jdk-24/src/hotspot/share/gc/g1/sparsePRT.cpp

/*
 * Copyright (c) 2001, 2019, 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
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 * questions.
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#include "precompiled.hpp"
#include "gc/g1/heapRegion.hpp"
#include "gc/g1/heapRegionBounds.inline.hpp"
#include "gc/g1/heapRegionRemSet.hpp"
#include "gc/g1/sparsePRT.hpp"
#include "gc/shared/cardTableBarrierSet.hpp"
#include "gc/shared/space.inline.hpp"
#include "memory/allocation.inline.hpp"

// Check that the size of the SparsePRTEntry is evenly divisible by the maximum
// member type to avoid SIGBUS when accessing them.
STATIC_ASSERT(sizeof(SparsePRTEntry) % sizeof(int) == 0);

void SparsePRTEntry::init(RegionIdx_t region_ind) {
  // Check that the card array element type can represent all cards in the region.
  // Choose a large SparsePRTEntry::card_elem_t (e.g. CardIdx_t) if required.
  assert(((size_t)1 << (sizeof(SparsePRTEntry::card_elem_t) * BitsPerByte)) *
         G1CardTable::card_size >= HeapRegionBounds::max_size(), "precondition");
  assert(G1RSetSparseRegionEntries > 0, "precondition");
  _region_ind = region_ind;
  _next_index = RSHashTable::NullEntry;
  _next_null = 0;
}

bool SparsePRTEntry::contains_card(CardIdx_t card_index) const {
  for (int i = 0; i < num_valid_cards(); i++) {
    if (card(i) == card_index) {
      return true;
    }
  }
  return false;
}

SparsePRT::AddCardResult SparsePRTEntry::add_card(CardIdx_t card_index) {
  for (int i = 0; i < num_valid_cards(); i++) {
    if (card(i) == card_index) {
      return SparsePRT::found;
    }
  }
  if (num_valid_cards() < cards_num() - 1) {
    _cards[_next_null] = (card_elem_t)card_index;
    _next_null++;
    return SparsePRT::added;
   }
  // Otherwise, we're full.
  return SparsePRT::overflow;
}

void SparsePRTEntry::copy_cards(card_elem_t* cards) const {
  memcpy(cards, _cards, cards_num() * sizeof(card_elem_t));
}

void SparsePRTEntry::copy_cards(SparsePRTEntry* e) const {
  copy_cards(e->_cards);
  assert(_next_null >= 0, "invariant");
  assert(_next_null <= cards_num(), "invariant");
  e->_next_null = _next_null;
}

// ----------------------------------------------------------------------

float RSHashTable::TableOccupancyFactor = 0.5f;

// The empty table can't hold any entries and is effectively immutable
// This means it can be used as an initial sentinel value
static int empty_buckets[] = { RSHashTable::NullEntry };
RSHashTable RSHashTable::empty_table;

RSHashTable::RSHashTable() :
  _num_entries(0),
  _capacity(0),
  _capacity_mask(0),
  _occupied_entries(0),
  _entries(NULL),
  _buckets(empty_buckets),
  _free_region(0),
  _free_list(NullEntry) { }

RSHashTable::RSHashTable(size_t capacity) :
  _num_entries((capacity * TableOccupancyFactor) + 1),
  _capacity(capacity),
  _capacity_mask(capacity - 1),
  _occupied_entries(0),
  _entries((SparsePRTEntry*)NEW_C_HEAP_ARRAY(char, _num_entries * SparsePRTEntry::size(), mtGC)),
  _buckets(NEW_C_HEAP_ARRAY(int, capacity, mtGC)),
  _free_region(0),
  _free_list(NullEntry)
{
  clear();
}

RSHashTable::~RSHashTable() {
  // Nothing to free for empty RSHashTable
  if (_buckets != empty_buckets) {
    assert(_entries != NULL, "invariant");
    FREE_C_HEAP_ARRAY(SparsePRTEntry, _entries);
    FREE_C_HEAP_ARRAY(int, _buckets);
  }
}

void RSHashTable::clear() {
  assert(_buckets != empty_buckets, "Shouldn't call this for the empty_table");
  _occupied_entries = 0;
  guarantee(_entries != NULL, "invariant");
  guarantee(_buckets != NULL, "invariant");

  guarantee(_capacity <= ((size_t)1 << (sizeof(int)*BitsPerByte-1)) - 1,
                "_capacity too large");

  // This will put -1 == NullEntry in the key field of all entries.
  memset((void*)_entries, NullEntry, _num_entries * SparsePRTEntry::size());
  memset((void*)_buckets, NullEntry, _capacity * sizeof(int));
  _free_list = NullEntry;
  _free_region = 0;
}

SparsePRT::AddCardResult RSHashTable::add_card(RegionIdx_t region_ind, CardIdx_t card_index) {
  assert(this != &empty_table, "can't add a card to the empty table");
  SparsePRTEntry* e = entry_for_region_ind_create(region_ind);
  assert(e != NULL && e->r_ind() == region_ind,
         "Postcondition of call above.");
  SparsePRT::AddCardResult res = e->add_card(card_index);
  assert(e->num_valid_cards() > 0, "Postcondition");
  return res;
}

SparsePRTEntry* RSHashTable::get_entry(RegionIdx_t region_ind) const {
  int ind = (int) (region_ind & capacity_mask());
  int cur_ind = _buckets[ind];
  SparsePRTEntry* cur;
  while (cur_ind != NullEntry &&
         (cur = entry(cur_ind))->r_ind() != region_ind) {
    cur_ind = cur->next_index();
  }

  if (cur_ind == NullEntry) return NULL;
  // Otherwise...
  assert(cur->r_ind() == region_ind, "Postcondition of loop + test above.");
  assert(cur->num_valid_cards() > 0, "Inv");
  return cur;
}

bool RSHashTable::delete_entry(RegionIdx_t region_ind) {
  int ind = (int) (region_ind & capacity_mask());
  int* prev_loc = &_buckets[ind];
  int cur_ind = *prev_loc;
  SparsePRTEntry* cur;
  while (cur_ind != NullEntry &&
         (cur = entry(cur_ind))->r_ind() != region_ind) {
    prev_loc = cur->next_index_addr();
    cur_ind = *prev_loc;
  }

  if (cur_ind == NullEntry) return false;
  // Otherwise, splice out "cur".
  *prev_loc = cur->next_index();
  free_entry(cur_ind);
  _occupied_entries--;
  return true;
}

SparsePRTEntry*
RSHashTable::entry_for_region_ind_create(RegionIdx_t region_ind) {
  SparsePRTEntry* res = get_entry(region_ind);
  if (res == NULL) {
    int new_ind = alloc_entry();
    res = entry(new_ind);
    res->init(region_ind);
    // Insert at front.
    int ind = (int) (region_ind & capacity_mask());
    res->set_next_index(_buckets[ind]);
    _buckets[ind] = new_ind;
    _occupied_entries++;
  }
  return res;
}

int RSHashTable::alloc_entry() {
  int res;
  if (_free_list != NullEntry) {
    res = _free_list;
    _free_list = entry(res)->next_index();
    return res;
  } else if ((size_t)_free_region < _num_entries) {
    res = _free_region;
    _free_region++;
    return res;
  } else {
    return NullEntry;
  }
}

void RSHashTable::free_entry(int fi) {
  entry(fi)->set_next_index(_free_list);
  _free_list = fi;
}

void RSHashTable::add_entry(SparsePRTEntry* e) {
  assert(e->num_valid_cards() > 0, "Precondition.");
  SparsePRTEntry* e2 = entry_for_region_ind_create(e->r_ind());
  e->copy_cards(e2);
  assert(e2->num_valid_cards() > 0, "Postcondition.");
}

bool RSHashTableBucketIter::has_next(SparsePRTEntry*& entry) {
  while (_bl_ind == RSHashTable::NullEntry)  {
    if (_tbl_ind + 1 >= _rsht->capacity()) {
      return false;
    }
    _tbl_ind++;
    _bl_ind = _rsht->_buckets[_tbl_ind];
  }
  entry = _rsht->entry(_bl_ind);
  _bl_ind = entry->next_index();
  return true;
}

bool RSHashTable::contains_card(RegionIdx_t region_index, CardIdx_t card_index) const {
  SparsePRTEntry* e = get_entry(region_index);
  return (e != NULL && e->contains_card(card_index));
}

size_t RSHashTable::mem_size() const {
  return sizeof(RSHashTable) +
    _num_entries * (SparsePRTEntry::size() + sizeof(int));
}

// ----------------------------------------------------------------------

SparsePRT::SparsePRT() :
  _table(&RSHashTable::empty_table) {
}


SparsePRT::~SparsePRT() {
  if (_table != &RSHashTable::empty_table) {
    delete _table;
  }
}


size_t SparsePRT::mem_size() const {
  // We ignore "_cur" here, because it either = _next, or else it is
  // on the deleted list.
  return sizeof(SparsePRT) + _table->mem_size();
}

SparsePRT::AddCardResult SparsePRT::add_card(RegionIdx_t region_id, CardIdx_t card_index) {
  if (_table->should_expand()) {
    expand();
  }
  return _table->add_card(region_id, card_index);
}

SparsePRTEntry* SparsePRT::get_entry(RegionIdx_t region_id) {
  return _table->get_entry(region_id);
}

bool SparsePRT::delete_entry(RegionIdx_t region_id) {
  return _table->delete_entry(region_id);
}

void SparsePRT::clear() {
  // If the entry table not at initial capacity, just reset to the empty table.
  if (_table->capacity() == InitialCapacity) {
    _table->clear();
  } else if (_table != &RSHashTable::empty_table) {
    delete _table;
    _table = &RSHashTable::empty_table;
  }
}

void SparsePRT::expand() {
  RSHashTable* last = _table;
  if (last != &RSHashTable::empty_table) {
    _table = new RSHashTable(last->capacity() * 2);
    for (size_t i = 0; i < last->num_entries(); i++) {
      SparsePRTEntry* e = last->entry((int)i);
      if (e->valid_entry()) {
        _table->add_entry(e);
      }
    }
    delete last;
  } else {
    _table = new RSHashTable(InitialCapacity);
  }
}