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/*
* Copyright (C) 2012 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_ACCOUNTING_MOD_UNION_TABLE_H_
#define ART_RUNTIME_GC_ACCOUNTING_MOD_UNION_TABLE_H_
#include "base/allocator.h"
#include "bitmap.h"
#include "card_table.h"
#include "globals.h"
#include "mirror/object_reference.h"
#include "safe_map.h"
#include <set>
#include <vector>
namespace art {
namespace mirror {
class Object;
} // namespace mirror
class MarkObjectVisitor;
namespace gc {
namespace space {
class ContinuousSpace;
} // namespace space
class Heap;
namespace accounting {
// The mod-union table is the union of modified cards. It is used to allow the card table to be
// cleared between GC phases, reducing the number of dirty cards that need to be scanned.
class ModUnionTable {
public:
// A callback for visiting an object in the heap.
using ObjectCallback = void (*)(mirror::Object*, void*);
typedef std::set<uint8_t*, std::less<uint8_t*>,
TrackingAllocator<uint8_t*, kAllocatorTagModUnionCardSet>> CardSet;
typedef MemoryRangeBitmap<CardTable::kCardSize> CardBitmap;
explicit ModUnionTable(const std::string& name, Heap* heap, space::ContinuousSpace* space)
: name_(name),
heap_(heap),
space_(space) {}
virtual ~ModUnionTable() {}
// Process cards for a memory range of a space. This doesn't immediately update the mod-union
// table, as updating the mod-union table may have an associated cost, such as determining
// references to track.
virtual void ProcessCards() = 0;
// Set all the cards.
virtual void SetCards() = 0;
// Clear all of the table.
virtual void ClearTable() = 0;
// Update the mod-union table using data stored by ProcessCards. There may be multiple
// ProcessCards before a call to update, for example, back-to-back sticky GCs. Also mark
// references to other spaces which are stored in the mod-union table.
virtual void UpdateAndMarkReferences(MarkObjectVisitor* visitor) = 0;
// Visit all of the objects that may contain references to other spaces.
virtual void VisitObjects(ObjectCallback callback, void* arg) = 0;
// Verification, sanity checks that we don't have clean cards which conflict with out cached data
// for said cards. Exclusive lock is required since verify sometimes uses
// SpaceBitmap::VisitMarkedRange and VisitMarkedRange can't know if the callback will modify the
// bitmap or not.
virtual void Verify() REQUIRES(Locks::heap_bitmap_lock_) = 0;
// Returns true if a card is marked inside the mod union table. Used for testing. The address
// doesn't need to be aligned.
virtual bool ContainsCardFor(uintptr_t addr) = 0;
// Filter out cards that don't need to be marked. Automatically done with UpdateAndMarkReferences.
void FilterCards();
virtual void Dump(std::ostream& os) = 0;
space::ContinuousSpace* GetSpace() {
return space_;
}
Heap* GetHeap() const {
return heap_;
}
const std::string& GetName() const {
return name_;
}
protected:
const std::string name_;
Heap* const heap_;
space::ContinuousSpace* const space_;
};
// Reference caching implementation. Caches references pointing to alloc space(s) for each card.
class ModUnionTableReferenceCache : public ModUnionTable {
public:
explicit ModUnionTableReferenceCache(const std::string& name, Heap* heap,
space::ContinuousSpace* space)
: ModUnionTable(name, heap, space) {}
virtual ~ModUnionTableReferenceCache() {}
// Clear and store cards for a space.
void ProcessCards() OVERRIDE;
// Update table based on cleared cards and mark all references to the other spaces.
void UpdateAndMarkReferences(MarkObjectVisitor* visitor) OVERRIDE
REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(Locks::heap_bitmap_lock_);
virtual void VisitObjects(ObjectCallback callback, void* arg) OVERRIDE
REQUIRES(Locks::heap_bitmap_lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Exclusive lock is required since verify uses SpaceBitmap::VisitMarkedRange and
// VisitMarkedRange can't know if the callback will modify the bitmap or not.
void Verify() OVERRIDE
REQUIRES_SHARED(Locks::mutator_lock_)
REQUIRES(Locks::heap_bitmap_lock_);
// Function that tells whether or not to add a reference to the table.
virtual bool ShouldAddReference(const mirror::Object* ref) const = 0;
virtual bool ContainsCardFor(uintptr_t addr) OVERRIDE;
virtual void Dump(std::ostream& os) OVERRIDE REQUIRES_SHARED(Locks::mutator_lock_);
virtual void SetCards() OVERRIDE;
virtual void ClearTable() OVERRIDE;
protected:
// Cleared card array, used to update the mod-union table.
ModUnionTable::CardSet cleared_cards_;
// Maps from dirty cards to their corresponding alloc space references.
AllocationTrackingSafeMap<const uint8_t*, std::vector<mirror::HeapReference<mirror::Object>*>,
kAllocatorTagModUnionReferenceArray> references_;
};
// Card caching implementation. Keeps track of which cards we cleared and only this information.
class ModUnionTableCardCache : public ModUnionTable {
public:
// Note: There is assumption that the space End() doesn't change.
explicit ModUnionTableCardCache(const std::string& name, Heap* heap,
space::ContinuousSpace* space);
virtual ~ModUnionTableCardCache() {}
// Clear and store cards for a space.
virtual void ProcessCards() OVERRIDE;
// Mark all references to the alloc space(s).
virtual void UpdateAndMarkReferences(MarkObjectVisitor* visitor) OVERRIDE
REQUIRES(Locks::heap_bitmap_lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
virtual void VisitObjects(ObjectCallback callback, void* arg) OVERRIDE
REQUIRES(Locks::heap_bitmap_lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Nothing to verify.
virtual void Verify() OVERRIDE {}
virtual void Dump(std::ostream& os) OVERRIDE;
virtual bool ContainsCardFor(uintptr_t addr) OVERRIDE;
virtual void SetCards() OVERRIDE;
virtual void ClearTable() OVERRIDE;
protected:
// Cleared card bitmap, used to update the mod-union table.
std::unique_ptr<CardBitmap> card_bitmap_;
};
} // namespace accounting
} // namespace gc
} // namespace art
#endif // ART_RUNTIME_GC_ACCOUNTING_MOD_UNION_TABLE_H_
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