/*
 * Copyright (c) 2011, 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.
 *
 */

#ifndef SHARE_VM_GC_G1_G1MONITORINGSUPPORT_HPP
#define SHARE_VM_GC_G1_G1MONITORINGSUPPORT_HPP

#include "gc/shared/collectorCounters.hpp"
#include "gc/shared/generationCounters.hpp"
#include "services/memoryManager.hpp"
#include "services/memoryService.hpp"
#include "runtime/mutex.hpp"

class CollectorCounters;
class G1CollectedHeap;
class HSpaceCounters;
class MemoryPool;

// Class for monitoring logical spaces in G1. It provides data for
// both G1's jstat counters as well as G1's memory pools.
//
// G1 splits the heap into heap regions and each heap region belongs
// to one of the following categories:
//
// * eden      : regions that have been allocated since the last GC
// * survivors : regions with objects that survived the last few GCs
// * old       : long-lived non-humongous regions
// * humongous : humongous regions
// * archive   : archive regions
// * free      : free regions
//
// The combination of eden and survivor regions form the equivalent of
// the young generation in the other GCs. The combination of old,
// humongous, and archive regions form the equivalent of the old
// generation in the other GCs. Archive regions are permanently
// allocated during heap initialization, e.g., for CDS. Free regions
// do not have a good equivalent in the other GCs, given that they can
// be allocated as any of the other region types.
//
// The monitoring tools expect the heap to contain one or more
// generations (young, old) and each generation to contain one or
// more spaces (young has eden and survivor, old has old, humongous and
// archive). Given that G1 does not maintain those spaces physically
// (e.g., the set of non-contiguous eden regions can be considered as
// a "logical" space), we provide the illusion that those generations and
// spaces exist. In reality, each generation and space refers to a set
// of heap regions that are potentially non-contiguous.
//
// This class provides interfaces to access the min, current, and max
// capacity and current occupancy for each of G1's logical spaces and
// generations we expose to the monitoring tools. Also provided are
// counters for G1 concurrent collections and stop-the-world full heap
// collections.
//
// Below is a description of how the various sizes are calculated.
//
// * Current Capacity
//
//    - heap_capacity = current heap capacity (e.g., current committed size)
//    - young_gen_capacity = current max young gen target capacity
//          (i.e., young gen target capacity + max allowed expansion capacity)
//    - survivor_capacity = current survivor region capacity
//    - eden_capacity = young_gen_capacity - survivor_capacity
//  In legacy mode:
//    - old_capacity = heap_capacity - young_gen_capacity
//  Otherwise:
//    - humongous_capacity = sum of humongous regions allocated
//    - archive_capacity = sum of archive regions allocated
//    - old_capacity = heap_capacity - young_gen_capacity -
//                     humongous_capacity - archive_capacity
//
//    What we do in the above is to distribute the free regions among
//    eden_capacity and old_capacity.
//
// * Occupancy
//
//    - young_gen_committed = current young region capacity
//    - survivor_used = survivor_capacity
//    - eden_used = young_gen_used - survivor_used
//  In legacy mode:
//    - old_used = overall_used - young_gen_used
//  Otherwise:
//    - humongous_used = sum of humongous regions allocated
//    - archive_used = sum of archive regions allocated
//    - old_used = overall_used - young_gen_used -
//                 humongous_used - archive_used
//
// * Min Capacity
//
//    We set this to 0 for all spaces.
//
// * Max Capacity
//
//    For jstat, we set the max capacity of all spaces to heap_capacity,
//    given that we don't always have a reasonable upper bound on how big
//    each space can grow. For the memory pools, we make the max
//    capacity undefined with the exception of the old memory pool for
//    which we make the max capacity same as the max heap capacity. This
//    allows users to sum memory pool max capacities to get something
//    reasonable.
//
// We update all the above synchronously and we store the results in
// this singleton class so we can just read them out when needed. A subtle
// point is that all the above sizes must be recalculated when the old
// gen changes capacity (after a GC or after a humongous allocation)
// but only the eden occupancy changes when a new eden region is
// allocated. So, in the latter case we have minimal recalculation to
// do, but we don't both special-casing it because doing the full
// recalculation is quite fast.

class G1MonitoringSupport : public CHeapObj<mtGC> {
  friend class VMStructs;
  friend class G1MonitoringScope;

  G1CollectedHeap* _g1h;

  // java.lang.management MemoryManager and MemoryPool support

  bool _use_legacy_monitoring; // For vmStructs and hsdb

  GCMemoryManager _full_memory_manager;
  // Legacy monitoring
  GCMemoryManager _incremental_memory_manager;
  // Default monitoring
  GCMemoryManager _young_memory_manager;
  GCMemoryManager _mixed_memory_manager;
  GCMemoryManager _conc_memory_manager;

  MemoryPool* _eden_space_pool;
  MemoryPool* _survivor_space_pool;
  MemoryPool* _old_space_pool;
  MemoryPool* _archive_space_pool;
  MemoryPool* _humongous_space_pool;

  // jstat performance counters
  //  incremental collections both young and mixed
  CollectorCounters*   _incremental_collection_counters;
  //  full stop-the-world collections
  CollectorCounters*   _full_collection_counters;
  //  stop-the-world phases in G1
  CollectorCounters*   _conc_collection_counters;
  //  young collection set counters.  The _eden_counters,
  // _from_counters, and _to_counters are associated with
  // this "generational" counter.
  GenerationCounters*  _young_gen_counters;
  //  old collection set counters. The _old_space_counters
  // below are associated with this "generational" counter.
  GenerationCounters*  _old_gen_counters;
  // Counters for the capacity and used for
  //   the whole heap
  HSpaceCounters*      _old_space_counters;
  //   the young collection
  HSpaceCounters*      _eden_space_counters;
  //   the survivor collection (only one, _to_counters, is actively used)
  HSpaceCounters*      _from_space_counters;
  HSpaceCounters*      _to_space_counters;

  // When it's appropriate to recalculate the various sizes (at the
  // end of a GC, when a new eden region is allocated, etc.) we store
  // them here so that we can easily report them when needed and not
  // have to recalculate them every time.

  size_t _overall_committed;
  size_t _overall_used;

  size_t _young_gen_committed;

  size_t _eden_space_committed;
  size_t _eden_space_used;
  size_t _survivor_space_committed;
  size_t _survivor_space_used;

  size_t _old_space_committed;
  size_t _old_space_used;
  size_t _archive_space_committed;
  size_t _archive_space_used;

  size_t _humongous_space_committed;
  size_t _humongous_space_used;

  // It returns x - y if x > y, 0 otherwise.
  // As described in the comment above, some of the inputs to the
  // calculations we have to do are obtained concurrently and hence
  // may be inconsistent with each other. So, this provides a
  // defensive way of performing the subtraction and avoids the value
  // going negative (which would mean a very large result, given that
  // the parameter are size_t).
  static size_t subtract_up_to_zero(size_t x, size_t y) {
    if (x > y) {
      return x - y;
    } else {
      return 0;
    }
  }

  // Recalculate all the space sizes.
  void recalculate_sizes();

public:
  G1MonitoringSupport(G1CollectedHeap* g1h);
  ~G1MonitoringSupport();

  void initialize_serviceability();

  GrowableArray<GCMemoryManager*> memory_managers();
  GrowableArray<MemoryPool*> memory_pools();

  bool use_legacy_monitoring() { return _use_legacy_monitoring; }
  GCMemoryManager* conc_memory_manager() { return &_conc_memory_manager; }

  // Unfortunately, the jstat tool assumes that no space has 0
  // capacity. In our case, given that each space is logical, it's
  // possible that no regions will be allocated to it, hence to have 0
  // capacity (e.g., if there are no survivor regions, the survivor
  // space has 0 capacity). The way we deal with this is to always pad
  // each capacity value we report to jstat by a very small amount to
  // make sure that it's never zero. Given that we sometimes have to
  // report a capacity of a generation that contains several spaces
  // (e.g., young gen includes one eden, two survivor spaces), the
  // mult parameter is provided in order to adding the appropriate
  // padding multiple times so that the capacities add up correctly.
  static size_t pad_capacity(size_t size_bytes, size_t mult = 1) {
    return size_bytes + MinObjAlignmentInBytes * mult;
  }

  // Recalculate all the space sizes from scratch and update
  // all jstat counters accordingly.
  void update_sizes();
  // Recalculate all the space sizes from scratch, but update
  // just the eden size and jstat counters.
  void update_eden_size();

  CollectorCounters* conc_collection_counters() {
    return _conc_collection_counters;
  }

  // Monitoring support used by
  //   MemoryService
  //   jstat counters
  //   Tracing
  // Values may not be consistent wrt to each other.

  size_t young_gen_committed()  { return _young_gen_committed; }

  size_t eden_space_used()      { return _eden_space_used; }
  size_t survivor_space_used()  { return _survivor_space_used; }

  size_t old_gen_committed();
  size_t old_gen_used();

  size_t old_space_committed()  { return _old_space_committed; }
  size_t old_space_used()       { return _old_space_used; }
  size_t archive_space_used()   { return _archive_space_used; }

  size_t humongous_space_used() { return _humongous_space_used; }

  // Monitoring support for MemoryPools. Values in the returned MemoryUsage are
  // guaranteed to be consistent with each other.
  MemoryUsage memory_usage();
  MemoryUsage eden_space_memory_usage(size_t initial_size, size_t max_size);
  MemoryUsage survivor_space_memory_usage(size_t initial_size, size_t max_size);
  MemoryUsage old_space_memory_usage(size_t initial_size, size_t max_size);
  MemoryUsage archive_space_memory_usage(size_t initial_size, size_t max_size);
  MemoryUsage humongous_space_memory_usage(size_t initial_size, size_t max_size);
};

// TraceMemoryManagerStats for concurrent cycle.
class TraceConcMemoryManagerStats : public TraceMemoryManagerStats {
 public:
  enum Stage {
    CycleStart,
    Remark,
    Cleanup,
    CycleEnd
  };
  TraceConcMemoryManagerStats(Stage stage, GCCause::Cause cause);
};

// Scope object for java.lang.management support.
class G1MonitoringScope : public StackObj {
  TraceCollectorStats     _tcs;
  TraceMemoryManagerStats _tms;
public:
  G1MonitoringScope(G1MonitoringSupport* g1mm, bool full_gc, bool mixed_gc);
};

#endif // SHARE_VM_GC_G1_G1MONITORINGSUPPORT_HPP