duke@435: /*
phh@3481:  * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #include "precompiled.hpp"
stefank@2314: #include "classfile/systemDictionary.hpp"
stefank@2314: #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
stefank@2314: #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
stefank@2314: #include "memory/genCollectedHeap.hpp"
stefank@2314: #include "oops/instanceRefKlass.hpp"
stefank@2314: #include "oops/oop.inline.hpp"
stefank@2314: #include "runtime/init.hpp"
stefank@2314: #include "runtime/interfaceSupport.hpp"
stefank@2314: #include "runtime/java.hpp"
stefank@2314: #include "runtime/javaCalls.hpp"
stefank@2314: #include "runtime/mutexLocker.hpp"
stefank@2314: #include "runtime/os.hpp"
stefank@2314: #include "runtime/vmThread.hpp"
duke@435: 
duke@435: // ======= Concurrent Mark Sweep Thread ========
duke@435: 
duke@435: // The CMS thread is created when Concurrent Mark Sweep is used in the
duke@435: // older of two generations in a generational memory system.
duke@435: 
duke@435: ConcurrentMarkSweepThread*
duke@435:      ConcurrentMarkSweepThread::_cmst     = NULL;
duke@435: CMSCollector* ConcurrentMarkSweepThread::_collector = NULL;
duke@435: bool ConcurrentMarkSweepThread::_should_terminate = false;
duke@435: int  ConcurrentMarkSweepThread::_CMS_flag         = CMS_nil;
duke@435: 
duke@435: volatile jint ConcurrentMarkSweepThread::_pending_yields      = 0;
duke@435: volatile jint ConcurrentMarkSweepThread::_pending_decrements  = 0;
duke@435: 
ysr@2647: volatile jint ConcurrentMarkSweepThread::_icms_disabled   = 0;
duke@435: volatile bool ConcurrentMarkSweepThread::_should_run     = false;
duke@435: // When icms is enabled, the icms thread is stopped until explicitly
duke@435: // started.
duke@435: volatile bool ConcurrentMarkSweepThread::_should_stop    = true;
duke@435: 
duke@435: SurrogateLockerThread*
duke@435:      ConcurrentMarkSweepThread::_slt = NULL;
duke@435: SurrogateLockerThread::SLT_msg_type
duke@435:      ConcurrentMarkSweepThread::_sltBuffer = SurrogateLockerThread::empty;
duke@435: Monitor*
duke@435:      ConcurrentMarkSweepThread::_sltMonitor = NULL;
duke@435: 
duke@435: ConcurrentMarkSweepThread::ConcurrentMarkSweepThread(CMSCollector* collector)
duke@435:   : ConcurrentGCThread() {
duke@435:   assert(UseConcMarkSweepGC,  "UseConcMarkSweepGC should be set");
duke@435:   assert(_cmst == NULL, "CMS thread already created");
duke@435:   _cmst = this;
duke@435:   assert(_collector == NULL, "Collector already set");
duke@435:   _collector = collector;
duke@435: 
duke@435:   set_name("Concurrent Mark-Sweep GC Thread");
duke@435: 
duke@435:   if (os::create_thread(this, os::cgc_thread)) {
phh@3481:     // An old comment here said: "Priority should be just less
phh@3481:     // than that of VMThread".  Since the VMThread runs at
phh@3481:     // NearMaxPriority, the old comment was inaccurate, but
phh@3481:     // changing the default priority to NearMaxPriority-1
phh@3481:     // could change current behavior, so the default of
phh@3481:     // NearMaxPriority stays in place.
phh@3481:     //
phh@3481:     // Note that there's a possibility of the VMThread
phh@3481:     // starving if UseCriticalCMSThreadPriority is on.
phh@3481:     // That won't happen on Solaris for various reasons,
phh@3481:     // but may well happen on non-Solaris platforms.
phh@3481:     int native_prio;
phh@3481:     if (UseCriticalCMSThreadPriority) {
phh@3481:       native_prio = os::java_to_os_priority[CriticalPriority];
phh@3481:     } else {
phh@3481:       native_prio = os::java_to_os_priority[NearMaxPriority];
phh@3481:     }
phh@3481:     os::set_native_priority(this, native_prio);
phh@3481: 
duke@435:     if (!DisableStartThread) {
duke@435:       os::start_thread(this);
duke@435:     }
duke@435:   }
duke@435:   _sltMonitor = SLT_lock;
ysr@2647:   assert(!CMSIncrementalMode || icms_is_enabled(), "Error");
duke@435: }
duke@435: 
duke@435: void ConcurrentMarkSweepThread::run() {
duke@435:   assert(this == cmst(), "just checking");
duke@435: 
duke@435:   this->record_stack_base_and_size();
duke@435:   this->initialize_thread_local_storage();
duke@435:   this->set_active_handles(JNIHandleBlock::allocate_block());
duke@435:   // From this time Thread::current() should be working.
duke@435:   assert(this == Thread::current(), "just checking");
duke@435:   if (BindCMSThreadToCPU && !os::bind_to_processor(CPUForCMSThread)) {
duke@435:     warning("Couldn't bind CMS thread to processor %u", CPUForCMSThread);
duke@435:   }
duke@435:   // Wait until Universe::is_fully_initialized()
duke@435:   {
duke@435:     CMSLoopCountWarn loopX("CMS::run", "waiting for "
duke@435:                            "Universe::is_fully_initialized()", 2);
duke@435:     MutexLockerEx x(CGC_lock, true);
duke@435:     set_CMS_flag(CMS_cms_wants_token);
duke@435:     // Wait until Universe is initialized and all initialization is completed.
duke@435:     while (!is_init_completed() && !Universe::is_fully_initialized() &&
duke@435:            !_should_terminate) {
duke@435:       CGC_lock->wait(true, 200);
duke@435:       loopX.tick();
duke@435:     }
duke@435:     // Wait until the surrogate locker thread that will do
duke@435:     // pending list locking on our behalf has been created.
duke@435:     // We cannot start the SLT thread ourselves since we need
duke@435:     // to be a JavaThread to do so.
duke@435:     CMSLoopCountWarn loopY("CMS::run", "waiting for SLT installation", 2);
duke@435:     while (_slt == NULL && !_should_terminate) {
duke@435:       CGC_lock->wait(true, 200);
duke@435:       loopY.tick();
duke@435:     }
duke@435:     clear_CMS_flag(CMS_cms_wants_token);
duke@435:   }
duke@435: 
duke@435:   while (!_should_terminate) {
duke@435:     sleepBeforeNextCycle();
duke@435:     if (_should_terminate) break;
sla@5237:     GCCause::Cause cause = _collector->_full_gc_requested ?
sla@5237:       _collector->_full_gc_cause : GCCause::_cms_concurrent_mark;
sla@5237:     _collector->collect_in_background(false, cause);
duke@435:   }
duke@435:   assert(_should_terminate, "just checking");
duke@435:   // Check that the state of any protocol for synchronization
duke@435:   // between background (CMS) and foreground collector is "clean"
duke@435:   // (i.e. will not potentially block the foreground collector,
duke@435:   // requiring action by us).
duke@435:   verify_ok_to_terminate();
duke@435:   // Signal that it is terminated
duke@435:   {
duke@435:     MutexLockerEx mu(Terminator_lock,
duke@435:                      Mutex::_no_safepoint_check_flag);
duke@435:     assert(_cmst == this, "Weird!");
duke@435:     _cmst = NULL;
duke@435:     Terminator_lock->notify();
duke@435:   }
duke@435: 
duke@435:   // Thread destructor usually does this..
duke@435:   ThreadLocalStorage::set_thread(NULL);
duke@435: }
duke@435: 
duke@435: #ifndef PRODUCT
duke@435: void ConcurrentMarkSweepThread::verify_ok_to_terminate() const {
duke@435:   assert(!(CGC_lock->owned_by_self() || cms_thread_has_cms_token() ||
duke@435:            cms_thread_wants_cms_token()),
duke@435:          "Must renounce all worldly possessions and desires for nirvana");
duke@435:   _collector->verify_ok_to_terminate();
duke@435: }
duke@435: #endif
duke@435: 
duke@435: // create and start a new ConcurrentMarkSweep Thread for given CMS generation
duke@435: ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::start(CMSCollector* collector) {
duke@435:   if (!_should_terminate) {
duke@435:     assert(cmst() == NULL, "start() called twice?");
duke@435:     ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);
duke@435:     assert(cmst() == th, "Where did the just-created CMS thread go?");
duke@435:     return th;
duke@435:   }
duke@435:   return NULL;
duke@435: }
duke@435: 
duke@435: void ConcurrentMarkSweepThread::stop() {
duke@435:   if (CMSIncrementalMode) {
duke@435:     // Disable incremental mode and wake up the thread so it notices the change.
duke@435:     disable_icms();
duke@435:     start_icms();
duke@435:   }
duke@435:   // it is ok to take late safepoints here, if needed
duke@435:   {
duke@435:     MutexLockerEx x(Terminator_lock);
duke@435:     _should_terminate = true;
duke@435:   }
duke@435:   { // Now post a notify on CGC_lock so as to nudge
duke@435:     // CMS thread(s) that might be slumbering in
duke@435:     // sleepBeforeNextCycle.
duke@435:     MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
duke@435:     CGC_lock->notify_all();
duke@435:   }
duke@435:   { // Now wait until (all) CMS thread(s) have exited
duke@435:     MutexLockerEx x(Terminator_lock);
duke@435:     while(cmst() != NULL) {
duke@435:       Terminator_lock->wait();
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {
duke@435:   assert(tc != NULL, "Null ThreadClosure");
duke@435:   if (_cmst != NULL) {
duke@435:     tc->do_thread(_cmst);
duke@435:   }
duke@435:   assert(Universe::is_fully_initialized(),
duke@435:          "Called too early, make sure heap is fully initialized");
duke@435:   if (_collector != NULL) {
duke@435:     AbstractWorkGang* gang = _collector->conc_workers();
duke@435:     if (gang != NULL) {
duke@435:       gang->threads_do(tc);
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: void ConcurrentMarkSweepThread::print_on(outputStream* st) const {
duke@435:   st->print("\"%s\" ", name());
duke@435:   Thread::print_on(st);
duke@435:   st->cr();
duke@435: }
duke@435: 
duke@435: void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {
duke@435:   if (_cmst != NULL) {
duke@435:     _cmst->print_on(st);
dholmes@4077:     st->cr();
duke@435:   }
duke@435:   if (_collector != NULL) {
duke@435:     AbstractWorkGang* gang = _collector->conc_workers();
duke@435:     if (gang != NULL) {
duke@435:       gang->print_worker_threads_on(st);
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {
duke@435:   assert(UseConcMarkSweepGC, "just checking");
duke@435: 
duke@435:   MutexLockerEx x(CGC_lock,
duke@435:                   Mutex::_no_safepoint_check_flag);
duke@435:   if (!is_cms_thread) {
duke@435:     assert(Thread::current()->is_VM_thread(), "Not a VM thread");
duke@435:     CMSSynchronousYieldRequest yr;
duke@435:     while (CMS_flag_is_set(CMS_cms_has_token)) {
duke@435:       // indicate that we want to get the token
duke@435:       set_CMS_flag(CMS_vm_wants_token);
duke@435:       CGC_lock->wait(true);
duke@435:     }
duke@435:     // claim the token and proceed
duke@435:     clear_CMS_flag(CMS_vm_wants_token);
duke@435:     set_CMS_flag(CMS_vm_has_token);
duke@435:   } else {
duke@435:     assert(Thread::current()->is_ConcurrentGC_thread(),
duke@435:            "Not a CMS thread");
duke@435:     // The following barrier assumes there's only one CMS thread.
duke@435:     // This will need to be modified is there are more CMS threads than one.
duke@435:     while (CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token)) {
duke@435:       set_CMS_flag(CMS_cms_wants_token);
duke@435:       CGC_lock->wait(true);
duke@435:     }
duke@435:     // claim the token
duke@435:     clear_CMS_flag(CMS_cms_wants_token);
duke@435:     set_CMS_flag(CMS_cms_has_token);
duke@435:   }
duke@435: }
duke@435: 
duke@435: void ConcurrentMarkSweepThread::desynchronize(bool is_cms_thread) {
duke@435:   assert(UseConcMarkSweepGC, "just checking");
duke@435: 
duke@435:   MutexLockerEx x(CGC_lock,
duke@435:                   Mutex::_no_safepoint_check_flag);
duke@435:   if (!is_cms_thread) {
duke@435:     assert(Thread::current()->is_VM_thread(), "Not a VM thread");
duke@435:     assert(CMS_flag_is_set(CMS_vm_has_token), "just checking");
duke@435:     clear_CMS_flag(CMS_vm_has_token);
duke@435:     if (CMS_flag_is_set(CMS_cms_wants_token)) {
duke@435:       // wake-up a waiting CMS thread
duke@435:       CGC_lock->notify();
duke@435:     }
duke@435:     assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),
duke@435:            "Should have been cleared");
duke@435:   } else {
duke@435:     assert(Thread::current()->is_ConcurrentGC_thread(),
duke@435:            "Not a CMS thread");
duke@435:     assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");
duke@435:     clear_CMS_flag(CMS_cms_has_token);
duke@435:     if (CMS_flag_is_set(CMS_vm_wants_token)) {
duke@435:       // wake-up a waiting VM thread
duke@435:       CGC_lock->notify();
duke@435:     }
duke@435:     assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
duke@435:            "Should have been cleared");
duke@435:   }
duke@435: }
duke@435: 
jmasa@4679: // Wait until any cms_lock event
ysr@2242: void ConcurrentMarkSweepThread::wait_on_cms_lock(long t_millis) {
duke@435:   MutexLockerEx x(CGC_lock,
duke@435:                   Mutex::_no_safepoint_check_flag);
ysr@2242:   if (_should_terminate || _collector->_full_gc_requested) {
ysr@2242:     return;
ysr@2242:   }
duke@435:   set_CMS_flag(CMS_cms_wants_token);   // to provoke notifies
ysr@2242:   CGC_lock->wait(Mutex::_no_safepoint_check_flag, t_millis);
duke@435:   clear_CMS_flag(CMS_cms_wants_token);
duke@435:   assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
duke@435:          "Should not be set");
duke@435: }
duke@435: 
jmasa@4679: // Wait until the next synchronous GC, a concurrent full gc request,
jmasa@4679: // or a timeout, whichever is earlier.
jmasa@4679: void ConcurrentMarkSweepThread::wait_on_cms_lock_for_scavenge(long t_millis) {
jmasa@4679:   // Wait time in millis or 0 value representing infinite wait for a scavenge
jmasa@4679:   assert(t_millis >= 0, "Wait time for scavenge should be 0 or positive");
jmasa@4679: 
jmasa@4679:   GenCollectedHeap* gch = GenCollectedHeap::heap();
jmasa@4679:   double start_time_secs = os::elapsedTime();
jmasa@4679:   double end_time_secs = start_time_secs + (t_millis / ((double) MILLIUNITS));
jmasa@4679: 
jmasa@4679:   // Total collections count before waiting loop
jmasa@4679:   unsigned int before_count;
jmasa@4679:   {
jmasa@4679:     MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);
jmasa@4679:     before_count = gch->total_collections();
jmasa@4679:   }
jmasa@4679: 
jmasa@4679:   unsigned int loop_count = 0;
jmasa@4679: 
jmasa@4679:   while(!_should_terminate) {
jmasa@4679:     double now_time = os::elapsedTime();
jmasa@4679:     long wait_time_millis;
jmasa@4679: 
jmasa@4679:     if(t_millis != 0) {
jmasa@4679:       // New wait limit
jmasa@4679:       wait_time_millis = (long) ((end_time_secs - now_time) * MILLIUNITS);
jmasa@4679:       if(wait_time_millis <= 0) {
jmasa@4679:         // Wait time is over
jmasa@4679:         break;
jmasa@4679:       }
jmasa@4679:     } else {
jmasa@4679:       // No wait limit, wait if necessary forever
jmasa@4679:       wait_time_millis = 0;
jmasa@4679:     }
jmasa@4679: 
jmasa@4679:     // Wait until the next event or the remaining timeout
jmasa@4679:     {
jmasa@4679:       MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
jmasa@4679: 
jmasa@4679:       if (_should_terminate || _collector->_full_gc_requested) {
jmasa@4679:         return;
jmasa@4679:       }
jmasa@4679:       set_CMS_flag(CMS_cms_wants_token);   // to provoke notifies
jmasa@4679:       assert(t_millis == 0 || wait_time_millis > 0, "Sanity");
jmasa@4679:       CGC_lock->wait(Mutex::_no_safepoint_check_flag, wait_time_millis);
jmasa@4679:       clear_CMS_flag(CMS_cms_wants_token);
jmasa@4679:       assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
jmasa@4679:              "Should not be set");
jmasa@4679:     }
jmasa@4679: 
jmasa@4679:     // Extra wait time check before entering the heap lock to get the collection count
jmasa@4679:     if(t_millis != 0 && os::elapsedTime() >= end_time_secs) {
jmasa@4679:       // Wait time is over
jmasa@4679:       break;
jmasa@4679:     }
jmasa@4679: 
jmasa@4679:     // Total collections count after the event
jmasa@4679:     unsigned int after_count;
jmasa@4679:     {
jmasa@4679:       MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);
jmasa@4679:       after_count = gch->total_collections();
jmasa@4679:     }
jmasa@4679: 
jmasa@4679:     if(before_count != after_count) {
jmasa@4679:       // There was a collection - success
jmasa@4679:       break;
jmasa@4679:     }
jmasa@4679: 
jmasa@4679:     // Too many loops warning
jmasa@4679:     if(++loop_count == 0) {
jmasa@4679:       warning("wait_on_cms_lock_for_scavenge() has looped %u times", loop_count - 1);
jmasa@4679:     }
jmasa@4679:   }
jmasa@4679: }
jmasa@4679: 
duke@435: void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {
duke@435:   while (!_should_terminate) {
duke@435:     if (CMSIncrementalMode) {
duke@435:       icms_wait();
jmasa@4679:       if(CMSWaitDuration >= 0) {
jmasa@4679:         // Wait until the next synchronous GC, a concurrent full gc
jmasa@4679:         // request or a timeout, whichever is earlier.
jmasa@4679:         wait_on_cms_lock_for_scavenge(CMSWaitDuration);
jmasa@4679:       }
duke@435:       return;
duke@435:     } else {
jmasa@4679:       if(CMSWaitDuration >= 0) {
jmasa@4679:         // Wait until the next synchronous GC, a concurrent full gc
jmasa@4679:         // request or a timeout, whichever is earlier.
jmasa@4679:         wait_on_cms_lock_for_scavenge(CMSWaitDuration);
jmasa@4679:       } else {
jmasa@4679:         // Wait until any cms_lock event or check interval not to call shouldConcurrentCollect permanently
jmasa@4679:         wait_on_cms_lock(CMSCheckInterval);
jmasa@4679:       }
duke@435:     }
duke@435:     // Check if we should start a CMS collection cycle
duke@435:     if (_collector->shouldConcurrentCollect()) {
duke@435:       return;
duke@435:     }
duke@435:     // .. collection criterion not yet met, let's go back
duke@435:     // and wait some more
duke@435:   }
duke@435: }
duke@435: 
duke@435: // Incremental CMS
duke@435: void ConcurrentMarkSweepThread::start_icms() {
duke@435:   assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
duke@435:   MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
duke@435:   trace_state("start_icms");
duke@435:   _should_run = true;
duke@435:   iCMS_lock->notify_all();
duke@435: }
duke@435: 
duke@435: void ConcurrentMarkSweepThread::stop_icms() {
duke@435:   assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
duke@435:   MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
duke@435:   if (!_should_stop) {
duke@435:     trace_state("stop_icms");
duke@435:     _should_stop = true;
duke@435:     _should_run = false;
duke@435:     asynchronous_yield_request();
duke@435:     iCMS_lock->notify_all();
duke@435:   }
duke@435: }
duke@435: 
duke@435: void ConcurrentMarkSweepThread::icms_wait() {
duke@435:   assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
ysr@2647:   if (_should_stop && icms_is_enabled()) {
duke@435:     MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
duke@435:     trace_state("pause_icms");
duke@435:     _collector->stats().stop_cms_timer();
ysr@2647:     while(!_should_run && icms_is_enabled()) {
duke@435:       iCMS_lock->wait(Mutex::_no_safepoint_check_flag);
duke@435:     }
duke@435:     _collector->stats().start_cms_timer();
duke@435:     _should_stop = false;
duke@435:     trace_state("pause_icms end");
duke@435:   }
duke@435: }
duke@435: 
duke@435: // Note: this method, although exported by the ConcurrentMarkSweepThread,
duke@435: // which is a non-JavaThread, can only be called by a JavaThread.
duke@435: // Currently this is done at vm creation time (post-vm-init) by the
duke@435: // main/Primordial (Java)Thread.
duke@435: // XXX Consider changing this in the future to allow the CMS thread
duke@435: // itself to create this thread?
duke@435: void ConcurrentMarkSweepThread::makeSurrogateLockerThread(TRAPS) {
duke@435:   assert(UseConcMarkSweepGC, "SLT thread needed only for CMS GC");
duke@435:   assert(_slt == NULL, "SLT already created");
duke@435:   _slt = SurrogateLockerThread::make(THREAD);
duke@435: }