37 // sweeper where memory is reclaimed. Note that sweep_code_cache() is not 38 // called at a safepoint. However, sweep_code_cache() stops executing if 39 // another thread requests a safepoint. Consequently, 'mark_active_nmethods()' 40 // and sweep_code_cache() cannot execute at the same time. 41 // To reclaim memory, nmethods are first marked as 'not-entrant'. Methods can 42 // be made not-entrant by (i) the sweeper, (ii) deoptimization, (iii) dependency 43 // invalidation, and (iv) being replaced be a different method version (tiered 44 // compilation). Not-entrant nmethod cannot be called by Java threads, but they 45 // can still be active on the stack. To ensure that active nmethod are not reclaimed, 46 // we have to wait until the next marking phase has completed. If a not-entrant 47 // nmethod was NOT marked as active, it can be converted to 'zombie' state. To safely 48 // remove the nmethod, all inline caches (IC) that point to the the nmethod must be 49 // cleared. After that, the nmethod can be evicted from the code cache. Each nmethod's 50 // state change happens during separate sweeps. It may take at least 3 sweeps before an 51 // nmethod's space is freed. Sweeping is currently done by compiler threads between 52 // compilations or at least each 5 sec (NmethodSweepCheckInterval) when the code cache 53 // is full. 54 55 class NMethodSweeper : public AllStatic { 56 static long _traversals; // Stack scan count, also sweep ID. 57 static nmethod* _current; // Current nmethod 58 static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache 59 static int _flushed_count; // Nof. nmethods flushed in current sweep 60 static int _zombified_count; // Nof. nmethods made zombie in current sweep 61 static int _marked_count; // Nof. nmethods marked for reclaim in current sweep 62 63 static volatile int _invocations; // No. of invocations left until we are completed with this pass 64 static volatile int _sweep_started; // Flag to control conc sweeper 65 66 //The following are reset in mark_active_nmethods and synchronized by the safepoint 67 static bool _request_mark_phase; // Indicates that a change has happend and we need another mark pahse, 68 // always checked and reset at a safepoint so memory will be in sync. 69 static int _locked_seen; // Number of locked nmethods encountered during the scan 70 static int _not_entrant_seen_on_stack; // Number of not entrant nmethod were are still on stack 71 72 // Stat counters 73 static int _total_nof_methods_reclaimed; // Accumulated nof methods flushed 74 static jlong _total_time_sweeping; // Accumulated time sweeping 75 static jlong _total_time_this_sweep; // Total time this sweep 76 static jlong _peak_sweep_time; // Peak time for a full sweep 77 static jlong _peak_sweep_fraction_time; // Peak time sweeping one fraction 78 79 static int process_nmethod(nmethod *nm); 80 static void release_nmethod(nmethod* nm); 81 82 static bool sweep_in_progress(); 83 static void sweep_code_cache(); 84 static void request_nmethod_marking() { _request_mark_phase = true; } 85 static void reset_nmethod_marking() { _request_mark_phase = false; } 86 static bool need_marking_phase() { return _request_mark_phase; } 87 88 static int _hotness_counter_reset_val; 89 90 public: 91 static long traversal_count() { return _traversals; } 92 static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; } 93 static jlong total_time_sweeping() { return _total_time_sweeping; } 94 static jlong peak_sweep_time() { return _peak_sweep_time; } 95 static jlong peak_sweep_fraction_time() { return _peak_sweep_fraction_time; } 96 static void log_sweep(const char* msg, const char* format = NULL, ...); 97 98 99 #ifdef ASSERT 100 static bool is_sweeping(nmethod* which) { return _current == which; } 101 // Keep track of sweeper activity in the ring buffer 102 static void record_sweep(nmethod* nm, int line); 103 static void report_events(int id, address entry); 104 static void report_events(); 105 #endif 106 107 static void mark_active_nmethods(); // Invoked at the end of each safepoint 108 static void possibly_sweep(); // Compiler threads call this to sweep 109 110 static int sort_nmethods_by_hotness(nmethod** nm1, nmethod** nm2); 111 static int hotness_counter_reset_val(); 112 113 static void notify() { 114 // Request a new sweep of the code cache from the beginning. No 115 // need to synchronize the setting of this flag since it only 116 // changes to false at safepoint so we can never overwrite it with false. 117 request_nmethod_marking(); 118 } 119 }; 120 | 37 // sweeper where memory is reclaimed. Note that sweep_code_cache() is not 38 // called at a safepoint. However, sweep_code_cache() stops executing if 39 // another thread requests a safepoint. Consequently, 'mark_active_nmethods()' 40 // and sweep_code_cache() cannot execute at the same time. 41 // To reclaim memory, nmethods are first marked as 'not-entrant'. Methods can 42 // be made not-entrant by (i) the sweeper, (ii) deoptimization, (iii) dependency 43 // invalidation, and (iv) being replaced be a different method version (tiered 44 // compilation). Not-entrant nmethod cannot be called by Java threads, but they 45 // can still be active on the stack. To ensure that active nmethod are not reclaimed, 46 // we have to wait until the next marking phase has completed. If a not-entrant 47 // nmethod was NOT marked as active, it can be converted to 'zombie' state. To safely 48 // remove the nmethod, all inline caches (IC) that point to the the nmethod must be 49 // cleared. After that, the nmethod can be evicted from the code cache. Each nmethod's 50 // state change happens during separate sweeps. It may take at least 3 sweeps before an 51 // nmethod's space is freed. Sweeping is currently done by compiler threads between 52 // compilations or at least each 5 sec (NmethodSweepCheckInterval) when the code cache 53 // is full. 54 55 class NMethodSweeper : public AllStatic { 56 static long _traversals; // Stack scan count, also sweep ID. 57 static nmethod* _current_nmethod; // Current nmethod 58 static int _current_type; // Current CodeBlobType 59 static int _seen; // Nof. nmethod we have currently processed in current pass of CodeCache 60 static int _flushed_count; // Nof. nmethods flushed in current sweep 61 static int _zombified_count; // Nof. nmethods made zombie in current sweep 62 static int _marked_count; // Nof. nmethods marked for reclaim in current sweep 63 64 static volatile int _invocations; // No. of invocations left until we are completed with this pass 65 static volatile int _sweep_started; // Flag to control conc sweeper 66 67 //The following are reset in mark_active_nmethods and synchronized by the safepoint 68 static bool _request_mark_phase; // Indicates that a change has happend and we need another mark pahse, 69 // always checked and reset at a safepoint so memory will be in sync. 70 static int _locked_seen; // Number of locked nmethods encountered during the scan 71 static int _not_entrant_seen_on_stack; // Number of not entrant nmethod were are still on stack 72 73 // Stat counters 74 static int _total_nof_methods_reclaimed; // Accumulated nof methods flushed 75 static jlong _total_time_sweeping; // Accumulated time sweeping 76 static jlong _total_time_this_sweep; // Total time this sweep 77 static jlong _peak_sweep_time; // Peak time for a full sweep 78 static jlong _peak_sweep_fraction_time; // Peak time sweeping one fraction 79 80 static int process_nmethod(nmethod *nm, CodeBlobType bt); 81 static void release_nmethod(nmethod* nm); 82 83 static bool sweep_in_progress(); 84 static void sweep_code_cache(); 85 static void request_nmethod_marking() { _request_mark_phase = true; } 86 static void reset_nmethod_marking() { _request_mark_phase = false; } 87 static bool need_marking_phase() { return _request_mark_phase; } 88 89 static int _hotness_counter_reset_val; 90 91 public: 92 static long traversal_count() { return _traversals; } 93 static int total_nof_methods_reclaimed() { return _total_nof_methods_reclaimed; } 94 static jlong total_time_sweeping() { return _total_time_sweeping; } 95 static jlong peak_sweep_time() { return _peak_sweep_time; } 96 static jlong peak_sweep_fraction_time() { return _peak_sweep_fraction_time; } 97 static void log_sweep(const char* msg, const char* format = NULL, ...); 98 99 100 #ifdef ASSERT 101 static bool is_sweeping(nmethod* which) { return _current_nmethod == 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 sort_nmethods_by_hotness(nmethod** nm1, nmethod** nm2); 112 static int hotness_counter_reset_val(); 113 114 static void notify() { 115 // Request a new sweep of the code cache from the beginning. No 116 // need to synchronize the setting of this flag since it only 117 // changes to false at safepoint so we can never overwrite it with false. 118 request_nmethod_marking(); 119 } 120 }; 121 |