1 /*
   2  * Copyright (c) 2013, 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 #include "precompiled.hpp"
  26 #include "gc/g1/g1CardCounts.hpp"
  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/shared/cardTableBarrierSet.hpp"
  29 #include "services/memTracker.hpp"
  30 #include "utilities/copy.hpp"
  31 
  32 void G1CardCountsMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
  33   if (zero_filled) {
  34     return;
  35   }
  36   MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_idx), num_regions * HeapRegion::GrainWords);
  37   _counts->clear_range(mr);
  38 }
  39 
  40 size_t G1CardCounts::compute_size(size_t mem_region_size_in_words) {
  41   // We keep card counts for every card, so the size of the card counts table must
  42   // be the same as the card table.
  43   return G1CardTable::compute_size(mem_region_size_in_words);
  44 }
  45 
  46 size_t G1CardCounts::heap_map_factor() {
  47   // See G1CardCounts::compute_size() why we reuse the card table value.
  48   return G1CardTable::heap_map_factor();
  49 }
  50 
  51 void G1CardCounts::clear_range(size_t from_card_num, size_t to_card_num) {
  52   if (has_count_table()) {
  53     assert(from_card_num < to_card_num,
  54            "Wrong order? from: " SIZE_FORMAT ", to: " SIZE_FORMAT,
  55            from_card_num, to_card_num);
  56     Copy::fill_to_bytes(&_card_counts[from_card_num], (to_card_num - from_card_num));
  57   }
  58 }
  59 
  60 G1CardCounts::G1CardCounts(G1CollectedHeap *g1h):
  61   _listener(), _g1h(g1h), _ct(NULL), _card_counts(NULL), _reserved_max_card_num(0), _ct_bot(NULL) {
  62   _listener.set_cardcounts(this);
  63 }
  64 
  65 void G1CardCounts::initialize(G1RegionToSpaceMapper* mapper) {
  66   assert(_g1h->reserved().byte_size() > 0, "initialization order");
  67   assert(_g1h->capacity() == 0, "initialization order");
  68 
  69   if (G1ConcRSHotCardLimit > 0) {
  70     // The max value we can store in the counts table is
  71     // max_jubyte. Guarantee the value of the hot
  72     // threshold limit is no more than this.
  73     guarantee(G1ConcRSHotCardLimit <= max_jubyte, "sanity");
  74 
  75     _ct = _g1h->card_table();
  76     _ct_bot = _ct->byte_for_const(_g1h->reserved().start());
  77 
  78     _card_counts = (jubyte*) mapper->reserved().start();
  79     _reserved_max_card_num = mapper->reserved().byte_size();
  80     mapper->set_mapping_changed_listener(&_listener);
  81   }
  82 }
  83 
  84 uint G1CardCounts::add_card_count(CardValue* card_ptr) {
  85   // Returns the number of times the card has been refined.
  86   // If we failed to reserve/commit the counts table, return 0.
  87   // If card_ptr is beyond the committed end of the counts table,
  88   // return 0.
  89   // Otherwise return the actual count.
  90   // Unless G1ConcRSHotCardLimit has been set appropriately,
  91   // returning 0 will result in the card being considered
  92   // cold and will be refined immediately.
  93   uint count = 0;
  94   if (has_count_table()) {
  95     size_t card_num = ptr_2_card_num(card_ptr);
  96     assert(card_num < _reserved_max_card_num,
  97            "Card " SIZE_FORMAT " outside of card counts table (max size " SIZE_FORMAT ")",
  98            card_num, _reserved_max_card_num);
  99     count = (uint) _card_counts[card_num];
 100     if (count < G1ConcRSHotCardLimit) {
 101       _card_counts[card_num] =
 102         (jubyte)(MIN2((uintx)(_card_counts[card_num] + 1), G1ConcRSHotCardLimit));
 103     }
 104   }
 105   return count;
 106 }
 107 
 108 bool G1CardCounts::is_hot(uint count) {
 109   return (count >= G1ConcRSHotCardLimit);
 110 }
 111 
 112 void G1CardCounts::clear_region(HeapRegion* hr) {
 113   MemRegion mr(hr->bottom(), hr->end());
 114   clear_range(mr);
 115 }
 116 
 117 void G1CardCounts::clear_range(MemRegion mr) {
 118   if (has_count_table()) {
 119     const CardValue* from_card_ptr = _ct->byte_for_const(mr.start());
 120     // We use the last address in the range as the range could represent the
 121     // last region in the heap. In which case trying to find the card will be an
 122     // OOB access to the card table.
 123     const CardValue* last_card_ptr = _ct->byte_for_const(mr.last());
 124 
 125 #ifdef ASSERT
 126     HeapWord* start_addr = _ct->addr_for(from_card_ptr);
 127     assert(start_addr == mr.start(), "MemRegion start must be aligned to a card.");
 128     HeapWord* last_addr = _ct->addr_for(last_card_ptr);
 129     assert((last_addr + G1CardTable::card_size_in_words) == mr.end(), "MemRegion end must be aligned to a card.");
 130 #endif // ASSERT
 131 
 132     // Clear the counts for the (exclusive) card range.
 133     size_t from_card_num = ptr_2_card_num(from_card_ptr);
 134     size_t to_card_num = ptr_2_card_num(last_card_ptr) + 1;
 135     clear_range(from_card_num, to_card_num);
 136   }
 137 }
 138 
 139 class G1CardCountsClearClosure : public HeapRegionClosure {
 140  private:
 141   G1CardCounts* _card_counts;
 142  public:
 143   G1CardCountsClearClosure(G1CardCounts* card_counts) :
 144     HeapRegionClosure(), _card_counts(card_counts) { }
 145 
 146 
 147   virtual bool do_heap_region(HeapRegion* r) {
 148     _card_counts->clear_region(r);
 149     return false;
 150   }
 151 };
 152 
 153 void G1CardCounts::clear_all() {
 154   assert(SafepointSynchronize::is_at_safepoint(), "don't call this otherwise");
 155   G1CardCountsClearClosure cl(this);
 156   _g1h->heap_region_iterate(&cl);
 157 }