Mercurial > hg > graal-jvmci-8
view src/share/vm/memory/cardTableModRefBS.hpp @ 1520:bb843ebc7c55
6919638: CMS: ExplicitGCInvokesConcurrent misinteracts with gc locker
Summary: GC-locker induced concurrent full gc should be asynchronous; policy now controlled by a separate flag, which defaults to false.
Reviewed-by: jmasa
author | ysr |
---|---|
date | Mon, 03 May 2010 20:19:05 -0700 |
parents | 0414c1049f15 |
children | c18cbe5936b8 |
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/* * Copyright 2000-2009 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, // 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 }; // 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; } // 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) }; 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; } // For RTTI simulation. bool is_a(BarrierSet::Name bsn) { return bsn == BarrierSet::CardTableModRef || ModRefBarrierSet::is_a(bsn); } CardTableModRefBS(MemRegion whole_heap, int max_covered_regions); // *** Barrier set functions. bool has_write_ref_pre_barrier() { return false; } inline bool write_ref_needs_barrier(void* 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); virtual void write_ref_field_work(void* 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. 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) { jbyte* byte = byte_for((void*)field); *byte = dirty_card; } // 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_claimed(size_t card_index) { jbyte val = _byte_map[card_index]; return (val & (clean_card_mask_val() | claimed_card_val())) == claimed_card_val(); } void set_card_claimed(size_t card_index) { jbyte val = _byte_map[card_index]; if (val == clean_card_val()) { val = (jbyte)claimed_card_val(); } else { val |= (jbyte)claimed_card_val(); } _byte_map[card_index] = val; } bool claim_card(size_t card_index); bool is_card_clean(size_t card_index) { return _byte_map[card_index] == clean_card_val(); } bool is_card_deferred(size_t card_index) { jbyte val = _byte_map[card_index]; return (val & (clean_card_mask_val() | deferred_card_val())) == deferred_card_val(); } bool mark_card_deferred(size_t card_index); // 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. virtual void invalidate(MemRegion mr, bool whole_heap = false); void clear(MemRegion mr); void dirty(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 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); // Set all the dirty cards in the given region to precleaned state. void preclean_dirty_cards(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"); 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; } // Mapping from address to card marking array index. size_t index_for(void* p) { assert(_whole_heap.contains(p), "out of bounds access to card marking array"); return byte_for(p) - _byte_map; } const jbyte* byte_for_index(const size_t card_index) const { return _byte_map + card_index; } void verify(); void verify_guard(); void verify_clean_region(MemRegion mr) PRODUCT_RETURN; void verify_dirty_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; } };