runtime/gc/accounting/card_table-inl.h - platform/art - Gitiles

 /*
  * Copyright (C) 2011 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_CARD_TABLE_INL_H_
 #define ART_RUNTIME_GC_ACCOUNTING_CARD_TABLE_INL_H_

 #include "atomic.h"
 #include "base/logging.h"
 #include "card_table.h"
 #include "mem_map.h"
 #include "space_bitmap.h"
 #include "utils.h"

 namespace art {
 namespace gc {
 namespace accounting {

 static inline bool byte_cas(uint8_t old_value, uint8_t new_value, uint8_t* address) {
 #if defined(__i386__) || defined(__x86_64__)
   Atomic<uint8_t>* byte_atomic = reinterpret_cast<Atomic<uint8_t>*>(address);
   return byte_atomic->CompareExchangeWeakRelaxed(old_value, new_value);
 #else
   // Little endian means most significant byte is on the left.
   const size_t shift_in_bytes = reinterpret_cast<uintptr_t>(address) % sizeof(uintptr_t);
   // Align the address down.
   address -= shift_in_bytes;
   const size_t shift_in_bits = shift_in_bytes * kBitsPerByte;
   Atomic<uintptr_t>* word_atomic = reinterpret_cast<Atomic<uintptr_t>*>(address);

   // Word with the byte we are trying to cas cleared.
   const uintptr_t cur_word = word_atomic->LoadRelaxed() &
       ~(static_cast<uintptr_t>(0xFF) << shift_in_bits);
   const uintptr_t old_word = cur_word | (static_cast<uintptr_t>(old_value) << shift_in_bits);
   const uintptr_t new_word = cur_word | (static_cast<uintptr_t>(new_value) << shift_in_bits);
   return word_atomic->CompareExchangeWeakRelaxed(old_word, new_word);
 #endif
 }

 template <bool kClearCard, typename Visitor>
 inline size_t CardTable::Scan(ContinuousSpaceBitmap* bitmap, uint8_t* scan_begin, uint8_t* scan_end,
                               const Visitor& visitor, const uint8_t minimum_age) const {
   DCHECK_GE(scan_begin, reinterpret_cast<uint8_t*>(bitmap->HeapBegin()));
   // scan_end is the byte after the last byte we scan.
   DCHECK_LE(scan_end, reinterpret_cast<uint8_t*>(bitmap->HeapLimit()));
   uint8_t* card_cur = CardFromAddr(scan_begin);
   uint8_t* card_end = CardFromAddr(AlignUp(scan_end, kCardSize));
   CheckCardValid(card_cur);
   CheckCardValid(card_end);
   size_t cards_scanned = 0;

   // Handle any unaligned cards at the start.
   while (!IsAligned<sizeof(intptr_t)>(card_cur) && card_cur < card_end) {
     if (*card_cur >= minimum_age) {
       uintptr_t start = reinterpret_cast<uintptr_t>(AddrFromCard(card_cur));
       bitmap->VisitMarkedRange(start, start + kCardSize, visitor);
       ++cards_scanned;
       if (kClearCard) {
         *card_cur = 0;
       }
     }
     ++card_cur;
   }

   uint8_t* aligned_end = card_end -
       (reinterpret_cast<uintptr_t>(card_end) & (sizeof(uintptr_t) - 1));

   uintptr_t* word_end = reinterpret_cast<uintptr_t*>(aligned_end);
   for (uintptr_t* word_cur = reinterpret_cast<uintptr_t*>(card_cur); word_cur < word_end;
       ++word_cur) {
     while (LIKELY(*word_cur == 0)) {
       ++word_cur;
       if (UNLIKELY(word_cur >= word_end)) {
         goto exit_for;
       }
     }

     // Find the first dirty card.
     uintptr_t start_word = *word_cur;
     uintptr_t start = reinterpret_cast<uintptr_t>(AddrFromCard(reinterpret_cast<uint8_t*>(word_cur)));
     // TODO: Investigate if processing continuous runs of dirty cards with a single bitmap visit is
     // more efficient.
     for (size_t i = 0; i < sizeof(uintptr_t); ++i) {
       if (static_cast<uint8_t>(start_word) >= minimum_age) {
         auto* card = reinterpret_cast<uint8_t*>(word_cur) + i;
         DCHECK(*card == static_cast<uint8_t>(start_word) || *card == kCardDirty)
             << "card " << static_cast<size_t>(*card) << " intptr_t " << (start_word & 0xFF);
         bitmap->VisitMarkedRange(start, start + kCardSize, visitor);
         ++cards_scanned;
         if (kClearCard) {
           *card = 0;
         }
       }
       start_word >>= 8;
       start += kCardSize;
     }
   }
   exit_for:

   // Handle any unaligned cards at the end.
   card_cur = reinterpret_cast<uint8_t*>(word_end);
   while (card_cur < card_end) {
     if (*card_cur >= minimum_age) {
       uintptr_t start = reinterpret_cast<uintptr_t>(AddrFromCard(card_cur));
       bitmap->VisitMarkedRange(start, start + kCardSize, visitor);
       ++cards_scanned;
       if (kClearCard) {
         *card_cur = 0;
       }
     }
     ++card_cur;
   }

   return cards_scanned;
 }

 /*
  * Visitor is expected to take in a card and return the new value. When a value is modified, the
  * modify visitor is called.
  * visitor: The visitor which modifies the cards. Returns the new value for a card given an old
  * value.
  * modified: Whenever the visitor modifies a card, this visitor is called on the card. Enables
  * us to know which cards got cleared.
  */
 template <typename Visitor, typename ModifiedVisitor>
 inline void CardTable::ModifyCardsAtomic(uint8_t* scan_begin, uint8_t* scan_end, const Visitor& visitor,
                                          const ModifiedVisitor& modified) {
   uint8_t* card_cur = CardFromAddr(scan_begin);
   uint8_t* card_end = CardFromAddr(AlignUp(scan_end, kCardSize));
   CheckCardValid(card_cur);
   CheckCardValid(card_end);

   // Handle any unaligned cards at the start.
   while (!IsAligned<sizeof(intptr_t)>(card_cur) && card_cur < card_end) {
     uint8_t expected, new_value;
     do {
       expected = *card_cur;
       new_value = visitor(expected);
     } while (expected != new_value && UNLIKELY(!byte_cas(expected, new_value, card_cur)));
     if (expected != new_value) {
       modified(card_cur, expected, new_value);
     }
     ++card_cur;
   }

   // Handle unaligned cards at the end.
   while (!IsAligned<sizeof(intptr_t)>(card_end) && card_end > card_cur) {
     --card_end;
     uint8_t expected, new_value;
     do {
       expected = *card_end;
       new_value = visitor(expected);
     } while (expected != new_value && UNLIKELY(!byte_cas(expected, new_value, card_end)));
     if (expected != new_value) {
       modified(card_end, expected, new_value);
     }
   }

   // Now we have the words, we can process words in parallel.
   uintptr_t* word_cur = reinterpret_cast<uintptr_t*>(card_cur);
   uintptr_t* word_end = reinterpret_cast<uintptr_t*>(card_end);
   // TODO: This is not big endian safe.
   union {
     uintptr_t expected_word;
     uint8_t expected_bytes[sizeof(uintptr_t)];
   };
   union {
     uintptr_t new_word;
     uint8_t new_bytes[sizeof(uintptr_t)];
   };

   // TODO: Parallelize.
   while (word_cur < word_end) {
     while (true) {
       expected_word = *word_cur;
       if (LIKELY(expected_word == 0)) {
         break;
       }
       for (size_t i = 0; i < sizeof(uintptr_t); ++i) {
         new_bytes[i] = visitor(expected_bytes[i]);
       }
       Atomic<uintptr_t>* atomic_word = reinterpret_cast<Atomic<uintptr_t>*>(word_cur);
       if (LIKELY(atomic_word->CompareExchangeWeakRelaxed(expected_word, new_word))) {
         for (size_t i = 0; i < sizeof(uintptr_t); ++i) {
           const uint8_t expected_byte = expected_bytes[i];
           const uint8_t new_byte = new_bytes[i];
           if (expected_byte != new_byte) {
             modified(reinterpret_cast<uint8_t*>(word_cur) + i, expected_byte, new_byte);
           }
         }
         break;
       }
     }
     ++word_cur;
   }
 }

 inline void* CardTable::AddrFromCard(const uint8_t *card_addr) const {
   DCHECK(IsValidCard(card_addr))
     << " card_addr: " << reinterpret_cast<const void*>(card_addr)
     << " begin: " << reinterpret_cast<void*>(mem_map_->Begin() + offset_)
     << " end: " << reinterpret_cast<void*>(mem_map_->End());
   uintptr_t offset = card_addr - biased_begin_;
   return reinterpret_cast<void*>(offset << kCardShift);
 }

 inline uint8_t* CardTable::CardFromAddr(const void *addr) const {
   uint8_t *card_addr = biased_begin_ + (reinterpret_cast<uintptr_t>(addr) >> kCardShift);
   // Sanity check the caller was asking for address covered by the card table
   DCHECK(IsValidCard(card_addr)) << "addr: " << addr
       << " card_addr: " << reinterpret_cast<void*>(card_addr);
   return card_addr;
 }

 inline bool CardTable::IsValidCard(const uint8_t* card_addr) const {
   uint8_t* begin = mem_map_->Begin() + offset_;
   uint8_t* end = mem_map_->End();
   return card_addr >= begin && card_addr < end;
 }

 inline void CardTable::CheckCardValid(uint8_t* card) const {
   DCHECK(IsValidCard(card))
       << " card_addr: " << reinterpret_cast<const void*>(card)
       << " begin: " << reinterpret_cast<void*>(mem_map_->Begin() + offset_)
       << " end: " << reinterpret_cast<void*>(mem_map_->End());
 }

 }  // namespace accounting
 }  // namespace gc
 }  // namespace art

 #endif  // ART_RUNTIME_GC_ACCOUNTING_CARD_TABLE_INL_H_
	/*
	* Copyright (C) 2011 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_CARD_TABLE_INL_H_
	#define ART_RUNTIME_GC_ACCOUNTING_CARD_TABLE_INL_H_

	#include "atomic.h"
	#include "base/logging.h"
	#include "card_table.h"
	#include "mem_map.h"
	#include "space_bitmap.h"
	#include "utils.h"

	namespace art {
	namespace gc {
	namespace accounting {

	static inline bool byte_cas(uint8_t old_value, uint8_t new_value, uint8_t* address) {
	#if defined(__i386__) \|\| defined(__x86_64__)
	Atomic<uint8_t>* byte_atomic = reinterpret_cast<Atomic<uint8_t>*>(address);
	return byte_atomic->CompareExchangeWeakRelaxed(old_value, new_value);
	#else
	// Little endian means most significant byte is on the left.
	const size_t shift_in_bytes = reinterpret_cast<uintptr_t>(address) % sizeof(uintptr_t);
	// Align the address down.
	address -= shift_in_bytes;
	const size_t shift_in_bits = shift_in_bytes * kBitsPerByte;
	Atomic<uintptr_t>* word_atomic = reinterpret_cast<Atomic<uintptr_t>*>(address);

	// Word with the byte we are trying to cas cleared.
	const uintptr_t cur_word = word_atomic->LoadRelaxed() &
	~(static_cast<uintptr_t>(0xFF) << shift_in_bits);
	const uintptr_t old_word = cur_word \| (static_cast<uintptr_t>(old_value) << shift_in_bits);
	const uintptr_t new_word = cur_word \| (static_cast<uintptr_t>(new_value) << shift_in_bits);
	return word_atomic->CompareExchangeWeakRelaxed(old_word, new_word);
	#endif
	}

	template <bool kClearCard, typename Visitor>
	inline size_t CardTable::Scan(ContinuousSpaceBitmap* bitmap, uint8_t* scan_begin, uint8_t* scan_end,
	const Visitor& visitor, const uint8_t minimum_age) const {
	DCHECK_GE(scan_begin, reinterpret_cast<uint8_t*>(bitmap->HeapBegin()));
	// scan_end is the byte after the last byte we scan.
	DCHECK_LE(scan_end, reinterpret_cast<uint8_t*>(bitmap->HeapLimit()));
	uint8_t* card_cur = CardFromAddr(scan_begin);
	uint8_t* card_end = CardFromAddr(AlignUp(scan_end, kCardSize));
	CheckCardValid(card_cur);
	CheckCardValid(card_end);
	size_t cards_scanned = 0;

	// Handle any unaligned cards at the start.
	while (!IsAligned<sizeof(intptr_t)>(card_cur) && card_cur < card_end) {
	if (*card_cur >= minimum_age) {
	uintptr_t start = reinterpret_cast<uintptr_t>(AddrFromCard(card_cur));
	bitmap->VisitMarkedRange(start, start + kCardSize, visitor);
	++cards_scanned;
	if (kClearCard) {
	*card_cur = 0;
	}
	}
	++card_cur;
	}

	uint8_t* aligned_end = card_end -
	(reinterpret_cast<uintptr_t>(card_end) & (sizeof(uintptr_t) - 1));

	uintptr_t* word_end = reinterpret_cast<uintptr_t*>(aligned_end);
	for (uintptr_t* word_cur = reinterpret_cast<uintptr_t*>(card_cur); word_cur < word_end;
	++word_cur) {
	while (LIKELY(*word_cur == 0)) {
	++word_cur;
	if (UNLIKELY(word_cur >= word_end)) {
	goto exit_for;
	}
	}

	// Find the first dirty card.
	uintptr_t start_word = *word_cur;
	uintptr_t start = reinterpret_cast<uintptr_t>(AddrFromCard(reinterpret_cast<uint8_t*>(word_cur)));
	// TODO: Investigate if processing continuous runs of dirty cards with a single bitmap visit is
	// more efficient.
	for (size_t i = 0; i < sizeof(uintptr_t); ++i) {
	if (static_cast<uint8_t>(start_word) >= minimum_age) {
	auto* card = reinterpret_cast<uint8_t*>(word_cur) + i;
	DCHECK(card == static_cast<uint8_t>(start_word) \|\| card == kCardDirty)
	<< "card " << static_cast<size_t>(*card) << " intptr_t " << (start_word & 0xFF);
	bitmap->VisitMarkedRange(start, start + kCardSize, visitor);
	++cards_scanned;
	if (kClearCard) {
	*card = 0;
	}
	}
	start_word >>= 8;
	start += kCardSize;
	}
	}
	exit_for:

	// Handle any unaligned cards at the end.
	card_cur = reinterpret_cast<uint8_t*>(word_end);
	while (card_cur < card_end) {
	if (*card_cur >= minimum_age) {
	uintptr_t start = reinterpret_cast<uintptr_t>(AddrFromCard(card_cur));
	bitmap->VisitMarkedRange(start, start + kCardSize, visitor);
	++cards_scanned;
	if (kClearCard) {
	*card_cur = 0;
	}
	}
	++card_cur;
	}

	return cards_scanned;
	}

	/*
	* Visitor is expected to take in a card and return the new value. When a value is modified, the
	* modify visitor is called.
	* visitor: The visitor which modifies the cards. Returns the new value for a card given an old
	* value.
	* modified: Whenever the visitor modifies a card, this visitor is called on the card. Enables
	* us to know which cards got cleared.
	*/
	template <typename Visitor, typename ModifiedVisitor>
	inline void CardTable::ModifyCardsAtomic(uint8_t* scan_begin, uint8_t* scan_end, const Visitor& visitor,
	const ModifiedVisitor& modified) {
	uint8_t* card_cur = CardFromAddr(scan_begin);
	uint8_t* card_end = CardFromAddr(AlignUp(scan_end, kCardSize));
	CheckCardValid(card_cur);
	CheckCardValid(card_end);

	// Handle any unaligned cards at the start.
	while (!IsAligned<sizeof(intptr_t)>(card_cur) && card_cur < card_end) {
	uint8_t expected, new_value;
	do {
	expected = *card_cur;
	new_value = visitor(expected);
	} while (expected != new_value && UNLIKELY(!byte_cas(expected, new_value, card_cur)));
	if (expected != new_value) {
	modified(card_cur, expected, new_value);
	}
	++card_cur;
	}

	// Handle unaligned cards at the end.
	while (!IsAligned<sizeof(intptr_t)>(card_end) && card_end > card_cur) {
	--card_end;
	uint8_t expected, new_value;
	do {
	expected = *card_end;
	new_value = visitor(expected);
	} while (expected != new_value && UNLIKELY(!byte_cas(expected, new_value, card_end)));
	if (expected != new_value) {
	modified(card_end, expected, new_value);
	}
	}

	// Now we have the words, we can process words in parallel.
	uintptr_t* word_cur = reinterpret_cast<uintptr_t*>(card_cur);
	uintptr_t* word_end = reinterpret_cast<uintptr_t*>(card_end);
	// TODO: This is not big endian safe.
	union {
	uintptr_t expected_word;
	uint8_t expected_bytes[sizeof(uintptr_t)];
	};
	union {
	uintptr_t new_word;
	uint8_t new_bytes[sizeof(uintptr_t)];
	};

	// TODO: Parallelize.
	while (word_cur < word_end) {
	while (true) {
	expected_word = *word_cur;
	if (LIKELY(expected_word == 0)) {
	break;
	}
	for (size_t i = 0; i < sizeof(uintptr_t); ++i) {
	new_bytes[i] = visitor(expected_bytes[i]);
	}
	Atomic<uintptr_t>* atomic_word = reinterpret_cast<Atomic<uintptr_t>*>(word_cur);
	if (LIKELY(atomic_word->CompareExchangeWeakRelaxed(expected_word, new_word))) {
	for (size_t i = 0; i < sizeof(uintptr_t); ++i) {
	const uint8_t expected_byte = expected_bytes[i];
	const uint8_t new_byte = new_bytes[i];
	if (expected_byte != new_byte) {
	modified(reinterpret_cast<uint8_t*>(word_cur) + i, expected_byte, new_byte);
	}
	}
	break;
	}
	}
	++word_cur;
	}
	}

	inline void* CardTable::AddrFromCard(const uint8_t *card_addr) const {
	DCHECK(IsValidCard(card_addr))
	<< " card_addr: " << reinterpret_cast<const void*>(card_addr)
	<< " begin: " << reinterpret_cast<void*>(mem_map_->Begin() + offset_)
	<< " end: " << reinterpret_cast<void*>(mem_map_->End());
	uintptr_t offset = card_addr - biased_begin_;
	return reinterpret_cast<void*>(offset << kCardShift);
	}

	inline uint8_t* CardTable::CardFromAddr(const void *addr) const {
	uint8_t *card_addr = biased_begin_ + (reinterpret_cast<uintptr_t>(addr) >> kCardShift);
	// Sanity check the caller was asking for address covered by the card table
	DCHECK(IsValidCard(card_addr)) << "addr: " << addr
	<< " card_addr: " << reinterpret_cast<void*>(card_addr);
	return card_addr;
	}

	inline bool CardTable::IsValidCard(const uint8_t* card_addr) const {
	uint8_t* begin = mem_map_->Begin() + offset_;
	uint8_t* end = mem_map_->End();
	return card_addr >= begin && card_addr < end;
	}

	inline void CardTable::CheckCardValid(uint8_t* card) const {
	DCHECK(IsValidCard(card))
	<< " card_addr: " << reinterpret_cast<const void*>(card)
	<< " begin: " << reinterpret_cast<void*>(mem_map_->Begin() + offset_)
	<< " end: " << reinterpret_cast<void*>(mem_map_->End());
	}

	} // namespace accounting
	} // namespace gc
	} // namespace art

	#endif // ART_RUNTIME_GC_ACCOUNTING_CARD_TABLE_INL_H_