37 // safepoint and marks all nmethods that are active on a thread's stack.
38 // 2) sweep nmethods
39 // Is done in sweep_code_cache(). This function is the only place in the
40 // sweeper where memory is reclaimed. Note that sweep_code_cache() is not
41 // called at a safepoint. However, sweep_code_cache() stops executing if
42 // another thread requests a safepoint. Consequently, 'mark_active_nmethods()'
43 // and sweep_code_cache() cannot execute at the same time.
44 // To reclaim memory, nmethods are first marked as 'not-entrant'. Methods can
45 // be made not-entrant by (i) the sweeper, (ii) deoptimization, (iii) dependency
46 // invalidation, and (iv) being replaced be a different method version (tiered
47 // compilation). Not-entrant nmethod cannot be called by Java threads, but they
48 // can still be active on the stack. To ensure that active nmethod are not reclaimed,
49 // we have to wait until the next marking phase has completed. If a not-entrant
50 // nmethod was NOT marked as active, it can be converted to 'zombie' state. To safely
51 // remove the nmethod, all inline caches (IC) that point to the the nmethod must be
52 // cleared. After that, the nmethod can be evicted from the code cache. Each nmethod's
53 // state change happens during separate sweeps. It may take at least 3 sweeps before an
54 // nmethod's space is freed.
55
56 class NMethodSweeper : public AllStatic {
57 friend class WhiteBox;
58 private:
59 enum MethodStateChange {
60 None,
61 MadeZombie,
62 MarkedForReclamation,
63 Flushed
64 };
65 static long _traversals; // Stack scan count, also sweep ID.
66 static long _total_nof_code_cache_sweeps; // Total number of full sweeps of the code cache
67 static long _time_counter; // Virtual time used to periodically invoke sweeper
68 static long _last_sweep; // Value of _time_counter when the last sweep happened
69 static NMethodIterator _current; // Current nmethod
70 static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache
71
72 static volatile int _sweep_started; // Flag to control conc sweeper
73 static volatile bool _should_sweep; // Indicates if we should invoke the sweeper
74 static volatile int _bytes_changed; // Counts the total nmethod size if the nmethod changed from:
75 // 1) alive -> not_entrant
76 // 2) not_entrant -> zombie
77 // 3) zombie -> marked_for_reclamation
78 // Stat counters
79 static long _total_nof_methods_reclaimed; // Accumulated nof methods flushed
80 static long _total_nof_c2_methods_reclaimed; // Accumulated nof C2-compiled methods flushed
81 static size_t _total_flushed_size; // Total size of flushed methods
82 static int _hotness_counter_reset_val;
83
84 static Tickspan _total_time_sweeping; // Accumulated time sweeping
85 static Tickspan _total_time_this_sweep; // Total time this sweep
86 static Tickspan _peak_sweep_time; // Peak time for a full sweep
87 static Tickspan _peak_sweep_fraction_time; // Peak time sweeping one fraction
88
89 static Monitor* _stat_lock;
90
91 static MethodStateChange process_nmethod(nmethod *nm);
92 static void release_nmethod(nmethod* nm);
93
100 public:
101 static long traversal_count() { return _traversals; }
102 static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; }
103 static const Tickspan total_time_sweeping() { return _total_time_sweeping; }
104 static const Tickspan peak_sweep_time() { return _peak_sweep_time; }
105 static const Tickspan peak_sweep_fraction_time() { return _peak_sweep_fraction_time; }
106 static void log_sweep(const char* msg, const char* format = NULL, ...) ATTRIBUTE_PRINTF(2, 3);
107
108
109 #ifdef ASSERT
110 static bool is_sweeping(nmethod* which) { return _current.method() == which; }
111 // Keep track of sweeper activity in the ring buffer
112 static void record_sweep(nmethod* nm, int line);
113 static void report_events(int id, address entry);
114 static void report_events();
115 #endif
116
117 static void mark_active_nmethods(); // Invoked at the end of each safepoint
118 static void sweeper_loop();
119 static void notify(int code_blob_type); // Possibly start the sweeper thread.
120
121 static int hotness_counter_reset_val();
122 static void report_state_change(nmethod* nm);
123 static void possibly_enable_sweeper();
124 static void possibly_flush(nmethod* nm);
125 static void print(); // Printing/debugging
126 };
127
128 #endif // SHARE_VM_RUNTIME_SWEEPER_HPP
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37 // safepoint and marks all nmethods that are active on a thread's stack.
38 // 2) sweep nmethods
39 // Is done in sweep_code_cache(). This function is the only place in the
40 // sweeper where memory is reclaimed. Note that sweep_code_cache() is not
41 // called at a safepoint. However, sweep_code_cache() stops executing if
42 // another thread requests a safepoint. Consequently, 'mark_active_nmethods()'
43 // and sweep_code_cache() cannot execute at the same time.
44 // To reclaim memory, nmethods are first marked as 'not-entrant'. Methods can
45 // be made not-entrant by (i) the sweeper, (ii) deoptimization, (iii) dependency
46 // invalidation, and (iv) being replaced be a different method version (tiered
47 // compilation). Not-entrant nmethod cannot be called by Java threads, but they
48 // can still be active on the stack. To ensure that active nmethod are not reclaimed,
49 // we have to wait until the next marking phase has completed. If a not-entrant
50 // nmethod was NOT marked as active, it can be converted to 'zombie' state. To safely
51 // remove the nmethod, all inline caches (IC) that point to the the nmethod must be
52 // cleared. After that, the nmethod can be evicted from the code cache. Each nmethod's
53 // state change happens during separate sweeps. It may take at least 3 sweeps before an
54 // nmethod's space is freed.
55
56 class NMethodSweeper : public AllStatic {
57 private:
58 enum MethodStateChange {
59 None,
60 MadeZombie,
61 MarkedForReclamation,
62 Flushed
63 };
64 static long _traversals; // Stack scan count, also sweep ID.
65 static long _total_nof_code_cache_sweeps; // Total number of full sweeps of the code cache
66 static long _time_counter; // Virtual time used to periodically invoke sweeper
67 static long _last_sweep; // Value of _time_counter when the last sweep happened
68 static NMethodIterator _current; // Current nmethod
69 static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache
70
71 static volatile int _sweep_started; // Flag to control conc sweeper
72 static volatile bool _should_sweep; // Indicates if we should invoke the sweeper
73 static volatile bool _force_sweep; // Indicates if we should force a sweep
74 static volatile int _bytes_changed; // Counts the total nmethod size if the nmethod changed from:
75 // 1) alive -> not_entrant
76 // 2) not_entrant -> zombie
77 // 3) zombie -> marked_for_reclamation
78 // Stat counters
79 static long _total_nof_methods_reclaimed; // Accumulated nof methods flushed
80 static long _total_nof_c2_methods_reclaimed; // Accumulated nof C2-compiled methods flushed
81 static size_t _total_flushed_size; // Total size of flushed methods
82 static int _hotness_counter_reset_val;
83
84 static Tickspan _total_time_sweeping; // Accumulated time sweeping
85 static Tickspan _total_time_this_sweep; // Total time this sweep
86 static Tickspan _peak_sweep_time; // Peak time for a full sweep
87 static Tickspan _peak_sweep_fraction_time; // Peak time sweeping one fraction
88
89 static Monitor* _stat_lock;
90
91 static MethodStateChange process_nmethod(nmethod *nm);
92 static void release_nmethod(nmethod* nm);
93
100 public:
101 static long traversal_count() { return _traversals; }
102 static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; }
103 static const Tickspan total_time_sweeping() { return _total_time_sweeping; }
104 static const Tickspan peak_sweep_time() { return _peak_sweep_time; }
105 static const Tickspan peak_sweep_fraction_time() { return _peak_sweep_fraction_time; }
106 static void log_sweep(const char* msg, const char* format = NULL, ...) ATTRIBUTE_PRINTF(2, 3);
107
108
109 #ifdef ASSERT
110 static bool is_sweeping(nmethod* which) { return _current.method() == which; }
111 // Keep track of sweeper activity in the ring buffer
112 static void record_sweep(nmethod* nm, int line);
113 static void report_events(int id, address entry);
114 static void report_events();
115 #endif
116
117 static void mark_active_nmethods(); // Invoked at the end of each safepoint
118 static void sweeper_loop();
119 static void notify(int code_blob_type); // Possibly start the sweeper thread.
120 static void force_sweep();
121
122 static int hotness_counter_reset_val();
123 static void report_state_change(nmethod* nm);
124 static void possibly_enable_sweeper();
125 static void possibly_flush(nmethod* nm);
126 static void print(); // Printing/debugging
127 };
128
129 #endif // SHARE_VM_RUNTIME_SWEEPER_HPP
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