| // Protocol Buffers - Google's data interchange format |
| // Copyright 2008 Google Inc. All rights reserved. |
| // https://developers.google.com/protocol-buffers/ |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following disclaimer |
| // in the documentation and/or other materials provided with the |
| // distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived from |
| // this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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| // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| // This file defines an Arena allocator for better allocation performance. |
| |
| #ifndef GOOGLE_PROTOBUF_ARENA_IMPL_H__ |
| #define GOOGLE_PROTOBUF_ARENA_IMPL_H__ |
| |
| #include <atomic> |
| #include <limits> |
| #include <typeinfo> |
| |
| #include <google/protobuf/stubs/common.h> |
| #include <google/protobuf/stubs/logging.h> |
| |
| #ifdef ADDRESS_SANITIZER |
| #include <sanitizer/asan_interface.h> |
| #endif // ADDRESS_SANITIZER |
| |
| #include <google/protobuf/port_def.inc> |
| |
| |
| namespace google { |
| namespace protobuf { |
| namespace internal { |
| |
| inline constexpr size_t AlignUpTo8(size_t n) { |
| // Align n to next multiple of 8 (from Hacker's Delight, Chapter 3.) |
| return (n + 7) & static_cast<size_t>(-8); |
| } |
| |
| using LifecycleIdAtomic = uint64_t; |
| |
| // MetricsCollector collects stats for a particular arena. |
| class PROTOBUF_EXPORT ArenaMetricsCollector { |
| public: |
| ArenaMetricsCollector(bool record_allocs) : record_allocs_(record_allocs) {} |
| |
| // Invoked when the arena is about to be destroyed. This method will |
| // typically finalize any metric collection and delete the collector. |
| // space_allocated is the space used by the arena. |
| virtual void OnDestroy(uint64 space_allocated) = 0; |
| |
| // OnReset() is called when the associated arena is reset. |
| // space_allocated is the space used by the arena just before the reset. |
| virtual void OnReset(uint64 space_allocated) = 0; |
| |
| // OnAlloc is called when an allocation happens. |
| // type_info is promised to be static - its lifetime extends to |
| // match program's lifetime (It is given by typeid operator). |
| // Note: typeid(void) will be passed as allocated_type every time we |
| // intentionally want to avoid monitoring an allocation. (i.e. internal |
| // allocations for managing the arena) |
| virtual void OnAlloc(const std::type_info* allocated_type, |
| uint64 alloc_size) = 0; |
| |
| // Does OnAlloc() need to be called? If false, metric collection overhead |
| // will be reduced since we will not do extra work per allocation. |
| bool RecordAllocs() { return record_allocs_; } |
| |
| protected: |
| // This class is destructed by the call to OnDestroy(). |
| ~ArenaMetricsCollector() = default; |
| const bool record_allocs_; |
| }; |
| |
| struct AllocationPolicy { |
| static constexpr size_t kDefaultStartBlockSize = 256; |
| static constexpr size_t kDefaultMaxBlockSize = 8192; |
| |
| size_t start_block_size = kDefaultStartBlockSize; |
| size_t max_block_size = kDefaultMaxBlockSize; |
| void* (*block_alloc)(size_t) = nullptr; |
| void (*block_dealloc)(void*, size_t) = nullptr; |
| ArenaMetricsCollector* metrics_collector = nullptr; |
| |
| bool IsDefault() const { |
| return start_block_size == kDefaultMaxBlockSize && |
| max_block_size == kDefaultMaxBlockSize && block_alloc == nullptr && |
| block_dealloc == nullptr && metrics_collector == nullptr; |
| } |
| }; |
| |
| // A simple arena allocator. Calls to allocate functions must be properly |
| // serialized by the caller, hence this class cannot be used as a general |
| // purpose allocator in a multi-threaded program. It serves as a building block |
| // for ThreadSafeArena, which provides a thread-safe arena allocator. |
| // |
| // This class manages |
| // 1) Arena bump allocation + owning memory blocks. |
| // 2) Maintaining a cleanup list. |
| // It delagetes the actual memory allocation back to ThreadSafeArena, which |
| // contains the information on block growth policy and backing memory allocation |
| // used. |
| class PROTOBUF_EXPORT SerialArena { |
| public: |
| struct Memory { |
| void* ptr; |
| size_t size; |
| }; |
| |
| // Node contains the ptr of the object to be cleaned up and the associated |
| // cleanup function ptr. |
| struct CleanupNode { |
| void* elem; // Pointer to the object to be cleaned up. |
| void (*cleanup)(void*); // Function pointer to the destructor or deleter. |
| }; |
| |
| // Creates a new SerialArena inside mem using the remaining memory as for |
| // future allocations. |
| static SerialArena* New(SerialArena::Memory mem, void* owner); |
| // Free SerialArena returning the memory passed in to New |
| template <typename Deallocator> |
| Memory Free(Deallocator deallocator); |
| |
| void CleanupList(); |
| uint64 SpaceAllocated() const { |
| return space_allocated_.load(std::memory_order_relaxed); |
| } |
| uint64 SpaceUsed() const; |
| |
| bool HasSpace(size_t n) { return n <= static_cast<size_t>(limit_ - ptr_); } |
| |
| void* AllocateAligned(size_t n, const AllocationPolicy* policy) { |
| GOOGLE_DCHECK_EQ(internal::AlignUpTo8(n), n); // Must be already aligned. |
| GOOGLE_DCHECK_GE(limit_, ptr_); |
| if (PROTOBUF_PREDICT_FALSE(!HasSpace(n))) { |
| return AllocateAlignedFallback(n, policy); |
| } |
| void* ret = ptr_; |
| ptr_ += n; |
| #ifdef ADDRESS_SANITIZER |
| ASAN_UNPOISON_MEMORY_REGION(ret, n); |
| #endif // ADDRESS_SANITIZER |
| return ret; |
| } |
| |
| // Allocate space if the current region provides enough space. |
| bool MaybeAllocateAligned(size_t n, void** out) { |
| GOOGLE_DCHECK_EQ(internal::AlignUpTo8(n), n); // Must be already aligned. |
| GOOGLE_DCHECK_GE(limit_, ptr_); |
| if (PROTOBUF_PREDICT_FALSE(!HasSpace(n))) return false; |
| void* ret = ptr_; |
| ptr_ += n; |
| #ifdef ADDRESS_SANITIZER |
| ASAN_UNPOISON_MEMORY_REGION(ret, n); |
| #endif // ADDRESS_SANITIZER |
| *out = ret; |
| return true; |
| } |
| |
| std::pair<void*, CleanupNode*> AllocateAlignedWithCleanup( |
| size_t n, const AllocationPolicy* policy) { |
| if (PROTOBUF_PREDICT_FALSE(!HasSpace(n + kCleanupSize))) { |
| return AllocateAlignedWithCleanupFallback(n, policy); |
| } |
| void* ret = ptr_; |
| ptr_ += n; |
| limit_ -= kCleanupSize; |
| #ifdef ADDRESS_SANITIZER |
| ASAN_UNPOISON_MEMORY_REGION(ret, n); |
| ASAN_UNPOISON_MEMORY_REGION(limit_, kCleanupSize); |
| #endif // ADDRESS_SANITIZER |
| return CreatePair(ret, reinterpret_cast<CleanupNode*>(limit_)); |
| } |
| |
| void AddCleanup(void* elem, void (*cleanup)(void*), |
| const AllocationPolicy* policy) { |
| auto res = AllocateAlignedWithCleanup(0, policy); |
| res.second->elem = elem; |
| res.second->cleanup = cleanup; |
| } |
| |
| void* owner() const { return owner_; } |
| SerialArena* next() const { return next_; } |
| void set_next(SerialArena* next) { next_ = next; } |
| |
| private: |
| // Blocks are variable length malloc-ed objects. The following structure |
| // describes the common header for all blocks. |
| struct Block { |
| char* Pointer(size_t n) { |
| GOOGLE_DCHECK(n <= size); |
| return reinterpret_cast<char*>(this) + n; |
| } |
| |
| Block* next; |
| size_t size; |
| CleanupNode* start; |
| // data follows |
| }; |
| |
| void* owner_; // &ThreadCache of this thread; |
| Block* head_; // Head of linked list of blocks. |
| SerialArena* next_; // Next SerialArena in this linked list. |
| size_t space_used_ = 0; // Necessary for metrics. |
| std::atomic<size_t> space_allocated_; |
| |
| // Next pointer to allocate from. Always 8-byte aligned. Points inside |
| // head_ (and head_->pos will always be non-canonical). We keep these |
| // here to reduce indirection. |
| char* ptr_; |
| char* limit_; |
| |
| // Constructor is private as only New() should be used. |
| inline SerialArena(Block* b, void* owner); |
| void* AllocateAlignedFallback(size_t n, const AllocationPolicy* policy); |
| std::pair<void*, CleanupNode*> AllocateAlignedWithCleanupFallback( |
| size_t n, const AllocationPolicy* policy); |
| void AllocateNewBlock(size_t n, const AllocationPolicy* policy); |
| |
| std::pair<void*, CleanupNode*> CreatePair(void* ptr, CleanupNode* node) { |
| return {ptr, node}; |
| } |
| |
| public: |
| static constexpr size_t kBlockHeaderSize = AlignUpTo8(sizeof(Block)); |
| static constexpr size_t kCleanupSize = AlignUpTo8(sizeof(CleanupNode)); |
| }; |
| |
| // This class provides the core Arena memory allocation library. Different |
| // implementations only need to implement the public interface below. |
| // Arena is not a template type as that would only be useful if all protos |
| // in turn would be templates, which will/cannot happen. However separating |
| // the memory allocation part from the cruft of the API users expect we can |
| // use #ifdef the select the best implementation based on hardware / OS. |
| class PROTOBUF_EXPORT ThreadSafeArena { |
| public: |
| ThreadSafeArena() { Init(false); } |
| |
| ThreadSafeArena(char* mem, size_t size) { InitializeFrom(mem, size); } |
| |
| explicit ThreadSafeArena(void* mem, size_t size, |
| const AllocationPolicy& policy) { |
| if (policy.IsDefault()) { |
| // Legacy code doesn't use the API above, but provides the initial block |
| // through ArenaOptions. I suspect most do not touch the allocation |
| // policy parameters. |
| InitializeFrom(mem, size); |
| } else { |
| auto collector = policy.metrics_collector; |
| bool record_allocs = collector && collector->RecordAllocs(); |
| InitializeWithPolicy(mem, size, record_allocs, policy); |
| } |
| } |
| |
| // Destructor deletes all owned heap allocated objects, and destructs objects |
| // that have non-trivial destructors, except for proto2 message objects whose |
| // destructors can be skipped. Also, frees all blocks except the initial block |
| // if it was passed in. |
| ~ThreadSafeArena(); |
| |
| uint64 Reset(); |
| |
| uint64 SpaceAllocated() const; |
| uint64 SpaceUsed() const; |
| |
| void* AllocateAligned(size_t n, const std::type_info* type) { |
| SerialArena* arena; |
| if (PROTOBUF_PREDICT_TRUE(GetSerialArenaFast(tag_and_id_, &arena))) { |
| return arena->AllocateAligned(n, AllocPolicy()); |
| } else { |
| return AllocateAlignedFallback(n, type); |
| } |
| } |
| |
| // This function allocates n bytes if the common happy case is true and |
| // returns true. Otherwise does nothing and returns false. This strange |
| // semantics is necessary to allow callers to program functions that only |
| // have fallback function calls in tail position. This substantially improves |
| // code for the happy path. |
| PROTOBUF_NDEBUG_INLINE bool MaybeAllocateAligned(size_t n, void** out) { |
| SerialArena* a; |
| if (PROTOBUF_PREDICT_TRUE(GetSerialArenaFromThreadCache(tag_and_id_, &a))) { |
| return a->MaybeAllocateAligned(n, out); |
| } |
| return false; |
| } |
| |
| std::pair<void*, SerialArena::CleanupNode*> AllocateAlignedWithCleanup( |
| size_t n, const std::type_info* type); |
| |
| // Add object pointer and cleanup function pointer to the list. |
| void AddCleanup(void* elem, void (*cleanup)(void*)); |
| |
| private: |
| // Unique for each arena. Changes on Reset(). |
| uint64 tag_and_id_; |
| // The LSB of tag_and_id_ indicates if allocs in this arena are recorded. |
| enum { kRecordAllocs = 1 }; |
| |
| intptr_t alloc_policy_ = 0; // Tagged pointer to AllocPolicy. |
| // The LSB of alloc_policy_ indicates if the user owns the initial block. |
| enum { kUserOwnedInitialBlock = 1 }; |
| |
| // Pointer to a linked list of SerialArena. |
| std::atomic<SerialArena*> threads_; |
| std::atomic<SerialArena*> hint_; // Fast thread-local block access |
| |
| const AllocationPolicy* AllocPolicy() const { |
| return reinterpret_cast<const AllocationPolicy*>(alloc_policy_ & -8); |
| } |
| void InitializeFrom(void* mem, size_t size); |
| void InitializeWithPolicy(void* mem, size_t size, bool record_allocs, |
| AllocationPolicy policy); |
| void* AllocateAlignedFallback(size_t n, const std::type_info* type); |
| std::pair<void*, SerialArena::CleanupNode*> |
| AllocateAlignedWithCleanupFallback(size_t n, const std::type_info* type); |
| void AddCleanupFallback(void* elem, void (*cleanup)(void*)); |
| |
| void Init(bool record_allocs); |
| void SetInitialBlock(void* mem, size_t size); |
| |
| // Delete or Destruct all objects owned by the arena. |
| void CleanupList(); |
| |
| inline bool ShouldRecordAlloc() const { return tag_and_id_ & kRecordAllocs; } |
| |
| inline uint64 LifeCycleId() const { |
| return tag_and_id_ & (-kRecordAllocs - 1); |
| } |
| |
| inline void RecordAlloc(const std::type_info* allocated_type, |
| size_t n) const { |
| AllocPolicy()->metrics_collector->OnAlloc(allocated_type, n); |
| } |
| |
| inline void CacheSerialArena(SerialArena* serial) { |
| thread_cache().last_serial_arena = serial; |
| thread_cache().last_lifecycle_id_seen = LifeCycleId(); |
| // TODO(haberman): evaluate whether we would gain efficiency by getting rid |
| // of hint_. It's the only write we do to ThreadSafeArena in the allocation |
| // path, which will dirty the cache line. |
| |
| hint_.store(serial, std::memory_order_release); |
| } |
| |
| PROTOBUF_NDEBUG_INLINE bool GetSerialArenaFast(uint64 lifecycle_id, |
| SerialArena** arena) { |
| if (GetSerialArenaFromThreadCache(lifecycle_id, arena)) return true; |
| if (lifecycle_id & kRecordAllocs) return false; |
| |
| // Check whether we own the last accessed SerialArena on this arena. This |
| // fast path optimizes the case where a single thread uses multiple arenas. |
| ThreadCache* tc = &thread_cache(); |
| SerialArena* serial = hint_.load(std::memory_order_acquire); |
| if (PROTOBUF_PREDICT_TRUE(serial != NULL && serial->owner() == tc)) { |
| *arena = serial; |
| return true; |
| } |
| return false; |
| } |
| |
| PROTOBUF_NDEBUG_INLINE bool GetSerialArenaFromThreadCache( |
| uint64 lifecycle_id, SerialArena** arena) { |
| // If this thread already owns a block in this arena then try to use that. |
| // This fast path optimizes the case where multiple threads allocate from |
| // the same arena. |
| ThreadCache* tc = &thread_cache(); |
| if (PROTOBUF_PREDICT_TRUE(tc->last_lifecycle_id_seen == lifecycle_id)) { |
| *arena = tc->last_serial_arena; |
| return true; |
| } |
| return false; |
| } |
| SerialArena* GetSerialArenaFallback(void* me); |
| |
| template <typename Functor> |
| void PerSerialArena(Functor fn) { |
| // By omitting an Acquire barrier we ensure that any user code that doesn't |
| // properly synchronize Reset() or the destructor will throw a TSAN warning. |
| SerialArena* serial = threads_.load(std::memory_order_relaxed); |
| |
| for (; serial; serial = serial->next()) fn(serial); |
| } |
| |
| // Releases all memory except the first block which it returns. The first |
| // block might be owned by the user and thus need some extra checks before |
| // deleting. |
| SerialArena::Memory Free(size_t* space_allocated); |
| |
| #ifdef _MSC_VER |
| #pragma warning(disable : 4324) |
| #endif |
| struct alignas(64) ThreadCache { |
| #if defined(GOOGLE_PROTOBUF_NO_THREADLOCAL) |
| // If we are using the ThreadLocalStorage class to store the ThreadCache, |
| // then the ThreadCache's default constructor has to be responsible for |
| // initializing it. |
| ThreadCache() |
| : next_lifecycle_id(0), |
| last_lifecycle_id_seen(-1), |
| last_serial_arena(NULL) {} |
| #endif |
| |
| // Number of per-thread lifecycle IDs to reserve. Must be power of two. |
| // To reduce contention on a global atomic, each thread reserves a batch of |
| // IDs. The following number is calculated based on a stress test with |
| // ~6500 threads all frequently allocating a new arena. |
| static constexpr size_t kPerThreadIds = 256; |
| // Next lifecycle ID available to this thread. We need to reserve a new |
| // batch, if `next_lifecycle_id & (kPerThreadIds - 1) == 0`. |
| uint64 next_lifecycle_id; |
| // The ThreadCache is considered valid as long as this matches the |
| // lifecycle_id of the arena being used. |
| uint64 last_lifecycle_id_seen; |
| SerialArena* last_serial_arena; |
| }; |
| |
| // Lifecycle_id can be highly contended variable in a situation of lots of |
| // arena creation. Make sure that other global variables are not sharing the |
| // cacheline. |
| #ifdef _MSC_VER |
| #pragma warning(disable : 4324) |
| #endif |
| struct alignas(64) CacheAlignedLifecycleIdGenerator { |
| std::atomic<LifecycleIdAtomic> id; |
| }; |
| static CacheAlignedLifecycleIdGenerator lifecycle_id_generator_; |
| #if defined(GOOGLE_PROTOBUF_NO_THREADLOCAL) |
| // Android ndk does not support __thread keyword so we use a custom thread |
| // local storage class we implemented. |
| // iOS also does not support the __thread keyword. |
| static ThreadCache& thread_cache(); |
| #elif defined(PROTOBUF_USE_DLLS) |
| // Thread local variables cannot be exposed through DLL interface but we can |
| // wrap them in static functions. |
| static ThreadCache& thread_cache(); |
| #else |
| static PROTOBUF_THREAD_LOCAL ThreadCache thread_cache_; |
| static ThreadCache& thread_cache() { return thread_cache_; } |
| #endif |
| |
| GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ThreadSafeArena); |
| // All protos have pointers back to the arena hence Arena must have |
| // pointer stability. |
| ThreadSafeArena(ThreadSafeArena&&) = delete; |
| ThreadSafeArena& operator=(ThreadSafeArena&&) = delete; |
| |
| public: |
| // kBlockHeaderSize is sizeof(Block), aligned up to the nearest multiple of 8 |
| // to protect the invariant that pos is always at a multiple of 8. |
| static constexpr size_t kBlockHeaderSize = SerialArena::kBlockHeaderSize; |
| static constexpr size_t kSerialArenaSize = |
| (sizeof(SerialArena) + 7) & static_cast<size_t>(-8); |
| static_assert(kBlockHeaderSize % 8 == 0, |
| "kBlockHeaderSize must be a multiple of 8."); |
| static_assert(kSerialArenaSize % 8 == 0, |
| "kSerialArenaSize must be a multiple of 8."); |
| }; |
| |
| } // namespace internal |
| } // namespace protobuf |
| } // namespace google |
| |
| #include <google/protobuf/port_undef.inc> |
| |
| #endif // GOOGLE_PROTOBUF_ARENA_IMPL_H__ |