/*

 * Copyright (c) 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/heuristics/shenandoahCompactHeuristics.hpp"

#include "gc/shenandoah/shenandoahFreeSet.hpp"

#include "gc/shenandoah/shenandoahHeapRegion.hpp"

#include "logging/log.hpp"

#include "logging/logTag.hpp"

ShenandoahCompactHeuristics::ShenandoahCompactHeuristics() : ShenandoahHeuristics() {

  SHENANDOAH_ERGO_ENABLE_FLAG(ExplicitGCInvokesConcurrent);

  SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahImplicitGCInvokesConcurrent);

  SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahUncommit);

  SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahAlwaysClearSoftRefs);

  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahAllocationThreshold,  10);

  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahImmediateThreshold,   100);

  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUncommitDelay,        1000);

  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahGuaranteedGCInterval, 30000);

  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahGarbageThreshold,     10);

  // Final configuration checks

  SHENANDOAH_CHECK_FLAG_SET(ShenandoahLoadRefBarrier);

  SHENANDOAH_CHECK_FLAG_SET(ShenandoahSATBBarrier);

  SHENANDOAH_CHECK_FLAG_SET(ShenandoahKeepAliveBarrier);

  SHENANDOAH_CHECK_FLAG_SET(ShenandoahCASBarrier);

  SHENANDOAH_CHECK_FLAG_SET(ShenandoahCloneBarrier);

}

bool ShenandoahCompactHeuristics::should_start_gc() const {

  ShenandoahHeap* heap = ShenandoahHeap::heap();

  size_t capacity = heap->max_capacity();

  size_t available = heap->free_set()->available();

  size_t threshold_bytes_allocated = capacity / 100 * ShenandoahAllocationThreshold;

  size_t min_threshold = capacity / 100 * ShenandoahMinFreeThreshold;

  if (available < min_threshold) {

    log_info(gc)("Trigger: Free (" SIZE_FORMAT "M) is below minimum threshold (" SIZE_FORMAT "M)",

                 available / M, min_threshold / M);

    return true;

  }

  if (available < threshold_bytes_allocated) {

    log_info(gc)("Trigger: Free (" SIZE_FORMAT "M) is lower than allocated recently (" SIZE_FORMAT "M)",

                 available / M, threshold_bytes_allocated / M);

    return true;

  }

  size_t bytes_allocated = heap->bytes_allocated_since_gc_start();

  if (bytes_allocated > threshold_bytes_allocated) {

    log_info(gc)("Trigger: Allocated since last cycle (" SIZE_FORMAT "M) is larger than allocation threshold (" SIZE_FORMAT "M)",

                 bytes_allocated / M, threshold_bytes_allocated / M);

    return true;

  }

  return ShenandoahHeuristics::should_start_gc();

}

void ShenandoahCompactHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,

                                                                        RegionData* data, size_t size,

                                                                        size_t actual_free) {

  // Do not select too large CSet that would overflow the available free space

  size_t max_cset = actual_free * 3 / 4;

  log_info(gc, ergo)("CSet Selection. Actual Free: " SIZE_FORMAT "M, Max CSet: " SIZE_FORMAT "M",

                     actual_free / M, max_cset / M);

  size_t threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100;

  size_t live_cset = 0;

  for (size_t idx = 0; idx < size; idx++) {

    ShenandoahHeapRegion* r = data[idx]._region;

    size_t new_cset = live_cset + r->get_live_data_bytes();

    if (new_cset < max_cset && r->garbage() > threshold) {

      live_cset = new_cset;

      cset->add_region(r);

    }

  }

}

const char* ShenandoahCompactHeuristics::name() {

  return "compact";

}

bool ShenandoahCompactHeuristics::is_diagnostic() {

  return false;

}

bool ShenandoahCompactHeuristics::is_experimental() {

  return false;

}