/*

 * 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.

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#include "gc/shared/concurrentGCThread.hpp"

// The G1YoungRemSetSamplingThread is used to re-assess the validity of

// the prediction for the remembered set lengths of the young generation.

//

// At the end of the GC G1 determines the length of the young gen based on

// how much time the next GC can take, and when the next GC may occur

// according to the MMU.

//

// The assumption is that a significant part of the GC is spent on scanning

// the remembered sets (and many other components), so this thread constantly

// reevaluates the prediction for the remembered set scanning costs, and potentially

// G1Policy resizes the young gen. This may do a premature GC or even

// increase the young gen size to keep pause time length goal.

class G1YoungRemSetSamplingThread: public ConcurrentGCThread {

private:

  Monitor _monitor;

  double _last_periodic_gc_attempt_s;

  double _vtime_accum;  // Accumulated virtual time.

  void sample_young_list_rs_lengths();

  void run_service();

  void check_for_periodic_gc();

  void stop_service();

  void sleep_before_next_cycle();

  bool should_start_periodic_gc();

public:

  G1YoungRemSetSamplingThread();

  double vtime_accum() { return _vtime_accum; }

};