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annotate src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp @ 19083:09292c24d555
LSStackSlotAllocator: hide inner class.
author | Josef Eisl <josef.eisl@jku.at> |
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date | Sat, 31 Jan 2015 11:07:15 +0100 |
parents | 52b4284cb496 |
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rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 2001, 2014, 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_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPTHREAD_HPP |
26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPTHREAD_HPP | |
27 | |
28 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp" | |
29 #include "gc_implementation/shared/concurrentGCThread.hpp" | |
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30 #include "runtime/thread.inline.hpp" |
1972 | 31 |
0 | 32 class ConcurrentMarkSweepGeneration; |
33 class CMSCollector; | |
34 | |
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35 // The Concurrent Mark Sweep GC Thread |
0 | 36 class ConcurrentMarkSweepThread: public ConcurrentGCThread { |
37 friend class VMStructs; | |
38 friend class ConcurrentMarkSweepGeneration; // XXX should remove friendship | |
39 friend class CMSCollector; | |
40 public: | |
41 virtual void run(); | |
42 | |
43 private: | |
44 static ConcurrentMarkSweepThread* _cmst; | |
45 static CMSCollector* _collector; | |
46 static SurrogateLockerThread* _slt; | |
47 static SurrogateLockerThread::SLT_msg_type _sltBuffer; | |
48 static Monitor* _sltMonitor; | |
49 | |
50 static bool _should_terminate; | |
51 | |
52 enum CMS_flag_type { | |
53 CMS_nil = NoBits, | |
54 CMS_cms_wants_token = nth_bit(0), | |
55 CMS_cms_has_token = nth_bit(1), | |
56 CMS_vm_wants_token = nth_bit(2), | |
57 CMS_vm_has_token = nth_bit(3) | |
58 }; | |
59 | |
60 static int _CMS_flag; | |
61 | |
62 static bool CMS_flag_is_set(int b) { return (_CMS_flag & b) != 0; } | |
63 static bool set_CMS_flag(int b) { return (_CMS_flag |= b) != 0; } | |
64 static bool clear_CMS_flag(int b) { return (_CMS_flag &= ~b) != 0; } | |
65 void sleepBeforeNextCycle(); | |
66 | |
67 // CMS thread should yield for a young gen collection, direct allocation, | |
68 // and iCMS activity. | |
69 static char _pad_1[64 - sizeof(jint)]; // prevent cache-line sharing | |
70 static volatile jint _pending_yields; | |
71 static volatile jint _pending_decrements; // decrements to _pending_yields | |
72 static char _pad_2[64 - sizeof(jint)]; // prevent cache-line sharing | |
73 | |
74 // Tracing messages, enabled by CMSTraceThreadState. | |
75 static inline void trace_state(const char* desc); | |
76 | |
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77 static volatile int _icms_disabled; // a counter to track #iCMS disable & enable |
0 | 78 static volatile bool _should_run; // iCMS may run |
79 static volatile bool _should_stop; // iCMS should stop | |
80 | |
81 // debugging | |
82 void verify_ok_to_terminate() const PRODUCT_RETURN; | |
83 | |
84 public: | |
85 // Constructor | |
86 ConcurrentMarkSweepThread(CMSCollector* collector); | |
87 | |
88 static void makeSurrogateLockerThread(TRAPS); | |
89 static SurrogateLockerThread* slt() { return _slt; } | |
90 | |
91 // Tester | |
92 bool is_ConcurrentGC_thread() const { return true; } | |
93 | |
94 static void threads_do(ThreadClosure* tc); | |
95 | |
96 // Printing | |
97 void print_on(outputStream* st) const; | |
98 void print() const { print_on(tty); } | |
99 static void print_all_on(outputStream* st); | |
100 static void print_all() { print_all_on(tty); } | |
101 | |
102 // Returns the CMS Thread | |
103 static ConcurrentMarkSweepThread* cmst() { return _cmst; } | |
104 static CMSCollector* collector() { return _collector; } | |
105 | |
106 // Create and start the CMS Thread, or stop it on shutdown | |
107 static ConcurrentMarkSweepThread* start(CMSCollector* collector); | |
108 static void stop(); | |
109 static bool should_terminate() { return _should_terminate; } | |
110 | |
111 // Synchronization using CMS token | |
112 static void synchronize(bool is_cms_thread); | |
113 static void desynchronize(bool is_cms_thread); | |
114 static bool vm_thread_has_cms_token() { | |
115 return CMS_flag_is_set(CMS_vm_has_token); | |
116 } | |
117 static bool cms_thread_has_cms_token() { | |
118 return CMS_flag_is_set(CMS_cms_has_token); | |
119 } | |
120 static bool vm_thread_wants_cms_token() { | |
121 return CMS_flag_is_set(CMS_vm_wants_token); | |
122 } | |
123 static bool cms_thread_wants_cms_token() { | |
124 return CMS_flag_is_set(CMS_cms_wants_token); | |
125 } | |
126 | |
127 // Wait on CMS lock until the next synchronous GC | |
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128 // or given timeout, whichever is earlier. A timeout value |
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129 // of 0 indicates that there is no upper bound on the wait time. |
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130 // A concurrent full gc request terminates the wait. |
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131 void wait_on_cms_lock(long t_millis); |
0 | 132 |
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133 // Wait on CMS lock until the next synchronous GC |
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134 // or given timeout, whichever is earlier. A timeout value |
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135 // of 0 indicates that there is no upper bound on the wait time. |
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136 // A concurrent full gc request terminates the wait. |
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137 void wait_on_cms_lock_for_scavenge(long t_millis); |
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138 |
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139 // The CMS thread will yield during the work portion of its cycle |
0 | 140 // only when requested to. Both synchronous and asychronous requests |
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141 // are provided: |
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142 // (1) A synchronous request is used for young gen collections and |
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143 // for direct allocations. The requesting thread increments |
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144 // _pending_yields at the beginning of an operation, and decrements |
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145 // _pending_yields when that operation is completed. |
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146 // In turn, the CMS thread yields when _pending_yields is positive, |
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147 // and continues to yield until the value reverts to 0. |
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148 // (2) An asynchronous request, on the other hand, is used by iCMS |
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149 // for the stop_icms() operation. A single yield satisfies all of |
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150 // the outstanding asynch yield requests, of which there may |
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151 // occasionally be several in close succession. To accomplish |
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152 // this, an asynch-requesting thread atomically increments both |
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153 // _pending_yields and _pending_decrements. An asynchr requesting |
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154 // thread does not wait and "acknowledge" completion of an operation |
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155 // and deregister the request, like the synchronous version described |
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156 // above does. In turn, after yielding, the CMS thread decrements both |
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157 // _pending_yields and _pending_decrements by the value seen in |
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158 // _pending_decrements before the decrement. |
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159 // NOTE: The above scheme is isomorphic to having two request counters, |
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160 // one for async requests and one for sync requests, and for the CMS thread |
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161 // to check the sum of the two counters to decide whether it should yield |
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162 // and to clear only the async counter when it yields. However, it turns out |
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163 // to be more efficient for CMS code to just check a single counter |
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164 // _pending_yields that holds the sum (of both sync and async requests), and |
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165 // a second counter _pending_decrements that only holds the async requests, |
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166 // for greater efficiency, since in a typical CMS run, there are many more |
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167 // pontential (i.e. static) yield points than there are actual |
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168 // (i.e. dynamic) yields because of requests, which are few and far between. |
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169 // |
0 | 170 // Note that, while "_pending_yields >= _pending_decrements" is an invariant, |
171 // we cannot easily test that invariant, since the counters are manipulated via | |
172 // atomic instructions without explicit locking and we cannot read | |
173 // the two counters atomically together: one suggestion is to | |
174 // use (for example) 16-bit counters so as to be able to read the | |
175 // two counters atomically even on 32-bit platforms. Notice that | |
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176 // the second assert in acknowledge_yield_request() below does indeed |
0 | 177 // check a form of the above invariant, albeit indirectly. |
178 | |
179 static void increment_pending_yields() { | |
180 Atomic::inc(&_pending_yields); | |
181 assert(_pending_yields >= 0, "can't be negative"); | |
182 } | |
183 static void decrement_pending_yields() { | |
184 Atomic::dec(&_pending_yields); | |
185 assert(_pending_yields >= 0, "can't be negative"); | |
186 } | |
187 static void asynchronous_yield_request() { | |
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188 assert(CMSIncrementalMode, "Currently only used w/iCMS"); |
0 | 189 increment_pending_yields(); |
190 Atomic::inc(&_pending_decrements); | |
191 assert(_pending_decrements >= 0, "can't be negative"); | |
192 } | |
193 static void acknowledge_yield_request() { | |
194 jint decrement = _pending_decrements; | |
195 if (decrement > 0) { | |
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196 assert(CMSIncrementalMode, "Currently only used w/iCMS"); |
0 | 197 // Order important to preserve: _pending_yields >= _pending_decrements |
198 Atomic::add(-decrement, &_pending_decrements); | |
199 Atomic::add(-decrement, &_pending_yields); | |
200 assert(_pending_decrements >= 0, "can't be negative"); | |
201 assert(_pending_yields >= 0, "can't be negative"); | |
202 } | |
203 } | |
204 static bool should_yield() { return _pending_yields > 0; } | |
205 | |
206 // CMS incremental mode. | |
207 static void start_icms(); // notify thread to start a quantum of work | |
208 static void stop_icms(); // request thread to stop working | |
209 void icms_wait(); // if asked to stop, wait until notified to start | |
210 | |
211 // Incremental mode is enabled globally by the flag CMSIncrementalMode. It | |
212 // must also be enabled/disabled dynamically to allow foreground collections. | |
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213 #define ICMS_ENABLING_ASSERT \ |
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214 assert((CMSIncrementalMode && _icms_disabled >= 0) || \ |
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215 (!CMSIncrementalMode && _icms_disabled <= 0), "Error") |
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216 |
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217 static inline void enable_icms() { |
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218 ICMS_ENABLING_ASSERT; |
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219 Atomic::dec(&_icms_disabled); |
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220 } |
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221 static inline void disable_icms() { |
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222 ICMS_ENABLING_ASSERT; |
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223 Atomic::inc(&_icms_disabled); |
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224 } |
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225 static inline bool icms_is_disabled() { |
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226 ICMS_ENABLING_ASSERT; |
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227 return _icms_disabled > 0; |
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228 } |
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229 static inline bool icms_is_enabled() { |
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230 return !icms_is_disabled(); |
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231 } |
0 | 232 }; |
233 | |
234 inline void ConcurrentMarkSweepThread::trace_state(const char* desc) { | |
235 if (CMSTraceThreadState) { | |
236 char buf[128]; | |
237 TimeStamp& ts = gclog_or_tty->time_stamp(); | |
238 if (!ts.is_updated()) { | |
239 ts.update(); | |
240 } | |
241 jio_snprintf(buf, sizeof(buf), " [%.3f: CMSThread %s] ", | |
242 ts.seconds(), desc); | |
243 buf[sizeof(buf) - 1] = '\0'; | |
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244 gclog_or_tty->print("%s", buf); |
0 | 245 } |
246 } | |
247 | |
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248 // For scoped increment/decrement of (synchronous) yield requests |
0 | 249 class CMSSynchronousYieldRequest: public StackObj { |
250 public: | |
251 CMSSynchronousYieldRequest() { | |
252 ConcurrentMarkSweepThread::increment_pending_yields(); | |
253 } | |
254 ~CMSSynchronousYieldRequest() { | |
255 ConcurrentMarkSweepThread::decrement_pending_yields(); | |
256 } | |
257 }; | |
258 | |
259 // Used to emit a warning in case of unexpectedly excessive | |
260 // looping (in "apparently endless loops") in CMS code. | |
261 class CMSLoopCountWarn: public StackObj { | |
262 private: | |
263 const char* _src; | |
264 const char* _msg; | |
265 const intx _threshold; | |
266 intx _ticks; | |
267 | |
268 public: | |
269 inline CMSLoopCountWarn(const char* src, const char* msg, | |
270 const intx threshold) : | |
271 _src(src), _msg(msg), _threshold(threshold), _ticks(0) { } | |
272 | |
273 inline void tick() { | |
274 _ticks++; | |
275 if (CMSLoopWarn && _ticks % _threshold == 0) { | |
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276 warning("%s has looped " INTX_FORMAT " times %s", _src, _ticks, _msg); |
0 | 277 } |
278 } | |
279 }; | |
1972 | 280 |
281 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPTHREAD_HPP |