1 /*

     2  * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 #ifndef SHARE_VM_GC_G1_G1CARDLIVEDATA_HPP

    26 #define SHARE_VM_GC_G1_G1CARDLIVEDATA_HPP

    27 

    28 #include "gc/g1/g1CollectedHeap.hpp"

    29 #include "utilities/bitMap.hpp"

    30 #include "utilities/globalDefinitions.hpp"

    31 

    32 class G1CollectedHeap;

    33 class G1CMBitMap;

    34 class WorkGang;

    35 

    36 // Information about object liveness on the Java heap on a "card" basis.

    37 // Can be used for various purposes, like as remembered set for completely

    38 // coarsened remembered sets, scrubbing remembered sets or estimating liveness.

    39 // This information is created as part of the concurrent marking cycle.

    40 class G1CardLiveData {

    41   friend class G1CardLiveDataHelper;

    42   friend class G1VerifyCardLiveDataTask;

    43 private:

    44   typedef BitMap::bm_word_t bm_word_t;

    45   // Store some additional information about the covered area to be able to test.

    46   size_t _max_capacity;

    47   size_t _cards_per_region;

    48 

    49   // Regions may be reclaimed while concurrently creating live data (e.g. due to humongous

    50   // eager reclaim). This results in wrong live data for these regions at the end.

    51   // So we need to somehow detect these regions, and during live data finalization completely

    52   // recreate their information.

    53   // This _gc_timestamp_at_create tracks the global timestamp when live data creation

    54   // has started. Any regions with a higher time stamp have been cleared after that

    55   // point in time, and need re-finalization.

    56   // Unsynchronized access to this variable is okay, since this value is only set during a

    57   // concurrent phase, and read only at the Cleanup safepoint. I.e. there is always

    58   // full memory synchronization inbetween.

    59   uint _gc_timestamp_at_create;

    60   // The per-card liveness bitmap.

    61   bm_word_t* _live_cards;

    62   size_t _live_cards_size_in_bits;

    63   // The per-region liveness bitmap.

    64   bm_word_t* _live_regions;

    65   size_t _live_regions_size_in_bits;

    66   // The bits in this bitmap contain for every card whether it contains

    67   // at least part of at least one live object.

    68   BitMapView live_cards_bm() const { return BitMapView(_live_cards, _live_cards_size_in_bits); }

    69   // The bits in this bitmap indicate that a given region contains some live objects.

    70   BitMapView live_regions_bm() const { return BitMapView(_live_regions, _live_regions_size_in_bits); }

    71 

    72   // Allocate a "large" bitmap from virtual memory with the given size in bits.

    73   bm_word_t* allocate_large_bitmap(size_t size_in_bits);

    74   void free_large_bitmap(bm_word_t* map, size_t size_in_bits);

    75 

    76   inline BitMapView live_card_bitmap(uint region);

    77 

    78   inline bool is_card_live_at(BitMap::idx_t idx) const;

    79 

    80   size_t live_region_bitmap_size_in_bits() const;

    81   size_t live_card_bitmap_size_in_bits() const;

    82 public:

    83   uint gc_timestamp_at_create() const { return _gc_timestamp_at_create; }

    84 

    85   inline bool is_region_live(uint region) const;

    86 

    87   inline void remove_nonlive_cards(uint region, BitMap* bm);

    88   inline void remove_nonlive_regions(BitMap* bm);

    89 

    90   G1CardLiveData();

    91   ~G1CardLiveData();

    92 

    93   void initialize(size_t max_capacity, uint num_max_regions);

    94   void pretouch();

    95 

    96   // Create the initial liveness data based on the marking result from the bottom

    97   // to the ntams of every region in the heap and the marks in the given bitmap.

    98   void create(WorkGang* workers, G1CMBitMap* mark_bitmap);

    99   // Finalize the liveness data.

   100   void finalize(WorkGang* workers, G1CMBitMap* mark_bitmap);

   101 

   102   // Verify that the liveness count data created concurrently matches one created

   103   // during this safepoint.

   104   void verify(WorkGang* workers, G1CMBitMap* actual_bitmap);

   105   // Clear all data structures, prepare for next processing.

   106   void clear(WorkGang* workers);

   107 

   108   void verify_is_clear() PRODUCT_RETURN;

   109 };

   110 

   111 #endif /* SHARE_VM_GC_G1_G1CARDLIVEDATA_HPP */

   112