jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.cpp@f90c822e73f8 (annotated)

src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.cpp@f90c822e73f8 (annotated)

src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.cpp

Wed, 27 Apr 2016 01:25:04 +0800

author: aoqi
date: Wed, 27 Apr 2016 01:25:04 +0800
changeset 0: f90c822e73f8
child 1: 2d8a650513c2
permissions: -rw-r--r--

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http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/
changeset: 6782:28b50d07f6f8
tag: jdk8u25-b17

 /*
  * Copyright (c) 2001, 2014, 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.
  *
  */
 #include "precompiled.hpp"
 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"
 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
 #include "gc_implementation/parallelScavenge/psTasks.hpp"
 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
 #include "oops/oop.inline.hpp"
 #include "oops/oop.psgc.inline.hpp"
 // Checks an individual oop for missing precise marks. Mark
 // may be either dirty or newgen.
 class CheckForUnmarkedOops : public OopClosure {
  private:
   PSYoungGen*         _young_gen;
   CardTableExtension* _card_table;
   HeapWord*           _unmarked_addr;
   jbyte*              _unmarked_card;
  protected:
   template <class T> void do_oop_work(T* p) {
     oop obj = oopDesc::load_decode_heap_oop(p);
     if (_young_gen->is_in_reserved(obj) &&
         !_card_table->addr_is_marked_imprecise(p)) {
       // Don't overwrite the first missing card mark
       if (_unmarked_addr == NULL) {
         _unmarked_addr = (HeapWord*)p;
         _unmarked_card = _card_table->byte_for(p);
       }
     }
   }
  public:
   CheckForUnmarkedOops(PSYoungGen* young_gen, CardTableExtension* card_table) :
     _young_gen(young_gen), _card_table(card_table), _unmarked_addr(NULL) { }
   virtual void do_oop(oop* p)       { CheckForUnmarkedOops::do_oop_work(p); }
   virtual void do_oop(narrowOop* p) { CheckForUnmarkedOops::do_oop_work(p); }
   bool has_unmarked_oop() {
     return _unmarked_addr != NULL;
   }
 };
 // Checks all objects for the existance of some type of mark,
 // precise or imprecise, dirty or newgen.
 class CheckForUnmarkedObjects : public ObjectClosure {
  private:
   PSYoungGen*         _young_gen;
   CardTableExtension* _card_table;
  public:
   CheckForUnmarkedObjects() {
     ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
     assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
     _young_gen = heap->young_gen();
     _card_table = (CardTableExtension*)heap->barrier_set();
     // No point in asserting barrier set type here. Need to make CardTableExtension
     // a unique barrier set type.
   }
   // Card marks are not precise. The current system can leave us with
   // a mismash of precise marks and beginning of object marks. This means
   // we test for missing precise marks first. If any are found, we don't
   // fail unless the object head is also unmarked.
   virtual void do_object(oop obj) {
     CheckForUnmarkedOops object_check(_young_gen, _card_table);
     obj->oop_iterate_no_header(&object_check);
     if (object_check.has_unmarked_oop()) {
       assert(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object");
     }
   }
 };
 // Checks for precise marking of oops as newgen.
 class CheckForPreciseMarks : public OopClosure {
  private:
   PSYoungGen*         _young_gen;
   CardTableExtension* _card_table;
  protected:
   template <class T> void do_oop_work(T* p) {
     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
     if (_young_gen->is_in_reserved(obj)) {
       assert(_card_table->addr_is_marked_precise(p), "Found unmarked precise oop");
       _card_table->set_card_newgen(p);
     }
   }
  public:
   CheckForPreciseMarks( PSYoungGen* young_gen, CardTableExtension* card_table ) :
     _young_gen(young_gen), _card_table(card_table) { }
   virtual void do_oop(oop* p)       { CheckForPreciseMarks::do_oop_work(p); }
   virtual void do_oop(narrowOop* p) { CheckForPreciseMarks::do_oop_work(p); }
 };
 // We get passed the space_top value to prevent us from traversing into
 // the old_gen promotion labs, which cannot be safely parsed.
 // Do not call this method if the space is empty.
 // It is a waste to start tasks and get here only to
 // do no work.  If this method needs to be called
 // when the space is empty, fix the calculation of
 // end_card to allow sp_top == sp->bottom().
 void CardTableExtension::scavenge_contents_parallel(ObjectStartArray* start_array,
                                                     MutableSpace* sp,
                                                     HeapWord* space_top,
                                                     PSPromotionManager* pm,
                                                     uint stripe_number,
                                                     uint stripe_total) {
   int ssize = 128; // Naked constant!  Work unit = 64k.
   int dirty_card_count = 0;
   // It is a waste to get here if empty.
   assert(sp->bottom() < sp->top(), "Should not be called if empty");
   oop* sp_top = (oop*)space_top;
   jbyte* start_card = byte_for(sp->bottom());
   jbyte* end_card   = byte_for(sp_top - 1) + 1;
   oop* last_scanned = NULL; // Prevent scanning objects more than once
   // The width of the stripe ssize*stripe_total must be
   // consistent with the number of stripes so that the complete slice
   // is covered.
   size_t slice_width = ssize * stripe_total;
   for (jbyte* slice = start_card; slice < end_card; slice += slice_width) {
     jbyte* worker_start_card = slice + stripe_number * ssize;
     if (worker_start_card >= end_card)
       return; // We're done.
     jbyte* worker_end_card = worker_start_card + ssize;
     if (worker_end_card > end_card)
       worker_end_card = end_card;
     // We do not want to scan objects more than once. In order to accomplish
     // this, we assert that any object with an object head inside our 'slice'
     // belongs to us. We may need to extend the range of scanned cards if the
     // last object continues into the next 'slice'.
     //
     // Note! ending cards are exclusive!
     HeapWord* slice_start = addr_for(worker_start_card);
     HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card));
 #ifdef ASSERT
     if (GCWorkerDelayMillis > 0) {
       // Delay 1 worker so that it proceeds after all the work
       // has been completed.
       if (stripe_number < 2) {
         os::sleep(Thread::current(), GCWorkerDelayMillis, false);
       }
     }
 #endif
     // If there are not objects starting within the chunk, skip it.
     if (!start_array->object_starts_in_range(slice_start, slice_end)) {
       continue;
     }
     // Update our beginning addr
     HeapWord* first_object = start_array->object_start(slice_start);
     debug_only(oop* first_object_within_slice = (oop*) first_object;)
     if (first_object < slice_start) {
       last_scanned = (oop*)(first_object + oop(first_object)->size());
       debug_only(first_object_within_slice = last_scanned;)
       worker_start_card = byte_for(last_scanned);
     }
     // Update the ending addr
     if (slice_end < (HeapWord*)sp_top) {
       // The subtraction is important! An object may start precisely at slice_end.
       HeapWord* last_object = start_array->object_start(slice_end - 1);
       slice_end = last_object + oop(last_object)->size();
       // worker_end_card is exclusive, so bump it one past the end of last_object's
       // covered span.
       worker_end_card = byte_for(slice_end) + 1;
       if (worker_end_card > end_card)
         worker_end_card = end_card;
     }
     assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary");
     assert(is_valid_card_address(worker_start_card), "Invalid worker start card");
     assert(is_valid_card_address(worker_end_card), "Invalid worker end card");
     // Note that worker_start_card >= worker_end_card is legal, and happens when
     // an object spans an entire slice.
     assert(worker_start_card <= end_card, "worker start card beyond end card");
     assert(worker_end_card <= end_card, "worker end card beyond end card");
     jbyte* current_card = worker_start_card;
     while (current_card < worker_end_card) {
       // Find an unclean card.
       while (current_card < worker_end_card && card_is_clean(*current_card)) {
         current_card++;
       }
       jbyte* first_unclean_card = current_card;
       // Find the end of a run of contiguous unclean cards
       while (current_card < worker_end_card && !card_is_clean(*current_card)) {
         while (current_card < worker_end_card && !card_is_clean(*current_card)) {
           current_card++;
         }
         if (current_card < worker_end_card) {
           // Some objects may be large enough to span several cards. If such
           // an object has more than one dirty card, separated by a clean card,
           // we will attempt to scan it twice. The test against "last_scanned"
           // prevents the redundant object scan, but it does not prevent newly
           // marked cards from being cleaned.
           HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1);
           size_t size_of_last_object = oop(last_object_in_dirty_region)->size();
           HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object;
           jbyte* ending_card_of_last_object = byte_for(end_of_last_object);
           assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card");
           if (ending_card_of_last_object > current_card) {
             // This means the object spans the next complete card.
             // We need to bump the current_card to ending_card_of_last_object
             current_card = ending_card_of_last_object;
           }
         }
       }
       jbyte* following_clean_card = current_card;
       if (first_unclean_card < worker_end_card) {
         oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card));
         assert((HeapWord*)p <= addr_for(first_unclean_card), "checking");
         // "p" should always be >= "last_scanned" because newly GC dirtied
         // cards are no longer scanned again (see comment at end
         // of loop on the increment of "current_card").  Test that
         // hypothesis before removing this code.
         // If this code is removed, deal with the first time through
         // the loop when the last_scanned is the object starting in
         // the previous slice.
         assert((p >= last_scanned) ||
                (last_scanned == first_object_within_slice),
                "Should no longer be possible");
         if (p < last_scanned) {
           // Avoid scanning more than once; this can happen because
           // newgen cards set by GC may a different set than the
           // originally dirty set
           p = last_scanned;
         }
         oop* to = (oop*)addr_for(following_clean_card);
         // Test slice_end first!
         if ((HeapWord*)to > slice_end) {
           to = (oop*)slice_end;
         } else if (to > sp_top) {
           to = sp_top;
         }
         // we know which cards to scan, now clear them
         if (first_unclean_card <= worker_start_card+1)
           first_unclean_card = worker_start_card+1;
         if (following_clean_card >= worker_end_card-1)
           following_clean_card = worker_end_card-1;
         while (first_unclean_card < following_clean_card) {
           *first_unclean_card++ = clean_card;
         }
         const int interval = PrefetchScanIntervalInBytes;
         // scan all objects in the range
         if (interval != 0) {
           while (p < to) {
             Prefetch::write(p, interval);
             oop m = oop(p);
             assert(m->is_oop_or_null(), "check for header");
             m->push_contents(pm);
             p += m->size();
           }
           pm->drain_stacks_cond_depth();
         } else {
           while (p < to) {
             oop m = oop(p);
             assert(m->is_oop_or_null(), "check for header");
             m->push_contents(pm);
             p += m->size();
           }
           pm->drain_stacks_cond_depth();
         }
         last_scanned = p;
       }
       // "current_card" is still the "following_clean_card" or
       // the current_card is >= the worker_end_card so the
       // loop will not execute again.
       assert((current_card == following_clean_card) ||
              (current_card >= worker_end_card),
         "current_card should only be incremented if it still equals "
         "following_clean_card");
       // Increment current_card so that it is not processed again.
       // It may now be dirty because a old-to-young pointer was
       // found on it an updated.  If it is now dirty, it cannot be
       // be safely cleaned in the next iteration.
       current_card++;
     }
   }
 }
 // This should be called before a scavenge.
 void CardTableExtension::verify_all_young_refs_imprecise() {
   CheckForUnmarkedObjects check;
   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
   PSOldGen* old_gen = heap->old_gen();
   old_gen->object_iterate(&check);
 }
 // This should be called immediately after a scavenge, before mutators resume.
 void CardTableExtension::verify_all_young_refs_precise() {
   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
   PSOldGen* old_gen = heap->old_gen();
   CheckForPreciseMarks check(heap->young_gen(), (CardTableExtension*)heap->barrier_set());
   old_gen->oop_iterate_no_header(&check);
   verify_all_young_refs_precise_helper(old_gen->object_space()->used_region());
 }
 void CardTableExtension::verify_all_young_refs_precise_helper(MemRegion mr) {
   CardTableExtension* card_table = (CardTableExtension*)Universe::heap()->barrier_set();
   // FIX ME ASSERT HERE
   jbyte* bot = card_table->byte_for(mr.start());
   jbyte* top = card_table->byte_for(mr.end());
   while(bot <= top) {
     assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark");
     if (*bot == verify_card)
       *bot = youngergen_card;
     bot++;
   }
 }
 bool CardTableExtension::addr_is_marked_imprecise(void *addr) {
   jbyte* p = byte_for(addr);
   jbyte val = *p;
   if (card_is_dirty(val))
     return true;
   if (card_is_newgen(val))
     return true;
   if (card_is_clean(val))
     return false;
   assert(false, "Found unhandled card mark type");
   return false;
 }
 // Also includes verify_card
 bool CardTableExtension::addr_is_marked_precise(void *addr) {
   jbyte* p = byte_for(addr);
   jbyte val = *p;
   if (card_is_newgen(val))
     return true;
   if (card_is_verify(val))
     return true;
   if (card_is_clean(val))
     return false;
   if (card_is_dirty(val))
     return false;
   assert(false, "Found unhandled card mark type");
   return false;
 }
 // Assumes that only the base or the end changes.  This allows indentification
 // of the region that is being resized.  The
 // CardTableModRefBS::resize_covered_region() is used for the normal case
 // where the covered regions are growing or shrinking at the high end.
 // The method resize_covered_region_by_end() is analogous to
 // CardTableModRefBS::resize_covered_region() but
 // for regions that grow or shrink at the low end.
 void CardTableExtension::resize_covered_region(MemRegion new_region) {
   for (int i = 0; i < _cur_covered_regions; i++) {
     if (_covered[i].start() == new_region.start()) {
       // Found a covered region with the same start as the
       // new region.  The region is growing or shrinking
       // from the start of the region.
       resize_covered_region_by_start(new_region);
       return;
     }
     if (_covered[i].start() > new_region.start()) {
       break;
     }
   }
   int changed_region = -1;
   for (int j = 0; j < _cur_covered_regions; j++) {
     if (_covered[j].end() == new_region.end()) {
       changed_region = j;
       // This is a case where the covered region is growing or shrinking
       // at the start of the region.
       assert(changed_region != -1, "Don't expect to add a covered region");
       assert(_covered[changed_region].byte_size() != new_region.byte_size(),
         "The sizes should be different here");
       resize_covered_region_by_end(changed_region, new_region);
       return;
     }
   }
   // This should only be a new covered region (where no existing
   // covered region matches at the start or the end).
   assert(_cur_covered_regions < _max_covered_regions,
     "An existing region should have been found");
   resize_covered_region_by_start(new_region);
 }
 void CardTableExtension::resize_covered_region_by_start(MemRegion new_region) {
   CardTableModRefBS::resize_covered_region(new_region);
   debug_only(verify_guard();)
 }
 void CardTableExtension::resize_covered_region_by_end(int changed_region,
                                                       MemRegion new_region) {
   assert(SafepointSynchronize::is_at_safepoint(),
     "Only expect an expansion at the low end at a GC");
   debug_only(verify_guard();)
 #ifdef ASSERT
   for (int k = 0; k < _cur_covered_regions; k++) {
     if (_covered[k].end() == new_region.end()) {
       assert(changed_region == k, "Changed region is incorrect");
       break;
     }
   }
 #endif
   // Commit new or uncommit old pages, if necessary.
   if (resize_commit_uncommit(changed_region, new_region)) {
     // Set the new start of the committed region
     resize_update_committed_table(changed_region, new_region);
   }
   // Update card table entries
   resize_update_card_table_entries(changed_region, new_region);
   // Update the covered region
   resize_update_covered_table(changed_region, new_region);
   if (TraceCardTableModRefBS) {
     int ind = changed_region;
     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, p2i(_covered[ind].start()),
                   ind, p2i(_covered[ind].last()));
     gclog_or_tty->print_cr("  "
                   "  _committed[%d].start(): " INTPTR_FORMAT
                   "  _committed[%d].last(): " INTPTR_FORMAT,
                   ind, p2i(_committed[ind].start()),
                   ind, p2i(_committed[ind].last()));
     gclog_or_tty->print_cr("  "
                   "  byte_for(start): " INTPTR_FORMAT
                   "  byte_for(last): " INTPTR_FORMAT,
                   p2i(byte_for(_covered[ind].start())),
                   p2i(byte_for(_covered[ind].last())));
     gclog_or_tty->print_cr("  "
                   "  addr_for(start): " INTPTR_FORMAT
                   "  addr_for(last): " INTPTR_FORMAT,
                   p2i(addr_for((jbyte*) _committed[ind].start())),
                   p2i(addr_for((jbyte*) _committed[ind].last())));
   }
   debug_only(verify_guard();)
 }
 bool CardTableExtension::resize_commit_uncommit(int changed_region,
                                                 MemRegion new_region) {
   bool result = false;
   // Commit new or uncommit old pages, if necessary.
   MemRegion cur_committed = _committed[changed_region];
   assert(_covered[changed_region].end() == new_region.end(),
     "The ends of the regions are expected to match");
   // Extend the start of this _committed region to
   // to cover the start of any previous _committed region.
   // This forms overlapping regions, but never interior regions.
   HeapWord* min_prev_start = lowest_prev_committed_start(changed_region);
   if (min_prev_start < cur_committed.start()) {
     // Only really need to set start of "cur_committed" to
     // the new start (min_prev_start) but assertion checking code
     // below use cur_committed.end() so make it correct.
     MemRegion new_committed =
         MemRegion(min_prev_start, cur_committed.end());
     cur_committed = new_committed;
   }
 #ifdef ASSERT
   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
   assert(cur_committed.start() ==
     (HeapWord*) align_size_up((uintptr_t) cur_committed.start(),
                               os::vm_page_size()),
     "Starts should have proper alignment");
 #endif
   jbyte* new_start = byte_for(new_region.start());
   // Round down because this is for the start address
   HeapWord* new_start_aligned =
     (HeapWord*)align_size_down((uintptr_t)new_start, os::vm_page_size());
   // The guard page is always committed and should not be committed over.
   // This method is used in cases where the generation is growing toward
   // lower addresses but the guard region is still at the end of the
   // card table.  That still makes sense when looking for writes
   // off the end of the card table.
   if (new_start_aligned < cur_committed.start()) {
     // Expand the committed region
     //
     // Case A
     //                                          |+ guard +|
     //                          |+ cur committed +++++++++|
     //                  |+ new committed +++++++++++++++++|
     //
     // Case B
     //                                          |+ guard +|
     //                        |+ cur committed +|
     //                  |+ new committed +++++++|
     //
     // These are not expected because the calculation of the
     // cur committed region and the new committed region
     // share the same end for the covered region.
     // Case C
     //                                          |+ guard +|
     //                        |+ cur committed +|
     //                  |+ new committed +++++++++++++++++|
     // Case D
     //                                          |+ guard +|
     //                        |+ cur committed +++++++++++|
     //                  |+ new committed +++++++|
     HeapWord* new_end_for_commit =
       MIN2(cur_committed.end(), _guard_region.start());
     if(new_start_aligned < new_end_for_commit) {
       MemRegion new_committed =
         MemRegion(new_start_aligned, new_end_for_commit);
       os::commit_memory_or_exit((char*)new_committed.start(),
                                 new_committed.byte_size(), !ExecMem,
                                 "card table expansion");
     }
     result = true;
   } else if (new_start_aligned > cur_committed.start()) {
     // Shrink the committed region
 #if 0 // uncommitting space is currently unsafe because of the interactions
       // of growing and shrinking regions.  One region A can uncommit space
       // that it owns but which is being used by another region B (maybe).
       // Region B has not committed the space because it was already
       // committed by region A.
     MemRegion uncommit_region = committed_unique_to_self(changed_region,
       MemRegion(cur_committed.start(), new_start_aligned));
     if (!uncommit_region.is_empty()) {
       if (!os::uncommit_memory((char*)uncommit_region.start(),
                                uncommit_region.byte_size())) {
         // If the uncommit fails, ignore it.  Let the
         // committed table resizing go even though the committed
         // table will over state the committed space.
       }
     }
 #else
     assert(!result, "Should be false with current workaround");
 #endif
   }
   assert(_committed[changed_region].end() == cur_committed.end(),
     "end should not change");
   return result;
 }
 void CardTableExtension::resize_update_committed_table(int changed_region,
                                                        MemRegion new_region) {
   jbyte* new_start = byte_for(new_region.start());
   // Set the new start of the committed region
   HeapWord* new_start_aligned =
     (HeapWord*)align_size_down((uintptr_t)new_start,
                              os::vm_page_size());
   MemRegion new_committed = MemRegion(new_start_aligned,
     _committed[changed_region].end());
   _committed[changed_region] = new_committed;
   _committed[changed_region].set_start(new_start_aligned);
 }
 void CardTableExtension::resize_update_card_table_entries(int changed_region,
                                                           MemRegion new_region) {
   debug_only(verify_guard();)
   MemRegion original_covered = _covered[changed_region];
   // Initialize the card entries.  Only consider the
   // region covered by the card table (_whole_heap)
   jbyte* entry;
   if (new_region.start() < _whole_heap.start()) {
     entry = byte_for(_whole_heap.start());
   } else {
     entry = byte_for(new_region.start());
   }
   jbyte* end = byte_for(original_covered.start());
   // If _whole_heap starts at the original covered regions start,
   // this loop will not execute.
   while (entry < end) { *entry++ = clean_card; }
 }
 void CardTableExtension::resize_update_covered_table(int changed_region,
                                                      MemRegion new_region) {
   // Update the covered region
   _covered[changed_region].set_start(new_region.start());
   _covered[changed_region].set_word_size(new_region.word_size());
   // reorder regions.  There should only be at most 1 out
   // of order.
   for (int i = _cur_covered_regions-1 ; i > 0; i--) {
     if (_covered[i].start() < _covered[i-1].start()) {
         MemRegion covered_mr = _covered[i-1];
         _covered[i-1] = _covered[i];
         _covered[i] = covered_mr;
         MemRegion committed_mr = _committed[i-1];
       _committed[i-1] = _committed[i];
       _committed[i] = committed_mr;
       break;
     }
   }
 #ifdef ASSERT
   for (int m = 0; m < _cur_covered_regions-1; m++) {
     assert(_covered[m].start() <= _covered[m+1].start(),
       "Covered regions out of order");
     assert(_committed[m].start() <= _committed[m+1].start(),
       "Committed regions out of order");
   }
 #endif
 }
 // Returns the start of any committed region that is lower than
 // the target committed region (index ind) and that intersects the
 // target region.  If none, return start of target region.
 //
 //      -------------
 //      |           |
 //      -------------
 //              ------------
 //              | target   |
 //              ------------
 //                               -------------
 //                               |           |
 //                               -------------
 //      ^ returns this
 //
 //      -------------
 //      |           |
 //      -------------
 //                      ------------
 //                      | target   |
 //                      ------------
 //                               -------------
 //                               |           |
 //                               -------------
 //                      ^ returns this
 HeapWord* CardTableExtension::lowest_prev_committed_start(int ind) const {
   assert(_cur_covered_regions >= 0, "Expecting at least on region");
   HeapWord* min_start = _committed[ind].start();
   for (int j = 0; j < ind; j++) {
     HeapWord* this_start = _committed[j].start();
     if ((this_start < min_start) &&
         !(_committed[j].intersection(_committed[ind])).is_empty()) {
        min_start = this_start;
     }
   }
   return min_start;
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.cpp@f90c822e73f8 (annotated)

src/share/vm/gc_implementation/parallelScavenge/cardTableExtension.cpp