1 // Copyright (c) 2016 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 // An arena that consists of a single inlined block of |ArenaSize|. Useful to 6 // avoid repeated calls to malloc/new and to improve memory locality. DCHECK's 7 // if an allocation out of the arena ever fails in debug builds; falls back to 8 // heap allocation in release builds. 9 10 #ifndef QUICHE_QUIC_CORE_QUIC_ONE_BLOCK_ARENA_H_ 11 #define QUICHE_QUIC_CORE_QUIC_ONE_BLOCK_ARENA_H_ 12 13 #include <cstdint> 14 15 #include "net/third_party/quiche/src/quic/core/quic_arena_scoped_ptr.h" 16 #include "net/third_party/quiche/src/quic/core/quic_types.h" 17 #include "net/third_party/quiche/src/quic/platform/api/quic_bug_tracker.h" 18 #include "net/third_party/quiche/src/quic/platform/api/quic_logging.h" 19 20 namespace quic { 21 22 template <uint32_t ArenaSize> 23 class QUIC_EXPORT_PRIVATE QuicOneBlockArena { 24 static const uint32_t kMaxAlign = 8; 25 26 public: 27 QuicOneBlockArena(); 28 QuicOneBlockArena(const QuicOneBlockArena&) = delete; 29 QuicOneBlockArena& operator=(const QuicOneBlockArena&) = delete; 30 31 // Instantiates an object of type |T| with |args|. |args| are perfectly 32 // forwarded to |T|'s constructor. The returned pointer's lifetime is 33 // controlled by QuicArenaScopedPtr. 34 template <typename T, typename... Args> 35 QuicArenaScopedPtr<T> New(Args&&... args); 36 37 private: 38 // Returns the size of |T| aligned up to |kMaxAlign|. 39 template <typename T> AlignedSize()40 static inline uint32_t AlignedSize() { 41 return ((sizeof(T) + (kMaxAlign - 1)) / kMaxAlign) * kMaxAlign; 42 } 43 44 // Actual storage. 45 // Subtle/annoying: the value '8' must be coded explicitly into the alignment 46 // declaration for MSVC. 47 alignas(8) char storage_[ArenaSize]; 48 // Current offset into the storage. 49 uint32_t offset_; 50 }; 51 52 template <uint32_t ArenaSize> QuicOneBlockArena()53QuicOneBlockArena<ArenaSize>::QuicOneBlockArena() : offset_(0) {} 54 55 template <uint32_t ArenaSize> 56 template <typename T, typename... Args> New(Args &&...args)57QuicArenaScopedPtr<T> QuicOneBlockArena<ArenaSize>::New(Args&&... args) { 58 DCHECK_LT(AlignedSize<T>(), ArenaSize) 59 << "Object is too large for the arena."; 60 static_assert(alignof(T) > 1, 61 "Objects added to the arena must be at least 2B aligned."); 62 if (QUIC_PREDICT_FALSE(offset_ > ArenaSize - AlignedSize<T>())) { 63 QUIC_BUG << "Ran out of space in QuicOneBlockArena at " << this 64 << ", max size was " << ArenaSize << ", failing request was " 65 << AlignedSize<T>() << ", end of arena was " << offset_; 66 return QuicArenaScopedPtr<T>(new T(std::forward<Args>(args)...)); 67 } 68 69 void* buf = &storage_[offset_]; 70 new (buf) T(std::forward<Args>(args)...); 71 offset_ += AlignedSize<T>(); 72 return QuicArenaScopedPtr<T>(buf, 73 QuicArenaScopedPtr<T>::ConstructFrom::kArena); 74 } 75 76 // QuicConnections currently use around 1KB of polymorphic types which would 77 // ordinarily be on the heap. Instead, store them inline in an arena. 78 using QuicConnectionArena = QuicOneBlockArena<1024>; 79 80 } // namespace quic 81 82 #endif // QUICHE_QUIC_CORE_QUIC_ONE_BLOCK_ARENA_H_ 83