jdk8-mips64-public/hotspot: src/share/vm/memory/cardTableModRefBS.hpp@c69b1043dfb1 (annotated)

src/share/vm/memory/cardTableModRefBS.hpp@c69b1043dfb1 (annotated)

src/share/vm/memory/cardTableModRefBS.hpp

Thu, 14 Apr 2011 12:10:15 -0700

author: ysr
date: Thu, 14 Apr 2011 12:10:15 -0700
changeset 2788: c69b1043dfb1
parent 2715: abdfc822206f
child 2819: c48ad6ab8bdf
permissions: -rw-r--r--

7036482: clear argument is redundant and unused in cardtable methods
Summary: Removed the unused clear argument to various cardtbale methods and unused mod_oop_in_space_iterate method. Unrelated to synopsis, added a pair of clarifying parens in AllocationStats constructor.
Reviewed-by: brutisso, jcoomes

 /*
  * Copyright (c) 2000, 2011, 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
  * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 #ifndef SHARE_VM_MEMORY_CARDTABLEMODREFBS_HPP
 #define SHARE_VM_MEMORY_CARDTABLEMODREFBS_HPP
 #include "memory/modRefBarrierSet.hpp"
 #include "oops/oop.hpp"
 #include "oops/oop.inline2.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.
 // 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.
   friend class SharkBuilder;
 #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);
   // Utility function used to implement the other versions below.
   void non_clean_card_iterate_work(MemRegion mr, MemRegionClosure* cl);
   void par_non_clean_card_iterate_work(Space* sp, MemRegion mr,
                                        DirtyCardToOopClosure* dcto_cl,
                                        MemRegionClosure* cl,
                                        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,
                       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);
   }
   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.
   // 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.)
   void mod_card_iterate(MemRegionClosure* cl) {
     non_clean_card_iterate_work(_whole_heap, cl);
   }
   // 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) {
     non_clean_card_iterate_work(mr, cl);
   }
   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; }
 };
 #endif // SHARE_VM_MEMORY_CARDTABLEMODREFBS_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/memory/cardTableModRefBS.hpp@c69b1043dfb1 (annotated)

src/share/vm/memory/cardTableModRefBS.hpp