/*

 * 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.

 *

 */

#ifndef SHARE_GC_SHENANDOAH_SHENANDOAHPACER_HPP

#define SHARE_GC_SHENANDOAH_SHENANDOAHPACER_HPP

#include "gc/shenandoah/shenandoahNumberSeq.hpp"

#include "memory/allocation.hpp"

class ShenandoahHeap;

#define PACING_PROGRESS_UNINIT (-1)

#define PACING_PROGRESS_ZERO   ( 0)

/**

 * ShenandoahPacer provides allocation pacing mechanism.

 *

 * Currently it implements simple tax-and-spend pacing policy: GC threads provide

 * credit, allocating thread spend the credit, or stall when credit is not available.

 */

class ShenandoahPacer : public CHeapObj<mtGC> {

private:

  ShenandoahHeap* _heap;

  BinaryMagnitudeSeq _delays;

  TruncatedSeq* _progress_history;

  // Set once per phase

  volatile intptr_t _epoch;

  volatile double _tax_rate;

  // Heavily updated, protect from accidental false sharing

  DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile intptr_t));

  volatile intptr_t _budget;

  DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, 0);

  // Heavily updated, protect from accidental false sharing

  DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile intptr_t));

  volatile intptr_t _progress;

  DEFINE_PAD_MINUS_SIZE(3, DEFAULT_CACHE_LINE_SIZE, 0);

public:

  ShenandoahPacer(ShenandoahHeap* heap) :

          _heap(heap),

          _progress_history(new TruncatedSeq(5)),

          _epoch(0),

          _tax_rate(1),

          _budget(0),

          _progress(PACING_PROGRESS_UNINIT) {}

  void setup_for_idle();

  void setup_for_mark();

  void setup_for_evac();

  void setup_for_updaterefs();

  void setup_for_traversal();

  inline void report_mark(size_t words);

  inline void report_evac(size_t words);

  inline void report_updaterefs(size_t words);

  inline void report_alloc(size_t words);

  bool claim_for_alloc(size_t words, bool force);

  void pace_for_alloc(size_t words);

  void unpace_for_alloc(intptr_t epoch, size_t words);

  intptr_t epoch();

  void print_on(outputStream* out) const;

private:

  inline void report_internal(size_t words);

  inline void report_progress_internal(size_t words);

  void restart_with(size_t non_taxable_bytes, double tax_rate);

  size_t update_and_get_progress_history();

};

#endif // SHARE_GC_SHENANDOAH_SHENANDOAHPACER_HPP