truffle: src/share/vm/memory/cardTableModRefBS.hpp comparison

comparison src/share/vm/memory/cardTableModRefBS.hpp @ 0:a61af66fc99e jdk7-b24

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author	duke
date	Sat, 01 Dec 2007 00:00:00 +0000
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children	ba764ed4b6f2

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+/*
+* 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; }
+};

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comparison src/share/vm/memory/cardTableModRefBS.hpp @ 0:a61af66fc99e jdk7-b24