1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_ 18 #define ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_ 19 20 #include "base/macros.h" 21 22 namespace art { 23 namespace mirror { 24 class Object; 25 } // namespace mirror 26 namespace gc { 27 namespace space { 28 class ContinuousSpace; 29 } // namespace space 30 31 namespace collector { 32 33 // An immune region is a continuous region of memory for which all objects contained are assumed to 34 // be marked. This is used as an optimization in the GC to avoid needing to test the mark bitmap of 35 // the zygote, image spaces, and sometimes non moving spaces. Doing the ContainsObject check is 36 // faster than doing a bitmap read. There is no support for discontinuous spaces and you need to be 37 // careful that your immune region doesn't contain any large objects. 38 class ImmuneRegion { 39 public: 40 ImmuneRegion(); 41 42 void Reset(); 43 44 // Returns true if an object is inside of the immune region (assumed to be marked). ContainsObject(const mirror::Object * obj)45 ALWAYS_INLINE bool ContainsObject(const mirror::Object* obj) const { 46 // Note: Relies on integer underflow behavior. 47 return reinterpret_cast<uintptr_t>(obj) - reinterpret_cast<uintptr_t>(begin_) < size_; 48 } 49 SetBegin(mirror::Object * begin)50 void SetBegin(mirror::Object* begin) { 51 begin_ = begin; 52 UpdateSize(); 53 } 54 SetEnd(mirror::Object * end)55 void SetEnd(mirror::Object* end) { 56 end_ = end; 57 UpdateSize(); 58 } 59 Begin()60 mirror::Object* Begin() const { 61 return begin_; 62 } 63 End()64 mirror::Object* End() const { 65 return end_; 66 } 67 Size()68 size_t Size() const { 69 return size_; 70 } 71 72 private: UpdateSize()73 void UpdateSize() { 74 size_ = reinterpret_cast<uintptr_t>(end_) - reinterpret_cast<uintptr_t>(begin_); 75 } 76 77 mirror::Object* begin_; 78 mirror::Object* end_; 79 uintptr_t size_; 80 }; 81 82 } // namespace collector 83 } // namespace gc 84 } // namespace art 85 86 #endif // ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_ 87