| /* |
| * Copyright (c) 2000, 2015, 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 |
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| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
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| |
| #ifndef SHARE_VM_GC_SHARED_CARDTABLEMODREFBS_HPP |
| #define SHARE_VM_GC_SHARED_CARDTABLEMODREFBS_HPP |
| |
| #include "gc/shared/modRefBarrierSet.hpp" |
| #include "oops/oop.hpp" |
| |
| // This kind of "BarrierSet" allows a "CollectedHeap" to detect and |
| // enumerate ref fields that have been modified (since the last |
| // enumeration.) |
| |
| // As it currently stands, this barrier is *imprecise*: when a ref field in |
| // an object "o" is modified, the card table entry for the card containing |
| // the head of "o" is dirtied, not necessarily the card containing the |
| // modified field itself. For object arrays, however, the barrier *is* |
| // precise; only the card containing the modified element is dirtied. |
| // Closures used to scan dirty cards should take these |
| // considerations into account. |
| |
| class CardTableModRefBS: public ModRefBarrierSet { |
| // Some classes get to look at some private stuff. |
| friend class VMStructs; |
| protected: |
| |
| 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); |
| |
| // The declaration order of these const fields is important; see the |
| // constructor before changing. |
| 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 |
| |
| 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; |
| |
| protected: |
| // 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_size_up(covered_words, card_size_in_words); |
| return words / card_size_in_words + 1; |
| } |
| |
| 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); |
| |
| // Resize one of the regions covered by the remembered set. |
| virtual void resize_covered_region(MemRegion new_region); |
| |
| // 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; |
| |
| // 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; |
| } |
| |
| protected: |
| // 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); |
| |
| public: |
| // Constants |
| enum SomePublicConstants { |
| card_shift = 9, |
| card_size = 1 << card_shift, |
| card_size_in_words = card_size / sizeof(HeapWord) |
| }; |
| |
| static int clean_card_val() { return clean_card; } |
| static int clean_card_mask_val() { return clean_card_mask; } |
| static int dirty_card_val() { return dirty_card; } |
| static int claimed_card_val() { return claimed_card; } |
| static int precleaned_card_val() { return precleaned_card; } |
| static int deferred_card_val() { return deferred_card; } |
| |
| virtual void initialize(); |
| |
| // *** Barrier set functions. |
| |
| bool has_write_ref_pre_barrier() { return false; } |
| |
| protected: |
| |
| CardTableModRefBS(MemRegion whole_heap, const BarrierSet::FakeRtti& fake_rtti); |
| ~CardTableModRefBS(); |
| |
| // Record a reference update. Note that these versions are precise! |
| // The scanning code has to handle the fact that the write barrier may be |
| // either precise or imprecise. We make non-virtual inline variants of |
| // these functions here for performance. |
| |
| void write_ref_field_work(oop obj, size_t offset, oop newVal); |
| virtual void write_ref_field_work(void* field, oop newVal, bool release); |
| public: |
| |
| bool has_write_ref_array_opt() { return true; } |
| bool has_write_region_opt() { return true; } |
| |
| inline void inline_write_region(MemRegion mr) { |
| dirty_MemRegion(mr); |
| } |
| protected: |
| void write_region_work(MemRegion mr) { |
| inline_write_region(mr); |
| } |
| public: |
| |
| inline void inline_write_ref_array(MemRegion mr) { |
| dirty_MemRegion(mr); |
| } |
| protected: |
| void write_ref_array_work(MemRegion mr) { |
| inline_write_ref_array(mr); |
| } |
| public: |
| |
| bool is_aligned(HeapWord* addr) { |
| return is_card_aligned(addr); |
| } |
| |
| // *** Card-table-barrier-specific things. |
| |
| template <class T> inline void inline_write_ref_field_pre(T* field, oop newVal) {} |
| |
| template <class T> inline void inline_write_ref_field(T* field, oop newVal, bool release); |
| |
| // These are used by G1, when it uses the card table as a temporary data |
| // structure for card claiming. |
| bool is_card_dirty(size_t card_index) { |
| return _byte_map[card_index] == dirty_card_val(); |
| } |
| |
| void mark_card_dirty(size_t card_index) { |
| _byte_map[card_index] = dirty_card_val(); |
| } |
| |
| bool is_card_clean(size_t card_index) { |
| return _byte_map[card_index] == clean_card_val(); |
| } |
| |
| // 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; |
| |
| // 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); |
| } |
| |
| HeapWord* align_to_card_boundary(HeapWord* p) { |
| jbyte* pcard = byte_for(p + card_size_in_words - 1); |
| return addr_for(pcard); |
| } |
| |
| // The kinds of precision a CardTableModRefBS may offer. |
| enum PrecisionStyle { |
| Precise, |
| ObjHeadPreciseArray |
| }; |
| |
| // Tells what style of precision this card table offers. |
| PrecisionStyle precision() { |
| return ObjHeadPreciseArray; // Only one supported for now. |
| } |
| |
| // ModRefBS functions. |
| virtual void invalidate(MemRegion mr, bool whole_heap = false); |
| void clear(MemRegion mr); |
| void dirty(MemRegion mr); |
| |
| // *** 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); |
| |
| // 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"); |
| 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; |
| } |
| |
| // Print a description of the memory for the barrier set |
| 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; |
| }; |
| |
| template<> |
| struct BarrierSet::GetName<CardTableModRefBS> { |
| static const BarrierSet::Name value = BarrierSet::CardTableModRef; |
| }; |
| |
| |
| #endif // SHARE_VM_GC_SHARED_CARDTABLEMODREFBS_HPP |