1 /*
   2  * Copyright (c) 2001, 2009, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // The Concurrent ZF Thread.  Performs concurrent zero-filling.
  26 
  27 class ConcurrentZFThread: public ConcurrentGCThread {
  28   friend class VMStructs;
  29   friend class ZeroFillRegionClosure;
  30 
  31  private:
  32 
  33   // Zero fill the heap region.
  34   void processHeapRegion(HeapRegion* r);
  35 
  36   // Stats
  37   //   Allocation (protected by heap lock).
  38   static int _region_allocs;  // Number of regions allocated
  39   static int _sync_zfs;       //   Synchronous zero-fills +
  40   static int _zf_waits;      //   Wait for conc zero-fill completion.
  41 
  42   // Number of regions CFZ thread fills.
  43   static int _regions_filled;
  44 
  45   double _vtime_start;  // Initial virtual time.
  46 
  47   // These are static because the "print_summary_info" method is, and
  48   // it currently assumes there is only one ZF thread.  We'll change when
  49   // we need to.
  50   static double _vtime_accum;  // Initial virtual time.
  51   static double vtime_accum() { return _vtime_accum; }
  52 
  53   // Offer yield for GC.  Returns true if yield occurred.
  54   bool offer_yield();
  55 
  56  public:
  57   // Constructor
  58   ConcurrentZFThread();
  59 
  60   // Main loop.
  61   virtual void run();
  62 
  63   // Printing
  64   void print_on(outputStream* st) const;
  65   void print() const;
  66 
  67   // Waits until "r" has been zero-filled.  Requires caller to hold the
  68   // ZF_mon.
  69   static void wait_for_ZF_completed(HeapRegion* r);
  70 
  71   // Get or clear the current unclean region.  Should be done
  72   // while holding the ZF_needed_mon lock.
  73 
  74   // shutdown
  75   void stop();
  76 
  77   // Stats
  78   static void note_region_alloc() {_region_allocs++; }
  79   static void note_sync_zfs() { _sync_zfs++; }
  80   static void note_zf_wait() { _zf_waits++; }
  81   static void note_region_filled() { _regions_filled++; }
  82 
  83   static void print_summary_info();
  84 };