diff -r fd16c54261b3 -r 489c9b5090e2 hotspot/src/share/vm/memory/cardTableModRefBS.hpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/hotspot/src/share/vm/memory/cardTableModRefBS.hpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,421 @@ +/* + * Copyright 2000-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +// 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. +// Any MemRegionClosures used to scan dirty cards should take these +// considerations into account. + +class Generation; +class OopsInGenClosure; +class DirtyCardToOopClosure; + +class CardTableModRefBS: public ModRefBarrierSet { + // Some classes get to look at some private stuff. + friend class BytecodeInterpreter; + friend class VMStructs; + friend class CardTableRS; + friend class CheckForUnmarkedOops; // Needs access to raw card bytes. +#ifndef PRODUCT + // For debugging. + friend class GuaranteeNotModClosure; +#endif + protected: + + enum CardValues { + clean_card = -1, + dirty_card = 0, + precleaned_card = 1, + last_card = 4, + CT_MR_BS_last_reserved = 10 + }; + + // dirty and precleaned are equivalent wrt younger_refs_iter. + static bool card_is_dirty_wrt_gen_iter(jbyte cv) { + return cv == dirty_card || cv == precleaned_card; + } + + // Returns "true" iff the value "cv" will cause the card containing it + // to be scanned in the current traversal. May be overridden by + // subtypes. + virtual bool card_will_be_scanned(jbyte cv) { + return CardTableModRefBS::card_is_dirty_wrt_gen_iter(cv); + } + + // Returns "true" iff the value "cv" may have represented a dirty card at + // some point. + virtual bool card_may_have_been_dirty(jbyte cv) { + return card_is_dirty_wrt_gen_iter(cv); + } + + // 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 + const 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 + const size_t _last_valid_index; // index of the last valid element + const size_t _page_size; // page size used when mapping _byte_map + const 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); + 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. + 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), + "out of bounds access to card marking array"); + 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; + } + + // 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), + "out of bounds accessor from card marking array"); + return result; + } + + // Iterate over the portion of the card-table which covers the given + // region mr in the given space and apply cl to any dirty sub-regions + // of mr. cl and dcto_cl must either be the same closure or cl must + // wrap dcto_cl. Both are required - neither may be NULL. Also, dcto_cl + // may be modified. Note that this function will operate in a parallel + // mode if worker threads are available. + void non_clean_card_iterate(Space* sp, MemRegion mr, + DirtyCardToOopClosure* dcto_cl, + MemRegionClosure* cl, + bool clear); + + // Utility function used to implement the other versions below. + void non_clean_card_iterate_work(MemRegion mr, MemRegionClosure* cl, + bool clear); + + void par_non_clean_card_iterate_work(Space* sp, MemRegion mr, + DirtyCardToOopClosure* dcto_cl, + MemRegionClosure* cl, + bool clear, + int n_threads); + + // 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); + + // *** Support for parallel card scanning. + + enum SomeConstantsForParallelism { + StridesPerThread = 2, + CardsPerStrideChunk = 256 + }; + + // This is an array, one element per covered region of the card table. + // Each entry is itself an array, with one element per chunk in the + // covered region. Each entry of these arrays is the lowest non-clean + // card of the corresponding chunk containing part of an object from the + // previous chunk, or else NULL. + typedef jbyte* CardPtr; + typedef CardPtr* CardArr; + CardArr* _lowest_non_clean; + size_t* _lowest_non_clean_chunk_size; + uintptr_t* _lowest_non_clean_base_chunk_index; + int* _last_LNC_resizing_collection; + + // Initializes "lowest_non_clean" to point to the array for the region + // covering "sp", and "lowest_non_clean_base_chunk_index" to the chunk + // index of the corresponding to the first element of that array. + // Ensures that these arrays are of sufficient size, allocating if necessary. + // May be called by several threads concurrently. + void get_LNC_array_for_space(Space* sp, + jbyte**& lowest_non_clean, + uintptr_t& lowest_non_clean_base_chunk_index, + size_t& lowest_non_clean_chunk_size); + + // Returns the number of chunks necessary to cover "mr". + size_t chunks_to_cover(MemRegion mr) { + return (size_t)(addr_to_chunk_index(mr.last()) - + addr_to_chunk_index(mr.start()) + 1); + } + + // Returns the index of the chunk in a stride which + // covers the given address. + uintptr_t addr_to_chunk_index(const void* addr) { + uintptr_t card = (uintptr_t) byte_for(addr); + return card / CardsPerStrideChunk; + } + + // Apply cl, which must either itself apply dcto_cl or be dcto_cl, + // to the cards in the stride (of n_strides) within the given space. + void process_stride(Space* sp, + MemRegion used, + jint stride, int n_strides, + DirtyCardToOopClosure* dcto_cl, + MemRegionClosure* cl, + bool clear, + jbyte** lowest_non_clean, + uintptr_t lowest_non_clean_base_chunk_index, + size_t lowest_non_clean_chunk_size); + + // Makes sure that chunk boundaries are handled appropriately, by + // adjusting the min_done of dcto_cl, and by using a special card-table + // value to indicate how min_done should be set. + void process_chunk_boundaries(Space* sp, + DirtyCardToOopClosure* dcto_cl, + MemRegion chunk_mr, + MemRegion used, + jbyte** lowest_non_clean, + uintptr_t lowest_non_clean_base_chunk_index, + size_t lowest_non_clean_chunk_size); + +public: + // Constants + enum SomePublicConstants { + card_shift = 9, + card_size = 1 << card_shift, + card_size_in_words = card_size / sizeof(HeapWord) + }; + + // For RTTI simulation. + BarrierSet::Name kind() { return BarrierSet::CardTableModRef; } + bool is_a(BarrierSet::Name bsn) { + return bsn == BarrierSet::CardTableModRef || bsn == BarrierSet::ModRef; + } + + CardTableModRefBS(MemRegion whole_heap, int max_covered_regions); + + // *** Barrier set functions. + + inline bool write_ref_needs_barrier(oop* field, oop new_val) { + // Note that this assumes the perm gen is the highest generation + // in the address space + return new_val != NULL && !new_val->is_perm(); + } + + // 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. +protected: + void write_ref_field_work(oop obj, size_t offset, oop newVal); + void write_ref_field_work(oop* field, oop newVal); +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. + + inline void inline_write_ref_field(oop* field, oop newVal) { + jbyte* byte = byte_for(field); + *byte = dirty_card; + } + + // 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); + } + + // 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. + void invalidate(MemRegion mr); + void clear(MemRegion mr); + void mod_oop_in_space_iterate(Space* sp, OopClosure* cl, + bool clear = false, + bool before_save_marks = false); + + // *** Card-table-RemSet-specific things. + + // Invoke "cl.do_MemRegion" on a set of MemRegions that collectively + // includes all the modified cards (expressing each card as a + // MemRegion). Thus, several modified cards may be lumped into one + // region. The regions are non-overlapping, and are visited in + // *decreasing* address order. (This order aids with imprecise card + // marking, where a dirty card may cause scanning, and summarization + // marking, of objects that extend onto subsequent cards.) + // If "clear" is true, the card is (conceptually) marked unmodified before + // applying the closure. + void mod_card_iterate(MemRegionClosure* cl, bool clear = false) { + non_clean_card_iterate_work(_whole_heap, cl, clear); + } + + // Like the "mod_cards_iterate" above, except only invokes the closure + // for cards within the MemRegion "mr" (which is required to be + // card-aligned and sized.) + void mod_card_iterate(MemRegion mr, MemRegionClosure* cl, + bool clear = false) { + non_clean_card_iterate_work(mr, cl, clear); + } + + static uintx ct_max_alignment_constraint(); + + // Apply closure cl to the dirty cards lying completely + // within MemRegion mr, setting the cards to precleaned. + 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, after + // marking those cards precleaned. + MemRegion dirty_card_range_after_preclean(MemRegion mr); + + // Set all the dirty cards in the given region to precleaned state. + void preclean_dirty_cards(MemRegion mr); + + // Mapping from address to card marking array index. + int index_for(void* p) { + assert(_whole_heap.contains(p), + "out of bounds access to card marking array"); + return byte_for(p) - _byte_map; + } + + void verify(); + void verify_guard(); + + void verify_clean_region(MemRegion mr) PRODUCT_RETURN; + + static size_t par_chunk_heapword_alignment() { + return CardsPerStrideChunk * card_size_in_words; + } +}; + +class CardTableRS; + +// A specialization for the CardTableRS gen rem set. +class CardTableModRefBSForCTRS: public CardTableModRefBS { + CardTableRS* _rs; +protected: + bool card_will_be_scanned(jbyte cv); + bool card_may_have_been_dirty(jbyte cv); +public: + CardTableModRefBSForCTRS(MemRegion whole_heap, + int max_covered_regions) : + CardTableModRefBS(whole_heap, max_covered_regions) {} + + void set_CTRS(CardTableRS* rs) { _rs = rs; } +};