--- old/src/share/vm/gc_implementation/g1/concurrentMarkThread.cpp 2015-05-13 13:55:01.063562263 +0200 +++ /dev/null 2015-03-18 17:10:38.111854831 +0100 @@ -1,350 +0,0 @@ - /* - * Copyright (c) 2001, 2015, 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 - * or visit www.oracle.com if you need additional information or have any - * questions. - * - */ - -#include "precompiled.hpp" -#include "gc_implementation/g1/concurrentMarkThread.inline.hpp" -#include "gc_implementation/g1/g1CollectedHeap.inline.hpp" -#include "gc_implementation/g1/g1CollectorPolicy.hpp" -#include "gc_implementation/g1/g1Log.hpp" -#include "gc_implementation/g1/g1MMUTracker.hpp" -#include "gc_implementation/g1/vm_operations_g1.hpp" -#include "gc_implementation/shared/gcTrace.hpp" -#include "memory/resourceArea.hpp" -#include "runtime/vmThread.hpp" - -// ======= Concurrent Mark Thread ======== - -// The CM thread is created when the G1 garbage collector is used - -SurrogateLockerThread* - ConcurrentMarkThread::_slt = NULL; - -ConcurrentMarkThread::ConcurrentMarkThread(ConcurrentMark* cm) : - ConcurrentGCThread(), - _cm(cm), - _started(false), - _in_progress(false), - _vtime_accum(0.0), - _vtime_mark_accum(0.0) { - - set_name("G1 Main Marker"); - create_and_start(); -} - -class CMCheckpointRootsFinalClosure: public VoidClosure { - - ConcurrentMark* _cm; -public: - - CMCheckpointRootsFinalClosure(ConcurrentMark* cm) : - _cm(cm) {} - - void do_void(){ - _cm->checkpointRootsFinal(false); // !clear_all_soft_refs - } -}; - -class CMCleanUp: public VoidClosure { - ConcurrentMark* _cm; -public: - - CMCleanUp(ConcurrentMark* cm) : - _cm(cm) {} - - void do_void(){ - _cm->cleanup(); - } -}; - - - -void ConcurrentMarkThread::run() { - initialize_in_thread(); - _vtime_start = os::elapsedVTime(); - wait_for_universe_init(); - - G1CollectedHeap* g1h = G1CollectedHeap::heap(); - G1CollectorPolicy* g1_policy = g1h->g1_policy(); - G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker(); - Thread *current_thread = Thread::current(); - - while (!_should_terminate) { - // wait until started is set. - sleepBeforeNextCycle(); - if (_should_terminate) { - break; - } - - { - ResourceMark rm; - HandleMark hm; - double cycle_start = os::elapsedVTime(); - - // We have to ensure that we finish scanning the root regions - // before the next GC takes place. To ensure this we have to - // make sure that we do not join the STS until the root regions - // have been scanned. If we did then it's possible that a - // subsequent GC could block us from joining the STS and proceed - // without the root regions have been scanned which would be a - // correctness issue. - - double scan_start = os::elapsedTime(); - if (!cm()->has_aborted()) { - if (G1Log::fine()) { - gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); - gclog_or_tty->print_cr("[GC concurrent-root-region-scan-start]"); - } - - _cm->scanRootRegions(); - - double scan_end = os::elapsedTime(); - if (G1Log::fine()) { - gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); - gclog_or_tty->print_cr("[GC concurrent-root-region-scan-end, %1.7lf secs]", - scan_end - scan_start); - } - } - - double mark_start_sec = os::elapsedTime(); - if (G1Log::fine()) { - gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); - gclog_or_tty->print_cr("[GC concurrent-mark-start]"); - } - - int iter = 0; - do { - iter++; - if (!cm()->has_aborted()) { - _cm->markFromRoots(); - } - - double mark_end_time = os::elapsedVTime(); - double mark_end_sec = os::elapsedTime(); - _vtime_mark_accum += (mark_end_time - cycle_start); - if (!cm()->has_aborted()) { - if (g1_policy->adaptive_young_list_length()) { - double now = os::elapsedTime(); - double remark_prediction_ms = g1_policy->predict_remark_time_ms(); - jlong sleep_time_ms = mmu_tracker->when_ms(now, remark_prediction_ms); - os::sleep(current_thread, sleep_time_ms, false); - } - - if (G1Log::fine()) { - gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); - gclog_or_tty->print_cr("[GC concurrent-mark-end, %1.7lf secs]", - mark_end_sec - mark_start_sec); - } - - CMCheckpointRootsFinalClosure final_cl(_cm); - VM_CGC_Operation op(&final_cl, "GC remark", true /* needs_pll */); - VMThread::execute(&op); - } - if (cm()->restart_for_overflow()) { - if (G1TraceMarkStackOverflow) { - gclog_or_tty->print_cr("Restarting conc marking because of MS overflow " - "in remark (restart #%d).", iter); - } - if (G1Log::fine()) { - gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); - gclog_or_tty->print_cr("[GC concurrent-mark-restart-for-overflow]"); - } - } - } while (cm()->restart_for_overflow()); - - double end_time = os::elapsedVTime(); - // Update the total virtual time before doing this, since it will try - // to measure it to get the vtime for this marking. We purposely - // neglect the presumably-short "completeCleanup" phase here. - _vtime_accum = (end_time - _vtime_start); - - if (!cm()->has_aborted()) { - if (g1_policy->adaptive_young_list_length()) { - double now = os::elapsedTime(); - double cleanup_prediction_ms = g1_policy->predict_cleanup_time_ms(); - jlong sleep_time_ms = mmu_tracker->when_ms(now, cleanup_prediction_ms); - os::sleep(current_thread, sleep_time_ms, false); - } - - CMCleanUp cl_cl(_cm); - VM_CGC_Operation op(&cl_cl, "GC cleanup", false /* needs_pll */); - VMThread::execute(&op); - } else { - // We don't want to update the marking status if a GC pause - // is already underway. - SuspendibleThreadSetJoiner sts_join; - g1h->set_marking_complete(); - } - - // Check if cleanup set the free_regions_coming flag. If it - // hasn't, we can just skip the next step. - if (g1h->free_regions_coming()) { - // The following will finish freeing up any regions that we - // found to be empty during cleanup. We'll do this part - // without joining the suspendible set. If an evacuation pause - // takes place, then we would carry on freeing regions in - // case they are needed by the pause. If a Full GC takes - // place, it would wait for us to process the regions - // reclaimed by cleanup. - - double cleanup_start_sec = os::elapsedTime(); - if (G1Log::fine()) { - gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); - gclog_or_tty->print_cr("[GC concurrent-cleanup-start]"); - } - - // Now do the concurrent cleanup operation. - _cm->completeCleanup(); - - // Notify anyone who's waiting that there are no more free - // regions coming. We have to do this before we join the STS - // (in fact, we should not attempt to join the STS in the - // interval between finishing the cleanup pause and clearing - // the free_regions_coming flag) otherwise we might deadlock: - // a GC worker could be blocked waiting for the notification - // whereas this thread will be blocked for the pause to finish - // while it's trying to join the STS, which is conditional on - // the GC workers finishing. - g1h->reset_free_regions_coming(); - - double cleanup_end_sec = os::elapsedTime(); - if (G1Log::fine()) { - gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); - gclog_or_tty->print_cr("[GC concurrent-cleanup-end, %1.7lf secs]", - cleanup_end_sec - cleanup_start_sec); - } - } - guarantee(cm()->cleanup_list_is_empty(), - "at this point there should be no regions on the cleanup list"); - - // There is a tricky race before recording that the concurrent - // cleanup has completed and a potential Full GC starting around - // the same time. We want to make sure that the Full GC calls - // abort() on concurrent mark after - // record_concurrent_mark_cleanup_completed(), since abort() is - // the method that will reset the concurrent mark state. If we - // end up calling record_concurrent_mark_cleanup_completed() - // after abort() then we might incorrectly undo some of the work - // abort() did. Checking the has_aborted() flag after joining - // the STS allows the correct ordering of the two methods. There - // are two scenarios: - // - // a) If we reach here before the Full GC, the fact that we have - // joined the STS means that the Full GC cannot start until we - // leave the STS, so record_concurrent_mark_cleanup_completed() - // will complete before abort() is called. - // - // b) If we reach here during the Full GC, we'll be held up from - // joining the STS until the Full GC is done, which means that - // abort() will have completed and has_aborted() will return - // true to prevent us from calling - // record_concurrent_mark_cleanup_completed() (and, in fact, it's - // not needed any more as the concurrent mark state has been - // already reset). - { - SuspendibleThreadSetJoiner sts_join; - if (!cm()->has_aborted()) { - g1_policy->record_concurrent_mark_cleanup_completed(); - } - } - - if (cm()->has_aborted()) { - if (G1Log::fine()) { - gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); - gclog_or_tty->print_cr("[GC concurrent-mark-abort]"); - } - } - - // We now want to allow clearing of the marking bitmap to be - // suspended by a collection pause. - // We may have aborted just before the remark. Do not bother clearing the - // bitmap then, as it has been done during mark abort. - if (!cm()->has_aborted()) { - _cm->clearNextBitmap(); - } else { - assert(!G1VerifyBitmaps || _cm->nextMarkBitmapIsClear(), "Next mark bitmap must be clear"); - } - } - - // Update the number of full collections that have been - // completed. This will also notify the FullGCCount_lock in case a - // Java thread is waiting for a full GC to happen (e.g., it - // called System.gc() with +ExplicitGCInvokesConcurrent). - { - SuspendibleThreadSetJoiner sts_join; - g1h->increment_old_marking_cycles_completed(true /* concurrent */); - g1h->register_concurrent_cycle_end(); - } - } - assert(_should_terminate, "just checking"); - - terminate(); -} - -void ConcurrentMarkThread::stop() { - { - MutexLockerEx ml(Terminator_lock); - _should_terminate = true; - } - - { - MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag); - CGC_lock->notify_all(); - } - - { - MutexLockerEx ml(Terminator_lock); - while (!_has_terminated) { - Terminator_lock->wait(); - } - } -} - -void ConcurrentMarkThread::sleepBeforeNextCycle() { - // We join here because we don't want to do the "shouldConcurrentMark()" - // below while the world is otherwise stopped. - assert(!in_progress(), "should have been cleared"); - - MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); - while (!started() && !_should_terminate) { - CGC_lock->wait(Mutex::_no_safepoint_check_flag); - } - - if (started()) { - set_in_progress(); - clear_started(); - } -} - -// Note: As is the case with CMS - this method, although exported -// by the ConcurrentMarkThread, 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 CM thread -// itself to create this thread? -void ConcurrentMarkThread::makeSurrogateLockerThread(TRAPS) { - assert(UseG1GC, "SLT thread needed only for concurrent GC"); - assert(THREAD->is_Java_thread(), "must be a Java thread"); - assert(_slt == NULL, "SLT already created"); - _slt = SurrogateLockerThread::make(THREAD); -} --- /dev/null 2015-03-18 17:10:38.111854831 +0100 +++ new/src/share/vm/gc/g1/concurrentMarkThread.cpp 2015-05-13 13:55:00.892555167 +0200 @@ -0,0 +1,350 @@ + /* + * Copyright (c) 2001, 2015, 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 + * or visit www.oracle.com if you need additional information or have any + * questions. + * + */ + +#include "precompiled.hpp" +#include "gc/g1/concurrentMarkThread.inline.hpp" +#include "gc/g1/g1CollectedHeap.inline.hpp" +#include "gc/g1/g1CollectorPolicy.hpp" +#include "gc/g1/g1Log.hpp" +#include "gc/g1/g1MMUTracker.hpp" +#include "gc/g1/vm_operations_g1.hpp" +#include "gc/shared/gcTrace.hpp" +#include "memory/resourceArea.hpp" +#include "runtime/vmThread.hpp" + +// ======= Concurrent Mark Thread ======== + +// The CM thread is created when the G1 garbage collector is used + +SurrogateLockerThread* + ConcurrentMarkThread::_slt = NULL; + +ConcurrentMarkThread::ConcurrentMarkThread(ConcurrentMark* cm) : + ConcurrentGCThread(), + _cm(cm), + _started(false), + _in_progress(false), + _vtime_accum(0.0), + _vtime_mark_accum(0.0) { + + set_name("G1 Main Marker"); + create_and_start(); +} + +class CMCheckpointRootsFinalClosure: public VoidClosure { + + ConcurrentMark* _cm; +public: + + CMCheckpointRootsFinalClosure(ConcurrentMark* cm) : + _cm(cm) {} + + void do_void(){ + _cm->checkpointRootsFinal(false); // !clear_all_soft_refs + } +}; + +class CMCleanUp: public VoidClosure { + ConcurrentMark* _cm; +public: + + CMCleanUp(ConcurrentMark* cm) : + _cm(cm) {} + + void do_void(){ + _cm->cleanup(); + } +}; + + + +void ConcurrentMarkThread::run() { + initialize_in_thread(); + _vtime_start = os::elapsedVTime(); + wait_for_universe_init(); + + G1CollectedHeap* g1h = G1CollectedHeap::heap(); + G1CollectorPolicy* g1_policy = g1h->g1_policy(); + G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker(); + Thread *current_thread = Thread::current(); + + while (!_should_terminate) { + // wait until started is set. + sleepBeforeNextCycle(); + if (_should_terminate) { + break; + } + + { + ResourceMark rm; + HandleMark hm; + double cycle_start = os::elapsedVTime(); + + // We have to ensure that we finish scanning the root regions + // before the next GC takes place. To ensure this we have to + // make sure that we do not join the STS until the root regions + // have been scanned. If we did then it's possible that a + // subsequent GC could block us from joining the STS and proceed + // without the root regions have been scanned which would be a + // correctness issue. + + double scan_start = os::elapsedTime(); + if (!cm()->has_aborted()) { + if (G1Log::fine()) { + gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); + gclog_or_tty->print_cr("[GC concurrent-root-region-scan-start]"); + } + + _cm->scanRootRegions(); + + double scan_end = os::elapsedTime(); + if (G1Log::fine()) { + gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); + gclog_or_tty->print_cr("[GC concurrent-root-region-scan-end, %1.7lf secs]", + scan_end - scan_start); + } + } + + double mark_start_sec = os::elapsedTime(); + if (G1Log::fine()) { + gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); + gclog_or_tty->print_cr("[GC concurrent-mark-start]"); + } + + int iter = 0; + do { + iter++; + if (!cm()->has_aborted()) { + _cm->markFromRoots(); + } + + double mark_end_time = os::elapsedVTime(); + double mark_end_sec = os::elapsedTime(); + _vtime_mark_accum += (mark_end_time - cycle_start); + if (!cm()->has_aborted()) { + if (g1_policy->adaptive_young_list_length()) { + double now = os::elapsedTime(); + double remark_prediction_ms = g1_policy->predict_remark_time_ms(); + jlong sleep_time_ms = mmu_tracker->when_ms(now, remark_prediction_ms); + os::sleep(current_thread, sleep_time_ms, false); + } + + if (G1Log::fine()) { + gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); + gclog_or_tty->print_cr("[GC concurrent-mark-end, %1.7lf secs]", + mark_end_sec - mark_start_sec); + } + + CMCheckpointRootsFinalClosure final_cl(_cm); + VM_CGC_Operation op(&final_cl, "GC remark", true /* needs_pll */); + VMThread::execute(&op); + } + if (cm()->restart_for_overflow()) { + if (G1TraceMarkStackOverflow) { + gclog_or_tty->print_cr("Restarting conc marking because of MS overflow " + "in remark (restart #%d).", iter); + } + if (G1Log::fine()) { + gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); + gclog_or_tty->print_cr("[GC concurrent-mark-restart-for-overflow]"); + } + } + } while (cm()->restart_for_overflow()); + + double end_time = os::elapsedVTime(); + // Update the total virtual time before doing this, since it will try + // to measure it to get the vtime for this marking. We purposely + // neglect the presumably-short "completeCleanup" phase here. + _vtime_accum = (end_time - _vtime_start); + + if (!cm()->has_aborted()) { + if (g1_policy->adaptive_young_list_length()) { + double now = os::elapsedTime(); + double cleanup_prediction_ms = g1_policy->predict_cleanup_time_ms(); + jlong sleep_time_ms = mmu_tracker->when_ms(now, cleanup_prediction_ms); + os::sleep(current_thread, sleep_time_ms, false); + } + + CMCleanUp cl_cl(_cm); + VM_CGC_Operation op(&cl_cl, "GC cleanup", false /* needs_pll */); + VMThread::execute(&op); + } else { + // We don't want to update the marking status if a GC pause + // is already underway. + SuspendibleThreadSetJoiner sts_join; + g1h->set_marking_complete(); + } + + // Check if cleanup set the free_regions_coming flag. If it + // hasn't, we can just skip the next step. + if (g1h->free_regions_coming()) { + // The following will finish freeing up any regions that we + // found to be empty during cleanup. We'll do this part + // without joining the suspendible set. If an evacuation pause + // takes place, then we would carry on freeing regions in + // case they are needed by the pause. If a Full GC takes + // place, it would wait for us to process the regions + // reclaimed by cleanup. + + double cleanup_start_sec = os::elapsedTime(); + if (G1Log::fine()) { + gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); + gclog_or_tty->print_cr("[GC concurrent-cleanup-start]"); + } + + // Now do the concurrent cleanup operation. + _cm->completeCleanup(); + + // Notify anyone who's waiting that there are no more free + // regions coming. We have to do this before we join the STS + // (in fact, we should not attempt to join the STS in the + // interval between finishing the cleanup pause and clearing + // the free_regions_coming flag) otherwise we might deadlock: + // a GC worker could be blocked waiting for the notification + // whereas this thread will be blocked for the pause to finish + // while it's trying to join the STS, which is conditional on + // the GC workers finishing. + g1h->reset_free_regions_coming(); + + double cleanup_end_sec = os::elapsedTime(); + if (G1Log::fine()) { + gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); + gclog_or_tty->print_cr("[GC concurrent-cleanup-end, %1.7lf secs]", + cleanup_end_sec - cleanup_start_sec); + } + } + guarantee(cm()->cleanup_list_is_empty(), + "at this point there should be no regions on the cleanup list"); + + // There is a tricky race before recording that the concurrent + // cleanup has completed and a potential Full GC starting around + // the same time. We want to make sure that the Full GC calls + // abort() on concurrent mark after + // record_concurrent_mark_cleanup_completed(), since abort() is + // the method that will reset the concurrent mark state. If we + // end up calling record_concurrent_mark_cleanup_completed() + // after abort() then we might incorrectly undo some of the work + // abort() did. Checking the has_aborted() flag after joining + // the STS allows the correct ordering of the two methods. There + // are two scenarios: + // + // a) If we reach here before the Full GC, the fact that we have + // joined the STS means that the Full GC cannot start until we + // leave the STS, so record_concurrent_mark_cleanup_completed() + // will complete before abort() is called. + // + // b) If we reach here during the Full GC, we'll be held up from + // joining the STS until the Full GC is done, which means that + // abort() will have completed and has_aborted() will return + // true to prevent us from calling + // record_concurrent_mark_cleanup_completed() (and, in fact, it's + // not needed any more as the concurrent mark state has been + // already reset). + { + SuspendibleThreadSetJoiner sts_join; + if (!cm()->has_aborted()) { + g1_policy->record_concurrent_mark_cleanup_completed(); + } + } + + if (cm()->has_aborted()) { + if (G1Log::fine()) { + gclog_or_tty->gclog_stamp(cm()->concurrent_gc_id()); + gclog_or_tty->print_cr("[GC concurrent-mark-abort]"); + } + } + + // We now want to allow clearing of the marking bitmap to be + // suspended by a collection pause. + // We may have aborted just before the remark. Do not bother clearing the + // bitmap then, as it has been done during mark abort. + if (!cm()->has_aborted()) { + _cm->clearNextBitmap(); + } else { + assert(!G1VerifyBitmaps || _cm->nextMarkBitmapIsClear(), "Next mark bitmap must be clear"); + } + } + + // Update the number of full collections that have been + // completed. This will also notify the FullGCCount_lock in case a + // Java thread is waiting for a full GC to happen (e.g., it + // called System.gc() with +ExplicitGCInvokesConcurrent). + { + SuspendibleThreadSetJoiner sts_join; + g1h->increment_old_marking_cycles_completed(true /* concurrent */); + g1h->register_concurrent_cycle_end(); + } + } + assert(_should_terminate, "just checking"); + + terminate(); +} + +void ConcurrentMarkThread::stop() { + { + MutexLockerEx ml(Terminator_lock); + _should_terminate = true; + } + + { + MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag); + CGC_lock->notify_all(); + } + + { + MutexLockerEx ml(Terminator_lock); + while (!_has_terminated) { + Terminator_lock->wait(); + } + } +} + +void ConcurrentMarkThread::sleepBeforeNextCycle() { + // We join here because we don't want to do the "shouldConcurrentMark()" + // below while the world is otherwise stopped. + assert(!in_progress(), "should have been cleared"); + + MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag); + while (!started() && !_should_terminate) { + CGC_lock->wait(Mutex::_no_safepoint_check_flag); + } + + if (started()) { + set_in_progress(); + clear_started(); + } +} + +// Note: As is the case with CMS - this method, although exported +// by the ConcurrentMarkThread, 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 CM thread +// itself to create this thread? +void ConcurrentMarkThread::makeSurrogateLockerThread(TRAPS) { + assert(UseG1GC, "SLT thread needed only for concurrent GC"); + assert(THREAD->is_Java_thread(), "must be a Java thread"); + assert(_slt == NULL, "SLT already created"); + _slt = SurrogateLockerThread::make(THREAD); +}