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 "base/logging.h"
 #include "card_table.h"
 #include "cutils/atomic-inline.h"
 #include "space_bitmap.h"
 #include "utils.h"

 namespace art {
 namespace gc {
 namespace accounting {

 static inline bool byte_cas(byte old_value, byte new_value, byte* address) {
   // 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;
   int32_t* word_address = reinterpret_cast<int32_t*>(address);
   // Word with the byte we are trying to cas cleared.
   const int32_t cur_word = *word_address & ~(0xFF << shift_in_bits);
   const int32_t old_word = cur_word | (static_cast<int32_t>(old_value) << shift_in_bits);
   const int32_t new_word = cur_word | (static_cast<int32_t>(new_value) << shift_in_bits);
   bool success = android_atomic_cas(old_word, new_word, word_address) == 0;
   return success;
 }

 template <typename Visitor>
 inline size_t CardTable::Scan(SpaceBitmap* bitmap, byte* scan_begin, byte* scan_end,
                               const Visitor& visitor, const byte minimum_age) const {
   DCHECK(bitmap->HasAddress(scan_begin));
   DCHECK(bitmap->HasAddress(scan_end - 1));  // scan_end is the byte after the last byte we scan.
   byte* card_cur = CardFromAddr(scan_begin);
   byte* card_end = CardFromAddr(scan_end);
   CheckCardValid(card_cur);
   CheckCardValid(card_end);
   size_t cards_scanned = 0;

   // Handle any unaligned cards at the start.
   while (!IsAligned<sizeof(word)>(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;
     }
     ++card_cur;
   }

   byte* 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<byte*>(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<byte>(start_word) >= minimum_age) {
         auto* card = reinterpret_cast<byte*>(word_cur) + i;
         DCHECK(*card == static_cast<byte>(start_word) || *card == kCardDirty)
             << "card " << static_cast<size_t>(*card) << " word " << (start_word & 0xFF);
         bitmap->VisitMarkedRange(start, start + kCardSize, visitor);
         ++cards_scanned;
       }
       start_word >>= 8;
       start += kCardSize;
     }
   }
   exit_for:

   // Handle any unaligned cards at the end.
   card_cur = reinterpret_cast<byte*>(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;
     }
     ++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(byte* scan_begin, byte* scan_end, const Visitor& visitor,
                                          const ModifiedVisitor& modified) {
   byte* card_cur = CardFromAddr(scan_begin);
   byte* card_end = CardFromAddr(AlignUp(scan_end, kCardSize));
   CheckCardValid(card_cur);
   CheckCardValid(card_end);

   // Handle any unaligned cards at the start.
   while (!IsAligned<sizeof(word)>(card_cur) && card_cur < card_end) {
     byte 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(word)>(card_end) && card_end > card_cur) {
     --card_end;
     byte 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);
   uintptr_t expected_word;
   uintptr_t new_word;

   // TODO: Parallelize.
   while (word_cur < word_end) {
     while ((expected_word = *word_cur) != 0) {
       new_word =
           (visitor((expected_word >> 0) & 0xFF) << 0) |
           (visitor((expected_word >> 8) & 0xFF) << 8) |
           (visitor((expected_word >> 16) & 0xFF) << 16) |
           (visitor((expected_word >> 24) & 0xFF) << 24);
       if (new_word == expected_word) {
         // No need to do a cas.
         break;
       }
       if (LIKELY(android_atomic_cas(expected_word, new_word,
                                     reinterpret_cast<int32_t*>(word_cur)) == 0)) {
         for (size_t i = 0; i < sizeof(uintptr_t); ++i) {
           const byte expected_byte = (expected_word >> (8 * i)) & 0xFF;
           const byte new_byte = (new_word >> (8 * i)) & 0xFF;
           if (expected_byte != new_byte) {
             modified(reinterpret_cast<byte*>(word_cur) + i, expected_byte, new_byte);
           }
         }
         break;
       }
     }
     ++word_cur;
   }
 }

 inline void* CardTable::AddrFromCard(const byte *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 byte* CardTable::CardFromAddr(const void *addr) const {
   byte *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 void CardTable::CheckCardValid(byte* 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 "base/logging.h"
	#include "card_table.h"
	#include "cutils/atomic-inline.h"
	#include "space_bitmap.h"
	#include "utils.h"

	namespace art {
	namespace gc {
	namespace accounting {

	static inline bool byte_cas(byte old_value, byte new_value, byte* address) {
	// 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;
	int32_t* word_address = reinterpret_cast<int32_t*>(address);
	// Word with the byte we are trying to cas cleared.
	const int32_t cur_word = *word_address & ~(0xFF << shift_in_bits);
	const int32_t old_word = cur_word \| (static_cast<int32_t>(old_value) << shift_in_bits);
	const int32_t new_word = cur_word \| (static_cast<int32_t>(new_value) << shift_in_bits);
	bool success = android_atomic_cas(old_word, new_word, word_address) == 0;
	return success;
	}

	template <typename Visitor>
	inline size_t CardTable::Scan(SpaceBitmap* bitmap, byte* scan_begin, byte* scan_end,
	const Visitor& visitor, const byte minimum_age) const {
	DCHECK(bitmap->HasAddress(scan_begin));
	DCHECK(bitmap->HasAddress(scan_end - 1)); // scan_end is the byte after the last byte we scan.
	byte* card_cur = CardFromAddr(scan_begin);
	byte* card_end = CardFromAddr(scan_end);
	CheckCardValid(card_cur);
	CheckCardValid(card_end);
	size_t cards_scanned = 0;

	// Handle any unaligned cards at the start.
	while (!IsAligned<sizeof(word)>(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;
	}
	++card_cur;
	}

	byte* 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<byte*>(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<byte>(start_word) >= minimum_age) {
	auto* card = reinterpret_cast<byte*>(word_cur) + i;
	DCHECK(card == static_cast<byte>(start_word) \|\| card == kCardDirty)
	<< "card " << static_cast<size_t>(*card) << " word " << (start_word & 0xFF);
	bitmap->VisitMarkedRange(start, start + kCardSize, visitor);
	++cards_scanned;
	}
	start_word >>= 8;
	start += kCardSize;
	}
	}
	exit_for:

	// Handle any unaligned cards at the end.
	card_cur = reinterpret_cast<byte*>(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;
	}
	++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(byte* scan_begin, byte* scan_end, const Visitor& visitor,
	const ModifiedVisitor& modified) {
	byte* card_cur = CardFromAddr(scan_begin);
	byte* card_end = CardFromAddr(AlignUp(scan_end, kCardSize));
	CheckCardValid(card_cur);
	CheckCardValid(card_end);

	// Handle any unaligned cards at the start.
	while (!IsAligned<sizeof(word)>(card_cur) && card_cur < card_end) {
	byte 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(word)>(card_end) && card_end > card_cur) {
	--card_end;
	byte 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);
	uintptr_t expected_word;
	uintptr_t new_word;

	// TODO: Parallelize.
	while (word_cur < word_end) {
	while ((expected_word = *word_cur) != 0) {
	new_word =
	(visitor((expected_word >> 0) & 0xFF) << 0) \|
	(visitor((expected_word >> 8) & 0xFF) << 8) \|
	(visitor((expected_word >> 16) & 0xFF) << 16) \|
	(visitor((expected_word >> 24) & 0xFF) << 24);
	if (new_word == expected_word) {
	// No need to do a cas.
	break;
	}
	if (LIKELY(android_atomic_cas(expected_word, new_word,
	reinterpret_cast<int32_t*>(word_cur)) == 0)) {
	for (size_t i = 0; i < sizeof(uintptr_t); ++i) {
	const byte expected_byte = (expected_word >> (8 * i)) & 0xFF;
	const byte new_byte = (new_word >> (8 * i)) & 0xFF;
	if (expected_byte != new_byte) {
	modified(reinterpret_cast<byte*>(word_cur) + i, expected_byte, new_byte);
	}
	}
	break;
	}
	}
	++word_cur;
	}
	}

	inline void* CardTable::AddrFromCard(const byte *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 byte* CardTable::CardFromAddr(const void *addr) const {
	byte *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 void CardTable::CheckCardValid(byte* 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_