src/hotspot/share/gc/shared/cardTable.hpp - platform/libcore - Git at Google

 /*
  * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */

 #ifndef SHARE_VM_GC_SHARED_CARDTABLE_HPP
 #define SHARE_VM_GC_SHARED_CARDTABLE_HPP

 #include "memory/allocation.hpp"
 #include "memory/memRegion.hpp"
 #include "oops/oopsHierarchy.hpp"
 #include "utilities/align.hpp"

 class CardTable: public CHeapObj<mtGC> {
   friend class VMStructs;
 protected:
   // The declaration order of these const fields is important; see the
   // constructor before changing.
   const bool      _scanned_concurrently;
   const MemRegion _whole_heap;       // the region covered by the card table
   size_t          _guard_index;      // index of very last element in the card
                                      // table; it is set to a guard value
                                      // (last_card) and should never be modified
   size_t          _last_valid_index; // index of the last valid element
   const size_t    _page_size;        // page size used when mapping _byte_map
   size_t          _byte_map_size;    // in bytes
   jbyte*          _byte_map;         // the card marking array
   jbyte*          _byte_map_base;

   int _cur_covered_regions;

   // The covered regions should be in address order.
   MemRegion* _covered;
   // The committed regions correspond one-to-one to the covered regions.
   // They represent the card-table memory that has been committed to service
   // the corresponding covered region.  It may be that committed region for
   // one covered region corresponds to a larger region because of page-size
   // roundings.  Thus, a committed region for one covered region may
   // actually extend onto the card-table space for the next covered region.
   MemRegion* _committed;

   // The last card is a guard card, and we commit the page for it so
   // we can use the card for verification purposes. We make sure we never
   // uncommit the MemRegion for that page.
   MemRegion _guard_region;

   inline size_t compute_byte_map_size();

   // Finds and return the index of the region, if any, to which the given
   // region would be contiguous.  If none exists, assign a new region and
   // returns its index.  Requires that no more than the maximum number of
   // covered regions defined in the constructor are ever in use.
   int find_covering_region_by_base(HeapWord* base);

   // Same as above, but finds the region containing the given address
   // instead of starting at a given base address.
   int find_covering_region_containing(HeapWord* addr);

   // Returns the leftmost end of a committed region corresponding to a
   // covered region before covered region "ind", or else "NULL" if "ind" is
   // the first covered region.
   HeapWord* largest_prev_committed_end(int ind) const;

   // Returns the part of the region mr that doesn't intersect with
   // any committed region other than self.  Used to prevent uncommitting
   // regions that are also committed by other regions.  Also protects
   // against uncommitting the guard region.
   MemRegion committed_unique_to_self(int self, MemRegion mr) const;

   // Some barrier sets create tables whose elements correspond to parts of
   // the heap; the CardTableBarrierSet is an example.  Such barrier sets will
   // normally reserve space for such tables, and commit parts of the table
   // "covering" parts of the heap that are committed. At most one covered
   // region per generation is needed.
   static const int _max_covered_regions = 2;

   enum CardValues {
     clean_card                  = -1,
     // The mask contains zeros in places for all other values.
     clean_card_mask             = clean_card - 31,

     dirty_card                  =  0,
     precleaned_card             =  1,
     claimed_card                =  2,
     deferred_card               =  4,
     last_card                   =  8,
     CT_MR_BS_last_reserved      = 16
   };

   // a word's worth (row) of clean card values
   static const intptr_t clean_card_row = (intptr_t)(-1);

 public:
   CardTable(MemRegion whole_heap, bool conc_scan);
   virtual ~CardTable();
   virtual void initialize();

   // The kinds of precision a CardTable may offer.
   enum PrecisionStyle {
     Precise,
     ObjHeadPreciseArray
   };

   // Tells what style of precision this card table offers.
   PrecisionStyle precision() {
     return ObjHeadPreciseArray; // Only one supported for now.
   }

   // *** Barrier set functions.

   // Initialization utilities; covered_words is the size of the covered region
   // in, um, words.
   inline size_t cards_required(size_t covered_words) {
     // Add one for a guard card, used to detect errors.
     const size_t words = align_up(covered_words, card_size_in_words);
     return words / card_size_in_words + 1;
   }

   // Dirty the bytes corresponding to "mr" (not all of which must be
   // covered.)
   void dirty_MemRegion(MemRegion mr);

   // Clear (to clean_card) the bytes entirely contained within "mr" (not
   // all of which must be covered.)
   void clear_MemRegion(MemRegion mr);

   // Return true if "p" is at the start of a card.
   bool is_card_aligned(HeapWord* p) {
     jbyte* pcard = byte_for(p);
     return (addr_for(pcard) == p);
   }

   // Mapping from address to card marking array entry
   jbyte* byte_for(const void* p) const {
     assert(_whole_heap.contains(p),
            "Attempt to access p = " PTR_FORMAT " out of bounds of "
            " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
            p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
     jbyte* result = &_byte_map_base[uintptr_t(p) >> card_shift];
     assert(result >= _byte_map && result < _byte_map + _byte_map_size,
            "out of bounds accessor for card marking array");
     return result;
   }

   // The card table byte one after the card marking array
   // entry for argument address. Typically used for higher bounds
   // for loops iterating through the card table.
   jbyte* byte_after(const void* p) const {
     return byte_for(p) + 1;
   }

   virtual void invalidate(MemRegion mr);
   void clear(MemRegion mr);
   void dirty(MemRegion mr);

   // Provide read-only access to the card table array.
   const jbyte* byte_for_const(const void* p) const {
     return byte_for(p);
   }
   const jbyte* byte_after_const(const void* p) const {
     return byte_after(p);
   }

   // Mapping from card marking array entry to address of first word
   HeapWord* addr_for(const jbyte* p) const {
     assert(p >= _byte_map && p < _byte_map + _byte_map_size,
            "out of bounds access to card marking array. p: " PTR_FORMAT
            " _byte_map: " PTR_FORMAT " _byte_map + _byte_map_size: " PTR_FORMAT,
            p2i(p), p2i(_byte_map), p2i(_byte_map + _byte_map_size));
     size_t delta = pointer_delta(p, _byte_map_base, sizeof(jbyte));
     HeapWord* result = (HeapWord*) (delta << card_shift);
     assert(_whole_heap.contains(result),
            "Returning result = " PTR_FORMAT " out of bounds of "
            " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
            p2i(result), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
     return result;
   }

   // Mapping from address to card marking array index.
   size_t index_for(void* p) {
     assert(_whole_heap.contains(p),
            "Attempt to access p = " PTR_FORMAT " out of bounds of "
            " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
            p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
     return byte_for(p) - _byte_map;
   }

   const jbyte* byte_for_index(const size_t card_index) const {
     return _byte_map + card_index;
   }

   // Resize one of the regions covered by the remembered set.
   virtual void resize_covered_region(MemRegion new_region);

   // *** Card-table-RemSet-specific things.

   static uintx ct_max_alignment_constraint();

   // Apply closure "cl" to the dirty cards containing some part of
   // MemRegion "mr".
   void dirty_card_iterate(MemRegion mr, MemRegionClosure* cl);

   // Return the MemRegion corresponding to the first maximal run
   // of dirty cards lying completely within MemRegion mr.
   // If reset is "true", then sets those card table entries to the given
   // value.
   MemRegion dirty_card_range_after_reset(MemRegion mr, bool reset,
                                          int reset_val);

   // Constants
   enum SomePublicConstants {
     card_shift                  = 9,
     card_size                   = 1 << card_shift,
     card_size_in_words          = card_size / sizeof(HeapWord)
   };

   static jbyte clean_card_val()          { return clean_card; }
   static jbyte clean_card_mask_val()     { return clean_card_mask; }
   static jbyte dirty_card_val()          { return dirty_card; }
   static jbyte claimed_card_val()        { return claimed_card; }
   static jbyte precleaned_card_val()     { return precleaned_card; }
   static jbyte deferred_card_val()       { return deferred_card; }
   static intptr_t clean_card_row_val()   { return clean_card_row; }

   // Card marking array base (adjusted for heap low boundary)
   // This would be the 0th element of _byte_map, if the heap started at 0x0.
   // But since the heap starts at some higher address, this points to somewhere
   // before the beginning of the actual _byte_map.
   jbyte* byte_map_base() const { return _byte_map_base; }
   bool scanned_concurrently() const { return _scanned_concurrently; }

   virtual bool is_in_young(oop obj) const = 0;

   // Print a description of the memory for the card table
   virtual void print_on(outputStream* st) const;

   void verify();
   void verify_guard();

   // val_equals -> it will check that all cards covered by mr equal val
   // !val_equals -> it will check that all cards covered by mr do not equal val
   void verify_region(MemRegion mr, jbyte val, bool val_equals) PRODUCT_RETURN;
   void verify_not_dirty_region(MemRegion mr) PRODUCT_RETURN;
   void verify_dirty_region(MemRegion mr) PRODUCT_RETURN;
 };

 #endif // SHARE_VM_GC_SHARED_CARDTABLE_HPP
	/*
	* Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*
	*/

	#ifndef SHARE_VM_GC_SHARED_CARDTABLE_HPP
	#define SHARE_VM_GC_SHARED_CARDTABLE_HPP

	#include "memory/allocation.hpp"
	#include "memory/memRegion.hpp"
	#include "oops/oopsHierarchy.hpp"
	#include "utilities/align.hpp"

	class CardTable: public CHeapObj<mtGC> {
	friend class VMStructs;
	protected:
	// The declaration order of these const fields is important; see the
	// constructor before changing.
	const bool _scanned_concurrently;
	const MemRegion _whole_heap; // the region covered by the card table
	size_t _guard_index; // index of very last element in the card
	// table; it is set to a guard value
	// (last_card) and should never be modified
	size_t _last_valid_index; // index of the last valid element
	const size_t _page_size; // page size used when mapping _byte_map
	size_t _byte_map_size; // in bytes
	jbyte* _byte_map; // the card marking array
	jbyte* _byte_map_base;

	int _cur_covered_regions;

	// The covered regions should be in address order.
	MemRegion* _covered;
	// The committed regions correspond one-to-one to the covered regions.
	// They represent the card-table memory that has been committed to service
	// the corresponding covered region. It may be that committed region for
	// one covered region corresponds to a larger region because of page-size
	// roundings. Thus, a committed region for one covered region may
	// actually extend onto the card-table space for the next covered region.
	MemRegion* _committed;

	// The last card is a guard card, and we commit the page for it so
	// we can use the card for verification purposes. We make sure we never
	// uncommit the MemRegion for that page.
	MemRegion _guard_region;

	inline size_t compute_byte_map_size();

	// Finds and return the index of the region, if any, to which the given
	// region would be contiguous. If none exists, assign a new region and
	// returns its index. Requires that no more than the maximum number of
	// covered regions defined in the constructor are ever in use.
	int find_covering_region_by_base(HeapWord* base);

	// Same as above, but finds the region containing the given address
	// instead of starting at a given base address.
	int find_covering_region_containing(HeapWord* addr);

	// Returns the leftmost end of a committed region corresponding to a
	// covered region before covered region "ind", or else "NULL" if "ind" is
	// the first covered region.
	HeapWord* largest_prev_committed_end(int ind) const;

	// Returns the part of the region mr that doesn't intersect with
	// any committed region other than self. Used to prevent uncommitting
	// regions that are also committed by other regions. Also protects
	// against uncommitting the guard region.
	MemRegion committed_unique_to_self(int self, MemRegion mr) const;

	// Some barrier sets create tables whose elements correspond to parts of
	// the heap; the CardTableBarrierSet is an example. Such barrier sets will
	// normally reserve space for such tables, and commit parts of the table
	// "covering" parts of the heap that are committed. At most one covered
	// region per generation is needed.
	static const int _max_covered_regions = 2;

	enum CardValues {
	clean_card = -1,
	// The mask contains zeros in places for all other values.
	clean_card_mask = clean_card - 31,

	dirty_card = 0,
	precleaned_card = 1,
	claimed_card = 2,
	deferred_card = 4,
	last_card = 8,
	CT_MR_BS_last_reserved = 16
	};

	// a word's worth (row) of clean card values
	static const intptr_t clean_card_row = (intptr_t)(-1);

	public:
	CardTable(MemRegion whole_heap, bool conc_scan);
	virtual ~CardTable();
	virtual void initialize();

	// The kinds of precision a CardTable may offer.
	enum PrecisionStyle {
	Precise,
	ObjHeadPreciseArray
	};

	// Tells what style of precision this card table offers.
	PrecisionStyle precision() {
	return ObjHeadPreciseArray; // Only one supported for now.
	}

	// *** Barrier set functions.

	// Initialization utilities; covered_words is the size of the covered region
	// in, um, words.
	inline size_t cards_required(size_t covered_words) {
	// Add one for a guard card, used to detect errors.
	const size_t words = align_up(covered_words, card_size_in_words);
	return words / card_size_in_words + 1;
	}

	// Dirty the bytes corresponding to "mr" (not all of which must be
	// covered.)
	void dirty_MemRegion(MemRegion mr);

	// Clear (to clean_card) the bytes entirely contained within "mr" (not
	// all of which must be covered.)
	void clear_MemRegion(MemRegion mr);

	// Return true if "p" is at the start of a card.
	bool is_card_aligned(HeapWord* p) {
	jbyte* pcard = byte_for(p);
	return (addr_for(pcard) == p);
	}

	// Mapping from address to card marking array entry
	jbyte* byte_for(const void* p) const {
	assert(_whole_heap.contains(p),
	"Attempt to access p = " PTR_FORMAT " out of bounds of "
	" card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
	p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
	jbyte* result = &_byte_map_base[uintptr_t(p) >> card_shift];
	assert(result >= _byte_map && result < _byte_map + _byte_map_size,
	"out of bounds accessor for card marking array");
	return result;
	}

	// The card table byte one after the card marking array
	// entry for argument address. Typically used for higher bounds
	// for loops iterating through the card table.
	jbyte* byte_after(const void* p) const {
	return byte_for(p) + 1;
	}

	virtual void invalidate(MemRegion mr);
	void clear(MemRegion mr);
	void dirty(MemRegion mr);

	// Provide read-only access to the card table array.
	const jbyte* byte_for_const(const void* p) const {
	return byte_for(p);
	}
	const jbyte* byte_after_const(const void* p) const {
	return byte_after(p);
	}

	// Mapping from card marking array entry to address of first word
	HeapWord* addr_for(const jbyte* p) const {
	assert(p >= _byte_map && p < _byte_map + _byte_map_size,
	"out of bounds access to card marking array. p: " PTR_FORMAT
	" _byte_map: " PTR_FORMAT " _byte_map + _byte_map_size: " PTR_FORMAT,
	p2i(p), p2i(_byte_map), p2i(_byte_map + _byte_map_size));
	size_t delta = pointer_delta(p, _byte_map_base, sizeof(jbyte));
	HeapWord* result = (HeapWord*) (delta << card_shift);
	assert(_whole_heap.contains(result),
	"Returning result = " PTR_FORMAT " out of bounds of "
	" card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
	p2i(result), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
	return result;
	}

	// Mapping from address to card marking array index.
	size_t index_for(void* p) {
	assert(_whole_heap.contains(p),
	"Attempt to access p = " PTR_FORMAT " out of bounds of "
	" card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")",
	p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end()));
	return byte_for(p) - _byte_map;
	}

	const jbyte* byte_for_index(const size_t card_index) const {
	return _byte_map + card_index;
	}

	// Resize one of the regions covered by the remembered set.
	virtual void resize_covered_region(MemRegion new_region);

	// *** Card-table-RemSet-specific things.

	static uintx ct_max_alignment_constraint();

	// Apply closure "cl" to the dirty cards containing some part of
	// MemRegion "mr".
	void dirty_card_iterate(MemRegion mr, MemRegionClosure* cl);

	// Return the MemRegion corresponding to the first maximal run
	// of dirty cards lying completely within MemRegion mr.
	// If reset is "true", then sets those card table entries to the given
	// value.
	MemRegion dirty_card_range_after_reset(MemRegion mr, bool reset,
	int reset_val);

	// Constants
	enum SomePublicConstants {
	card_shift = 9,
	card_size = 1 << card_shift,
	card_size_in_words = card_size / sizeof(HeapWord)
	};

	static jbyte clean_card_val() { return clean_card; }
	static jbyte clean_card_mask_val() { return clean_card_mask; }
	static jbyte dirty_card_val() { return dirty_card; }
	static jbyte claimed_card_val() { return claimed_card; }
	static jbyte precleaned_card_val() { return precleaned_card; }
	static jbyte deferred_card_val() { return deferred_card; }
	static intptr_t clean_card_row_val() { return clean_card_row; }

	// Card marking array base (adjusted for heap low boundary)
	// This would be the 0th element of _byte_map, if the heap started at 0x0.
	// But since the heap starts at some higher address, this points to somewhere
	// before the beginning of the actual _byte_map.
	jbyte* byte_map_base() const { return _byte_map_base; }
	bool scanned_concurrently() const { return _scanned_concurrently; }

	virtual bool is_in_young(oop obj) const = 0;

	// Print a description of the memory for the card table
	virtual void print_on(outputStream* st) const;

	void verify();
	void verify_guard();

	// val_equals -> it will check that all cards covered by mr equal val
	// !val_equals -> it will check that all cards covered by mr do not equal val
	void verify_region(MemRegion mr, jbyte val, bool val_equals) PRODUCT_RETURN;
	void verify_not_dirty_region(MemRegion mr) PRODUCT_RETURN;
	void verify_dirty_region(MemRegion mr) PRODUCT_RETURN;
	};

	#endif // SHARE_VM_GC_SHARED_CARDTABLE_HPP