--- /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; }
+};