34 #include "utilities/ostream.hpp"
35
36 //
37 // Safepoint synchronization
38 ////
39 // The VMThread or CMS_thread uses the SafepointSynchronize::begin/end
40 // methods to enter/exit a safepoint region. The begin method will roll
41 // all JavaThreads forward to a safepoint.
42 //
43 // JavaThreads must use the ThreadSafepointState abstraction (defined in
44 // thread.hpp) to indicate that that they are at a safepoint.
45 //
46 // The Mutex/Condition variable and ObjectLocker classes calls the enter/
47 // exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/
48 // exit points *must* be at a safepoint.
49
50
51 class ThreadSafepointState;
52 class SnippetCache;
53 class nmethod;
54 class WorkGang;
55 class SubTasksDone;
56
57 //
58 // Implements roll-forward to safepoint (safepoint synchronization)
59 //
60 class SafepointSynchronize : AllStatic {
61 public:
62 enum SynchronizeState {
63 _not_synchronized = 0, // Threads not synchronized at a safepoint
64 // Keep this value 0. See the comment in do_call_back()
65 _synchronizing = 1, // Synchronizing in progress
66 _synchronized = 2 // All Java threads are stopped at a safepoint. Only VM thread is running
67 };
68
69 enum SafepointingThread {
70 _null_thread = 0,
71 _vm_thread = 1,
72 _other_thread = 2
73 };
74
75 enum SafepointTimeoutReason {
76 _spinning_timeout = 0,
77 _blocking_timeout = 1
78 };
79
80 typedef struct {
81 float _time_stamp; // record when the current safepoint occurs in seconds
82 int _vmop_type; // type of VM operation triggers the safepoint
83 int _nof_total_threads; // total number of Java threads
84 int _nof_initial_running_threads; // total number of initially seen running threads
85 int _nof_threads_wait_to_block; // total number of threads waiting for to block
86 bool _page_armed; // true if polling page is armed, false otherwise
87 int _nof_threads_hit_page_trap; // total number of threads hitting the page trap
88 jlong _time_to_spin; // total time in millis spent in spinning
89 jlong _time_to_wait_to_block; // total time in millis spent in waiting for to block
90 jlong _time_to_do_cleanups; // total time in millis spent in performing cleanups
91 jlong _time_to_sync; // total time in millis spent in getting to _synchronized
92 jlong _time_to_exec_vmop; // total time in millis spent in vm operation itself
93 } SafepointStats;
94
95 enum SafepointCleanupTasks {
96 SAFEPOINT_CLEANUP_DEFLATE_MONITORS,
97 SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES,
98 SAFEPOINT_CLEANUP_COMPILATION_POLICY,
99 SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH,
100 SAFEPOINT_CLEANUP_STRING_TABLE_REHASH,
101 SAFEPOINT_CLEANUP_CLD_PURGE,
102 // Leave this one last.
103 SAFEPOINT_CLEANUP_NUM_TASKS
104 };
105
106 private:
107 static volatile SynchronizeState _state; // Threads might read this flag directly, without acquiring the Threads_lock
108 static volatile int _waiting_to_block; // number of threads we are waiting for to block
109 static int _current_jni_active_count; // Counts the number of active critical natives during the safepoint
110
111 // This counter is used for fast versions of jni_Get<Primitive>Field.
112 // An even value means there is no ongoing safepoint operations.
113 // The counter is incremented ONLY at the beginning and end of each
114 // safepoint. The fact that Threads_lock is held throughout each pair of
115 // increments (at the beginning and end of each safepoint) guarantees
116 // race freedom.
117 public:
118 static volatile int _safepoint_counter;
119 private:
120 static long _end_of_last_safepoint; // Time of last safepoint in milliseconds
121
122 // Statistics
123 static jlong _safepoint_begin_time; // time when safepoint begins
124 static SafepointStats* _safepoint_stats; // array of SafepointStats struct
125 static int _cur_stat_index; // current index to the above array
126 static julong _safepoint_reasons[]; // safepoint count for each VM op
127 static julong _coalesced_vmop_count; // coalesced vmop count
128 static jlong _max_sync_time; // maximum sync time in nanos
129 static jlong _max_vmop_time; // maximum vm operation time in nanos
130 static float _ts_of_current_safepoint; // time stamp of current safepoint in seconds
131
132 static void begin_statistics(int nof_threads, int nof_running);
133 static void update_statistics_on_spin_end();
134 static void update_statistics_on_sync_end(jlong end_time);
135 static void update_statistics_on_cleanup_end(jlong end_time);
136 static void end_statistics(jlong end_time);
137 static void print_statistics();
138 inline static void inc_page_trap_count() {
139 Atomic::inc(&_safepoint_stats[_cur_stat_index]._nof_threads_hit_page_trap);
140 }
141
142 // For debug long safepoint
143 static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason);
144
145 // Parallel cleanup
146 static WorkGang* _cleanup_workers;
147 static SubTasksDone* _cleanup_subtasks;
148
149 public:
150
151 // Main entry points
152
153 // Roll all threads forward to safepoint. Must be called by the
154 // VMThread or CMS_thread.
155 static void begin();
156 static void end(); // Start all suspended threads again...
157
158 static bool safepoint_safe(JavaThread *thread, JavaThreadState state);
159
160 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state);
161
162 // Query
163 inline static bool is_at_safepoint() { return _state == _synchronized; }
164 inline static bool is_synchronizing() { return _state == _synchronizing; }
165 inline static int safepoint_counter() { return _safepoint_counter; }
166
167 inline static bool do_call_back() {
168 return (_state != _not_synchronized);
173 _current_jni_active_count++;
174 }
175
176 // Called when a thread voluntarily blocks
177 static void block(JavaThread *thread);
178 static void signal_thread_at_safepoint() { _waiting_to_block--; }
179
180 // Exception handling for page polling
181 static void handle_polling_page_exception(JavaThread *thread);
182
183 // VM Thread interface for determining safepoint rate
184 static long last_non_safepoint_interval() {
185 return os::javaTimeMillis() - _end_of_last_safepoint;
186 }
187 static long end_of_last_safepoint() {
188 return _end_of_last_safepoint;
189 }
190 static bool is_cleanup_needed();
191 static void do_cleanup_tasks();
192
193 private:
194 static void serial_cleanup();
195 static void parallel_cleanup();
196
197 public:
198 // Debugging
199 static void print_state() PRODUCT_RETURN;
200 static void safepoint_msg(const char* format, ...) ATTRIBUTE_PRINTF(1, 2) PRODUCT_RETURN;
201
202 static void deferred_initialize_stat();
203 static void print_stat_on_exit();
204 inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; }
205
206 static void set_is_at_safepoint() { _state = _synchronized; }
207 static void set_is_not_at_safepoint() { _state = _not_synchronized; }
208
209 // Assembly support
210 static address address_of_state() { return (address)&_state; }
211
212 static address safepoint_counter_addr() { return (address)&_safepoint_counter; }
213 };
214
215 // State class for a thread suspended at a safepoint
216 class ThreadSafepointState: public CHeapObj<mtInternal> {
217 public:
|
34 #include "utilities/ostream.hpp"
35
36 //
37 // Safepoint synchronization
38 ////
39 // The VMThread or CMS_thread uses the SafepointSynchronize::begin/end
40 // methods to enter/exit a safepoint region. The begin method will roll
41 // all JavaThreads forward to a safepoint.
42 //
43 // JavaThreads must use the ThreadSafepointState abstraction (defined in
44 // thread.hpp) to indicate that that they are at a safepoint.
45 //
46 // The Mutex/Condition variable and ObjectLocker classes calls the enter/
47 // exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/
48 // exit points *must* be at a safepoint.
49
50
51 class ThreadSafepointState;
52 class SnippetCache;
53 class nmethod;
54
55 //
56 // Implements roll-forward to safepoint (safepoint synchronization)
57 //
58 class SafepointSynchronize : AllStatic {
59 public:
60 enum SynchronizeState {
61 _not_synchronized = 0, // Threads not synchronized at a safepoint
62 // Keep this value 0. See the comment in do_call_back()
63 _synchronizing = 1, // Synchronizing in progress
64 _synchronized = 2 // All Java threads are stopped at a safepoint. Only VM thread is running
65 };
66
67 enum SafepointingThread {
68 _null_thread = 0,
69 _vm_thread = 1,
70 _other_thread = 2
71 };
72
73 enum SafepointTimeoutReason {
74 _spinning_timeout = 0,
75 _blocking_timeout = 1
76 };
77
78 typedef struct {
79 float _time_stamp; // record when the current safepoint occurs in seconds
80 int _vmop_type; // type of VM operation triggers the safepoint
81 int _nof_total_threads; // total number of Java threads
82 int _nof_initial_running_threads; // total number of initially seen running threads
83 int _nof_threads_wait_to_block; // total number of threads waiting for to block
84 bool _page_armed; // true if polling page is armed, false otherwise
85 int _nof_threads_hit_page_trap; // total number of threads hitting the page trap
86 jlong _time_to_spin; // total time in millis spent in spinning
87 jlong _time_to_wait_to_block; // total time in millis spent in waiting for to block
88 jlong _time_to_do_cleanups; // total time in millis spent in performing cleanups
89 jlong _time_to_sync; // total time in millis spent in getting to _synchronized
90 jlong _time_to_exec_vmop; // total time in millis spent in vm operation itself
91 } SafepointStats;
92
93 private:
94 static volatile SynchronizeState _state; // Threads might read this flag directly, without acquiring the Threads_lock
95 static volatile int _waiting_to_block; // number of threads we are waiting for to block
96 static int _current_jni_active_count; // Counts the number of active critical natives during the safepoint
97
98 // This counter is used for fast versions of jni_Get<Primitive>Field.
99 // An even value means there is no ongoing safepoint operations.
100 // The counter is incremented ONLY at the beginning and end of each
101 // safepoint. The fact that Threads_lock is held throughout each pair of
102 // increments (at the beginning and end of each safepoint) guarantees
103 // race freedom.
104 public:
105 static volatile int _safepoint_counter;
106 private:
107 static long _end_of_last_safepoint; // Time of last safepoint in milliseconds
108
109 // Statistics
110 static jlong _safepoint_begin_time; // time when safepoint begins
111 static SafepointStats* _safepoint_stats; // array of SafepointStats struct
112 static int _cur_stat_index; // current index to the above array
113 static julong _safepoint_reasons[]; // safepoint count for each VM op
114 static julong _coalesced_vmop_count; // coalesced vmop count
115 static jlong _max_sync_time; // maximum sync time in nanos
116 static jlong _max_vmop_time; // maximum vm operation time in nanos
117 static float _ts_of_current_safepoint; // time stamp of current safepoint in seconds
118
119 static void begin_statistics(int nof_threads, int nof_running);
120 static void update_statistics_on_spin_end();
121 static void update_statistics_on_sync_end(jlong end_time);
122 static void update_statistics_on_cleanup_end(jlong end_time);
123 static void end_statistics(jlong end_time);
124 static void print_statistics();
125 inline static void inc_page_trap_count() {
126 Atomic::inc(&_safepoint_stats[_cur_stat_index]._nof_threads_hit_page_trap);
127 }
128
129 // For debug long safepoint
130 static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason);
131
132 public:
133
134 // Main entry points
135
136 // Roll all threads forward to safepoint. Must be called by the
137 // VMThread or CMS_thread.
138 static void begin();
139 static void end(); // Start all suspended threads again...
140
141 static bool safepoint_safe(JavaThread *thread, JavaThreadState state);
142
143 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state);
144
145 // Query
146 inline static bool is_at_safepoint() { return _state == _synchronized; }
147 inline static bool is_synchronizing() { return _state == _synchronizing; }
148 inline static int safepoint_counter() { return _safepoint_counter; }
149
150 inline static bool do_call_back() {
151 return (_state != _not_synchronized);
156 _current_jni_active_count++;
157 }
158
159 // Called when a thread voluntarily blocks
160 static void block(JavaThread *thread);
161 static void signal_thread_at_safepoint() { _waiting_to_block--; }
162
163 // Exception handling for page polling
164 static void handle_polling_page_exception(JavaThread *thread);
165
166 // VM Thread interface for determining safepoint rate
167 static long last_non_safepoint_interval() {
168 return os::javaTimeMillis() - _end_of_last_safepoint;
169 }
170 static long end_of_last_safepoint() {
171 return _end_of_last_safepoint;
172 }
173 static bool is_cleanup_needed();
174 static void do_cleanup_tasks();
175
176 // Debugging
177 static void print_state() PRODUCT_RETURN;
178 static void safepoint_msg(const char* format, ...) ATTRIBUTE_PRINTF(1, 2) PRODUCT_RETURN;
179
180 static void deferred_initialize_stat();
181 static void print_stat_on_exit();
182 inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; }
183
184 static void set_is_at_safepoint() { _state = _synchronized; }
185 static void set_is_not_at_safepoint() { _state = _not_synchronized; }
186
187 // Assembly support
188 static address address_of_state() { return (address)&_state; }
189
190 static address safepoint_counter_addr() { return (address)&_safepoint_counter; }
191 };
192
193 // State class for a thread suspended at a safepoint
194 class ThreadSafepointState: public CHeapObj<mtInternal> {
195 public:
|