/* * Copyright (C) 2011 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #ifndef ART_RUNTIME_INTERN_TABLE_H_ #define ART_RUNTIME_INTERN_TABLE_H_ #include #include "atomic.h" #include "base/allocator.h" #include "base/hash_set.h" #include "base/mutex.h" #include "gc_root.h" #include "gc/weak_root_state.h" #include "object_callbacks.h" namespace art { namespace gc { namespace space { class ImageSpace; } // namespace space } // namespace gc enum VisitRootFlags : uint8_t; namespace mirror { class String; } // namespace mirror class Transaction; /** * Used to intern strings. * * There are actually two tables: one that holds strong references to its strings, and one that * holds weak references. The former is used for string literals, for which there is an effective * reference from the constant pool. The latter is used for strings interned at runtime via * String.intern. Some code (XML parsers being a prime example) relies on being able to intern * arbitrarily many strings for the duration of a parse without permanently increasing the memory * footprint. */ class InternTable { public: InternTable(); // Interns a potentially new string in the 'strong' table. May cause thread suspension. mirror::String* InternStrong(int32_t utf16_length, const char* utf8_data) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Roles::uninterruptible_); // Only used by image writer. Special version that may not cause thread suspension since the GC // can not be running while we are doing image writing. Maybe be called while while holding a // lock since there will not be thread suspension. mirror::String* InternStrongImageString(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_); // Interns a potentially new string in the 'strong' table. May cause thread suspension. mirror::String* InternStrong(const char* utf8_data) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Roles::uninterruptible_); // Interns a potentially new string in the 'strong' table. May cause thread suspension. mirror::String* InternStrong(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Roles::uninterruptible_); // Interns a potentially new string in the 'weak' table. May cause thread suspension. mirror::String* InternWeak(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Roles::uninterruptible_); void SweepInternTableWeaks(IsMarkedVisitor* visitor) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Locks::intern_table_lock_); bool ContainsWeak(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Locks::intern_table_lock_); // Total number of interned strings. size_t Size() const REQUIRES(!Locks::intern_table_lock_); // Total number of weakly live interned strings. size_t StrongSize() const REQUIRES(!Locks::intern_table_lock_); // Total number of strongly live interned strings. size_t WeakSize() const REQUIRES(!Locks::intern_table_lock_); void VisitRoots(RootVisitor* visitor, VisitRootFlags flags) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Locks::intern_table_lock_); void DumpForSigQuit(std::ostream& os) const REQUIRES(!Locks::intern_table_lock_); void BroadcastForNewInterns() SHARED_REQUIRES(Locks::mutator_lock_); // Adds all of the resolved image strings from the image space into the intern table. The // advantage of doing this is preventing expensive DexFile::FindStringId calls. void AddImageStringsToTable(gc::space::ImageSpace* image_space) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Locks::intern_table_lock_); // Copy the post zygote tables to pre zygote to save memory by preventing dirty pages. void SwapPostZygoteWithPreZygote() SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Locks::intern_table_lock_); // Add an intern table which was serialized to the image. void AddImageInternTable(gc::space::ImageSpace* image_space) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Locks::intern_table_lock_); // Read the intern table from memory. The elements aren't copied, the intern hash set data will // point to somewhere within ptr. Only reads the strong interns. size_t ReadFromMemory(const uint8_t* ptr) REQUIRES(!Locks::intern_table_lock_) SHARED_REQUIRES(Locks::mutator_lock_); // Write the post zygote intern table to a pointer. Only writes the strong interns since it is // expected that there is no weak interns since this is called from the image writer. size_t WriteToMemory(uint8_t* ptr) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(!Locks::intern_table_lock_); // Change the weak root state. May broadcast to waiters. void ChangeWeakRootState(gc::WeakRootState new_state) REQUIRES(!Locks::intern_table_lock_); private: class StringHashEquals { public: std::size_t operator()(const GcRoot& root) const NO_THREAD_SAFETY_ANALYSIS; bool operator()(const GcRoot& a, const GcRoot& b) const NO_THREAD_SAFETY_ANALYSIS; }; class GcRootEmptyFn { public: void MakeEmpty(GcRoot& item) const { item = GcRoot(); } bool IsEmpty(const GcRoot& item) const { return item.IsNull(); } }; // Table which holds pre zygote and post zygote interned strings. There is one instance for // weak interns and strong interns. class Table { public: Table(); mirror::String* Find(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); void Insert(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); void Remove(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); void VisitRoots(RootVisitor* visitor) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); void SweepWeaks(IsMarkedVisitor* visitor) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); void SwapPostZygoteWithPreZygote() REQUIRES(Locks::intern_table_lock_); size_t Size() const REQUIRES(Locks::intern_table_lock_); // Read pre zygote table is called from ReadFromMemory which happens during runtime creation // when we load the image intern table. Returns how many bytes were read. size_t ReadIntoPreZygoteTable(const uint8_t* ptr) REQUIRES(Locks::intern_table_lock_) SHARED_REQUIRES(Locks::mutator_lock_); // The image writer calls WritePostZygoteTable through WriteToMemory, it writes the interns in // the post zygote table. Returns how many bytes were written. size_t WriteFromPostZygoteTable(uint8_t* ptr) REQUIRES(Locks::intern_table_lock_) SHARED_REQUIRES(Locks::mutator_lock_); private: typedef HashSet, GcRootEmptyFn, StringHashEquals, StringHashEquals, TrackingAllocator, kAllocatorTagInternTable>> UnorderedSet; void SweepWeaks(UnorderedSet* set, IsMarkedVisitor* visitor) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); // We call SwapPostZygoteWithPreZygote when we create the zygote to reduce private dirty pages // caused by modifying the zygote intern table hash table. The pre zygote table are the // interned strings which were interned before we created the zygote space. Post zygote is self // explanatory. UnorderedSet pre_zygote_table_; UnorderedSet post_zygote_table_; }; // Insert if non null, otherwise return null. Must be called holding the mutator lock. // If holding_locks is true, then we may also hold other locks. If holding_locks is true, then we // require GC is not running since it is not safe to wait while holding locks. mirror::String* Insert(mirror::String* s, bool is_strong, bool holding_locks) REQUIRES(!Locks::intern_table_lock_) SHARED_REQUIRES(Locks::mutator_lock_); mirror::String* LookupStrong(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); mirror::String* LookupWeak(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); mirror::String* InsertStrong(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); mirror::String* InsertWeak(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); void RemoveStrong(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); void RemoveWeak(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); // Transaction rollback access. mirror::String* LookupStringFromImage(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); mirror::String* InsertStrongFromTransaction(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); mirror::String* InsertWeakFromTransaction(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); void RemoveStrongFromTransaction(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); void RemoveWeakFromTransaction(mirror::String* s) SHARED_REQUIRES(Locks::mutator_lock_) REQUIRES(Locks::intern_table_lock_); size_t ReadFromMemoryLocked(const uint8_t* ptr) REQUIRES(Locks::intern_table_lock_) SHARED_REQUIRES(Locks::mutator_lock_); // Change the weak root state. May broadcast to waiters. void ChangeWeakRootStateLocked(gc::WeakRootState new_state) REQUIRES(Locks::intern_table_lock_); // Wait until we can read weak roots. void WaitUntilAccessible(Thread* self) REQUIRES(Locks::intern_table_lock_) SHARED_REQUIRES(Locks::mutator_lock_); bool image_added_to_intern_table_ GUARDED_BY(Locks::intern_table_lock_); bool log_new_roots_ GUARDED_BY(Locks::intern_table_lock_); ConditionVariable weak_intern_condition_ GUARDED_BY(Locks::intern_table_lock_); // Since this contains (strong) roots, they need a read barrier to // enable concurrent intern table (strong) root scan. Do not // directly access the strings in it. Use functions that contain // read barriers. Table strong_interns_ GUARDED_BY(Locks::intern_table_lock_); std::vector> new_strong_intern_roots_ GUARDED_BY(Locks::intern_table_lock_); // Since this contains (weak) roots, they need a read barrier. Do // not directly access the strings in it. Use functions that contain // read barriers. Table weak_interns_ GUARDED_BY(Locks::intern_table_lock_); // Weak root state, used for concurrent system weak processing and more. gc::WeakRootState weak_root_state_ GUARDED_BY(Locks::intern_table_lock_); friend class Transaction; DISALLOW_COPY_AND_ASSIGN(InternTable); }; } // namespace art #endif // ART_RUNTIME_INTERN_TABLE_H_