizeInBytes = sizeof(CallCountingStub);
AllocMemHolder<void> allocationAddressHolder(heap->AllocAlignedMem(sizeInBytes, 1));
CallCountingStub *stub = (CallCountingStub*)(void*)allocationAddressHolder;
allocationAddressHolder.SuppressRelease();
stub->Initialize(targetForMethod, remainingCallCountCell);
return stub;
}
#if defined(TARGET_ARM64) && defined(TARGET_UNIX)
#define ENUM_PAGE_SIZE(size) \
extern "C" void CallCountingStubCode##size(); \
extern "C" void CallCountingStubCode##size##_End();
ENUM_PAGE_SIZES
#undef ENUM_PAGE_SIZE
#else
extern "C" void CallCountingStubCode();
extern "C" void CallCountingStubCode_End();
#endif
#ifdef TARGET_X86
extern "C" size_t CallCountingStubCode_RemainingCallCountCell_Offset;
extern "C" size_t CallCountingStubCode_TargetForMethod_Offset;
extern "C" size_t CallCountingStubCode_TargetForThresholdReached_Offset;
#define SYMBOL_VALUE(name) ((size_t)&name)
#endif
#if defined(TARGET_ARM64) && defined(TARGET_UNIX)
void (*CallCountingStub::CallCountingStubCode)();
#endif
#ifndef DACCESS_COMPILE
void CallCountingStub::StaticInitialize()
{
#if defined(TARGET_ARM64) && defined(TARGET_UNIX)
int pageSize = GetStubCodePageSize();
#define ENUM_PAGE_SIZE(size) \
case size: \
CallCountingStubCode = CallCountingStubCode##size; \
_ASSERTE((SIZE_T)((BYTE*)CallCountingStubCode##size##_End - (BYTE*)CallCountingStubCode##size) <= CallCountingStub::CodeSize); \
break;
switch (pageSize)
{
ENUM_PAGE_SIZES
default:
EEPOLICY_HANDLE_FATAL_ERROR_WITH_MESSAGE(COR_E_EXECUTIONENGINE, W("Unsupported OS page size"));
}
#undef ENUM_PAGE_SIZE
#else
_ASSERTE((SIZE_T)((BYTE*)CallCountingStubCode_End - (BYTE*)CallCountingStubCode) <= CallCountingStub::CodeSize);
#endif
}
#endif // DACCESS_COMPILE
void CallCountingStub::GenerateCodePage(BYTE* pageBase, BYTE* pageBaseRX, SIZE_T pageSize)
{
#ifdef TARGET_X86
int totalCodeSize = (pageSize / CallCountingStub::CodeSize) * CallCountingStub::CodeSize;
for (int i = 0; i < totalCodeSize; i += CallCountingStub::CodeSize)
{
memcpy(pageBase + i, (const void*)CallCountingStubCode, CallCountingStub::CodeSize);
// Set absolute addresses of the slots in the stub
BYTE* pCounterSlot = pageBaseRX + i + pageSize + offsetof(CallCountingStubData, RemainingCallCountCell);
*(BYTE**)(pageBase + i + SYMBOL_VALUE(CallCountingStubCode_RemainingCallCountCell_Offset)) = pCounterSlot;
BYTE* pTargetSlot = pageBaseRX + i + pageSize + offsetof(CallCountingStubData, TargetForMethod);
*(BYTE**)(pageBase + i + SYMBOL_VALUE(CallCountingStubCode_TargetForMethod_Offset)) = pTargetSlot;
BYTE* pCountReachedZeroSlot = pageBaseRX + i + pageSize + offsetof(CallCountingStubData, TargetForThresholdReached);
*(BYTE**)(pageBase + i + SYMBOL_VALUE(CallCountingStubCode_TargetForThresholdReached_Offset)) = pCountReachedZeroSlot;
}
#else // TARGET_X86
FillStubCodePage(pageBase, (const void*)PCODEToPINSTR((PCODE)CallCountingStubCode), CallCountingStub::CodeSize, pageSize);
#endif
}
NOINLINE LoaderHeap *CallCountingManager::CallCountingStubAllocator::AllocateHeap()
{
CONTRACTL
{
THROWS;
GC_NOTRIGGER;
MODE_ANY;
}
CONTRACTL_END;
_ASSERTE(m_heap == nullptr);
LoaderHeap *heap = new LoaderHeap(0, 0, &m_heapRangeList, UnlockedLoaderHeap::HeapKind::Interleaved, true /* fUnlocked */, CallCountingStub::GenerateCodePage, CallCountingStub::CodeSize);
m_heap = heap;
return heap;
}
#endif // !DACCESS_COMPILE
bool CallCountingManager::CallCountingStubAllocator::IsStub(TADDR entryPoint)
{
WRAPPER_NO_CONTRACT;
_ASSERTE(entryPoint != (TADDR)NULL);
return !!m_heapRangeList.IsInRange(entryPoint);
}
#ifdef DACCESS_COMPILE
void CallCountingManager::CallCountingStubAllocator::EnumerateHeapRanges(CLRDataEnumMemoryFlags flags)
{
WRAPPER_NO_CONTRACT;
m_heapRangeList.EnumMemoryRegions(flags);
}
#endif // DACCESS_COMPILE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// CallCountingManager::MethodDescForwarderStubHashTraits
CallCountingManager::MethodDescForwarderStubHashTraits::key_t
CallCountingManager::MethodDescForwarderStubHashTraits::GetKey(const element_t &e)
{
WRAPPER_NO_CONTRACT;
return e->GetMethodDesc();
}
BOOL CallCountingManager::MethodDescForwarderStubHashTraits::Equals(const key_t &k1, const key_t &k2)
{
WRAPPER_NO_CONTRACT;
return k1 == k2;
}
CallCountingManager::MethodDescForwarderStubHashTraits::count_t
CallCountingManager::MethodDescForwarderStubHashTraits::Hash(const key_t &k)
{
WRAPPER_NO_CONTRACT;
return (count_t)(size_t)k;
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// CallCountingManager::CallCountingManagerHashTraits
CallCountingManager::CallCountingManagerHashTraits::key_t
CallCountingManager::CallCountingManagerHashTraits::GetKey(const element_t &e)
{
WRAPPER_NO_CONTRACT;
return e;
}
BOOL CallCountingManager::CallCountingManagerHashTraits::Equals(const key_t &k1, const key_t &k2)
{
WRAPPER_NO_CONTRACT;
return k1 == k2;
}
CallCountingManager::CallCountingManagerHashTraits::count_t
CallCountingManager::CallCountingManagerHashTraits::Hash(const key_t &k)
{
WRAPPER_NO_CONTRACT;
return (count_t)dac_cast<TADDR>(k);
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// CallCountingManager
CallCountingManager::PTR_CallCountingManagerHash CallCountingManager::s_callCountingManagers = PTR_NULL;
COUNT_T CallCountingManager::s_callCountingStubCount = 0;
COUNT_T CallCountingManager::s_activeCallCountingStubCount = 0;
COUNT_T CallCountingManager::s_completedCallCountingStubCount = 0;
CallCountingManager::CallCountingManager()
{
CONTRACTL
{
THROWS;
GC_NOTRIGGER;
MODE_ANY;
}
CONTRACTL_END;
#ifndef DACCESS_COMPILE
CodeVersionManager::LockHolder codeVersioningLockHolder;
s_callCountingManagers->Add(this);
#endif
}
CallCountingManager::~CallCountingManager()
{
CONTRACTL
{
NOTHROW;
GC_NOTRIGGER;
MODE_ANY;
}
CONTRACTL_END;
#ifndef DACCESS_COMPILE
CodeVersionManager::LockHolder codeVersioningLockHolder;
for (auto itEnd = m_callCountingInfoByCodeVersionHash.End(), it = m_callCountingInfoByCodeVersionHash.Begin();
it != itEnd;
++it)
{
CallCountingInfo *callCountingInfo = *it;
delete callCountingInfo;
}
s_callCountingManagers->Remove(this);
#endif
}
#ifndef DACCESS_COMPILE
void CallCountingManager::StaticInitialize()
{
WRAPPER_NO_CONTRACT;
s_callCountingManagers = PTR_CallCountingManagerHash(new CallCountingManagerHash());
CallCountingStub::StaticInitialize();
}
#endif
bool CallCountingManager::IsCallCountingEnabled(NativeCodeVersion codeVersion)
{
CONTRACTL
{
NOTHROW;
GC_NOTRIGGER;
MODE_ANY;
}
CONTRACTL_END;
_ASSERTE(!codeVersion.IsNull());
_ASSERTE(codeVersion.IsDefaultVersion());
_ASSERTE(codeVersion.GetMethodDesc()->IsEligibleForTieredCompilation());
CodeVersionManager::LockHolder codeVersioningLockHolder;
PTR_CallCountingInfo callCountingInfo = m_callCountingInfoByCodeVersionHash.Lookup(codeVersion);
return callCountingInfo == NULL || callCountingInfo->GetStage() != CallCountingInfo::Stage::Disabled;
}
#ifndef DACCESS_COMPILE
void CallCountingManager::DisableCallCounting(NativeCodeVersion codeVersion)
{
CONTRACTL
{
THROWS;
GC_NOTRIGGER;
MODE_ANY;
}
CONTRACTL_END;
_ASSERTE(!codeVersion.IsNull());
_ASSERTE(codeVersion.IsDefaultVersion());
_ASSERTE(codeVersion.GetMethodDesc()->IsEligibleForTieredCompilation());
CodeVersionManager::LockHolder codeVersioningLockHolder;
CallCountingInfo *callCountingInfo = m_callCountingInfoByCodeVersionHash.Lookup(codeVersion);
if (callCountingInfo != nullptr)
{
// Call counting may already have been disabled due to the possibility of concurrent or reentering JIT of the same
// native code version of a method. The call counting info is created with call counting enabled or disabled and it
// cannot be changed thereafter for consistency in dependents of the info.
_ASSERTE(callCountingInfo->GetStage() == CallCountingInfo::Stage::Disabled);
return;
}
NewHolder<CallCountingInfo> callCountingInfoHolder = CallCountingInfo::CreateWithCallCountingDisabled(codeVersion);
m_callCountingInfoByCodeVersionHash.Add(callCountingInfoHolder);
callCountingInfoHolder.SuppressRelease();
}
// Returns true if the code entry point was updated to reflect the active code version, false otherwise. In normal paths, the
// code entry point is not updated only when the use of call counting stubs is disabled, as in that case returning to the
// prestub is necessary for further call counting. On exception, the code entry point may or may not have been updated and it's
// up to the caller to decide how to proceed.
bool CallCountingManager::SetCodeEntryPoint(
NativeCodeVersion activeCodeVersion,
PCODE codeEntryPoint,
bool wasMethodCalled,
bool *createTieringBackgroundWorkerRef)
{
CONTRACTL
{
THROWS;
GC_NOTRIGGER;
PRECONDITION(!activeCodeVersion.IsNull());
MODE_ANY;
}
CONTRACTL_END;
MethodDesc *methodDesc = activeCodeVersion.GetMethodDesc();
_ASSERTE(!methodDesc->MayHaveEntryPointSlotsToBackpatch() || MethodDescBackpatchInfoTracker::IsLockOwnedByCurrentThread());
_ASSERTE(CodeVersionManager::IsLockOwnedByCurrentThread());
_ASSERTE(
activeCodeVersion ==
methodDesc->GetCodeVersionManager()->GetActiveILCodeVersion(methodDesc).GetActiveNativeCodeVersion(methodDesc));
_ASSERTE(codeEntryPoint != (PCODE)NULL);
_ASSERTE(codeEntryPoint == activeCodeVersion.GetNativeCode());
_ASSERTE(!wasMethodCalled || createTieringBackgroundWorkerRef != nullptr);
_ASSERTE(createTieringBackgroundWorkerRef == nullptr || !*createTieringBackgroundWorkerRef);
if (!methodDesc->IsEligibleForTieredCompilation() ||
(
// For a default code version that is not tier 0, call counting will have been disabled by this time (checked
// below). Avoid the redundant and not-insignificant expense of GetOptimizationTier() on a default code version.
!activeCodeVersion.IsDefaultVersion() &&
activeCodeVersion.IsFinalTier()
) ||
!g_pConfig->TieredCompilation_CallCounting())
{
methodDesc->SetCodeEntryPoint(codeEntryPoint);
return true;
}
const CallCountingStub *callCountingStub;
CallCountingManager *callCountingManager = methodDesc->GetLoaderAllocator()->GetCallCountingManager();
CallCountingInfoByCodeVersionHash &callCountingInfoByCodeVersionHash =
callCountingManager->m_callCountingInfoByCodeVersionHash;
CallCountingInfo *callCountingInfo = callCountingInfoByCodeVersionHash.Lookup(activeCodeVersion);
do
{
if (callCountingInfo != nullptr)
{
_ASSERTE(callCountingInfo->GetCodeVersion() == activeCodeVersion);
CallCountingInfo::Stage callCountingStage = callCountingInfo->GetStage();
if (callCountingStage >= CallCountingInfo::Stage::PendingCompletion)
{
// Call counting is disabled, complete, or pending completion. The pending completion stage here would be
// relatively rare, let it be handled elsewhere.
methodDesc->SetCodeEntryPoint(codeEntryPoint);
return true;
}
_ASSERTE(!activeCodeVersion.IsFinalTier());
// If the tiering delay is active, postpone further work
if (GetAppDomain()
->GetTieredCompilationManager()
->TrySetCodeEntryPointAndRecordMethodForCallCounting(methodDesc, codeEntryPoint))
{
if (callCountingStage == CallCountingInfo::Stage::StubMayBeActive)
{
callCountingInfo->SetStage(CallCountingInfo::Stage::StubIsNotActive);
}
return true;
}
do
{
if (!wasMethodCalled)
{
break;
}
CallCount remainingCallCount = --*callCountingInfo->GetRemainingCallCountCell();
if (remainingCallCount != 0)
{
break;
}
callCountingInfo->SetStage(CallCountingInfo::Stage::PendingCompletion);
if (!activeCodeVersion.GetILCodeVersion().HasAnyOptimizedNativeCodeVersion(activeCodeVersion))
{
GetAppDomain()
->GetTieredCompilationManager()
->AsyncPromoteToTier1(activeCodeVersion, createTieringBackgroundWorkerRef);
}
methodDesc->SetCodeEntryPoint(codeEntryPoint);
callCountingInfo->SetStage(CallCountingInfo::Stage::Complete);
return true;
} while (false);
callCountingStub = callCountingInfo->GetCallCountingStub();
if (callCountingStub != nullptr)
{
break;
}
}
else
{
_ASSERTE(!activeCodeVersion.IsFinalTier());
// If the tiering delay is active, postpone further work
if (GetAppDomain()
->GetTieredCompilationManager()
->TrySetCodeEntryPointAndRecordMethodForCallCounting(methodDesc, codeEntryPoint))
{
return true;
}
CallCount callCountThreshold = g_pConfig->TieredCompilation_CallCountThreshold();
_ASSERTE(callCountThreshold != 0);
// Let's tier up all cast helpers faster than other methods. This is because we want to import them as
// direct calls in codegen and they need to be promoted earlier than their callers.
if (methodDesc->GetMethodTable() == g_pCastHelpers)
{
callCountThreshold = max<CallCount>(1, (CallCount)(callCountThreshold / 2));
}
NewHolder<CallCountingInfo> callCountingInfoHolder = new CallCountingInfo(activeCodeVersion, callCountThreshold);
callCountingInfoByCodeVersionHash.Add(callCountingInfoHolder);
callCountingInfo = callCountingInfoHolder.Extract();
}
if (!g_pConfig->TieredCompilation_UseCallCountingStubs())
{
// Call counting is not yet complete, so reset or don't set the code entry point to continue counting calls
if (wasMethodCalled)
{
return false;
}
// This path is reached after activating a code version when publishing its code entry point. The method may
// currently be pointing to the code entry point of a different code version, so an explicit reset is necessary.
methodDesc->ResetCodeEntryPoint();
return true;
}
callCountingStub =
callCountingManager->m_callCountingStubAllocator.AllocateStub(
callCountingInfo->GetRemainingCallCountCell(),
codeEntryPoint);
callCountingInfo->SetCallCountingStub(callCountingStub);
} while (false);
PCODE callCountingCodeEntryPoint = callCountingStub->GetEntryPoint();
if (methodDesc->MayHaveEntryPointSlotsToBackpatch())
{
// The call counting stub should not be the entry point that is called first in the process of a call
// - Stubs should be deletable. Many methods will have call counting stubs associated with them, and although the memory
// involved is typically insignificant compared to the average memory overhead per method, by steady-state it would
// otherwise be unnecessary memory overhead serving no purpose.
// - In order to be able to delete a stub, the jitted code of a method cannot be allowed to load the stub as the entry
// point of a callee into a register in a GC-safe point that allows for the stub to be deleted before the register is
// reused to call the stub. On some processor architectures, perhaps the JIT can guarantee that it would not load the
// entry point into a register before the call, but this is not possible on arm32 or arm64. Rather, perhaps the
// region containing the load and call would not be considered GC-safe. Calls are considered GC-safe points, and this
// may cause many methods that are currently fully interruptible to have to be partially interruptible and record
// extra GC info instead. This would be nontrivial and there would be tradeoffs.
// - For any method that may have an entry point slot that would be backpatched with the call counting stub's entry
// point, a small forwarder stub (precode) is created. The forwarder stub has loader allocator lifetime and forwards to
// the larger call counting stub. This is a simple solution for now and seems to have negligible impact.
// - Reusing FuncPtrStubs was considered. FuncPtrStubs are currently not used as a code entry point for a virtual or
// interface method and may be bypassed. For example, a call may call through the vtable slot, or a devirtualized call
// may call through a FuncPtrStub. The target of a FuncPtrStub is a code entry point and is backpatched when a
// method's active code entry point changes. Mixing the current use of FuncPtrStubs with the use as a forwarder for
// call counting does not seem trivial and would likely complicate its use. There may not be much gain in reusing
// FuncPtrStubs, as typically, they are created for only a small percentage of virtual/interface methods.
MethodDescForwarderStubHash &methodDescForwarderStubHash = callCountingManager->m_methodDescForwarderStubHash;
Precode *forwarderStub = methodDescForwarderStubHash.Lookup(methodDesc);
if (forwarderStub == nullptr)
{
AllocMemTracker forwarderStubAllocationTracker;
forwarderStub =
Precode::Allocate(
methodDesc->GetPrecodeType(),
methodDesc,
methodDesc->GetLoaderAllocator(),
&forwarderStubAllocationTracker);
methodDescForwarderStubHash.Add(forwarderStub);
forwarderStubAllocationTracker.SuppressRelease();
}
forwarderStub->SetTargetInterlocked(callCountingCodeEntryPoint, false);
callCountingCodeEntryPoint = forwarderStub->GetEntryPoint();
}
else
{
_ASSERTE(methodDesc->IsVersionableWithPrecode());
}
methodDesc->SetCodeEntryPoint(callCountingCodeEntryPoint);
callCountingInfo->SetStage(CallCountingInfo::Stage::StubMayBeActive);
return true;
}
extern "C" PCODE STDCALL OnCallCountThresholdReached(TransitionBlock *transitionBlock, TADDR stubIdentifyingToken)
{
WRAPPER_NO_CONTRACT;
return CallCountingManager::OnCallCountThresholdReached(transitionBlock, stubIdentifyingToken);
}
PCODE CallCountingManager::OnCallCountThresholdReached(TransitionBlock *transitionBlock, TADDR stubIdentifyingToken)
{
STATIC_CONTRACT_THROWS;
STATIC_CONTRACT_GC_TRIGGERS;
STATIC_CONTRACT_MODE_COOPERATIVE;
PCODE codeEntryPoint = 0;
PreserveLastErrorHolder preserveLastError;
MAKE_CURRENT_THREAD_AVAILABLE();
#ifdef _DEBUG
Thread::ObjectRefFlush(CURRENT_THREAD);
#endif
// Get the code version from the call counting stub/info in cooperative GC mode to synchronize with deletion. The stub/info
// may be deleted only when the runtime is suspended, so when we are in cooperative GC mode it is safe to read from them.
NativeCodeVersion codeVersion =
CallCountingInfo::From(CallCountingStub::From(stubIdentifyingToken)->GetRemainingCallCountCell())->GetCodeVersion();
MethodDesc *methodDesc = codeVersion.GetMethodDesc();
CallCountingHelperFrame callCountingFrame(transitionBlock, methodDesc);
CallCountingHelperFrame *frame = &callCountingFrame;
frame->Push(CURRENT_THREAD);
INSTALL_MANAGED_EXCEPTION_DISPATCHER;
INSTALL_UNWIND_AND_CONTINUE_HANDLER;
// The switch to preemptive GC mode no longer guarantees that the stub/info will be valid. Only the code version will be
// used going forward under appropriate locking to synchronize further with deletion.
GCX_PREEMP_THREAD_EXISTS(CURRENT_THREAD);
_ASSERTE(!codeVersion.IsFinalTier());
codeEntryPoint = codeVersion.GetNativeCode();
do
{
{
CallCountingManager *callCountingManager = methodDesc->GetLoaderAllocator()->GetCallCountingManager();
CodeVersionManager::LockHolder codeVersioningLockHolder;
CallCountingInfo *callCountingInfo = callCountingManager->m_callCountingInfoByCodeVersionHash.Lookup(codeVersion);
if (callCountingInfo == nullptr)
{
break;
}
CallCountingInfo::Stage callCountingStage = callCountingInfo->GetStage();
if (callCountingStage >= CallCountingInfo::Stage::PendingCompletion)
{
break;
}
// Fully completing call counting for a method is relative expensive. Call counting with stubs is relatively cheap.
// Since many methods will typically reach the call count threshold at roughly the same time (a perf spike),
// delegate as much of the overhead as possible to the background. This significantly decreases the degree of the
// perf spike.
callCountingManager->m_callCountingInfosPendingCompletion.Append(callCountingInfo);
callCountingInfo->SetStage(CallCountingInfo::Stage::PendingCompletion);
}
GetAppDomain()->GetTieredCompilationManager()->AsyncCompleteCallCounting();
} while (false);
UNINSTALL_UNWIND_AND_CONTINUE_HANDLER;
UNINSTALL_MANAGED_EXCEPTION_DISPATCHER;
frame->Pop(CURRENT_THREAD);
return codeEntryPoint;
}
COUNT_T CallCountingManager::GetCountOfCodeVersionsPendingCompletion()
{
CONTRACTL
{
NOTHROW;
GC_NOTRIGGER;
MODE_PREEMPTIVE;
}
CONTRACTL_END;
COUNT_T count = 0;
CodeVersionManager::LockHolder codeVersioningLockHolder;
for (auto itEnd = s_callCountingManagers->End(), it = s_callCountingManagers->Begin(); it != itEnd; ++it)
{
CallCountingManager *callCountingManager = *it;
count += callCountingManager->m_callCountingInfosPendingCompletion.GetCount();
}
return count;
}
void CallCountingManager::CompleteCallCounting()
{
CONTRACTL
{
THROWS;
GC_TRIGGERS;
MODE_PREEMPTIVE;
}
CONTRACTL_END;
_ASSERTE(GetThreadNULLOk() == TieredCompilationManager::GetBackgroundWorkerThread());
AppDomain *appDomain = GetAppDomain();
TieredCompilationManager *tieredCompilationManager = appDomain->GetTieredCompilationManager();
CodeVersionManager *codeVersionManager = appDomain->GetCodeVersionManager();
MethodDescBackpatchInfoTracker::ConditionalLockHolder slotBackpatchLockHolder;
CodeVersionManager::LockHolder codeVersioningLockHolder;
for (auto itEnd = s_callCountingManagers->End(), it = s_callCountingManagers->Begin(); it != itEnd; ++it)
{
CallCountingManager *callCountingManager = *it;
SArray<CallCountingInfo *> &callCountingInfosPendingCompletion =
callCountingManager->m_callCountingInfosPendingCompletion;
COUNT_T callCountingInfoCount = callCountingInfosPendingCompletion.GetCount();
if (callCountingInfoCount == 0)
{
continue;
}
CallCountingInfo **callCountingInfos = callCountingInfosPendingCompletion.GetElements();
for (COUNT_T i = 0; i < callCountingInfoCount; ++i)
{
CallCountingInfo *callCountingInfo = callCountingInfos[i];
CallCountingInfo::Stage callCountingStage = callCountingInfo->GetStage();
if (callCountingStage != CallCountingInfo::Stage::PendingCompletion)
{
continue;
}
NativeCodeVersion codeVersion = callCountingInfo->GetCodeVersion();
MethodDesc *methodDesc = codeVersion.GetMethodDesc();
_ASSERTE(codeVersionManager == methodDesc->GetCodeVersionManager());
EX_TRY
{
if (!codeVersion.GetILCodeVersion().HasAnyOptimizedNativeCodeVersion(codeVersion))
{
bool createTieringBackgroundWorker = false;
tieredCompilationManager->AsyncPromoteToTier1(codeVersion, &createTieringBackgroundWorker);
_ASSERTE(!createTieringBackgroundWorker); // the current thread is the background worker thread
}
// The active code version may have changed externally after the call counting stub was activated,
// deactivating the call counting stub without our knowledge. Check the active code version and determine
// what needs to be done.
NativeCodeVersion activeCodeVersion =
codeVersionManager->GetActiveILCodeVersion(methodDesc).GetActiveNativeCodeVersion(methodDesc);
do
{
if (activeCodeVersion == codeVersion)
{
methodDesc->SetCodeEntryPoint(activeCodeVersion.GetNativeCode());
break;
}
// There is at least one case where the IL code version is changed inside the code versioning lock, the
// lock is released and reacquired, then the method's code entry point is reset. So if this path is
// reached between those locks, the method would still be pointing to the call counting stub. Once the
// stub is marked as complete, it may be deleted, so in all cases update the method's code entry point
// to ensure that the method is no longer pointing to the call counting stub.
if (!activeCodeVersion.IsNull())
{
PCODE activeNativeCode = activeCodeVersion.GetNativeCode();
if (activeNativeCode != 0)
{
methodDesc->SetCodeEntryPoint(activeNativeCode);
break;
}
}
methodDesc->ResetCodeEntryPoint();
} while (false);
callCountingInfo->SetStage(CallCountingInfo::Stage::Complete);
}
EX_CATCH
{
// Avoid abandoning call counting completion for all recorded call counting infos on exception. Since this
// is happening on a background thread, following the general policy so far, the exception will be caught,
// logged, and ignored anyway, so make an attempt to complete call counting for each item. Individual items
// that fail will result in those code versions not getting promoted (similar to elsewhere).
STRESS_LOG1(LF_TIEREDCOMPILATION, LL_WARNING, "CallCountingManager::CompleteCallCounting: "
"Exception, hr=0x%x\n",
GET_EXCEPTION()->GetHR());
}
EX_END_CATCH(RethrowTerminalExceptions);
}
callCountingInfosPendingCompletion.Clear();
if (callCountingInfosPendingCompletion.GetAllocation() > 64)
{
callCountingInfosPendingCompletion.Trim();
EX_TRY
{
callCountingInfosPendingCompletion.Preallocate(64);
}
EX_CATCH
{
}
EX_END_CATCH(RethrowTerminalExceptions);
}
}
}
void CallCountingManager::StopAndDeleteAllCallCountingStubs()
{
CONTRACTL
{
THROWS;
GC_TRIGGERS;
MODE_PREEMPTIVE;
}
CONTRACTL_END;
_ASSERTE(GetThreadNULLOk() == TieredCompilationManager::GetBackgroundWorkerThread());
// If a number of call counting stubs have completed, we can try to delete them to reclaim some memory. Deleting
// involves suspending the runtime and will delete all call counting stubs, and after that some call counting stubs may
// be recreated in the foreground. The threshold is to decrease the impact of both of those overheads.
COUNT_T deleteCallCountingStubsAfter = g_pConfig->TieredCompilation_DeleteCallCountingStubsAfter();
if (deleteCallCountingStubsAfter == 0 || s_completedCallCountingStubCount < deleteCallCountingStubsAfter)
{
return;
}
TieredCompilationManager *tieredCompilationManager = GetAppDomain()->GetTieredCompilationManager();
ThreadSuspend::SuspendEE(ThreadSuspend::SUSPEND_OTHER);
struct AutoRestartEE
{
~AutoRestartEE()
{
WRAPPER_NO_CONTRACT;
ThreadSuspend::RestartEE(false, true);
}
} autoRestartEE;
MethodDescBackpatchInfoTracker::ConditionalLockHolder slotBackpatchLockHolder;