/*

 * Copyright (c) 2016, 2018, Red Hat, Inc. All rights reserved.

 *

 * 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/shenandoah/shenandoahCollectionSet.hpp"

#include "gc/shenandoah/shenandoahHeap.inline.hpp"

#include "gc/shenandoah/shenandoahHeapRegionSet.hpp"

#include "gc/shenandoah/shenandoahUtils.hpp"

#include "runtime/atomic.hpp"

#include "services/memTracker.hpp"

#include "utilities/copy.hpp"

ShenandoahCollectionSet::ShenandoahCollectionSet(ShenandoahHeap* heap, char* heap_base, size_t size) :

  _map_size(heap->num_regions()),

  _region_size_bytes_shift(ShenandoahHeapRegion::region_size_bytes_shift()),

  _map_space(align_up(((uintx)heap_base + size) >> _region_size_bytes_shift, os::vm_allocation_granularity())),

  _cset_map(_map_space.base() + ((uintx)heap_base >> _region_size_bytes_shift)),

  _biased_cset_map(_map_space.base()),

  _heap(heap),

  _garbage(0),

  _live_data(0),

  _used(0),

  _region_count(0),

  _current_index(0) {

  // The collection set map is reserved to cover the entire heap *and* zero addresses.

  // This is needed to accept in-cset checks for both heap oops and NULLs, freeing

  // high-performance code from checking for NULL first.

  //

  // Since heap_base can be far away, committing the entire map would waste memory.

  // Therefore, we only commit the parts that are needed to operate: the heap view,

  // and the zero page.

  //

  // Note: we could instead commit the entire map, and piggyback on OS virtual memory

  // subsystem for mapping not-yet-written-to pages to a single physical backing page,

  // but this is not guaranteed, and would confuse NMT and other memory accounting tools.

  MemTracker::record_virtual_memory_type(_map_space.base(), mtGC);

  size_t page_size = (size_t)os::vm_page_size();

  if (!_map_space.special()) {

    // Commit entire pages that cover the heap cset map.

    char* bot_addr = align_down(_cset_map, page_size);

    char* top_addr = align_up(_cset_map + _map_size, page_size);

    os::commit_memory_or_exit(bot_addr, pointer_delta(top_addr, bot_addr, 1), false,

                              "Unable to commit collection set bitmap: heap");

    // Commit the zero page, if not yet covered by heap cset map.

    if (bot_addr != _biased_cset_map) {

      os::commit_memory_or_exit(_biased_cset_map, page_size, false,

                                "Unable to commit collection set bitmap: zero page");

    }

  }

  Copy::zero_to_bytes(_cset_map, _map_size);

  Copy::zero_to_bytes(_biased_cset_map, page_size);

}

void ShenandoahCollectionSet::add_region(ShenandoahHeapRegion* r) {

  assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");

  assert(Thread::current()->is_VM_thread(), "Must be VMThread");

  assert(!is_in(r), "Already in collection set");

  _cset_map[r->region_number()] = 1;

  _region_count ++;

  _garbage += r->garbage();

  _live_data += r->get_live_data_bytes();

  _used += r->used();

}

bool ShenandoahCollectionSet::add_region_check_for_duplicates(ShenandoahHeapRegion* r) {

  if (!is_in(r)) {

    add_region(r);

    return true;

  } else {

    return false;

  }

}

void ShenandoahCollectionSet::remove_region(ShenandoahHeapRegion* r) {

  assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");

  assert(Thread::current()->is_VM_thread(), "Must be VMThread");

  assert(is_in(r), "Not in collection set");

  _cset_map[r->region_number()] = 0;

  _region_count --;

}

void ShenandoahCollectionSet::update_region_status() {

  for (size_t index = 0; index < _heap->num_regions(); index ++) {

    ShenandoahHeapRegion* r = _heap->get_region(index);

    if (is_in(r)) {

      r->make_cset();

    } else {

      assert (!r->is_cset(), "should not be cset");

    }

  }

}

void ShenandoahCollectionSet::clear() {

  assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");

  Copy::zero_to_bytes(_cset_map, _map_size);

#ifdef ASSERT

  for (size_t index = 0; index < _heap->num_regions(); index ++) {

    assert (!_heap->get_region(index)->is_cset(), "should have been cleared before");

  }

#endif

  _garbage = 0;

  _live_data = 0;

  _used = 0;

  _region_count = 0;

  _current_index = 0;

}

ShenandoahHeapRegion* ShenandoahCollectionSet::claim_next() {

  size_t num_regions = _heap->num_regions();

  if (_current_index >= (jint)num_regions) {

    return NULL;

  }

  jint saved_current = _current_index;

  size_t index = (size_t)saved_current;

  while(index < num_regions) {

    if (is_in(index)) {

      jint cur = Atomic::cmpxchg((jint)(index + 1), &_current_index, saved_current);

      assert(cur >= (jint)saved_current, "Must move forward");

      if (cur == saved_current) {

        assert(is_in(index), "Invariant");

        return _heap->get_region(index);

      } else {

        index = (size_t)cur;

        saved_current = cur;

      }

    } else {

      index ++;

    }

  }

  return NULL;

}

ShenandoahHeapRegion* ShenandoahCollectionSet::next() {

  assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");

  assert(Thread::current()->is_VM_thread(), "Must be VMThread");

  size_t num_regions = _heap->num_regions();

  for (size_t index = (size_t)_current_index; index < num_regions; index ++) {

    if (is_in(index)) {

      _current_index = (jint)(index + 1);

      return _heap->get_region(index);

    }

  }

  return NULL;

}

void ShenandoahCollectionSet::print_on(outputStream* out) const {

  out->print_cr("Collection Set : " SIZE_FORMAT "", count());

  debug_only(size_t regions = 0;)

  for (size_t index = 0; index < _heap->num_regions(); index ++) {

    if (is_in(index)) {

      _heap->get_region(index)->print_on(out);

      debug_only(regions ++;)

    }

  }

  assert(regions == count(), "Must match");

}