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 #include "base/mutex.h" 22 23 namespace art { 24 namespace mirror { 25 class Object; 26 } // namespace mirror 27 namespace gc { 28 namespace space { 29 class ContinuousSpace; 30 } // namespace space 31 32 namespace collector { 33 34 // An immune region is a continuous region of memory for which all objects contained are assumed to 35 // be marked. This is used as an optimization in the GC to avoid needing to test the mark bitmap of 36 // the zygote, image spaces, and sometimes non moving spaces. Doing the ContainsObject check is 37 // faster than doing a bitmap read. There is no support for discontinuous spaces and you need to be 38 // careful that your immune region doesn't contain any large objects. 39 class ImmuneRegion { 40 public: 41 ImmuneRegion(); 42 void Reset(); 43 bool AddContinuousSpace(space::ContinuousSpace* space) 44 EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_); 45 bool ContainsSpace(const space::ContinuousSpace* space) const; 46 // Returns true if an object is inside of the immune region (assumed to be marked). ContainsObject(const mirror::Object * obj)47 bool ContainsObject(const mirror::Object* obj) const ALWAYS_INLINE { 48 // Note: Relies on integer underflow behavior. 49 return reinterpret_cast<uintptr_t>(obj) - reinterpret_cast<uintptr_t>(begin_) < size_; 50 } SetBegin(mirror::Object * begin)51 void SetBegin(mirror::Object* begin) { 52 begin_ = begin; 53 UpdateSize(); 54 } SetEnd(mirror::Object * end)55 void SetEnd(mirror::Object* end) { 56 end_ = end; 57 UpdateSize(); 58 } 59 60 private: IsEmpty()61 bool IsEmpty() const { 62 return size_ == 0; 63 } UpdateSize()64 void UpdateSize() { 65 size_ = reinterpret_cast<uintptr_t>(end_) - reinterpret_cast<uintptr_t>(begin_); 66 } 67 68 mirror::Object* begin_; 69 mirror::Object* end_; 70 uintptr_t size_; 71 }; 72 73 } // namespace collector 74 } // namespace gc 75 } // namespace art 76 77 #endif // ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_ 78