Modified revert of "Add couple DexCache read-barriers."
Remove the DexCache read-barriers again (the revert) since
there is measurable performance difference in app startup (~1%).
It turns out they are on very hot path in the interpreter.
The lazy array initialization made the DexCache fields mutable.
However, instead of the read-barriers, we can just ensure we get
the right to-space object on the array-initialization slow path.
Test: test.py -b -r --host
Change-Id: I3f0123141e9a7875a26f088bff68d50641b66883
diff --git a/runtime/class_linker-inl.h b/runtime/class_linker-inl.h
index 26c422b..e51d5a7 100644
--- a/runtime/class_linker-inl.h
+++ b/runtime/class_linker-inl.h
@@ -70,7 +70,10 @@
ArtField* referrer) {
Thread::PoisonObjectPointersIfDebug();
DCHECK(!Thread::Current()->IsExceptionPending());
- ObjPtr<mirror::String> resolved = referrer->GetDexCache()->GetResolvedString(string_idx);
+ // We do not need the read barrier for getting the DexCache for the initial resolved type
+ // lookup as both from-space and to-space copies point to the same native resolved types array.
+ ObjPtr<mirror::String> resolved =
+ referrer->GetDexCache<kWithoutReadBarrier>()->GetResolvedString(string_idx);
if (resolved == nullptr) {
resolved = DoResolveString(string_idx, referrer->GetDexCache());
}
@@ -81,7 +84,10 @@
ArtMethod* referrer) {
Thread::PoisonObjectPointersIfDebug();
DCHECK(!Thread::Current()->IsExceptionPending());
- ObjPtr<mirror::String> resolved = referrer->GetDexCache()->GetResolvedString(string_idx);
+ // We do not need the read barrier for getting the DexCache for the initial resolved type
+ // lookup as both from-space and to-space copies point to the same native resolved types array.
+ ObjPtr<mirror::String> resolved =
+ referrer->GetDexCache<kWithoutReadBarrier>()->GetResolvedString(string_idx);
if (resolved == nullptr) {
resolved = DoResolveString(string_idx, referrer->GetDexCache());
}
@@ -116,8 +122,10 @@
Thread::Current()->PoisonObjectPointers();
}
DCHECK(!Thread::Current()->IsExceptionPending());
+ // We do not need the read barrier for getting the DexCache for the initial resolved type
+ // lookup as both from-space and to-space copies point to the same native resolved types array.
ObjPtr<mirror::Class> resolved_type =
- referrer->GetDexCache<kDefaultVerifyFlags>()->GetResolvedType(type_idx);
+ referrer->GetDexCache<kDefaultVerifyFlags, kWithoutReadBarrier>()->GetResolvedType(type_idx);
if (resolved_type == nullptr) {
resolved_type = DoResolveType(type_idx, referrer);
}
@@ -128,7 +136,10 @@
ArtField* referrer) {
Thread::PoisonObjectPointersIfDebug();
DCHECK(!Thread::Current()->IsExceptionPending());
- ObjPtr<mirror::Class> resolved_type = referrer->GetDexCache()->GetResolvedType(type_idx);
+ // We do not need the read barrier for getting the DexCache for the initial resolved type
+ // lookup as both from-space and to-space copies point to the same native resolved types array.
+ ObjPtr<mirror::Class> resolved_type =
+ referrer->GetDexCache<kWithoutReadBarrier>()->GetResolvedType(type_idx);
if (UNLIKELY(resolved_type == nullptr)) {
resolved_type = DoResolveType(type_idx, referrer);
}
@@ -139,7 +150,10 @@
ArtMethod* referrer) {
Thread::PoisonObjectPointersIfDebug();
DCHECK(!Thread::Current()->IsExceptionPending());
- ObjPtr<mirror::Class> resolved_type = referrer->GetDexCache()->GetResolvedType(type_idx);
+ // We do not need the read barrier for getting the DexCache for the initial resolved type
+ // lookup as both from-space and to-space copies point to the same native resolved types array.
+ ObjPtr<mirror::Class> resolved_type =
+ referrer->GetDexCache<kWithoutReadBarrier>()->GetResolvedType(type_idx);
if (UNLIKELY(resolved_type == nullptr)) {
resolved_type = DoResolveType(type_idx, referrer);
}
@@ -161,8 +175,10 @@
inline ObjPtr<mirror::Class> ClassLinker::LookupResolvedType(dex::TypeIndex type_idx,
ObjPtr<mirror::Class> referrer) {
+ // We do not need the read barrier for getting the DexCache for the initial resolved type
+ // lookup as both from-space and to-space copies point to the same native resolved types array.
ObjPtr<mirror::Class> type =
- referrer->GetDexCache<kDefaultVerifyFlags>()->GetResolvedType(type_idx);
+ referrer->GetDexCache<kDefaultVerifyFlags, kWithoutReadBarrier>()->GetResolvedType(type_idx);
if (type == nullptr) {
type = DoLookupResolvedType(type_idx, referrer);
}
@@ -171,7 +187,10 @@
inline ObjPtr<mirror::Class> ClassLinker::LookupResolvedType(dex::TypeIndex type_idx,
ArtField* referrer) {
- ObjPtr<mirror::Class> type = referrer->GetDexCache()->GetResolvedType(type_idx);
+ // We do not need the read barrier for getting the DexCache for the initial resolved type
+ // lookup as both from-space and to-space copies point to the same native resolved types array.
+ ObjPtr<mirror::Class> type =
+ referrer->GetDexCache<kWithoutReadBarrier>()->GetResolvedType(type_idx);
if (type == nullptr) {
type = DoLookupResolvedType(type_idx, referrer->GetDeclaringClass());
}
@@ -180,7 +199,10 @@
inline ObjPtr<mirror::Class> ClassLinker::LookupResolvedType(dex::TypeIndex type_idx,
ArtMethod* referrer) {
- ObjPtr<mirror::Class> type = referrer->GetDexCache()->GetResolvedType(type_idx);
+ // We do not need the read barrier for getting the DexCache for the initial resolved type
+ // lookup as both from-space and to-space copies point to the same native resolved types array.
+ ObjPtr<mirror::Class> type =
+ referrer->GetDexCache<kWithoutReadBarrier>()->GetResolvedType(type_idx);
if (type == nullptr) {
type = DoLookupResolvedType(type_idx, referrer->GetDeclaringClass());
}
@@ -289,7 +311,10 @@
// lookup in the context of the original method from where it steals the code.
// However, we delay the GetInterfaceMethodIfProxy() until needed.
DCHECK(!referrer->IsProxyMethod() || referrer->IsConstructor());
- ArtMethod* resolved_method = referrer->GetDexCache()->GetResolvedMethod(method_idx);
+ // We do not need the read barrier for getting the DexCache for the initial resolved method
+ // lookup as both from-space and to-space copies point to the same native resolved methods array.
+ ArtMethod* resolved_method = referrer->GetDexCache<kWithoutReadBarrier>()->GetResolvedMethod(
+ method_idx);
if (resolved_method == nullptr) {
return nullptr;
}
@@ -339,7 +364,10 @@
// However, we delay the GetInterfaceMethodIfProxy() until needed.
DCHECK(!referrer->IsProxyMethod() || referrer->IsConstructor());
Thread::PoisonObjectPointersIfDebug();
- ArtMethod* resolved_method = referrer->GetDexCache()->GetResolvedMethod(method_idx);
+ // We do not need the read barrier for getting the DexCache for the initial resolved method
+ // lookup as both from-space and to-space copies point to the same native resolved methods array.
+ ArtMethod* resolved_method = referrer->GetDexCache<kWithoutReadBarrier>()->GetResolvedMethod(
+ method_idx);
DCHECK(resolved_method == nullptr || !resolved_method->IsRuntimeMethod());
if (UNLIKELY(resolved_method == nullptr)) {
referrer = referrer->GetInterfaceMethodIfProxy(image_pointer_size_);
@@ -502,7 +530,10 @@
inline ArtField* ClassLinker::LookupResolvedField(uint32_t field_idx,
ArtMethod* referrer,
bool is_static) {
- ArtField* field = referrer->GetDexCache()->GetResolvedField(field_idx);
+ // We do not need the read barrier for getting the DexCache for the initial resolved field
+ // lookup as both from-space and to-space copies point to the same native resolved fields array.
+ ArtField* field = referrer->GetDexCache<kWithoutReadBarrier>()->GetResolvedField(
+ field_idx);
if (field == nullptr) {
referrer = referrer->GetInterfaceMethodIfProxy(image_pointer_size_);
ObjPtr<mirror::ClassLoader> class_loader = referrer->GetDeclaringClass()->GetClassLoader();
@@ -515,7 +546,10 @@
ArtMethod* referrer,
bool is_static) {
Thread::PoisonObjectPointersIfDebug();
- ArtField* resolved_field = referrer->GetDexCache()->GetResolvedField(field_idx);
+ // We do not need the read barrier for getting the DexCache for the initial resolved field
+ // lookup as both from-space and to-space copies point to the same native resolved fields array.
+ ArtField* resolved_field = referrer->GetDexCache<kWithoutReadBarrier>()->GetResolvedField(
+ field_idx);
if (UNLIKELY(resolved_field == nullptr)) {
StackHandleScope<2> hs(Thread::Current());
referrer = referrer->GetInterfaceMethodIfProxy(image_pointer_size_);
diff --git a/runtime/mirror/dex_cache-inl.h b/runtime/mirror/dex_cache-inl.h
index a8c2a75..31f2bd2 100644
--- a/runtime/mirror/dex_cache-inl.h
+++ b/runtime/mirror/dex_cache-inl.h
@@ -54,24 +54,29 @@
template<typename T, size_t kMaxCacheSize>
T* DexCache::AllocArray(MemberOffset obj_offset, MemberOffset num_offset, size_t num) {
- ReadBarrier::AssertToSpaceInvariant(this);
num = std::min<size_t>(num, kMaxCacheSize);
if (num == 0) {
return nullptr;
}
+ mirror::DexCache* dex_cache = this;
+ if (kUseReadBarrier && Thread::Current()->GetIsGcMarking()) {
+ // Several code paths use DexCache without read-barrier for performance.
+ // We have to check the "to-space" object here to avoid allocating twice.
+ dex_cache = reinterpret_cast<DexCache*>(ReadBarrier::Mark(dex_cache));
+ }
Thread* self = Thread::Current();
ClassLinker* linker = Runtime::Current()->GetClassLinker();
LinearAlloc* alloc = linker->GetOrCreateAllocatorForClassLoader(GetClassLoader());
MutexLock mu(self, *Locks::dex_cache_lock_); // Avoid allocation by multiple threads.
- T* array = GetFieldPtr64<T*>(obj_offset);
+ T* array = dex_cache->GetFieldPtr64<T*>(obj_offset);
if (array != nullptr) {
DCHECK(alloc->Contains(array));
return array; // Other thread just allocated the array.
}
array = reinterpret_cast<T*>(alloc->AllocAlign16(self, RoundUp(num * sizeof(T), 16)));
InitializeArray(array); // Ensure other threads see the array initialized.
- SetField32Volatile<false, false>(num_offset, num);
- SetField64Volatile<false, false>(obj_offset, reinterpret_cast64<uint64_t>(array));
+ dex_cache->SetField32Volatile<false, false>(num_offset, num);
+ dex_cache->SetField64Volatile<false, false>(obj_offset, reinterpret_cast64<uint64_t>(array));
return array;
}