/*

 * Copyright (c) 2018, 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/g1/collectionSetChooser.hpp"

#include "gc/g1/g1RemSetTrackingPolicy.hpp"

#include "gc/g1/heapRegion.inline.hpp"

#include "gc/g1/heapRegionRemSet.hpp"

#include "runtime/safepoint.hpp"

bool G1RemSetTrackingPolicy::is_interesting_humongous_region(HeapRegion* r) const {

  return r->is_starts_humongous() && oop(r->bottom())->is_typeArray();

}

bool G1RemSetTrackingPolicy::needs_scan_for_rebuild(HeapRegion* r) const {

  // All non-free, non-young, non-closed archive regions need to be scanned for references;

  // At every gc we gather references to other regions in young, and closed archive

  // regions by definition do not have references going outside the closed archive.

  // Free regions trivially do not need scanning because they do not contain live

  // objects.

  return !(r->is_young() || r->is_closed_archive() || r->is_free());

}

void G1RemSetTrackingPolicy::update_at_allocate(HeapRegion* r) {

  if (r->is_young()) {

    // Always collect remembered set for young regions.

    r->rem_set()->set_state_complete();

  } else if (r->is_humongous()) {

    // Collect remembered sets for humongous regions by default to allow eager reclaim.

    r->rem_set()->set_state_complete();

  } else if (r->is_archive()) {

    // Archive regions never move ever. So never build remembered sets for them.

    r->rem_set()->set_state_empty();

  } else if (r->is_old()) {

    // By default, do not create remembered set for new old regions.

    r->rem_set()->set_state_empty();

  } else {

    guarantee(false, "Unhandled region %u with heap region type %s", r->hrm_index(), r->get_type_str());

  }

}

void G1RemSetTrackingPolicy::update_at_free(HeapRegion* r) {

  /* nothing to do */

}

bool G1RemSetTrackingPolicy::update_before_rebuild(HeapRegion* r, size_t live_bytes) {

  assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");

  bool selected_for_rebuild = false;

  // Only consider updating the remembered set for old gen regions - excluding archive regions

  // which never move (but are "Old" regions).

  if (r->is_old_or_humongous() && !r->is_archive()) {

    size_t between_ntams_and_top = (r->top() - r->next_top_at_mark_start()) * HeapWordSize;

    size_t total_live_bytes = live_bytes + between_ntams_and_top;

    // Completely free regions after rebuild are of no interest wrt rebuilding the

    // remembered set.

    assert(!r->rem_set()->is_updating(), "Remembered set of region %u is updating before rebuild", r->hrm_index());

    // To be of interest for rebuilding the remembered set the following must apply:

    // - They must contain some live data in them.

    // - We always try to update the remembered sets of humongous regions containing

    // type arrays if they are empty as they might have been reset after full gc.

    // - Only need to rebuild non-complete remembered sets.

    // - Otherwise only add those old gen regions which occupancy is low enough that there

    // is a chance that we will ever evacuate them in the mixed gcs.

    if ((total_live_bytes > 0) &&

        (is_interesting_humongous_region(r) || CollectionSetChooser::region_occupancy_low_enough_for_evac(total_live_bytes)) &&

        !r->rem_set()->is_tracked()) {

      r->rem_set()->set_state_updating();

      selected_for_rebuild = true;

    }

    log_trace(gc, remset, tracking)("Before rebuild region %u "

                                    "(ntams: " PTR_FORMAT ") "

                                    "total_live_bytes " SIZE_FORMAT " "

                                    "selected %s "

                                    "(live_bytes " SIZE_FORMAT " "

                                    "next_marked " SIZE_FORMAT " "

                                    "marked " SIZE_FORMAT " "

                                    "type %s)",

                                    r->hrm_index(),

                                    p2i(r->next_top_at_mark_start()),

                                    total_live_bytes,

                                    BOOL_TO_STR(selected_for_rebuild),

                                    live_bytes,

                                    r->next_marked_bytes(),

                                    r->marked_bytes(),

                                    r->get_type_str());

  }

  return selected_for_rebuild;

}

void G1RemSetTrackingPolicy::update_after_rebuild(HeapRegion* r) {

  assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");

  if (r->is_old_or_humongous()) {

    if (r->rem_set()->is_updating()) {

      r->rem_set()->set_state_complete();

    }

    // We can drop remembered sets of humongous regions that have a too large remembered set:

    // We will never try to eagerly reclaim or move them anyway until the next concurrent

    // cycle as e.g. remembered set entries will always be added.

    if (r->is_humongous() && !G1CollectedHeap::heap()->is_potential_eager_reclaim_candidate(r)) {

      r->rem_set()->clear_locked(true /* only_cardset */);

    }

    assert(!r->is_continues_humongous() || r->rem_set()->is_empty(), "Continues humongous object remsets should be empty");

    G1ConcurrentMark* cm = G1CollectedHeap::heap()->concurrent_mark();

    log_trace(gc, remset, tracking)("After rebuild region %u "

                                    "(ntams " PTR_FORMAT " "

                                    "liveness " SIZE_FORMAT " "

                                    "next_marked_bytes " SIZE_FORMAT " "

                                    "remset occ " SIZE_FORMAT " "

                                    "size " SIZE_FORMAT ")",

                                    r->hrm_index(),

                                    p2i(r->next_top_at_mark_start()),

                                    cm->liveness(r->hrm_index()) * HeapWordSize,

                                    r->next_marked_bytes(),

                                    r->rem_set()->occupied_locked(),

                                    r->rem_set()->mem_size());

  }

}