epsilonHeap.hpp

/*
 * Copyright (c) 2017, 2018, Red Hat, Inc. 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
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#ifndef SHARE_GC_EPSILON_EPSILONHEAP_HPP
#define SHARE_GC_EPSILON_EPSILONHEAP_HPP

#include "gc/shared/collectedHeap.hpp"
#include "gc/shared/softRefPolicy.hpp"
#include "gc/shared/space.hpp"
#include "gc/epsilon/epsilonMonitoringSupport.hpp"
#include "gc/epsilon/epsilonBarrierSet.hpp"
#include "services/memoryManager.hpp"

class EpsilonHeap : public CollectedHeap {
  friend class VMStructs;
private:
  SoftRefPolicy _soft_ref_policy;
  EpsilonMonitoringSupport* _monitoring_support;
  MemoryPool* _pool;
  GCMemoryManager _memory_manager;
  ContiguousSpace* _space;
  VirtualSpace _virtual_space;
  size_t _max_tlab_size;
  size_t _step_counter_update;
  size_t _step_heap_print;
  int64_t _decay_time_ns;
  volatile size_t _last_counter_update;
  volatile size_t _last_heap_print;

public:
  static EpsilonHeap* heap();

  EpsilonHeap() :
          _memory_manager("Epsilon Heap", ""),
          _space(NULL) {};

  virtual Name kind() const {
    return CollectedHeap::Epsilon;
  }

  virtual const char* name() const {
    return "Epsilon";
  }

  virtual SoftRefPolicy* soft_ref_policy() {
    return &_soft_ref_policy;
  }

  virtual jint initialize();
  virtual void post_initialize();
  virtual void initialize_serviceability();

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

  virtual size_t max_capacity() const { return _virtual_space.reserved_size();  }
  virtual size_t capacity()     const { return _virtual_space.committed_size(); }
  virtual size_t used()         const { return _space->used(); }

  virtual bool is_in(const void* p) const {
    return _space->is_in(p);
  }

  virtual bool is_maximal_no_gc() const {
    // No GC is going to happen. Return "we are at max", when we are about to fail.
    return used() == capacity();
  }

  // Allocation
  HeapWord* allocate_work(size_t size);
  virtual HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded);
  virtual HeapWord* allocate_new_tlab(size_t min_size,
                                      size_t requested_size,
                                      size_t* actual_size);

  // TLAB allocation
  virtual size_t tlab_capacity(Thread* thr)         const { return capacity();     }
  virtual size_t tlab_used(Thread* thr)             const { return used();         }
  virtual size_t max_tlab_size()                    const { return _max_tlab_size; }
  virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;

  virtual void collect(GCCause::Cause cause);
  virtual void do_full_collection(bool clear_all_soft_refs);

  // Heap walking support
  virtual void object_iterate(ObjectClosure* cl);

  // Object pinning support: every object is implicitly pinned
  virtual bool supports_object_pinning() const           { return true; }
  virtual oop pin_object(JavaThread* thread, oop obj)    { return obj; }
  virtual void unpin_object(JavaThread* thread, oop obj) { }

  // No support for block parsing.
  HeapWord* block_start(const void* addr) const { return NULL;  }
  bool block_is_obj(const HeapWord* addr) const { return false; }

  // No GC threads
  virtual void gc_threads_do(ThreadClosure* tc) const {}

  // No nmethod handling
  virtual void register_nmethod(nmethod* nm) {}
  virtual void unregister_nmethod(nmethod* nm) {}
  virtual void flush_nmethod(nmethod* nm) {}
  virtual void verify_nmethod(nmethod* nm) {}

  // No heap verification
  virtual void prepare_for_verify() {}
  virtual void verify(VerifyOption option) {}

  MemRegion reserved_region() const { return _reserved; }
  bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }

  virtual void print_on(outputStream* st) const;
  virtual void print_tracing_info() const;
  virtual bool print_location(outputStream* st, void* addr) const;

private:
  void print_heap_info(size_t used) const;
  void print_metaspace_info() const;

};

#endif // SHARE_GC_EPSILON_EPSILONHEAP_HPP