hotspot/src/share/vm/runtime/sweeper.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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,
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#ifndef SHARE_VM_RUNTIME_SWEEPER_HPP
#define SHARE_VM_RUNTIME_SWEEPER_HPP

// An NmethodSweeper is an incremental cleaner for:
//    - cleanup inline caches
//    - reclamation of unreferences zombie nmethods
//

class NMethodSweeper : public AllStatic {
  static long      _traversals;      // Stack scan count, also sweep ID.
  static nmethod*  _current;         // Current nmethod
  static int       _seen;            // Nof. nmethod we have currently processed in current pass of CodeCache
  static int       _flushed_count;   // Nof. nmethods flushed in current sweep
  static int       _zombified_count; // Nof. nmethods made zombie in current sweep
  static int       _marked_count;    // Nof. nmethods marked for reclaim in current sweep

  static volatile int  _invocations;   // No. of invocations left until we are completed with this pass
  static volatile int  _sweep_started; // Flag to control conc sweeper

  //The following are reset in scan_stacks and synchronized by the safepoint
  static bool      _resweep;           // Indicates that a change has happend and we want another sweep,
                                       // always checked and reset at a safepoint so memory will be in sync.
  static int       _locked_seen;       // Number of locked nmethods encountered during the scan
  static int       _not_entrant_seen_on_stack; // Number of not entrant nmethod were are still on stack
  static jint      _flush_token;       // token that guards method flushing, making sure it is executed only once.

  // These are set during a flush, a VM-operation
  static long      _last_flush_traversal_id; // trav number at last flush unloading
  static jlong     _last_full_flush_time;    // timestamp of last emergency unloading

  // These are synchronized by the _sweep_started token
  static int       _highest_marked;   // highest compile id dumped at last emergency unloading
  static int       _dead_compile_ids; // number of compile ids that where not in the cache last flush

  // Stat counters
  static int       _number_of_flushes;            // Total of full traversals caused by full cache
  static int       _total_nof_methods_reclaimed;  // Accumulated nof methods flushed
  static jlong     _total_time_sweeping;          // Accumulated time sweeping
  static jlong     _total_time_this_sweep;        // Total time this sweep
  static jlong     _peak_sweep_time;              // Peak time for a full sweep
  static jlong     _peak_sweep_fraction_time;     // Peak time sweeping one fraction
  static jlong     _total_disconnect_time;        // Total time cleaning code mem
  static jlong     _peak_disconnect_time;         // Peak time cleaning code mem

  static void process_nmethod(nmethod *nm);
  static void release_nmethod(nmethod* nm);

  static void log_sweep(const char* msg, const char* format = NULL, ...);
  static bool sweep_in_progress();

 public:
  static long traversal_count()              { return _traversals; }
  static int  number_of_flushes()            { return _number_of_flushes; }
  static int  total_nof_methods_reclaimed()  { return _total_nof_methods_reclaimed; }
  static jlong total_time_sweeping()         { return _total_time_sweeping; }
  static jlong peak_sweep_time()             { return _peak_sweep_time; }
  static jlong peak_sweep_fraction_time()    { return _peak_sweep_fraction_time; }
  static jlong total_disconnect_time()       { return _total_disconnect_time; }
  static jlong peak_disconnect_time()        { return _peak_disconnect_time; }

#ifdef ASSERT
  // Keep track of sweeper activity in the ring buffer
  static void record_sweep(nmethod* nm, int line);
  static void report_events(int id, address entry);
  static void report_events();
#endif

  static void scan_stacks();      // Invoked at the end of each safepoint
  static void sweep_code_cache(); // Concurrent part of sweep job
  static void possibly_sweep();   // Compiler threads call this to sweep

  static void notify(nmethod* nm) {
    // Request a new sweep of the code cache from the beginning. No
    // need to synchronize the setting of this flag since it only
    // changes to false at safepoint so we can never overwrite it with false.
     _resweep = true;
  }

  static void handle_full_code_cache(bool is_full); // Called by compilers who fail to allocate
  static void speculative_disconnect_nmethods(bool was_full);   // Called by vm op to deal with alloc failure
};

#endif // SHARE_VM_RUNTIME_SWEEPER_HPP