rev 4482 : 8013934: Garbage collection event for CMS has wrong cause for System.gc()

   1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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.
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  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  *
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/systemDictionary.hpp"
  27 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
  28 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  29 #include "memory/genCollectedHeap.hpp"
  30 #include "oops/instanceRefKlass.hpp"
  31 #include "oops/oop.inline.hpp"
  32 #include "runtime/init.hpp"
  33 #include "runtime/interfaceSupport.hpp"
  34 #include "runtime/java.hpp"
  35 #include "runtime/javaCalls.hpp"
  36 #include "runtime/mutexLocker.hpp"
  37 #include "runtime/os.hpp"
  38 #include "runtime/vmThread.hpp"
  39 
  40 // ======= Concurrent Mark Sweep Thread ========
  41 
  42 // The CMS thread is created when Concurrent Mark Sweep is used in the
  43 // older of two generations in a generational memory system.
  44 
  45 ConcurrentMarkSweepThread*
  46      ConcurrentMarkSweepThread::_cmst     = NULL;
  47 CMSCollector* ConcurrentMarkSweepThread::_collector = NULL;
  48 bool ConcurrentMarkSweepThread::_should_terminate = false;
  49 int  ConcurrentMarkSweepThread::_CMS_flag         = CMS_nil;
  50 
  51 volatile jint ConcurrentMarkSweepThread::_pending_yields      = 0;
  52 volatile jint ConcurrentMarkSweepThread::_pending_decrements  = 0;
  53 
  54 volatile jint ConcurrentMarkSweepThread::_icms_disabled   = 0;
  55 volatile bool ConcurrentMarkSweepThread::_should_run     = false;
  56 // When icms is enabled, the icms thread is stopped until explicitly
  57 // started.
  58 volatile bool ConcurrentMarkSweepThread::_should_stop    = true;
  59 
  60 SurrogateLockerThread*
  61      ConcurrentMarkSweepThread::_slt = NULL;
  62 SurrogateLockerThread::SLT_msg_type
  63      ConcurrentMarkSweepThread::_sltBuffer = SurrogateLockerThread::empty;
  64 Monitor*
  65      ConcurrentMarkSweepThread::_sltMonitor = NULL;
  66 
  67 ConcurrentMarkSweepThread::ConcurrentMarkSweepThread(CMSCollector* collector)
  68   : ConcurrentGCThread() {
  69   assert(UseConcMarkSweepGC,  "UseConcMarkSweepGC should be set");
  70   assert(_cmst == NULL, "CMS thread already created");
  71   _cmst = this;
  72   assert(_collector == NULL, "Collector already set");
  73   _collector = collector;
  74 
  75   set_name("Concurrent Mark-Sweep GC Thread");
  76 
  77   if (os::create_thread(this, os::cgc_thread)) {
  78     // An old comment here said: "Priority should be just less
  79     // than that of VMThread".  Since the VMThread runs at
  80     // NearMaxPriority, the old comment was inaccurate, but
  81     // changing the default priority to NearMaxPriority-1
  82     // could change current behavior, so the default of
  83     // NearMaxPriority stays in place.
  84     //
  85     // Note that there's a possibility of the VMThread
  86     // starving if UseCriticalCMSThreadPriority is on.
  87     // That won't happen on Solaris for various reasons,
  88     // but may well happen on non-Solaris platforms.
  89     int native_prio;
  90     if (UseCriticalCMSThreadPriority) {
  91       native_prio = os::java_to_os_priority[CriticalPriority];
  92     } else {
  93       native_prio = os::java_to_os_priority[NearMaxPriority];
  94     }
  95     os::set_native_priority(this, native_prio);
  96 
  97     if (!DisableStartThread) {
  98       os::start_thread(this);
  99     }
 100   }
 101   _sltMonitor = SLT_lock;
 102   assert(!CMSIncrementalMode || icms_is_enabled(), "Error");
 103 }
 104 
 105 void ConcurrentMarkSweepThread::run() {
 106   assert(this == cmst(), "just checking");
 107 
 108   this->record_stack_base_and_size();
 109   this->initialize_thread_local_storage();
 110   this->set_active_handles(JNIHandleBlock::allocate_block());
 111   // From this time Thread::current() should be working.
 112   assert(this == Thread::current(), "just checking");
 113   if (BindCMSThreadToCPU && !os::bind_to_processor(CPUForCMSThread)) {
 114     warning("Couldn't bind CMS thread to processor %u", CPUForCMSThread);
 115   }
 116   // Wait until Universe::is_fully_initialized()
 117   {
 118     CMSLoopCountWarn loopX("CMS::run", "waiting for "
 119                            "Universe::is_fully_initialized()", 2);
 120     MutexLockerEx x(CGC_lock, true);
 121     set_CMS_flag(CMS_cms_wants_token);
 122     // Wait until Universe is initialized and all initialization is completed.
 123     while (!is_init_completed() && !Universe::is_fully_initialized() &&
 124            !_should_terminate) {
 125       CGC_lock->wait(true, 200);
 126       loopX.tick();
 127     }
 128     // Wait until the surrogate locker thread that will do
 129     // pending list locking on our behalf has been created.
 130     // We cannot start the SLT thread ourselves since we need
 131     // to be a JavaThread to do so.
 132     CMSLoopCountWarn loopY("CMS::run", "waiting for SLT installation", 2);
 133     while (_slt == NULL && !_should_terminate) {
 134       CGC_lock->wait(true, 200);
 135       loopY.tick();
 136     }
 137     clear_CMS_flag(CMS_cms_wants_token);
 138   }
 139 
 140   while (!_should_terminate) {
 141     sleepBeforeNextCycle();
 142     if (_should_terminate) break;
 143     GCCause::Cause cause = _collector->_full_gc_requested ?
 144       _collector->_full_gc_cause : GCCause::_cms_concurrent_mark;
 145     _collector->collect_in_background(false, cause);
 146   }
 147   assert(_should_terminate, "just checking");
 148   // Check that the state of any protocol for synchronization
 149   // between background (CMS) and foreground collector is "clean"
 150   // (i.e. will not potentially block the foreground collector,
 151   // requiring action by us).
 152   verify_ok_to_terminate();
 153   // Signal that it is terminated
 154   {
 155     MutexLockerEx mu(Terminator_lock,
 156                      Mutex::_no_safepoint_check_flag);
 157     assert(_cmst == this, "Weird!");
 158     _cmst = NULL;
 159     Terminator_lock->notify();
 160   }
 161 
 162   // Thread destructor usually does this..
 163   ThreadLocalStorage::set_thread(NULL);
 164 }
 165 
 166 #ifndef PRODUCT
 167 void ConcurrentMarkSweepThread::verify_ok_to_terminate() const {
 168   assert(!(CGC_lock->owned_by_self() || cms_thread_has_cms_token() ||
 169            cms_thread_wants_cms_token()),
 170          "Must renounce all worldly possessions and desires for nirvana");
 171   _collector->verify_ok_to_terminate();
 172 }
 173 #endif
 174 
 175 // create and start a new ConcurrentMarkSweep Thread for given CMS generation
 176 ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::start(CMSCollector* collector) {
 177   if (!_should_terminate) {
 178     assert(cmst() == NULL, "start() called twice?");
 179     ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);
 180     assert(cmst() == th, "Where did the just-created CMS thread go?");
 181     return th;
 182   }
 183   return NULL;
 184 }
 185 
 186 void ConcurrentMarkSweepThread::stop() {
 187   if (CMSIncrementalMode) {
 188     // Disable incremental mode and wake up the thread so it notices the change.
 189     disable_icms();
 190     start_icms();
 191   }
 192   // it is ok to take late safepoints here, if needed
 193   {
 194     MutexLockerEx x(Terminator_lock);
 195     _should_terminate = true;
 196   }
 197   { // Now post a notify on CGC_lock so as to nudge
 198     // CMS thread(s) that might be slumbering in
 199     // sleepBeforeNextCycle.
 200     MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
 201     CGC_lock->notify_all();
 202   }
 203   { // Now wait until (all) CMS thread(s) have exited
 204     MutexLockerEx x(Terminator_lock);
 205     while(cmst() != NULL) {
 206       Terminator_lock->wait();
 207     }
 208   }
 209 }
 210 
 211 void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {
 212   assert(tc != NULL, "Null ThreadClosure");
 213   if (_cmst != NULL) {
 214     tc->do_thread(_cmst);
 215   }
 216   assert(Universe::is_fully_initialized(),
 217          "Called too early, make sure heap is fully initialized");
 218   if (_collector != NULL) {
 219     AbstractWorkGang* gang = _collector->conc_workers();
 220     if (gang != NULL) {
 221       gang->threads_do(tc);
 222     }
 223   }
 224 }
 225 
 226 void ConcurrentMarkSweepThread::print_on(outputStream* st) const {
 227   st->print("\"%s\" ", name());
 228   Thread::print_on(st);
 229   st->cr();
 230 }
 231 
 232 void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {
 233   if (_cmst != NULL) {
 234     _cmst->print_on(st);
 235   }
 236   if (_collector != NULL) {
 237     AbstractWorkGang* gang = _collector->conc_workers();
 238     if (gang != NULL) {
 239       gang->print_worker_threads_on(st);
 240     }
 241   }
 242 }
 243 
 244 void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {
 245   assert(UseConcMarkSweepGC, "just checking");
 246 
 247   MutexLockerEx x(CGC_lock,
 248                   Mutex::_no_safepoint_check_flag);
 249   if (!is_cms_thread) {
 250     assert(Thread::current()->is_VM_thread(), "Not a VM thread");
 251     CMSSynchronousYieldRequest yr;
 252     while (CMS_flag_is_set(CMS_cms_has_token)) {
 253       // indicate that we want to get the token
 254       set_CMS_flag(CMS_vm_wants_token);
 255       CGC_lock->wait(true);
 256     }
 257     // claim the token and proceed
 258     clear_CMS_flag(CMS_vm_wants_token);
 259     set_CMS_flag(CMS_vm_has_token);
 260   } else {
 261     assert(Thread::current()->is_ConcurrentGC_thread(),
 262            "Not a CMS thread");
 263     // The following barrier assumes there's only one CMS thread.
 264     // This will need to be modified is there are more CMS threads than one.
 265     while (CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token)) {
 266       set_CMS_flag(CMS_cms_wants_token);
 267       CGC_lock->wait(true);
 268     }
 269     // claim the token
 270     clear_CMS_flag(CMS_cms_wants_token);
 271     set_CMS_flag(CMS_cms_has_token);
 272   }
 273 }
 274 
 275 void ConcurrentMarkSweepThread::desynchronize(bool is_cms_thread) {
 276   assert(UseConcMarkSweepGC, "just checking");
 277 
 278   MutexLockerEx x(CGC_lock,
 279                   Mutex::_no_safepoint_check_flag);
 280   if (!is_cms_thread) {
 281     assert(Thread::current()->is_VM_thread(), "Not a VM thread");
 282     assert(CMS_flag_is_set(CMS_vm_has_token), "just checking");
 283     clear_CMS_flag(CMS_vm_has_token);
 284     if (CMS_flag_is_set(CMS_cms_wants_token)) {
 285       // wake-up a waiting CMS thread
 286       CGC_lock->notify();
 287     }
 288     assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),
 289            "Should have been cleared");
 290   } else {
 291     assert(Thread::current()->is_ConcurrentGC_thread(),
 292            "Not a CMS thread");
 293     assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");
 294     clear_CMS_flag(CMS_cms_has_token);
 295     if (CMS_flag_is_set(CMS_vm_wants_token)) {
 296       // wake-up a waiting VM thread
 297       CGC_lock->notify();
 298     }
 299     assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
 300            "Should have been cleared");
 301   }
 302 }
 303 
 304 // Wait until the next synchronous GC, a concurrent full gc request,
 305 // or a timeout, whichever is earlier.
 306 void ConcurrentMarkSweepThread::wait_on_cms_lock(long t_millis) {
 307   MutexLockerEx x(CGC_lock,
 308                   Mutex::_no_safepoint_check_flag);
 309   if (_should_terminate || _collector->_full_gc_requested) {
 310     return;
 311   }
 312   set_CMS_flag(CMS_cms_wants_token);   // to provoke notifies
 313   CGC_lock->wait(Mutex::_no_safepoint_check_flag, t_millis);
 314   clear_CMS_flag(CMS_cms_wants_token);
 315   assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
 316          "Should not be set");
 317 }
 318 
 319 void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {
 320   while (!_should_terminate) {
 321     if (CMSIncrementalMode) {
 322       icms_wait();
 323       return;
 324     } else {
 325       // Wait until the next synchronous GC, a concurrent full gc
 326       // request or a timeout, whichever is earlier.
 327       wait_on_cms_lock(CMSWaitDuration);
 328     }
 329     // Check if we should start a CMS collection cycle
 330     if (_collector->shouldConcurrentCollect()) {
 331       return;
 332     }
 333     // .. collection criterion not yet met, let's go back
 334     // and wait some more
 335   }
 336 }
 337 
 338 // Incremental CMS
 339 void ConcurrentMarkSweepThread::start_icms() {
 340   assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
 341   MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
 342   trace_state("start_icms");
 343   _should_run = true;
 344   iCMS_lock->notify_all();
 345 }
 346 
 347 void ConcurrentMarkSweepThread::stop_icms() {
 348   assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
 349   MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
 350   if (!_should_stop) {
 351     trace_state("stop_icms");
 352     _should_stop = true;
 353     _should_run = false;
 354     asynchronous_yield_request();
 355     iCMS_lock->notify_all();
 356   }
 357 }
 358 
 359 void ConcurrentMarkSweepThread::icms_wait() {
 360   assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
 361   if (_should_stop && icms_is_enabled()) {
 362     MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
 363     trace_state("pause_icms");
 364     _collector->stats().stop_cms_timer();
 365     while(!_should_run && icms_is_enabled()) {
 366       iCMS_lock->wait(Mutex::_no_safepoint_check_flag);
 367     }
 368     _collector->stats().start_cms_timer();
 369     _should_stop = false;
 370     trace_state("pause_icms end");
 371   }
 372 }
 373 
 374 // Note: this method, although exported by the ConcurrentMarkSweepThread,
 375 // which is a non-JavaThread, can only be called by a JavaThread.
 376 // Currently this is done at vm creation time (post-vm-init) by the
 377 // main/Primordial (Java)Thread.
 378 // XXX Consider changing this in the future to allow the CMS thread
 379 // itself to create this thread?
 380 void ConcurrentMarkSweepThread::makeSurrogateLockerThread(TRAPS) {
 381   assert(UseConcMarkSweepGC, "SLT thread needed only for CMS GC");
 382   assert(_slt == NULL, "SLT already created");
 383   _slt = SurrogateLockerThread::make(THREAD);
 384 }
--- EOF ---