sweeper.hpp revision 6412:53a41e7cbe05 
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24
25#ifndef SHARE_VM_RUNTIME_SWEEPER_HPP
26#define SHARE_VM_RUNTIME_SWEEPER_HPP
27
28#include "utilities/ticks.hpp"
29// An NmethodSweeper is an incremental cleaner for:
30//    - cleanup inline caches
31//    - reclamation of nmethods
32// Removing nmethods from the code cache includes two operations
33//  1) mark active nmethods
34//     Is done in 'mark_active_nmethods()'. This function is called at a
35//     safepoint and marks all nmethods that are active on a thread's stack.
36//  2) sweep nmethods
37//     Is done in sweep_code_cache(). This function is the only place in the
38//     sweeper where memory is reclaimed. Note that sweep_code_cache() is not
39//     called at a safepoint. However, sweep_code_cache() stops executing if
40//     another thread requests a safepoint. Consequently, 'mark_active_nmethods()'
41//     and sweep_code_cache() cannot execute at the same time.
42//     To reclaim memory, nmethods are first marked as 'not-entrant'. Methods can
43//     be made not-entrant by (i) the sweeper, (ii) deoptimization, (iii) dependency
44//     invalidation, and (iv) being replaced be a different method version (tiered
45//     compilation). Not-entrant nmethod cannot be called by Java threads, but they
46//     can still be active on the stack. To ensure that active nmethod are not reclaimed,
47//     we have to wait until the next marking phase has completed. If a not-entrant
48//     nmethod was NOT marked as active, it can be converted to 'zombie' state. To safely
49//     remove the nmethod, all inline caches (IC) that point to the the nmethod must be
50//     cleared. After that, the nmethod can be evicted from the code cache. Each nmethod's
51//     state change happens during separate sweeps. It may take at least 3 sweeps before an
52//     nmethod's space is freed. Sweeping is currently done by compiler threads between
53//     compilations or at least each 5 sec (NmethodSweepCheckInterval) when the code cache
54//     is full.
55
56class NMethodSweeper : public AllStatic {
57  static long      _traversals;                     // Stack scan count, also sweep ID.
58  static long      _total_nof_code_cache_sweeps;    // Total number of full sweeps of the code cache
59  static long      _time_counter;                   // Virtual time used to periodically invoke sweeper
60  static long      _last_sweep;                     // Value of _time_counter when the last sweep happened
61  static nmethod*  _current;                        // Current nmethod
62  static int       _seen;                           // Nof. nmethod we have currently processed in current pass of CodeCache
63  static int       _flushed_count;                  // Nof. nmethods flushed in current sweep
64  static int       _zombified_count;                // Nof. nmethods made zombie in current sweep
65  static int       _marked_for_reclamation_count;   // Nof. nmethods marked for reclaim in current sweep
66
67  static volatile int  _sweep_fractions_left;       // Nof. invocations left until we are completed with this pass
68  static volatile int  _sweep_started;              // Flag to control conc sweeper
69  static volatile bool _should_sweep;               // Indicates if we should invoke the sweeper
70  static volatile int  _bytes_changed;              // Counts the total nmethod size if the nmethod changed from:
71                                                    //   1) alive       -> not_entrant
72                                                    //   2) not_entrant -> zombie
73                                                    //   3) zombie      -> marked_for_reclamation
74  // Stat counters
75  static long      _total_nof_methods_reclaimed;    // Accumulated nof methods flushed
76  static long      _total_nof_c2_methods_reclaimed; // Accumulated nof C2-compiled methods flushed
77  static size_t    _total_flushed_size;             // Total size of flushed methods
78  static int       _hotness_counter_reset_val;
79
80  static Tickspan  _total_time_sweeping;            // Accumulated time sweeping
81  static Tickspan  _total_time_this_sweep;          // Total time this sweep
82  static Tickspan  _peak_sweep_time;                // Peak time for a full sweep
83  static Tickspan  _peak_sweep_fraction_time;       // Peak time sweeping one fraction
84
85  static int  process_nmethod(nmethod *nm);
86  static void release_nmethod(nmethod* nm);
87
88  static bool sweep_in_progress();
89  static void sweep_code_cache();
90
91 public:
92  static long traversal_count()              { return _traversals; }
93  static int  total_nof_methods_reclaimed()  { return _total_nof_methods_reclaimed; }
94  static const Tickspan total_time_sweeping()      { return _total_time_sweeping; }
95  static const Tickspan peak_sweep_time()          { return _peak_sweep_time; }
96  static const Tickspan peak_sweep_fraction_time() { return _peak_sweep_fraction_time; }
97  static void log_sweep(const char* msg, const char* format = NULL, ...) ATTRIBUTE_PRINTF(2, 3);
98
99
100#ifdef ASSERT
101  static bool is_sweeping(nmethod* which) { return _current == which; }
102  // Keep track of sweeper activity in the ring buffer
103  static void record_sweep(nmethod* nm, int line);
104  static void report_events(int id, address entry);
105  static void report_events();
106#endif
107
108  static void mark_active_nmethods();      // Invoked at the end of each safepoint
109  static void possibly_sweep();            // Compiler threads call this to sweep
110
111  static int hotness_counter_reset_val();
112  static void report_state_change(nmethod* nm);
113  static void possibly_enable_sweeper();
114  static void print();   // Printing/debugging
115};
116
117#endif // SHARE_VM_RUNTIME_SWEEPER_HPP
118