1 /*
   2  * Copyright (c) 1997, 2013, 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
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  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
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  23  */
  24 
  25 #ifndef SHARE_VM_RUNTIME_SWEEPER_HPP
  26 #define SHARE_VM_RUNTIME_SWEEPER_HPP
  27 
  28 // An NmethodSweeper is an incremental cleaner for:
  29 //    - cleanup inline caches
  30 //    - reclamation of unreferences zombie nmethods
  31 //
  32 
  33 class NMethodSweeper : public AllStatic {
  34   static long      _traversals;      // Stack scan count, also sweep ID.
  35   static nmethod*  _current;         // Current nmethod
  36   static int       _seen;            // Nof. nmethod we have currently processed in current pass of CodeCache
  37   static int       _flushed_count;   // Nof. nmethods flushed in current sweep
  38   static int       _zombified_count; // Nof. nmethods made zombie in current sweep
  39   static int       _marked_count;    // Nof. nmethods marked for reclaim in current sweep
  40 
  41   static volatile int  _invocations;   // No. of invocations left until we are completed with this pass
  42   static volatile int  _sweep_started; // Flag to control conc sweeper
  43 
  44   //The following are reset in scan_stacks and synchronized by the safepoint
  45   static bool      _resweep;           // Indicates that a change has happend and we want another sweep,
  46                                        // always checked and reset at a safepoint so memory will be in sync.
  47   static int       _locked_seen;       // Number of locked nmethods encountered during the scan
  48   static int       _not_entrant_seen_on_stack; // Number of not entrant nmethod were are still on stack
  49   static jint      _flush_token;       // token that guards method flushing, making sure it is executed only once.
  50 
  51   // These are set during a flush, a VM-operation
  52   static long      _last_flush_traversal_id; // trav number at last flush unloading
  53   static jlong     _last_full_flush_time;    // timestamp of last emergency unloading
  54 
  55   // Stat counters
  56   static int       _number_of_flushes;            // Total of full traversals caused by full cache
  57   static int       _total_nof_methods_reclaimed;  // Accumulated nof methods flushed
  58   static jlong     _total_time_sweeping;          // Accumulated time sweeping
  59   static jlong     _total_time_this_sweep;        // Total time this sweep
  60   static jlong     _peak_sweep_time;              // Peak time for a full sweep
  61   static jlong     _peak_sweep_fraction_time;     // Peak time sweeping one fraction
  62   static jlong     _total_disconnect_time;        // Total time cleaning code mem
  63   static jlong     _peak_disconnect_time;         // Peak time cleaning code mem
  64 
  65   static void process_nmethod(nmethod *nm);
  66   static void release_nmethod(nmethod* nm);
  67 
  68   static void log_sweep(const char* msg, const char* format = NULL, ...);
  69   static bool sweep_in_progress();
  70   static void sweep_code_cache(); // Concurrent part of sweep job
  71 
  72  public:
  73   static long traversal_count()              { return _traversals; }
  74   static int  number_of_flushes()            { return _number_of_flushes; }
  75   static int  total_nof_methods_reclaimed()  { return _total_nof_methods_reclaimed; }
  76   static jlong total_time_sweeping()         { return _total_time_sweeping; }
  77   static jlong peak_sweep_time()             { return _peak_sweep_time; }
  78   static jlong peak_sweep_fraction_time()    { return _peak_sweep_fraction_time; }
  79   static jlong total_disconnect_time()       { return _total_disconnect_time; }
  80   static jlong peak_disconnect_time()        { return _peak_disconnect_time; }
  81 
  82   static const int hc_reset_value = 100; // Value to which _hotness_counter of a method is set during stack scanning
  83   static const int hc_dec_value   = 1;   // Value by which the hotness counter is decremented
  84 
  85 #ifdef ASSERT
  86   // Keep track of sweeper activity in the ring buffer
  87   static void record_sweep(nmethod* nm, int line);
  88   static void report_events(int id, address entry);
  89   static void report_events();
  90 #endif
  91 
  92   static void scan_stacks();      // Invoked at the end of each safepoint
  93   static void possibly_sweep();   // Compiler threads call this to sweep
  94 
  95   static int  sort_nmentod_by_hotness(nmethod** nm1, nmethod** nm2);
  96 
  97   static void notify(nmethod* nm) {
  98     // Request a new sweep of the code cache from the beginning. No
  99     // need to synchronize the setting of this flag since it only
 100     // changes to false at safepoint so we can never overwrite it with false.
 101      _resweep = true;
 102   }
 103 
 104   static void handle_full_code_cache(bool is_full); // Called by compilers who fail to allocate
 105   static void speculative_disconnect_nmethods(bool was_full);   // Called by vm op to deal with alloc failure
 106 };
 107 
 108 #endif // SHARE_VM_RUNTIME_SWEEPER_HPP