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 56 class 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 NMethodIterator _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.method() == 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 possibly_flush(nmethod* nm); 115 static void print(); // Printing/debugging 116 }; 117 118 #endif // SHARE_VM_RUNTIME_SWEEPER_HPP | 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. 53 54 class NMethodSweeper : public AllStatic { 55 static long _traversals; // Stack scan count, also sweep ID. 56 static long _total_nof_code_cache_sweeps; // Total number of full sweeps of the code cache 57 static long _time_counter; // Virtual time used to periodically invoke sweeper 58 static long _last_sweep; // Value of _time_counter when the last sweep happened 59 static NMethodIterator _current; // Current nmethod 60 static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache 61 static int _flushed_count; // Nof. nmethods flushed in current sweep 62 static int _zombified_count; // Nof. nmethods made zombie in current sweep 63 static int _marked_for_reclamation_count; // Nof. nmethods marked for reclaim in current sweep 64 65 static volatile int _sweep_started; // Flag to control conc sweeper 66 static volatile bool _should_sweep; // Indicates if we should invoke the sweeper 67 static volatile int _bytes_changed; // Counts the total nmethod size if the nmethod changed from: 68 // 1) alive -> not_entrant 69 // 2) not_entrant -> zombie 70 // 3) zombie -> marked_for_reclamation 71 // Stat counters 72 static long _total_nof_methods_reclaimed; // Accumulated nof methods flushed 73 static long _total_nof_c2_methods_reclaimed; // Accumulated nof C2-compiled methods flushed 74 static size_t _total_flushed_size; // Total size of flushed methods 75 static int _hotness_counter_reset_val; 76 77 static Tickspan _total_time_sweeping; // Accumulated time sweeping 78 static Tickspan _total_time_this_sweep; // Total time this sweep 79 static Tickspan _peak_sweep_time; // Peak time for a full sweep 80 static Tickspan _peak_sweep_fraction_time; // Peak time sweeping one fraction 81 82 static int process_nmethod(nmethod *nm); 83 static void release_nmethod(nmethod* nm); 84 85 static void init_log_sweeer() NOT_DEBUG_RETURN; 86 static bool wait_for_stack_scanning(); 87 static void sweep_code_cache(); 88 static void handle_safepoint_request(); 89 static void do_stack_scanning(bool force_sweep); 90 static void possibly_sweep(); 91 92 public: 93 static long traversal_count() { return _traversals; } 94 static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; } 95 static const Tickspan total_time_sweeping() { return _total_time_sweeping; } 96 static const Tickspan peak_sweep_time() { return _peak_sweep_time; } 97 static const Tickspan peak_sweep_fraction_time() { return _peak_sweep_fraction_time; } 98 static void log_sweep(const char* msg, const char* format = NULL, ...) ATTRIBUTE_PRINTF(2, 3); 99 100 101 #ifdef ASSERT 102 static bool is_sweeping(nmethod* which) { return _current.method() == which; } 103 // Keep track of sweeper activity in the ring buffer 104 static void record_sweep(nmethod* nm, int line); 105 static void report_events(int id, address entry); 106 static void report_events(); 107 #endif 108 109 static void mark_active_nmethods(); // Invoked at the end of each safepoint 110 static void sweeper_loop(); 111 static void notify(); // Possibly start the sweeper thread. 112 113 static int hotness_counter_reset_val(); 114 static void report_state_change(nmethod* nm); 115 static void possibly_enable_sweeper(); 116 static void possibly_flush(nmethod* nm); 117 static void print(); // Printing/debugging 118 }; 119 120 #endif // SHARE_VM_RUNTIME_SWEEPER_HPP |