Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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  */

 #include "precompiled.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"

 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"

 #include "memory/genCollectedHeap.hpp"

 #include "oops/instanceRefKlass.hpp"

 #include "oops/oop.inline.hpp"

 #include "runtime/init.hpp"

 #include "runtime/interfaceSupport.hpp"

 #include "runtime/java.hpp"

 #include "runtime/javaCalls.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "runtime/os.hpp"

 #include "runtime/vmThread.hpp"

 // ======= Concurrent Mark Sweep Thread ========

 // The CMS thread is created when Concurrent Mark Sweep is used in the

 // older of two generations in a generational memory system.

 ConcurrentMarkSweepThread*

      ConcurrentMarkSweepThread::_cmst     = NULL;

 CMSCollector* ConcurrentMarkSweepThread::_collector = NULL;

 bool ConcurrentMarkSweepThread::_should_terminate = false;

 int  ConcurrentMarkSweepThread::_CMS_flag         = CMS_nil;

 volatile jint ConcurrentMarkSweepThread::_pending_yields      = 0;

 volatile jint ConcurrentMarkSweepThread::_pending_decrements  = 0;

 volatile jint ConcurrentMarkSweepThread::_icms_disabled   = 0;

 volatile bool ConcurrentMarkSweepThread::_should_run     = false;

 // When icms is enabled, the icms thread is stopped until explicitly

 // started.

 volatile bool ConcurrentMarkSweepThread::_should_stop    = true;

 SurrogateLockerThread*

      ConcurrentMarkSweepThread::_slt = NULL;

 SurrogateLockerThread::SLT_msg_type

      ConcurrentMarkSweepThread::_sltBuffer = SurrogateLockerThread::empty;

 Monitor*

      ConcurrentMarkSweepThread::_sltMonitor = NULL;

 ConcurrentMarkSweepThread::ConcurrentMarkSweepThread(CMSCollector* collector)

   : ConcurrentGCThread() {

   assert(UseConcMarkSweepGC,  "UseConcMarkSweepGC should be set");

   assert(_cmst == NULL, "CMS thread already created");

   _cmst = this;

   assert(_collector == NULL, "Collector already set");

   _collector = collector;

   set_name("Concurrent Mark-Sweep GC Thread");

   if (os::create_thread(this, os::cgc_thread)) {

     // An old comment here said: "Priority should be just less

     // than that of VMThread".  Since the VMThread runs at

     // NearMaxPriority, the old comment was inaccurate, but

     // changing the default priority to NearMaxPriority-1

     // could change current behavior, so the default of

     // NearMaxPriority stays in place.

     //

     // Note that there's a possibility of the VMThread

     // starving if UseCriticalCMSThreadPriority is on.

     // That won't happen on Solaris for various reasons,

     // but may well happen on non-Solaris platforms.

     int native_prio;

     if (UseCriticalCMSThreadPriority) {

       native_prio = os::java_to_os_priority[CriticalPriority];

     } else {

       native_prio = os::java_to_os_priority[NearMaxPriority];

     }

     os::set_native_priority(this, native_prio);

     if (!DisableStartThread) {

       os::start_thread(this);

     }

   }

   _sltMonitor = SLT_lock;

   assert(!CMSIncrementalMode || icms_is_enabled(), "Error");

 }

 void ConcurrentMarkSweepThread::run() {

   assert(this == cmst(), "just checking");

   this->record_stack_base_and_size();

   this->initialize_thread_local_storage();

   this->set_active_handles(JNIHandleBlock::allocate_block());

   // From this time Thread::current() should be working.

   assert(this == Thread::current(), "just checking");

   if (BindCMSThreadToCPU && !os::bind_to_processor(CPUForCMSThread)) {

     warning("Couldn't bind CMS thread to processor " UINTX_FORMAT, CPUForCMSThread);

   }

   // Wait until Universe::is_fully_initialized()

   {

     CMSLoopCountWarn loopX("CMS::run", "waiting for "

                            "Universe::is_fully_initialized()", 2);

     MutexLockerEx x(CGC_lock, true);

     set_CMS_flag(CMS_cms_wants_token);

     // Wait until Universe is initialized and all initialization is completed.

     while (!is_init_completed() && !Universe::is_fully_initialized() &&

            !_should_terminate) {

       CGC_lock->wait(true, 200);

       loopX.tick();

     }

     // Wait until the surrogate locker thread that will do

     // pending list locking on our behalf has been created.

     // We cannot start the SLT thread ourselves since we need

     // to be a JavaThread to do so.

     CMSLoopCountWarn loopY("CMS::run", "waiting for SLT installation", 2);

     while (_slt == NULL && !_should_terminate) {

       CGC_lock->wait(true, 200);

       loopY.tick();

     }

     clear_CMS_flag(CMS_cms_wants_token);

   }

   while (!_should_terminate) {

     sleepBeforeNextCycle();

     if (_should_terminate) break;

     GCCause::Cause cause = _collector->_full_gc_requested ?

       _collector->_full_gc_cause : GCCause::_cms_concurrent_mark;

     _collector->collect_in_background(false, cause);

   }

   assert(_should_terminate, "just checking");

   // Check that the state of any protocol for synchronization

   // between background (CMS) and foreground collector is "clean"

   // (i.e. will not potentially block the foreground collector,

   // requiring action by us).

   verify_ok_to_terminate();

   // Signal that it is terminated

   {

     MutexLockerEx mu(Terminator_lock,

                      Mutex::_no_safepoint_check_flag);

     assert(_cmst == this, "Weird!");

     _cmst = NULL;

     Terminator_lock->notify();

   }

   // Thread destructor usually does this..

   ThreadLocalStorage::set_thread(NULL);

 }

 #ifndef PRODUCT

 void ConcurrentMarkSweepThread::verify_ok_to_terminate() const {

   assert(!(CGC_lock->owned_by_self() || cms_thread_has_cms_token() ||

            cms_thread_wants_cms_token()),

          "Must renounce all worldly possessions and desires for nirvana");

   _collector->verify_ok_to_terminate();

 }

 #endif

 // create and start a new ConcurrentMarkSweep Thread for given CMS generation

 ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::start(CMSCollector* collector) {

   if (!_should_terminate) {

     assert(cmst() == NULL, "start() called twice?");

     ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);

     assert(cmst() == th, "Where did the just-created CMS thread go?");

     return th;

   }

   return NULL;

 }

 void ConcurrentMarkSweepThread::stop() {

   if (CMSIncrementalMode) {

     // Disable incremental mode and wake up the thread so it notices the change.

     disable_icms();

     start_icms();

   }

   // it is ok to take late safepoints here, if needed

   {

     MutexLockerEx x(Terminator_lock);

     _should_terminate = true;

   }

   { // Now post a notify on CGC_lock so as to nudge

     // CMS thread(s) that might be slumbering in

     // sleepBeforeNextCycle.

     MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);

     CGC_lock->notify_all();

   }

   { // Now wait until (all) CMS thread(s) have exited

     MutexLockerEx x(Terminator_lock);

     while(cmst() != NULL) {

       Terminator_lock->wait();

     }

   }

 }

 void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {

   assert(tc != NULL, "Null ThreadClosure");

   if (_cmst != NULL) {

     tc->do_thread(_cmst);

   }

   assert(Universe::is_fully_initialized(),

          "Called too early, make sure heap is fully initialized");

   if (_collector != NULL) {

     AbstractWorkGang* gang = _collector->conc_workers();

     if (gang != NULL) {

       gang->threads_do(tc);

     }

   }

 }

 void ConcurrentMarkSweepThread::print_on(outputStream* st) const {

   st->print("\"%s\" ", name());

   Thread::print_on(st);

   st->cr();

 }

 void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {

   if (_cmst != NULL) {

     _cmst->print_on(st);

     st->cr();

   }

   if (_collector != NULL) {

     AbstractWorkGang* gang = _collector->conc_workers();

     if (gang != NULL) {

       gang->print_worker_threads_on(st);

     }

   }

 }

 void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {

   assert(UseConcMarkSweepGC, "just checking");

   MutexLockerEx x(CGC_lock,

                   Mutex::_no_safepoint_check_flag);

   if (!is_cms_thread) {

     assert(Thread::current()->is_VM_thread(), "Not a VM thread");

     CMSSynchronousYieldRequest yr;

     while (CMS_flag_is_set(CMS_cms_has_token)) {

       // indicate that we want to get the token

       set_CMS_flag(CMS_vm_wants_token);

       CGC_lock->wait(true);

     }

     // claim the token and proceed

     clear_CMS_flag(CMS_vm_wants_token);

     set_CMS_flag(CMS_vm_has_token);

   } else {

     assert(Thread::current()->is_ConcurrentGC_thread(),

            "Not a CMS thread");

     // The following barrier assumes there's only one CMS thread.

     // This will need to be modified is there are more CMS threads than one.

     while (CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token)) {

       set_CMS_flag(CMS_cms_wants_token);

       CGC_lock->wait(true);

     }

     // claim the token

     clear_CMS_flag(CMS_cms_wants_token);

     set_CMS_flag(CMS_cms_has_token);

   }

 }

 void ConcurrentMarkSweepThread::desynchronize(bool is_cms_thread) {

   assert(UseConcMarkSweepGC, "just checking");

   MutexLockerEx x(CGC_lock,

                   Mutex::_no_safepoint_check_flag);

   if (!is_cms_thread) {

     assert(Thread::current()->is_VM_thread(), "Not a VM thread");

     assert(CMS_flag_is_set(CMS_vm_has_token), "just checking");

     clear_CMS_flag(CMS_vm_has_token);

     if (CMS_flag_is_set(CMS_cms_wants_token)) {

       // wake-up a waiting CMS thread

       CGC_lock->notify();

     }

     assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),

            "Should have been cleared");

   } else {

     assert(Thread::current()->is_ConcurrentGC_thread(),

            "Not a CMS thread");

     assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");

     clear_CMS_flag(CMS_cms_has_token);

     if (CMS_flag_is_set(CMS_vm_wants_token)) {

       // wake-up a waiting VM thread

       CGC_lock->notify();

     }

     assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),

            "Should have been cleared");

   }

 }

 // Wait until any cms_lock event

 void ConcurrentMarkSweepThread::wait_on_cms_lock(long t_millis) {

   MutexLockerEx x(CGC_lock,

                   Mutex::_no_safepoint_check_flag);

   if (_should_terminate || _collector->_full_gc_requested) {

     return;

   }

   set_CMS_flag(CMS_cms_wants_token);   // to provoke notifies

   CGC_lock->wait(Mutex::_no_safepoint_check_flag, t_millis);

   clear_CMS_flag(CMS_cms_wants_token);

   assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),

          "Should not be set");

 }

 // Wait until the next synchronous GC, a concurrent full gc request,

 // or a timeout, whichever is earlier.

 void ConcurrentMarkSweepThread::wait_on_cms_lock_for_scavenge(long t_millis) {

   // Wait time in millis or 0 value representing infinite wait for a scavenge

   assert(t_millis >= 0, "Wait time for scavenge should be 0 or positive");

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   double start_time_secs = os::elapsedTime();

   double end_time_secs = start_time_secs + (t_millis / ((double) MILLIUNITS));

   // Total collections count before waiting loop

   unsigned int before_count;

   {

     MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);

     before_count = gch->total_collections();

   }

   unsigned int loop_count = 0;

   while(!_should_terminate) {

     double now_time = os::elapsedTime();

     long wait_time_millis;

     if(t_millis != 0) {

       // New wait limit

       wait_time_millis = (long) ((end_time_secs - now_time) * MILLIUNITS);

       if(wait_time_millis <= 0) {

         // Wait time is over

         break;

       }

     } else {

       // No wait limit, wait if necessary forever

       wait_time_millis = 0;

     }

     // Wait until the next event or the remaining timeout

     {

       MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);

       if (_should_terminate || _collector->_full_gc_requested) {

         return;

       }

       set_CMS_flag(CMS_cms_wants_token);   // to provoke notifies

       assert(t_millis == 0 || wait_time_millis > 0, "Sanity");

       CGC_lock->wait(Mutex::_no_safepoint_check_flag, wait_time_millis);

       clear_CMS_flag(CMS_cms_wants_token);

       assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),

              "Should not be set");

     }

     // Extra wait time check before entering the heap lock to get the collection count

     if(t_millis != 0 && os::elapsedTime() >= end_time_secs) {

       // Wait time is over

       break;

     }

     // Total collections count after the event

     unsigned int after_count;

     {

       MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);

       after_count = gch->total_collections();

     }

     if(before_count != after_count) {

       // There was a collection - success

       break;

     }

     // Too many loops warning

     if(++loop_count == 0) {

       warning("wait_on_cms_lock_for_scavenge() has looped %u times", loop_count - 1);

     }

   }

 }

 void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {

   while (!_should_terminate) {

     if (CMSIncrementalMode) {

       icms_wait();

       if(CMSWaitDuration >= 0) {

         // Wait until the next synchronous GC, a concurrent full gc

         // request or a timeout, whichever is earlier.

         wait_on_cms_lock_for_scavenge(CMSWaitDuration);

       }

       return;

     } else {

       if(CMSWaitDuration >= 0) {

         // Wait until the next synchronous GC, a concurrent full gc

         // request or a timeout, whichever is earlier.

         wait_on_cms_lock_for_scavenge(CMSWaitDuration);

       } else {

         // Wait until any cms_lock event or check interval not to call shouldConcurrentCollect permanently

         wait_on_cms_lock(CMSCheckInterval);

       }

     }

     // Check if we should start a CMS collection cycle

     if (_collector->shouldConcurrentCollect()) {

       return;

     }

     // .. collection criterion not yet met, let's go back

     // and wait some more

   }

 }

 // Incremental CMS

 void ConcurrentMarkSweepThread::start_icms() {

   assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");

   MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);

   trace_state("start_icms");

   _should_run = true;

   iCMS_lock->notify_all();

 }

 void ConcurrentMarkSweepThread::stop_icms() {

   assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");

   MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);

   if (!_should_stop) {

     trace_state("stop_icms");

     _should_stop = true;

     _should_run = false;

     asynchronous_yield_request();

     iCMS_lock->notify_all();

   }

 }

 void ConcurrentMarkSweepThread::icms_wait() {

   assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");

   if (_should_stop && icms_is_enabled()) {

     MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);

     trace_state("pause_icms");

     _collector->stats().stop_cms_timer();

     while(!_should_run && icms_is_enabled()) {

       iCMS_lock->wait(Mutex::_no_safepoint_check_flag);

     }

     _collector->stats().start_cms_timer();

     _should_stop = false;

     trace_state("pause_icms end");

   }

 }

 // Note: this method, although exported by the ConcurrentMarkSweepThread,

 // which is a non-JavaThread, can only be called by a JavaThread.

 // Currently this is done at vm creation time (post-vm-init) by the

 // main/Primordial (Java)Thread.

 // XXX Consider changing this in the future to allow the CMS thread

 // itself to create this thread?

 void ConcurrentMarkSweepThread::makeSurrogateLockerThread(TRAPS) {

   assert(UseConcMarkSweepGC, "SLT thread needed only for CMS GC");

   assert(_slt == NULL, "SLT already created");

   _slt = SurrogateLockerThread::make(THREAD);

 }