vmGCOperations.hpp

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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// The following class hierarchy represents
// a set of operations (VM_Operation) related to GC.
//
//  VM_Operation
//      VM_GC_Operation
//          VM_GC_HeapInspection
//          VM_GenCollectForAllocation
//          VM_GenCollectFull
//          VM_GenCollectFullConcurrent
//          VM_ParallelGCFailedAllocation
//          VM_ParallelGCFailedPermanentAllocation
//          VM_ParallelGCSystemGC
//  VM_GC_Operation
//   - implements methods common to all classes in the hierarchy:
//     prevents multiple gc requests and manages lock on heap;
//
//  VM_GC_HeapInspection
//   - prints class histogram on SIGBREAK if PrintClassHistogram
//     is specified; and also the attach "inspectheap" operation
//
//  VM_GenCollectForAllocation
//  VM_GenCollectForPermanentAllocation
//  VM_ParallelGCFailedAllocation
//  VM_ParallelGCFailedPermanentAllocation
//   - this operation is invoked when allocation is failed;
//     operation performs garbage collection and tries to
//     allocate afterwards;
//
//  VM_GenCollectFull
//  VM_GenCollectFullConcurrent
//  VM_ParallelGCSystemGC
//   - these operations preform full collection of heaps of
//     different kind
//

class VM_GC_Operation: public VM_Operation {
 protected:
  BasicLock     _pending_list_basic_lock; // for refs pending list notification (PLL)
  unsigned int  _gc_count_before;         // gc count before acquiring PLL
  unsigned int  _full_gc_count_before;    // full gc count before acquiring PLL
  bool          _full;                    // whether a "full" collection
  bool          _prologue_succeeded;      // whether doit_prologue succeeded
  GCCause::Cause _gc_cause;                // the putative cause for this gc op
  bool          _gc_locked;               // will be set if gc was locked

  virtual bool skip_operation() const;

  // java.lang.ref.Reference support
  void acquire_pending_list_lock();
  void release_and_notify_pending_list_lock();

 public:
  VM_GC_Operation(unsigned int gc_count_before,
                  unsigned int full_gc_count_before = 0,
                  bool full = false) {
    _full = full;
    _prologue_succeeded = false;
    _gc_count_before    = gc_count_before;

    // A subclass constructor will likely overwrite the following
    _gc_cause           = GCCause::_no_cause_specified;

    _gc_locked = false;

    _full_gc_count_before = full_gc_count_before;
    // In ParallelScavengeHeap::mem_allocate() collections can be
    // executed within a loop and _all_soft_refs_clear can be set
    // true after they have been cleared by a collection and another
    // collection started so that _all_soft_refs_clear can be true
    // when this collection is started.  Don't assert that
    // _all_soft_refs_clear have to be false here even though
    // mutators have run.  Soft refs will be cleared again in this
    // collection.
  }
  ~VM_GC_Operation() {
    CollectedHeap* ch = Universe::heap();
    ch->collector_policy()->set_all_soft_refs_clear(false);
  }

  // Acquire the reference synchronization lock
  virtual bool doit_prologue();
  // Do notifyAll (if needed) and release held lock
  virtual void doit_epilogue();

  virtual bool allow_nested_vm_operations() const  { return true; }
  bool prologue_succeeded() const { return _prologue_succeeded; }

  void set_gc_locked() { _gc_locked = true; }
  bool gc_locked() const  { return _gc_locked; }

  static void notify_gc_begin(bool full = false);
  static void notify_gc_end();
};


class VM_GC_HeapInspection: public VM_GC_Operation {
 private:
  outputStream* _out;
  bool _full_gc;
  bool _need_prologue;
 public:
  VM_GC_HeapInspection(outputStream* out, bool request_full_gc,
                       bool need_prologue) :
    VM_GC_Operation(0 /* total collections,      dummy, ignored */,
                    0 /* total full collections, dummy, ignored */,
                    request_full_gc) {
    _out = out;
    _full_gc = request_full_gc;
    _need_prologue = need_prologue;
  }

  ~VM_GC_HeapInspection() {}
  virtual VMOp_Type type() const { return VMOp_GC_HeapInspection; }
  virtual bool skip_operation() const;
  virtual bool doit_prologue();
  virtual void doit();
};


class VM_GenCollectForAllocation: public VM_GC_Operation {
 private:
  HeapWord*   _res;
  size_t      _size;                       // size of object to be allocated.
  bool        _tlab;                       // alloc is of a tlab.
 public:
  VM_GenCollectForAllocation(size_t size,
                             bool tlab,
                             unsigned int gc_count_before)
    : VM_GC_Operation(gc_count_before),
      _size(size),
      _tlab(tlab) {
    _res = NULL;
  }
  ~VM_GenCollectForAllocation()  {}
  virtual VMOp_Type type() const { return VMOp_GenCollectForAllocation; }
  virtual void doit();
  HeapWord* result() const       { return _res; }
};


// VM operation to invoke a collection of the heap as a
// GenCollectedHeap heap.
class VM_GenCollectFull: public VM_GC_Operation {
 private:
  int _max_level;
 public:
  VM_GenCollectFull(unsigned int gc_count_before,
                    unsigned int full_gc_count_before,
                    GCCause::Cause gc_cause,
                      int max_level)
    : VM_GC_Operation(gc_count_before, full_gc_count_before, true /* full */),
      _max_level(max_level)
  { _gc_cause = gc_cause; }
  ~VM_GenCollectFull() {}
  virtual VMOp_Type type() const { return VMOp_GenCollectFull; }
  virtual void doit();
};

class VM_GenCollectForPermanentAllocation: public VM_GC_Operation {
 private:
  HeapWord*   _res;
  size_t      _size;                       // size of object to be allocated
 public:
  VM_GenCollectForPermanentAllocation(size_t size,
                                      unsigned int gc_count_before,
                                      unsigned int full_gc_count_before,
                                      GCCause::Cause gc_cause)
    : VM_GC_Operation(gc_count_before, full_gc_count_before, true),
      _size(size) {
    _res = NULL;
    _gc_cause = gc_cause;
  }
  ~VM_GenCollectForPermanentAllocation()  {}
  virtual VMOp_Type type() const { return VMOp_GenCollectForPermanentAllocation; }
  virtual void doit();
  HeapWord* result() const       { return _res; }
};