87 lines
2.3 KiB
C++
87 lines
2.3 KiB
C++
/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_
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#define ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_
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#include "base/macros.h"
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namespace art {
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namespace mirror {
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class Object;
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} // namespace mirror
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namespace gc {
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namespace space {
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class ContinuousSpace;
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} // namespace space
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namespace collector {
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// An immune region is a continuous region of memory for which all objects contained are assumed to
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// be marked. This is used as an optimization in the GC to avoid needing to test the mark bitmap of
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// the zygote, image spaces, and sometimes non moving spaces. Doing the ContainsObject check is
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// faster than doing a bitmap read. There is no support for discontinuous spaces and you need to be
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// careful that your immune region doesn't contain any large objects.
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class ImmuneRegion {
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public:
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ImmuneRegion();
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void Reset();
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// Returns true if an object is inside of the immune region (assumed to be marked).
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ALWAYS_INLINE bool ContainsObject(const mirror::Object* obj) const {
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// Note: Relies on integer underflow behavior.
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return reinterpret_cast<uintptr_t>(obj) - reinterpret_cast<uintptr_t>(begin_) < size_;
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}
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void SetBegin(mirror::Object* begin) {
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begin_ = begin;
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UpdateSize();
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}
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void SetEnd(mirror::Object* end) {
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end_ = end;
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UpdateSize();
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}
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mirror::Object* Begin() const {
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return begin_;
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}
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mirror::Object* End() const {
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return end_;
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}
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size_t Size() const {
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return size_;
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}
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private:
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void UpdateSize() {
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size_ = reinterpret_cast<uintptr_t>(end_) - reinterpret_cast<uintptr_t>(begin_);
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}
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mirror::Object* begin_;
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mirror::Object* end_;
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uintptr_t size_;
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};
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} // namespace collector
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} // namespace gc
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} // namespace art
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#endif // ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_
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