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/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_
#define ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_
#include "base/macros.h"
#include "base/mutex.h"
#include "gc/space/space-inl.h"
namespace art {
namespace mirror {
class Object;
} // namespace mirror
namespace gc {
namespace space {
class ContinuousSpace;
} // namespace space
namespace collector {
// An immune region is a continuous region of memory for which all objects contained are assumed to
// be marked. This is used as an optimization in the GC to avoid needing to test the mark bitmap of
// the zygote, image spaces, and sometimes non moving spaces. Doing the ContainsObject check is
// faster than doing a bitmap read. There is no support for discontinuous spaces and you need to be
// careful that your immune region doesn't contain any large objects.
class ImmuneRegion {
public:
ImmuneRegion();
void Reset();
bool AddContinuousSpace(space::ContinuousSpace* space)
EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
bool ContainsSpace(const space::ContinuousSpace* space) const;
// Returns true if an object is inside of the immune region (assumed to be marked).
bool ContainsObject(const mirror::Object* obj) const ALWAYS_INLINE {
// Note: Relies on integer underflow behavior.
return reinterpret_cast<uintptr_t>(obj) - reinterpret_cast<uintptr_t>(begin_) < size_;
}
void SetBegin(mirror::Object* begin) {
begin_ = begin;
UpdateSize();
}
void SetEnd(mirror::Object* end) {
end_ = end;
UpdateSize();
}
private:
bool IsEmpty() const {
return size_ == 0;
}
void UpdateSize() {
size_ = reinterpret_cast<uintptr_t>(end_) - reinterpret_cast<uintptr_t>(begin_);
}
mirror::Object* begin_;
mirror::Object* end_;
uintptr_t size_;
};
} // namespace collector
} // namespace gc
} // namespace art
#endif // ART_RUNTIME_GC_COLLECTOR_IMMUNE_REGION_H_
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