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annotate src/share/vm/runtime/safepoint.hpp @ 4724:0841c0ec2ed6
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Reviewed-by: jcoomes
author | amurillo |
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date | Fri, 23 Dec 2011 15:29:34 -0800 |
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0 | 1 /* |
1783 | 2 * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved. |
0 | 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
4 * | |
5 * This code is free software; you can redistribute it and/or modify it | |
6 * under the terms of the GNU General Public License version 2 only, as | |
7 * published by the Free Software Foundation. | |
8 * | |
9 * This code is distributed in the hope that it will be useful, but WITHOUT | |
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
12 * version 2 for more details (a copy is included in the LICENSE file that | |
13 * accompanied this code). | |
14 * | |
15 * You should have received a copy of the GNU General Public License version | |
16 * 2 along with this work; if not, write to the Free Software Foundation, | |
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
18 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #ifndef SHARE_VM_RUNTIME_SAFEPOINT_HPP |
26 #define SHARE_VM_RUNTIME_SAFEPOINT_HPP | |
27 | |
28 #include "asm/assembler.hpp" | |
29 #include "code/nmethod.hpp" | |
30 #include "memory/allocation.hpp" | |
31 #include "runtime/extendedPC.hpp" | |
32 #include "runtime/os.hpp" | |
33 #include "utilities/ostream.hpp" | |
34 | |
0 | 35 // |
36 // Safepoint synchronization | |
37 //// | |
38 // The VMThread or CMS_thread uses the SafepointSynchronize::begin/end | |
39 // methods to enter/exit a safepoint region. The begin method will roll | |
40 // all JavaThreads forward to a safepoint. | |
41 // | |
42 // JavaThreads must use the ThreadSafepointState abstraction (defined in | |
43 // thread.hpp) to indicate that that they are at a safepoint. | |
44 // | |
45 // The Mutex/Condition variable and ObjectLocker classes calls the enter/ | |
46 // exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/ | |
47 // exit points *must* be at a safepoint. | |
48 | |
49 | |
50 class ThreadSafepointState; | |
51 class SnippetCache; | |
52 class nmethod; | |
53 | |
54 // | |
55 // Implements roll-forward to safepoint (safepoint synchronization) | |
56 // | |
57 class SafepointSynchronize : AllStatic { | |
58 public: | |
59 enum SynchronizeState { | |
60 _not_synchronized = 0, // Threads not synchronized at a safepoint | |
61 // Keep this value 0. See the coment in do_call_back() | |
62 _synchronizing = 1, // Synchronizing in progress | |
63 _synchronized = 2 // All Java threads are stopped at a safepoint. Only VM thread is running | |
64 }; | |
65 | |
66 enum SafepointingThread { | |
67 _null_thread = 0, | |
68 _vm_thread = 1, | |
69 _other_thread = 2 | |
70 }; | |
71 | |
72 enum SafepointTimeoutReason { | |
73 _spinning_timeout = 0, | |
74 _blocking_timeout = 1 | |
75 }; | |
76 | |
77 typedef struct { | |
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78 float _time_stamp; // record when the current safepoint occurs in seconds |
0 | 79 int _vmop_type; // type of VM operation triggers the safepoint |
80 int _nof_total_threads; // total number of Java threads | |
81 int _nof_initial_running_threads; // total number of initially seen running threads | |
82 int _nof_threads_wait_to_block; // total number of threads waiting for to block | |
83 bool _page_armed; // true if polling page is armed, false otherwise | |
84 int _nof_threads_hit_page_trap; // total number of threads hitting the page trap | |
85 jlong _time_to_spin; // total time in millis spent in spinning | |
86 jlong _time_to_wait_to_block; // total time in millis spent in waiting for to block | |
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87 jlong _time_to_do_cleanups; // total time in millis spent in performing cleanups |
0 | 88 jlong _time_to_sync; // total time in millis spent in getting to _synchronized |
89 jlong _time_to_exec_vmop; // total time in millis spent in vm operation itself | |
90 } SafepointStats; | |
91 | |
92 private: | |
93 static volatile SynchronizeState _state; // Threads might read this flag directly, without acquireing the Threads_lock | |
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94 static volatile int _waiting_to_block; // number of threads we are waiting for to block |
0 | 95 |
96 // This counter is used for fast versions of jni_Get<Primitive>Field. | |
97 // An even value means there is no ongoing safepoint operations. | |
98 // The counter is incremented ONLY at the beginning and end of each | |
99 // safepoint. The fact that Threads_lock is held throughout each pair of | |
100 // increments (at the beginning and end of each safepoint) guarantees | |
101 // race freedom. | |
102 public: | |
103 static volatile int _safepoint_counter; | |
104 private: | |
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105 static long _end_of_last_safepoint; // Time of last safepoint in milliseconds |
0 | 106 |
107 // statistics | |
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108 static jlong _safepoint_begin_time; // time when safepoint begins |
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109 static SafepointStats* _safepoint_stats; // array of SafepointStats struct |
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110 static int _cur_stat_index; // current index to the above array |
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111 static julong _safepoint_reasons[]; // safepoint count for each VM op |
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112 static julong _coalesced_vmop_count; // coalesced vmop count |
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113 static jlong _max_sync_time; // maximum sync time in nanos |
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114 static jlong _max_vmop_time; // maximum vm operation time in nanos |
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115 static float _ts_of_current_safepoint; // time stamp of current safepoint in seconds |
0 | 116 |
117 static void begin_statistics(int nof_threads, int nof_running); | |
118 static void update_statistics_on_spin_end(); | |
119 static void update_statistics_on_sync_end(jlong end_time); | |
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120 static void update_statistics_on_cleanup_end(jlong end_time); |
0 | 121 static void end_statistics(jlong end_time); |
122 static void print_statistics(); | |
123 inline static void inc_page_trap_count() { | |
124 Atomic::inc(&_safepoint_stats[_cur_stat_index]._nof_threads_hit_page_trap); | |
125 } | |
126 | |
127 // For debug long safepoint | |
128 static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason); | |
129 | |
130 public: | |
131 | |
132 // Main entry points | |
133 | |
134 // Roll all threads forward to safepoint. Must be called by the | |
135 // VMThread or CMS_thread. | |
136 static void begin(); | |
137 static void end(); // Start all suspended threads again... | |
138 | |
139 static bool safepoint_safe(JavaThread *thread, JavaThreadState state); | |
140 | |
141 // Query | |
142 inline static bool is_at_safepoint() { return _state == _synchronized; } | |
143 inline static bool is_synchronizing() { return _state == _synchronizing; } | |
144 | |
145 inline static bool do_call_back() { | |
146 return (_state != _not_synchronized); | |
147 } | |
148 | |
149 // Called when a thread volantary blocks | |
150 static void block(JavaThread *thread); | |
151 static void signal_thread_at_safepoint() { _waiting_to_block--; } | |
152 | |
153 // Exception handling for page polling | |
154 static void handle_polling_page_exception(JavaThread *thread); | |
155 | |
156 // VM Thread interface for determining safepoint rate | |
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157 static long last_non_safepoint_interval() { |
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158 return os::javaTimeMillis() - _end_of_last_safepoint; |
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159 } |
1783 | 160 static long end_of_last_safepoint() { |
161 return _end_of_last_safepoint; | |
162 } | |
0 | 163 static bool is_cleanup_needed(); |
164 static void do_cleanup_tasks(); | |
165 | |
166 // debugging | |
167 static void print_state() PRODUCT_RETURN; | |
168 static void safepoint_msg(const char* format, ...) PRODUCT_RETURN; | |
169 | |
170 static void deferred_initialize_stat(); | |
171 static void print_stat_on_exit(); | |
172 inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; } | |
173 | |
174 static void set_is_at_safepoint() { _state = _synchronized; } | |
175 static void set_is_not_at_safepoint() { _state = _not_synchronized; } | |
176 | |
177 // assembly support | |
178 static address address_of_state() { return (address)&_state; } | |
179 | |
180 static address safepoint_counter_addr() { return (address)&_safepoint_counter; } | |
181 }; | |
182 | |
183 // State class for a thread suspended at a safepoint | |
184 class ThreadSafepointState: public CHeapObj { | |
185 public: | |
186 // These states are maintained by VM thread while threads are being brought | |
187 // to a safepoint. After SafepointSynchronize::end(), they are reset to | |
188 // _running. | |
189 enum suspend_type { | |
190 _running = 0, // Thread state not yet determined (i.e., not at a safepoint yet) | |
191 _at_safepoint = 1, // Thread at a safepoint (f.ex., when blocked on a lock) | |
192 _call_back = 2 // Keep executing and wait for callback (if thread is in interpreted or vm) | |
193 }; | |
194 private: | |
195 volatile bool _at_poll_safepoint; // At polling page safepoint (NOT a poll return safepoint) | |
196 // Thread has called back the safepoint code (for debugging) | |
197 bool _has_called_back; | |
198 | |
199 JavaThread * _thread; | |
200 volatile suspend_type _type; | |
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201 JavaThreadState _orig_thread_state; |
0 | 202 |
203 | |
204 public: | |
205 ThreadSafepointState(JavaThread *thread); | |
206 | |
207 // examine/roll-forward/restart | |
208 void examine_state_of_thread(); | |
209 void roll_forward(suspend_type type); | |
210 void restart(); | |
211 | |
212 // Query | |
213 JavaThread* thread() const { return _thread; } | |
214 suspend_type type() const { return _type; } | |
215 bool is_running() const { return (_type==_running); } | |
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216 JavaThreadState orig_thread_state() const { return _orig_thread_state; } |
0 | 217 |
218 // Support for safepoint timeout (debugging) | |
219 bool has_called_back() const { return _has_called_back; } | |
220 void set_has_called_back(bool val) { _has_called_back = val; } | |
221 bool is_at_poll_safepoint() { return _at_poll_safepoint; } | |
222 void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; } | |
223 | |
224 void handle_polling_page_exception(); | |
225 | |
226 // debugging | |
227 void print_on(outputStream* st) const; | |
228 void print() const { print_on(tty); } | |
229 | |
230 // Initialize | |
231 static void create(JavaThread *thread); | |
232 static void destroy(JavaThread *thread); | |
233 | |
234 void safepoint_msg(const char* format, ...) { | |
235 if (ShowSafepointMsgs) { | |
236 va_list ap; | |
237 va_start(ap, format); | |
238 tty->vprint_cr(format, ap); | |
239 va_end(ap); | |
240 } | |
241 } | |
242 }; | |
243 | |
1783 | 244 |
1972 | 245 |
246 #endif // SHARE_VM_RUNTIME_SAFEPOINT_HPP |