Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp @ 6273:4c8f2a12e757 hs24-b20
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| author | twisti |
|---|---|
| date | Fri, 10 Aug 2012 17:50:24 -0700 |
| parents | f08d439fab8c |
| children | f34d701e952e |
| rev | line source |
|---|---|
| 0 | 1 /* |
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2 * Copyright (c) 2001, 2011, 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" | |
| 30 #ifdef TARGET_OS_FAMILY_linux | |
| 31 # include "thread_linux.inline.hpp" | |
| 32 #endif | |
| 33 #ifdef TARGET_OS_FAMILY_solaris | |
| 34 # include "thread_solaris.inline.hpp" | |
| 35 #endif | |
| 36 #ifdef TARGET_OS_FAMILY_windows | |
| 37 # include "thread_windows.inline.hpp" | |
| 38 #endif | |
| 3960 | 39 #ifdef TARGET_OS_FAMILY_bsd |
| 40 # include "thread_bsd.inline.hpp" | |
| 41 #endif | |
| 1972 | 42 |
| 0 | 43 class ConcurrentMarkSweepGeneration; |
| 44 class CMSCollector; | |
| 45 | |
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46 // The Concurrent Mark Sweep GC Thread |
| 0 | 47 class ConcurrentMarkSweepThread: public ConcurrentGCThread { |
| 48 friend class VMStructs; | |
| 49 friend class ConcurrentMarkSweepGeneration; // XXX should remove friendship | |
| 50 friend class CMSCollector; | |
| 51 public: | |
| 52 virtual void run(); | |
| 53 | |
| 54 private: | |
| 55 static ConcurrentMarkSweepThread* _cmst; | |
| 56 static CMSCollector* _collector; | |
| 57 static SurrogateLockerThread* _slt; | |
| 58 static SurrogateLockerThread::SLT_msg_type _sltBuffer; | |
| 59 static Monitor* _sltMonitor; | |
| 60 | |
| 61 static bool _should_terminate; | |
| 62 | |
| 63 enum CMS_flag_type { | |
| 64 CMS_nil = NoBits, | |
| 65 CMS_cms_wants_token = nth_bit(0), | |
| 66 CMS_cms_has_token = nth_bit(1), | |
| 67 CMS_vm_wants_token = nth_bit(2), | |
| 68 CMS_vm_has_token = nth_bit(3) | |
| 69 }; | |
| 70 | |
| 71 static int _CMS_flag; | |
| 72 | |
| 73 static bool CMS_flag_is_set(int b) { return (_CMS_flag & b) != 0; } | |
| 74 static bool set_CMS_flag(int b) { return (_CMS_flag |= b) != 0; } | |
| 75 static bool clear_CMS_flag(int b) { return (_CMS_flag &= ~b) != 0; } | |
| 76 void sleepBeforeNextCycle(); | |
| 77 | |
| 78 // CMS thread should yield for a young gen collection, direct allocation, | |
| 79 // and iCMS activity. | |
| 80 static char _pad_1[64 - sizeof(jint)]; // prevent cache-line sharing | |
| 81 static volatile jint _pending_yields; | |
| 82 static volatile jint _pending_decrements; // decrements to _pending_yields | |
| 83 static char _pad_2[64 - sizeof(jint)]; // prevent cache-line sharing | |
| 84 | |
| 85 // Tracing messages, enabled by CMSTraceThreadState. | |
| 86 static inline void trace_state(const char* desc); | |
| 87 | |
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88 static volatile int _icms_disabled; // a counter to track #iCMS disable & enable |
| 0 | 89 static volatile bool _should_run; // iCMS may run |
| 90 static volatile bool _should_stop; // iCMS should stop | |
| 91 | |
| 92 // debugging | |
| 93 void verify_ok_to_terminate() const PRODUCT_RETURN; | |
| 94 | |
| 95 public: | |
| 96 // Constructor | |
| 97 ConcurrentMarkSweepThread(CMSCollector* collector); | |
| 98 | |
| 99 static void makeSurrogateLockerThread(TRAPS); | |
| 100 static SurrogateLockerThread* slt() { return _slt; } | |
| 101 | |
| 102 // Tester | |
| 103 bool is_ConcurrentGC_thread() const { return true; } | |
| 104 | |
| 105 static void threads_do(ThreadClosure* tc); | |
| 106 | |
| 107 // Printing | |
| 108 void print_on(outputStream* st) const; | |
| 109 void print() const { print_on(tty); } | |
| 110 static void print_all_on(outputStream* st); | |
| 111 static void print_all() { print_all_on(tty); } | |
| 112 | |
| 113 // Returns the CMS Thread | |
| 114 static ConcurrentMarkSweepThread* cmst() { return _cmst; } | |
| 115 static CMSCollector* collector() { return _collector; } | |
| 116 | |
| 117 // Create and start the CMS Thread, or stop it on shutdown | |
| 118 static ConcurrentMarkSweepThread* start(CMSCollector* collector); | |
| 119 static void stop(); | |
| 120 static bool should_terminate() { return _should_terminate; } | |
| 121 | |
| 122 // Synchronization using CMS token | |
| 123 static void synchronize(bool is_cms_thread); | |
| 124 static void desynchronize(bool is_cms_thread); | |
| 125 static bool vm_thread_has_cms_token() { | |
| 126 return CMS_flag_is_set(CMS_vm_has_token); | |
| 127 } | |
| 128 static bool cms_thread_has_cms_token() { | |
| 129 return CMS_flag_is_set(CMS_cms_has_token); | |
| 130 } | |
| 131 static bool vm_thread_wants_cms_token() { | |
| 132 return CMS_flag_is_set(CMS_vm_wants_token); | |
| 133 } | |
| 134 static bool cms_thread_wants_cms_token() { | |
| 135 return CMS_flag_is_set(CMS_cms_wants_token); | |
| 136 } | |
| 137 | |
| 138 // Wait on CMS lock until the next synchronous GC | |
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139 // or given timeout, whichever is earlier. A timeout value |
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140 // of 0 indicates that there is no upper bound on the wait time. |
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141 // A concurrent full gc request terminates the wait. |
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142 void wait_on_cms_lock(long t_millis); |
| 0 | 143 |
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144 // The CMS thread will yield during the work portion of its cycle |
| 0 | 145 // only when requested to. Both synchronous and asychronous requests |
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146 // are provided: |
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147 // (1) A synchronous request is used for young gen collections and |
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148 // for direct allocations. The requesting thread increments |
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149 // _pending_yields at the beginning of an operation, and decrements |
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150 // _pending_yields when that operation is completed. |
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151 // In turn, the CMS thread yields when _pending_yields is positive, |
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152 // and continues to yield until the value reverts to 0. |
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153 // (2) An asynchronous request, on the other hand, is used by iCMS |
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154 // for the stop_icms() operation. A single yield satisfies all of |
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155 // the outstanding asynch yield requests, of which there may |
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156 // occasionally be several in close succession. To accomplish |
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157 // this, an asynch-requesting thread atomically increments both |
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158 // _pending_yields and _pending_decrements. An asynchr requesting |
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159 // thread does not wait and "acknowledge" completion of an operation |
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160 // and deregister the request, like the synchronous version described |
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161 // above does. In turn, after yielding, the CMS thread decrements both |
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162 // _pending_yields and _pending_decrements by the value seen in |
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163 // _pending_decrements before the decrement. |
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164 // NOTE: The above scheme is isomorphic to having two request counters, |
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165 // one for async requests and one for sync requests, and for the CMS thread |
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166 // to check the sum of the two counters to decide whether it should yield |
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167 // and to clear only the async counter when it yields. However, it turns out |
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168 // to be more efficient for CMS code to just check a single counter |
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169 // _pending_yields that holds the sum (of both sync and async requests), and |
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170 // a second counter _pending_decrements that only holds the async requests, |
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171 // for greater efficiency, since in a typical CMS run, there are many more |
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172 // pontential (i.e. static) yield points than there are actual |
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173 // (i.e. dynamic) yields because of requests, which are few and far between. |
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174 // |
| 0 | 175 // Note that, while "_pending_yields >= _pending_decrements" is an invariant, |
| 176 // we cannot easily test that invariant, since the counters are manipulated via | |
| 177 // atomic instructions without explicit locking and we cannot read | |
| 178 // the two counters atomically together: one suggestion is to | |
| 179 // use (for example) 16-bit counters so as to be able to read the | |
| 180 // two counters atomically even on 32-bit platforms. Notice that | |
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181 // the second assert in acknowledge_yield_request() below does indeed |
| 0 | 182 // check a form of the above invariant, albeit indirectly. |
| 183 | |
| 184 static void increment_pending_yields() { | |
| 185 Atomic::inc(&_pending_yields); | |
| 186 assert(_pending_yields >= 0, "can't be negative"); | |
| 187 } | |
| 188 static void decrement_pending_yields() { | |
| 189 Atomic::dec(&_pending_yields); | |
| 190 assert(_pending_yields >= 0, "can't be negative"); | |
| 191 } | |
| 192 static void asynchronous_yield_request() { | |
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193 assert(CMSIncrementalMode, "Currently only used w/iCMS"); |
| 0 | 194 increment_pending_yields(); |
| 195 Atomic::inc(&_pending_decrements); | |
| 196 assert(_pending_decrements >= 0, "can't be negative"); | |
| 197 } | |
| 198 static void acknowledge_yield_request() { | |
| 199 jint decrement = _pending_decrements; | |
| 200 if (decrement > 0) { | |
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201 assert(CMSIncrementalMode, "Currently only used w/iCMS"); |
| 0 | 202 // Order important to preserve: _pending_yields >= _pending_decrements |
| 203 Atomic::add(-decrement, &_pending_decrements); | |
| 204 Atomic::add(-decrement, &_pending_yields); | |
| 205 assert(_pending_decrements >= 0, "can't be negative"); | |
| 206 assert(_pending_yields >= 0, "can't be negative"); | |
| 207 } | |
| 208 } | |
| 209 static bool should_yield() { return _pending_yields > 0; } | |
| 210 | |
| 211 // CMS incremental mode. | |
| 212 static void start_icms(); // notify thread to start a quantum of work | |
| 213 static void stop_icms(); // request thread to stop working | |
| 214 void icms_wait(); // if asked to stop, wait until notified to start | |
| 215 | |
| 216 // Incremental mode is enabled globally by the flag CMSIncrementalMode. It | |
| 217 // must also be enabled/disabled dynamically to allow foreground collections. | |
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218 #define ICMS_ENABLING_ASSERT \ |
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219 assert((CMSIncrementalMode && _icms_disabled >= 0) || \ |
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220 (!CMSIncrementalMode && _icms_disabled <= 0), "Error") |
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221 |
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222 static inline void enable_icms() { |
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223 ICMS_ENABLING_ASSERT; |
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224 Atomic::dec(&_icms_disabled); |
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225 } |
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226 static inline void disable_icms() { |
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227 ICMS_ENABLING_ASSERT; |
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228 Atomic::inc(&_icms_disabled); |
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229 } |
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230 static inline bool icms_is_disabled() { |
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231 ICMS_ENABLING_ASSERT; |
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232 return _icms_disabled > 0; |
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233 } |
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234 static inline bool icms_is_enabled() { |
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235 return !icms_is_disabled(); |
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236 } |
| 0 | 237 }; |
| 238 | |
| 239 inline void ConcurrentMarkSweepThread::trace_state(const char* desc) { | |
| 240 if (CMSTraceThreadState) { | |
| 241 char buf[128]; | |
| 242 TimeStamp& ts = gclog_or_tty->time_stamp(); | |
| 243 if (!ts.is_updated()) { | |
| 244 ts.update(); | |
| 245 } | |
| 246 jio_snprintf(buf, sizeof(buf), " [%.3f: CMSThread %s] ", | |
| 247 ts.seconds(), desc); | |
| 248 buf[sizeof(buf) - 1] = '\0'; | |
| 249 gclog_or_tty->print(buf); | |
| 250 } | |
| 251 } | |
| 252 | |
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253 // For scoped increment/decrement of (synchronous) yield requests |
| 0 | 254 class CMSSynchronousYieldRequest: public StackObj { |
| 255 public: | |
| 256 CMSSynchronousYieldRequest() { | |
| 257 ConcurrentMarkSweepThread::increment_pending_yields(); | |
| 258 } | |
| 259 ~CMSSynchronousYieldRequest() { | |
| 260 ConcurrentMarkSweepThread::decrement_pending_yields(); | |
| 261 } | |
| 262 }; | |
| 263 | |
| 264 // Used to emit a warning in case of unexpectedly excessive | |
| 265 // looping (in "apparently endless loops") in CMS code. | |
| 266 class CMSLoopCountWarn: public StackObj { | |
| 267 private: | |
| 268 const char* _src; | |
| 269 const char* _msg; | |
| 270 const intx _threshold; | |
| 271 intx _ticks; | |
| 272 | |
| 273 public: | |
| 274 inline CMSLoopCountWarn(const char* src, const char* msg, | |
| 275 const intx threshold) : | |
| 276 _src(src), _msg(msg), _threshold(threshold), _ticks(0) { } | |
| 277 | |
| 278 inline void tick() { | |
| 279 _ticks++; | |
| 280 if (CMSLoopWarn && _ticks % _threshold == 0) { | |
| 281 warning("%s has looped %d times %s", _src, _ticks, _msg); | |
| 282 } | |
| 283 } | |
| 284 }; | |
| 1972 | 285 |
| 286 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPTHREAD_HPP |