/*

 * 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

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

 * questions.

 *

 */

#include "precompiled.hpp"

#include "gc/parallel/objectStartArray.inline.hpp"

#include "gc/parallel/parallelScavengeHeap.inline.hpp"

#include "gc/parallel/psCardTable.hpp"

#include "gc/parallel/psPromotionManager.inline.hpp"

#include "gc/parallel/psScavenge.inline.hpp"

#include "gc/parallel/psYoungGen.hpp"

#include "memory/iterator.inline.hpp"

#include "oops/access.inline.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/prefetch.inline.hpp"

#include "utilities/align.hpp"

// Checks an individual oop for missing precise marks. Mark

// may be either dirty or newgen.

class CheckForUnmarkedOops : public BasicOopIterateClosure {

 private:

  PSYoungGen*  _young_gen;

  PSCardTable* _card_table;

  HeapWord*    _unmarked_addr;

 protected:

  template <class T> void do_oop_work(T* p) {

    oop obj = RawAccess<>::oop_load(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;

      }

    }

  }

 public:

  CheckForUnmarkedOops(PSYoungGen* young_gen, PSCardTable* 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 existence of some type of mark,

// precise or imprecise, dirty or newgen.

class CheckForUnmarkedObjects : public ObjectClosure {

 private:

  PSYoungGen*  _young_gen;

  PSCardTable* _card_table;

 public:

  CheckForUnmarkedObjects() {

    ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();

    _young_gen = heap->young_gen();

    _card_table = heap->card_table();

  }

  // Card marks are not precise. The current system can leave us with

  // a mismatch 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(&object_check);

    if (object_check.has_unmarked_oop()) {

      guarantee(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object");

    }

  }

};

// Checks for precise marking of oops as newgen.

class CheckForPreciseMarks : public BasicOopIterateClosure {

 private:

  PSYoungGen*  _young_gen;

  PSCardTable* _card_table;

 protected:

  template <class T> void do_oop_work(T* p) {

    oop obj = RawAccess<IS_NOT_NULL>::oop_load(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, PSCardTable* 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().

// The generation (old gen) is divided into slices, which are further

// subdivided into stripes, with one stripe per GC thread. The size of

// a stripe is a constant, ssize.

//

//      +===============+        slice 0

//      |  stripe 0     |

//      +---------------+

//      |  stripe 1     |

//      +---------------+

//      |  stripe 2     |

//      +---------------+

//      |  stripe 3     |

//      +===============+        slice 1

//      |  stripe 0     |

//      +---------------+

//      |  stripe 1     |

//      +---------------+

//      |  stripe 2     |

//      +---------------+

//      |  stripe 3     |

//      +===============+        slice 2

//      ...

//

// In this case there are 4 threads, so 4 stripes.  A GC thread first works on

// its stripe within slice 0 and then moves to its stripe in the next slice

// until it has exceeded the top of the generation.  The distance to stripe in

// the next slice is calculated based on the number of stripes.  The next

// stripe is at ssize * number_of_stripes (= slice_stride)..  So after

// finishing stripe 0 in slice 0, the thread finds the stripe 0 in slice1 by

// adding slice_stride to the start of stripe 0 in slice 0 to get to the start

// of stride 0 in slice 1.

void PSCardTable::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;

  CardValue* start_card = byte_for(sp->bottom());

  CardValue* 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 (CardValue* slice = start_card; slice < end_card; slice += slice_width) {

    CardValue* worker_start_card = slice + stripe_number * ssize;

    if (worker_start_card >= end_card)

      return; // We're done.

    CardValue* 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) {

      }

    }

#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");

    CardValue* 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++;

      }

      CardValue* 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;

          CardValue* 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;

          }

        }

      }

      CardValue* 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(oopDesc::is_oop_or_null(m), "Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m));

            pm->push_contents(m);

            p += m->size();

          }

          pm->drain_stacks_cond_depth();

        } else {

          while (p < to) {

            oop m = oop(p);

            assert(oopDesc::is_oop_or_null(m), "Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m));

            pm->push_contents(m);

            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 PSCardTable::verify_all_young_refs_imprecise() {

  CheckForUnmarkedObjects check;

  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();

  PSOldGen* old_gen = heap->old_gen();

  old_gen->object_iterate(&check);

}

// This should be called immediately after a scavenge, before mutators resume.

void PSCardTable::verify_all_young_refs_precise() {

  ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();

  PSOldGen* old_gen = heap->old_gen();

  CheckForPreciseMarks check(heap->young_gen(), this);

  old_gen->oop_iterate(&check);

  verify_all_young_refs_precise_helper(old_gen->object_space()->used_region());

}

void PSCardTable::verify_all_young_refs_precise_helper(MemRegion mr) {

  CardValue* bot = byte_for(mr.start());

  CardValue* top = 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 PSCardTable::addr_is_marked_imprecise(void *addr) {

  CardValue* p = byte_for(addr);

  CardValue 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 PSCardTable::addr_is_marked_precise(void *addr) {

  CardValue* p = byte_for(addr);

  CardValue 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

// CardTable::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

// CardTable::resize_covered_region() but

// for regions that grow or shrink at the low end.

void PSCardTable::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 PSCardTable::resize_covered_region_by_start(MemRegion new_region) {

  CardTable::resize_covered_region(new_region);

  debug_only(verify_guard();)

}

void PSCardTable::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);

  int ind = changed_region;

  log_trace(gc, barrier)("CardTable::resize_covered_region: ");

  log_trace(gc, barrier)("    _covered[%d].start(): " INTPTR_FORMAT "  _covered[%d].last(): " INTPTR_FORMAT,

                ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last()));

  log_trace(gc, barrier)("    _committed[%d].start(): " INTPTR_FORMAT "  _committed[%d].last(): " INTPTR_FORMAT,

                ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last()));

  log_trace(gc, barrier)("    byte_for(start): " INTPTR_FORMAT "  byte_for(last): " INTPTR_FORMAT,

                p2i(byte_for(_covered[ind].start())),  p2i(byte_for(_covered[ind].last())));

  log_trace(gc, barrier)("    addr_for(start): " INTPTR_FORMAT "  addr_for(last): " INTPTR_FORMAT,

                p2i(addr_for((CardValue*) _committed[ind].start())), p2i(addr_for((CardValue*) _committed[ind].last())));