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hotspot/src/share/vm/memory/cardTableModRefBS.cpp

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+/*
+ * 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.)
+
+# include "incls/_precompiled.incl"
+# include "incls/_cardTableModRefBS.cpp.incl"
+
+size_t CardTableModRefBS::cards_required(size_t covered_words)
+{
+  // Add one for a guard card, used to detect errors.
+  const size_t words = align_size_up(covered_words, card_size_in_words);
+  return words / card_size_in_words + 1;
+}
+
+size_t CardTableModRefBS::compute_byte_map_size()
+{
+  assert(_guard_index == cards_required(_whole_heap.word_size()) - 1,
+                                        "unitialized, check declaration order");
+  assert(_page_size != 0, "unitialized, check declaration order");
+  const size_t granularity = os::vm_allocation_granularity();
+  return align_size_up(_guard_index + 1, MAX2(_page_size, granularity));
+}
+
+CardTableModRefBS::CardTableModRefBS(MemRegion whole_heap,
+                                     int max_covered_regions):
+  ModRefBarrierSet(max_covered_regions),
+  _whole_heap(whole_heap),
+  _guard_index(cards_required(whole_heap.word_size()) - 1),
+  _last_valid_index(_guard_index - 1),
+  _page_size(os::page_size_for_region(_guard_index + 1, _guard_index + 1, 1)),
+  _byte_map_size(compute_byte_map_size())
+{
+  _kind = BarrierSet::CardTableModRef;
+
+  HeapWord* low_bound  = _whole_heap.start();
+  HeapWord* high_bound = _whole_heap.end();
+  assert((uintptr_t(low_bound)  & (card_size - 1))  == 0, "heap must start at card boundary");
+  assert((uintptr_t(high_bound) & (card_size - 1))  == 0, "heap must end at card boundary");
+
+  assert(card_size <= 512, "card_size must be less than 512"); // why?
+
+  _covered   = new MemRegion[max_covered_regions];
+  _committed = new MemRegion[max_covered_regions];
+  if (_covered == NULL || _committed == NULL)
+    vm_exit_during_initialization("couldn't alloc card table covered region set.");
+  int i;
+  for (i = 0; i < max_covered_regions; i++) {
+    _covered[i].set_word_size(0);
+    _committed[i].set_word_size(0);
+  }
+  _cur_covered_regions = 0;
+
+  const size_t rs_align = _page_size == (size_t) os::vm_page_size() ? 0 :
+    MAX2(_page_size, (size_t) os::vm_allocation_granularity());
+  ReservedSpace heap_rs(_byte_map_size, rs_align, false);
+  os::trace_page_sizes("card table", _guard_index + 1, _guard_index + 1,
+                       _page_size, heap_rs.base(), heap_rs.size());
+  if (!heap_rs.is_reserved()) {
+    vm_exit_during_initialization("Could not reserve enough space for the "
+                                  "card marking array");
+  }
+
+  // The assember store_check code will do an unsigned shift of the oop,
+  // then add it to byte_map_base, i.e.
+  //
+  //   _byte_map = byte_map_base + (uintptr_t(low_bound) >> card_shift)
+  _byte_map = (jbyte*) heap_rs.base();
+  byte_map_base = _byte_map - (uintptr_t(low_bound) >> card_shift);
+  assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
+  assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
+
+  jbyte* guard_card = &_byte_map[_guard_index];
+  uintptr_t guard_page = align_size_down((uintptr_t)guard_card, _page_size);
+  _guard_region = MemRegion((HeapWord*)guard_page, _page_size);
+  if (!os::commit_memory((char*)guard_page, _page_size, _page_size)) {
+    // Do better than this for Merlin
+    vm_exit_out_of_memory(_page_size, "card table last card");
+  }
+  *guard_card = last_card;
+
+   _lowest_non_clean =
+    NEW_C_HEAP_ARRAY(CardArr, max_covered_regions);
+  _lowest_non_clean_chunk_size =
+    NEW_C_HEAP_ARRAY(size_t, max_covered_regions);
+  _lowest_non_clean_base_chunk_index =
+    NEW_C_HEAP_ARRAY(uintptr_t, max_covered_regions);
+  _last_LNC_resizing_collection =
+    NEW_C_HEAP_ARRAY(int, max_covered_regions);
+  if (_lowest_non_clean == NULL
+      || _lowest_non_clean_chunk_size == NULL
+      || _lowest_non_clean_base_chunk_index == NULL
+      || _last_LNC_resizing_collection == NULL)
+    vm_exit_during_initialization("couldn't allocate an LNC array.");
+  for (i = 0; i < max_covered_regions; i++) {
+    _lowest_non_clean[i] = NULL;
+    _lowest_non_clean_chunk_size[i] = 0;
+    _last_LNC_resizing_collection[i] = -1;
+  }
+
+  if (TraceCardTableModRefBS) {
+    gclog_or_tty->print_cr("CardTableModRefBS::CardTableModRefBS: ");
+    gclog_or_tty->print_cr("  "
+                  "  &_byte_map[0]: " INTPTR_FORMAT
+                  "  &_byte_map[_last_valid_index]: " INTPTR_FORMAT,
+                  &_byte_map[0],
+                  &_byte_map[_last_valid_index]);
+    gclog_or_tty->print_cr("  "
+                  "  byte_map_base: " INTPTR_FORMAT,
+                  byte_map_base);
+  }
+}
+
+int CardTableModRefBS::find_covering_region_by_base(HeapWord* base) {
+  int i;
+  for (i = 0; i < _cur_covered_regions; i++) {
+    if (_covered[i].start() == base) return i;
+    if (_covered[i].start() > base) break;
+  }
+  // If we didn't find it, create a new one.
+  assert(_cur_covered_regions < _max_covered_regions,
+         "too many covered regions");
+  // Move the ones above up, to maintain sorted order.
+  for (int j = _cur_covered_regions; j > i; j--) {
+    _covered[j] = _covered[j-1];
+    _committed[j] = _committed[j-1];
+  }
+  int res = i;
+  _cur_covered_regions++;
+  _covered[res].set_start(base);
+  _covered[res].set_word_size(0);
+  jbyte* ct_start = byte_for(base);
+  uintptr_t ct_start_aligned = align_size_down((uintptr_t)ct_start, _page_size);
+  _committed[res].set_start((HeapWord*)ct_start_aligned);
+  _committed[res].set_word_size(0);
+  return res;
+}
+
+int CardTableModRefBS::find_covering_region_containing(HeapWord* addr) {
+  for (int i = 0; i < _cur_covered_regions; i++) {
+    if (_covered[i].contains(addr)) {
+      return i;
+    }
+  }
+  assert(0, "address outside of heap?");
+  return -1;
+}
+
+HeapWord* CardTableModRefBS::largest_prev_committed_end(int ind) const {
+  HeapWord* max_end = NULL;
+  for (int j = 0; j < ind; j++) {
+    HeapWord* this_end = _committed[j].end();
+    if (this_end > max_end) max_end = this_end;
+  }
+  return max_end;
+}
+
+MemRegion CardTableModRefBS::committed_unique_to_self(int self,
+                                                      MemRegion mr) const {
+  MemRegion result = mr;
+  for (int r = 0; r < _cur_covered_regions; r += 1) {
+    if (r != self) {
+      result = result.minus(_committed[r]);
+    }
+  }
+  // Never include the guard page.
+  result = result.minus(_guard_region);
+  return result;
+}
+
+void CardTableModRefBS::resize_covered_region(MemRegion new_region) {
+  // We don't change the start of a region, only the end.
+  assert(_whole_heap.contains(new_region),
+           "attempt to cover area not in reserved area");
+  debug_only(verify_guard();)
+  int ind = find_covering_region_by_base(new_region.start());
+  MemRegion old_region = _covered[ind];
+  assert(old_region.start() == new_region.start(), "just checking");
+  if (new_region.word_size() != old_region.word_size()) {
+    // Commit new or uncommit old pages, if necessary.
+    MemRegion cur_committed = _committed[ind];
+    // Extend the end of this _commited region
+    // to cover the end of any lower _committed regions.
+    // This forms overlapping regions, but never interior regions.
+    HeapWord* max_prev_end = largest_prev_committed_end(ind);
+    if (max_prev_end > cur_committed.end()) {
+      cur_committed.set_end(max_prev_end);
+    }
+    // Align the end up to a page size (starts are already aligned).
+    jbyte* new_end = byte_after(new_region.last());
+    HeapWord* new_end_aligned =
+      (HeapWord*)align_size_up((uintptr_t)new_end, _page_size);
+    assert(new_end_aligned >= (HeapWord*) new_end,
+           "align up, but less");
+    // The guard page is always committed and should not be committed over.
+    HeapWord* new_end_for_commit = MIN2(new_end_aligned, _guard_region.start());
+    if (new_end_for_commit > cur_committed.end()) {
+      // Must commit new pages.
+      MemRegion new_committed =
+        MemRegion(cur_committed.end(), new_end_for_commit);
+
+      assert(!new_committed.is_empty(), "Region should not be empty here");
+      if (!os::commit_memory((char*)new_committed.start(),
+                             new_committed.byte_size(), _page_size)) {
+        // Do better than this for Merlin
+        vm_exit_out_of_memory(new_committed.byte_size(),
+                "card table expansion");
+      }
+    // Use new_end_aligned (as opposed to new_end_for_commit) because
+    // the cur_committed region may include the guard region.
+    } else if (new_end_aligned < cur_committed.end()) {
+      // Must uncommit pages.
+      MemRegion uncommit_region =
+        committed_unique_to_self(ind, MemRegion(new_end_aligned,
+                                                cur_committed.end()));
+      if (!uncommit_region.is_empty()) {
+        if (!os::uncommit_memory((char*)uncommit_region.start(),
+                                 uncommit_region.byte_size())) {
+          // Do better than this for Merlin
+          vm_exit_out_of_memory(uncommit_region.byte_size(),
+            "card table contraction");
+        }
+      }
+    }
+    // In any case, we can reset the end of the current committed entry.
+    _committed[ind].set_end(new_end_aligned);
+
+    // The default of 0 is not necessarily clean cards.
+    jbyte* entry;
+    if (old_region.last() < _whole_heap.start()) {
+      entry = byte_for(_whole_heap.start());
+    } else {
+      entry = byte_after(old_region.last());
+    }
+    assert(index_for(new_region.last()) < (int) _guard_index,
+      "The guard card will be overwritten");
+    jbyte* end = byte_after(new_region.last());
+    // do nothing if we resized downward.
+    if (entry < end) {
+      memset(entry, clean_card, pointer_delta(end, entry, sizeof(jbyte)));
+    }
+  }
+  // In any case, the covered size changes.
+  _covered[ind].set_word_size(new_region.word_size());
+  if (TraceCardTableModRefBS) {
+    gclog_or_tty->print_cr("CardTableModRefBS::resize_covered_region: ");
+    gclog_or_tty->print_cr("  "
+                  "  _covered[%d].start(): " INTPTR_FORMAT
+                  "  _covered[%d].last(): " INTPTR_FORMAT,
+                  ind, _covered[ind].start(),
+                  ind, _covered[ind].last());
+    gclog_or_tty->print_cr("  "
+                  "  _committed[%d].start(): " INTPTR_FORMAT
+                  "  _committed[%d].last(): " INTPTR_FORMAT,
+                  ind, _committed[ind].start(),
+                  ind, _committed[ind].last());
+    gclog_or_tty->print_cr("  "
+                  "  byte_for(start): " INTPTR_FORMAT
+                  "  byte_for(last): " INTPTR_FORMAT,
+                  byte_for(_covered[ind].start()),
+                  byte_for(_covered[ind].last()));
+    gclog_or_tty->print_cr("  "
+                  "  addr_for(start): " INTPTR_FORMAT
+                  "  addr_for(last): " INTPTR_FORMAT,
+                  addr_for((jbyte*) _committed[ind].start()),
+                  addr_for((jbyte*) _committed[ind].last()));
+  }
+  debug_only(verify_guard();)
+}
+
+// Note that these versions are precise!  The scanning code has to handle the
+// fact that the write barrier may be either precise or imprecise.
+
+void CardTableModRefBS::write_ref_field_work(oop* field, oop newVal) {
+  inline_write_ref_field(field, newVal);
+}
+
+
+void CardTableModRefBS::non_clean_card_iterate(Space* sp,
+                                               MemRegion mr,
+                                               DirtyCardToOopClosure* dcto_cl,
+                                               MemRegionClosure* cl,
+                                               bool clear) {
+  if (!mr.is_empty()) {
+    int n_threads = SharedHeap::heap()->n_par_threads();
+    if (n_threads > 0) {
+#ifndef SERIALGC
+      par_non_clean_card_iterate_work(sp, mr, dcto_cl, cl, clear, n_threads);
+#else  // SERIALGC
+      fatal("Parallel gc not supported here.");
+#endif // SERIALGC
+    } else {
+      non_clean_card_iterate_work(mr, cl, clear);
+    }
+  }
+}
+
+// NOTE: For this to work correctly, it is important that
+// we look for non-clean cards below (so as to catch those
+// marked precleaned), rather than look explicitly for dirty
+// cards (and miss those marked precleaned). In that sense,
+// the name precleaned is currently somewhat of a misnomer.
+void CardTableModRefBS::non_clean_card_iterate_work(MemRegion mr,
+                                                    MemRegionClosure* cl,
+                                                    bool clear) {
+  // Figure out whether we have to worry about parallelism.
+  bool is_par = (SharedHeap::heap()->n_par_threads() > 1);
+  for (int i = 0; i < _cur_covered_regions; i++) {
+    MemRegion mri = mr.intersection(_covered[i]);
+    if (mri.word_size() > 0) {
+      jbyte* cur_entry = byte_for(mri.last());
+      jbyte* limit = byte_for(mri.start());
+      while (cur_entry >= limit) {
+        jbyte* next_entry = cur_entry - 1;
+        if (*cur_entry != clean_card) {
+          size_t non_clean_cards = 1;
+          // Should the next card be included in this range of dirty cards.
+          while (next_entry >= limit && *next_entry != clean_card) {
+            non_clean_cards++;
+            cur_entry = next_entry;
+            next_entry--;
+          }
+          // The memory region may not be on a card boundary.  So that
+          // objects beyond the end of the region are not processed, make
+          // cur_cards precise with regard to the end of the memory region.
+          MemRegion cur_cards(addr_for(cur_entry),
+                              non_clean_cards * card_size_in_words);
+          MemRegion dirty_region = cur_cards.intersection(mri);
+          if (clear) {
+            for (size_t i = 0; i < non_clean_cards; i++) {
+              // Clean the dirty cards (but leave the other non-clean
+              // alone.)  If parallel, do the cleaning atomically.
+              jbyte cur_entry_val = cur_entry[i];
+              if (card_is_dirty_wrt_gen_iter(cur_entry_val)) {
+                if (is_par) {
+                  jbyte res = Atomic::cmpxchg(clean_card, &cur_entry[i], cur_entry_val);
+                  assert(res != clean_card,
+                         "Dirty card mysteriously cleaned");
+                } else {
+                  cur_entry[i] = clean_card;
+                }
+              }
+            }
+          }
+          cl->do_MemRegion(dirty_region);
+        }
+        cur_entry = next_entry;
+      }
+    }
+  }
+}
+
+void CardTableModRefBS::mod_oop_in_space_iterate(Space* sp,
+                                                 OopClosure* cl,
+                                                 bool clear,
+                                                 bool before_save_marks) {
+  // Note that dcto_cl is resource-allocated, so there is no
+  // corresponding "delete".
+  DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision());
+  MemRegion used_mr;
+  if (before_save_marks) {
+    used_mr = sp->used_region_at_save_marks();
+  } else {
+    used_mr = sp->used_region();
+  }
+  non_clean_card_iterate(sp, used_mr, dcto_cl, dcto_cl, clear);
+}
+
+void CardTableModRefBS::dirty_MemRegion(MemRegion mr) {
+  jbyte* cur  = byte_for(mr.start());
+  jbyte* last = byte_after(mr.last());
+  while (cur < last) {
+    *cur = dirty_card;
+    cur++;
+  }
+}
+
+void CardTableModRefBS::invalidate(MemRegion mr) {
+  for (int i = 0; i < _cur_covered_regions; i++) {
+    MemRegion mri = mr.intersection(_covered[i]);
+    if (!mri.is_empty()) dirty_MemRegion(mri);
+  }
+}
+
+void CardTableModRefBS::clear_MemRegion(MemRegion mr) {
+  // Be conservative: only clean cards entirely contained within the
+  // region.
+  jbyte* cur;
+  if (mr.start() == _whole_heap.start()) {
+    cur = byte_for(mr.start());
+  } else {
+    assert(mr.start() > _whole_heap.start(), "mr is not covered.");
+    cur = byte_after(mr.start() - 1);
+  }
+  jbyte* last = byte_after(mr.last());
+  memset(cur, clean_card, pointer_delta(last, cur, sizeof(jbyte)));
+}
+
+void CardTableModRefBS::clear(MemRegion mr) {
+  for (int i = 0; i < _cur_covered_regions; i++) {
+    MemRegion mri = mr.intersection(_covered[i]);
+    if (!mri.is_empty()) clear_MemRegion(mri);
+  }
+}
+
+// NOTES:
+// (1) Unlike mod_oop_in_space_iterate() above, dirty_card_iterate()
+//     iterates over dirty cards ranges in increasing address order.
+// (2) Unlike, e.g., dirty_card_range_after_preclean() below,
+//     this method does not make the dirty cards prelceaned.
+void CardTableModRefBS::dirty_card_iterate(MemRegion mr,
+                                           MemRegionClosure* cl) {
+  for (int i = 0; i < _cur_covered_regions; i++) {
+    MemRegion mri = mr.intersection(_covered[i]);
+    if (!mri.is_empty()) {
+      jbyte *cur_entry, *next_entry, *limit;
+      for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
+           cur_entry <= limit;
+           cur_entry  = next_entry) {
+        next_entry = cur_entry + 1;
+        if (*cur_entry == dirty_card) {
+          size_t dirty_cards;
+          // Accumulate maximal dirty card range, starting at cur_entry
+          for (dirty_cards = 1;
+               next_entry <= limit && *next_entry == dirty_card;
+               dirty_cards++, next_entry++);
+          MemRegion cur_cards(addr_for(cur_entry),
+                              dirty_cards*card_size_in_words);
+          cl->do_MemRegion(cur_cards);
+        }
+      }
+    }
+  }
+}
+
+MemRegion CardTableModRefBS::dirty_card_range_after_preclean(MemRegion mr) {
+  for (int i = 0; i < _cur_covered_regions; i++) {
+    MemRegion mri = mr.intersection(_covered[i]);
+    if (!mri.is_empty()) {
+      jbyte* cur_entry, *next_entry, *limit;
+      for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
+           cur_entry <= limit;
+           cur_entry  = next_entry) {
+        next_entry = cur_entry + 1;
+        if (*cur_entry == dirty_card) {
+          size_t dirty_cards;
+          // Accumulate maximal dirty card range, starting at cur_entry
+          for (dirty_cards = 1;
+               next_entry <= limit && *next_entry == dirty_card;
+               dirty_cards++, next_entry++);
+          MemRegion cur_cards(addr_for(cur_entry),
+                              dirty_cards*card_size_in_words);
+          for (size_t i = 0; i < dirty_cards; i++) {
+             cur_entry[i] = precleaned_card;
+          }
+          return cur_cards;
+        }
+      }
+    }
+  }
+  return MemRegion(mr.end(), mr.end());
+}
+
+// Set all the dirty cards in the given region to "precleaned" state.
+void CardTableModRefBS::preclean_dirty_cards(MemRegion mr) {
+  for (int i = 0; i < _cur_covered_regions; i++) {
+    MemRegion mri = mr.intersection(_covered[i]);
+    if (!mri.is_empty()) {
+      jbyte *cur_entry, *limit;
+      for (cur_entry = byte_for(mri.start()), limit = byte_for(mri.last());
+           cur_entry <= limit;
+           cur_entry++) {
+        if (*cur_entry == dirty_card) {
+          *cur_entry = precleaned_card;
+        }
+      }
+    }
+  }
+}
+
+uintx CardTableModRefBS::ct_max_alignment_constraint() {
+  return card_size * os::vm_page_size();
+}
+
+void CardTableModRefBS::verify_guard() {
+  // For product build verification
+  guarantee(_byte_map[_guard_index] == last_card,
+            "card table guard has been modified");
+}
+
+void CardTableModRefBS::verify() {
+  verify_guard();
+}
+
+#ifndef PRODUCT
+class GuaranteeNotModClosure: public MemRegionClosure {
+  CardTableModRefBS* _ct;
+public:
+  GuaranteeNotModClosure(CardTableModRefBS* ct) : _ct(ct) {}
+  void do_MemRegion(MemRegion mr) {
+    jbyte* entry = _ct->byte_for(mr.start());
+    guarantee(*entry != CardTableModRefBS::clean_card,
+              "Dirty card in region that should be clean");
+  }
+};
+
+void CardTableModRefBS::verify_clean_region(MemRegion mr) {
+  GuaranteeNotModClosure blk(this);
+  non_clean_card_iterate_work(mr, &blk, false);
+}
+#endif
+
+bool CardTableModRefBSForCTRS::card_will_be_scanned(jbyte cv) {
+  return
+    CardTableModRefBS::card_will_be_scanned(cv) ||
+    _rs->is_prev_nonclean_card_val(cv);
+};
+
+bool CardTableModRefBSForCTRS::card_may_have_been_dirty(jbyte cv) {
+  return
+    cv != clean_card &&
+    (CardTableModRefBS::card_may_have_been_dirty(cv) ||
+     CardTableRS::youngergen_may_have_been_dirty(cv));
+};