/*
* Copyright (c) 2013, 2019, Red Hat, Inc. All rights reserved.
*
* 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 "classfile/symbolTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "code/codeCache.hpp"
#include "gc/shared/weakProcessor.inline.hpp"
#include "gc/shared/gcTimer.hpp"
#include "gc/shared/referenceProcessor.hpp"
#include "gc/shared/referenceProcessorPhaseTimes.hpp"
#include "gc/shared/strongRootsScope.hpp"
#include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
#include "gc/shenandoah/shenandoahClosures.inline.hpp"
#include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
#include "gc/shenandoah/shenandoahMarkCompact.hpp"
#include "gc/shenandoah/shenandoahHeap.inline.hpp"
#include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
#include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
#include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
#include "gc/shenandoah/shenandoahTimingTracker.hpp"
#include "gc/shenandoah/shenandoahUtils.hpp"
#include "memory/iterator.inline.hpp"
#include "memory/metaspace.hpp"
#include "memory/resourceArea.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/handles.inline.hpp"
template<UpdateRefsMode UPDATE_REFS>
class ShenandoahInitMarkRootsClosure : public OopClosure {
private:
ShenandoahObjToScanQueue* _queue;
ShenandoahHeap* _heap;
ShenandoahMarkingContext* const _mark_context;
template <class T>
inline void do_oop_work(T* p) {
ShenandoahConcurrentMark::mark_through_ref<T, UPDATE_REFS, NO_DEDUP>(p, _heap, _queue, _mark_context);
}
public:
ShenandoahInitMarkRootsClosure(ShenandoahObjToScanQueue* q) :
_queue(q),
_heap(ShenandoahHeap::heap()),
_mark_context(_heap->marking_context()) {};
void do_oop(narrowOop* p) { do_oop_work(p); }
void do_oop(oop* p) { do_oop_work(p); }
};
ShenandoahMarkRefsSuperClosure::ShenandoahMarkRefsSuperClosure(ShenandoahObjToScanQueue* q, ReferenceProcessor* rp) :
MetadataVisitingOopIterateClosure(rp),
_queue(q),
_heap(ShenandoahHeap::heap()),
_mark_context(_heap->marking_context())
{ }
template<UpdateRefsMode UPDATE_REFS>
class ShenandoahInitMarkRootsTask : public AbstractGangTask {
private:
ShenandoahAllRootScanner* _rp;
bool _process_refs;
public:
ShenandoahInitMarkRootsTask(ShenandoahAllRootScanner* rp, bool process_refs) :
AbstractGangTask("Shenandoah init mark roots task"),
_rp(rp),
_process_refs(process_refs) {
}
void work(uint worker_id) {
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
ShenandoahParallelWorkerSession worker_session(worker_id);
ShenandoahHeap* heap = ShenandoahHeap::heap();
ShenandoahObjToScanQueueSet* queues = heap->concurrent_mark()->task_queues();
assert(queues->get_reserved() > worker_id, "Queue has not been reserved for worker id: %d", worker_id);
ShenandoahObjToScanQueue* q = queues->queue(worker_id);
ShenandoahInitMarkRootsClosure<UPDATE_REFS> mark_cl(q);
do_work(heap, &mark_cl, worker_id);
}
private:
void do_work(ShenandoahHeap* heap, OopClosure* oops, uint worker_id) {
// The rationale for selecting the roots to scan is as follows:
// a. With unload_classes = true, we only want to scan the actual strong roots from the
// code cache. This will allow us to identify the dead classes, unload them, *and*
// invalidate the relevant code cache blobs. This could be only done together with
// class unloading.
// b. With unload_classes = false, we have to nominally retain all the references from code
// cache, because there could be the case of embedded class/oop in the generated code,
// which we will never visit during mark. Without code cache invalidation, as in (a),
// we risk executing that code cache blob, and crashing.
if (heap->unload_classes()) {
_rp->strong_roots_do(worker_id, oops);
} else {
_rp->roots_do(worker_id, oops);
}
}
};
class ShenandoahUpdateRootsTask : public AbstractGangTask {
private:
ShenandoahRootUpdater* _root_updater;
public:
ShenandoahUpdateRootsTask(ShenandoahRootUpdater* root_updater) :
AbstractGangTask("Shenandoah update roots task"),
_root_updater(root_updater) {
}
void work(uint worker_id) {
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
ShenandoahParallelWorkerSession worker_session(worker_id);
ShenandoahHeap* heap = ShenandoahHeap::heap();
ShenandoahUpdateRefsClosure cl;
AlwaysTrueClosure always_true;
_root_updater->roots_do<AlwaysTrueClosure, ShenandoahUpdateRefsClosure>(worker_id, &always_true, &cl);
}
};
class ShenandoahConcurrentMarkingTask : public AbstractGangTask {
private:
ShenandoahConcurrentMark* _cm;
ShenandoahTaskTerminator* _terminator;
public:
ShenandoahConcurrentMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator) :
AbstractGangTask("Root Region Scan"), _cm(cm), _terminator(terminator) {
}
void work(uint worker_id) {
ShenandoahHeap* heap = ShenandoahHeap::heap();
ShenandoahConcurrentWorkerSession worker_session(worker_id);
ShenandoahSuspendibleThreadSetJoiner stsj(ShenandoahSuspendibleWorkers);
ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
ReferenceProcessor* rp;
if (heap->process_references()) {
rp = heap->ref_processor();
shenandoah_assert_rp_isalive_installed();
} else {
rp = NULL;
}
_cm->concurrent_scan_code_roots(worker_id, rp);
_cm->mark_loop(worker_id, _terminator, rp,
true, // cancellable
ShenandoahStringDedup::is_enabled()); // perform string dedup
}
};
class ShenandoahSATBThreadsClosure : public ThreadClosure {
private:
ShenandoahSATBBufferClosure* _satb_cl;
uintx _claim_token;
public:
ShenandoahSATBThreadsClosure(ShenandoahSATBBufferClosure* satb_cl) :
_satb_cl(satb_cl),
_claim_token(Threads::thread_claim_token()) {}
void do_thread(Thread* thread) {
if (thread->claim_threads_do(true, _claim_token)) {
ShenandoahThreadLocalData::satb_mark_queue(thread).apply_closure_and_empty(_satb_cl);
}
}
};
class ShenandoahFinalMarkingTask : public AbstractGangTask {
private:
ShenandoahConcurrentMark* _cm;
ShenandoahTaskTerminator* _terminator;
bool _dedup_string;
public:
ShenandoahFinalMarkingTask(ShenandoahConcurrentMark* cm, ShenandoahTaskTerminator* terminator, bool dedup_string) :
AbstractGangTask("Shenandoah Final Marking"), _cm(cm), _terminator(terminator), _dedup_string(dedup_string) {
}
void work(uint worker_id) {
ShenandoahHeap* heap = ShenandoahHeap::heap();
ShenandoahParallelWorkerSession worker_session(worker_id);
// First drain remaining SATB buffers.
// Notice that this is not strictly necessary for mark-compact. But since
// it requires a StrongRootsScope around the task, we need to claim the
// threads, and performance-wise it doesn't really matter. Adds about 1ms to
// full-gc.
{
ShenandoahObjToScanQueue* q = _cm->get_queue(worker_id);
ShenandoahSATBBufferClosure cl(q);
SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
while (satb_mq_set.apply_closure_to_completed_buffer(&cl));
ShenandoahSATBThreadsClosure tc(&cl);
Threads::threads_do(&tc);
}
ReferenceProcessor* rp;
if (heap->process_references()) {
rp = heap->ref_processor();
shenandoah_assert_rp_isalive_installed();
} else {
rp = NULL;
}
if (heap->is_degenerated_gc_in_progress()) {
// Degenerated cycle may bypass concurrent cycle, so code roots might not be scanned,
// let's check here.
_cm->concurrent_scan_code_roots(worker_id, rp);
}
_cm->mark_loop(worker_id, _terminator, rp,
false, // not cancellable
_dedup_string);
assert(_cm->task_queues()->is_empty(), "Should be empty");
}
};
void ShenandoahConcurrentMark::mark_roots(ShenandoahPhaseTimings::Phase root_phase) {
assert(Thread::current()->is_VM_thread(), "can only do this in VMThread");
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
ShenandoahHeap* heap = ShenandoahHeap::heap();
ShenandoahGCPhase phase(root_phase);
WorkGang* workers = heap->workers();
uint nworkers = workers->active_workers();
assert(nworkers <= task_queues()->size(), "Just check");
ShenandoahAllRootScanner root_proc(nworkers, root_phase);
TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
task_queues()->reserve(nworkers);
if (heap->has_forwarded_objects()) {
ShenandoahInitMarkRootsTask<RESOLVE> mark_roots(&root_proc, _heap->process_references());
workers->run_task(&mark_roots);
} else {
// No need to update references, which means the heap is stable.
// Can save time not walking through forwarding pointers.
ShenandoahInitMarkRootsTask<NONE> mark_roots(&root_proc, _heap->process_references());
workers->run_task(&mark_roots);
}
if (ShenandoahConcurrentScanCodeRoots) {
clear_claim_codecache();
}
}
void ShenandoahConcurrentMark::update_roots(ShenandoahPhaseTimings::Phase root_phase) {
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
assert(root_phase == ShenandoahPhaseTimings::full_gc_roots ||
root_phase == ShenandoahPhaseTimings::degen_gc_update_roots,
"Only for these phases");
ShenandoahGCPhase phase(root_phase);
#if COMPILER2_OR_JVMCI
DerivedPointerTable::clear();
#endif
uint nworkers = _heap->workers()->active_workers();
ShenandoahRootUpdater root_updater(nworkers, root_phase);
ShenandoahUpdateRootsTask update_roots(&root_updater);
_heap->workers()->run_task(&update_roots);
#if COMPILER2_OR_JVMCI
DerivedPointerTable::update_pointers();
#endif
}
class ShenandoahUpdateThreadRootsTask : public AbstractGangTask {
private:
ShenandoahThreadRoots _thread_roots;
ShenandoahPhaseTimings::Phase _phase;
public:
ShenandoahUpdateThreadRootsTask(bool is_par, ShenandoahPhaseTimings::Phase phase) :
AbstractGangTask("Shenandoah Update Thread Roots"),
_thread_roots(is_par),
_phase(phase) {
ShenandoahHeap::heap()->phase_timings()->record_workers_start(_phase);
}
~ShenandoahUpdateThreadRootsTask() {
ShenandoahHeap::heap()->phase_timings()->record_workers_end(_phase);
}
void work(uint worker_id) {
ShenandoahUpdateRefsClosure cl;
_thread_roots.oops_do(&cl, NULL, worker_id);
}
};
void ShenandoahConcurrentMark::update_thread_roots(ShenandoahPhaseTimings::Phase root_phase) {
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
ShenandoahGCPhase phase(root_phase);
#if COMPILER2_OR_JVMCI
DerivedPointerTable::clear();
#endif
WorkGang* workers = _heap->workers();
bool is_par = workers->active_workers() > 1;
ShenandoahUpdateThreadRootsTask task(is_par, root_phase);
workers->run_task(&task);
#if COMPILER2_OR_JVMCI
DerivedPointerTable::update_pointers();
#endif
}
void ShenandoahConcurrentMark::initialize(uint workers) {
_heap = ShenandoahHeap::heap();
uint num_queues = MAX2(workers, 1U);
_task_queues = new ShenandoahObjToScanQueueSet((int) num_queues);
for (uint i = 0; i < num_queues; ++i) {
ShenandoahObjToScanQueue* task_queue = new ShenandoahObjToScanQueue();
task_queue->initialize();
_task_queues->register_queue(i, task_queue);
}
}
void ShenandoahConcurrentMark::concurrent_scan_code_roots(uint worker_id, ReferenceProcessor* rp) {
if (ShenandoahConcurrentScanCodeRoots && claim_codecache()) {
ShenandoahObjToScanQueue* q = task_queues()->queue(worker_id);
if (!_heap->unload_classes()) {
MutexLocker mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
// TODO: We can not honor StringDeduplication here, due to lock ranking
// inversion. So, we may miss some deduplication candidates.
if (_heap->has_forwarded_objects()) {
ShenandoahMarkResolveRefsClosure cl(q, rp);
CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
CodeCache::blobs_do(&blobs);
} else {
ShenandoahMarkRefsClosure cl(q, rp);
CodeBlobToOopClosure blobs(&cl, !CodeBlobToOopClosure::FixRelocations);
CodeCache::blobs_do(&blobs);
}
}
}
}
void ShenandoahConcurrentMark::mark_from_roots() {
WorkGang* workers = _heap->workers();
uint nworkers = workers->active_workers();
ShenandoahGCPhase conc_mark_phase(ShenandoahPhaseTimings::conc_mark);
if (_heap->process_references()) {
ReferenceProcessor* rp = _heap->ref_processor();
rp->set_active_mt_degree(nworkers);
// enable ("weak") refs discovery
rp->enable_discovery(true /*verify_no_refs*/);
rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
}
shenandoah_assert_rp_isalive_not_installed();
ShenandoahIsAliveSelector is_alive;
ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
task_queues()->reserve(nworkers);
{
ShenandoahTerminationTracker term(ShenandoahPhaseTimings::conc_termination);
ShenandoahTaskTerminator terminator(nworkers, task_queues());
ShenandoahConcurrentMarkingTask task(this, &terminator);
workers->run_task(&task);
}
assert(task_queues()->is_empty() || _heap->cancelled_gc(), "Should be empty when not cancelled");
}
void ShenandoahConcurrentMark::finish_mark_from_roots(bool full_gc) {
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
uint nworkers = _heap->workers()->active_workers();
// Finally mark everything else we've got in our queues during the previous steps.
// It does two different things for concurrent vs. mark-compact GC:
// - For concurrent GC, it starts with empty task queues, drains the remaining
// SATB buffers, and then completes the marking closure.
// - For mark-compact GC, it starts out with the task queues seeded by initial
// root scan, and completes the closure, thus marking through all live objects
// The implementation is the same, so it's shared here.
{
ShenandoahGCPhase phase(full_gc ?
ShenandoahPhaseTimings::full_gc_mark_finish_queues :
ShenandoahPhaseTimings::finish_queues);
task_queues()->reserve(nworkers);
shenandoah_assert_rp_isalive_not_installed();
ShenandoahIsAliveSelector is_alive;
ReferenceProcessorIsAliveMutator fix_isalive(_heap->ref_processor(), is_alive.is_alive_closure());
ShenandoahTerminationTracker termination_tracker(full_gc ?
ShenandoahPhaseTimings::full_gc_mark_termination :
ShenandoahPhaseTimings::termination);
StrongRootsScope scope(nworkers);
ShenandoahTaskTerminator terminator(nworkers, task_queues());
ShenandoahFinalMarkingTask task(this, &terminator, ShenandoahStringDedup::is_enabled());
_heap->workers()->run_task(&task);
}
assert(task_queues()->is_empty(), "Should be empty");
// When we're done marking everything, we process weak references.
if (_heap->process_references()) {
weak_refs_work(full_gc);
}
_heap->parallel_cleaning(full_gc);
assert(task_queues()->is_empty(), "Should be empty");
TASKQUEUE_STATS_ONLY(task_queues()->print_taskqueue_stats());
TASKQUEUE_STATS_ONLY(task_queues()->reset_taskqueue_stats());
}
// Weak Reference Closures
class ShenandoahCMDrainMarkingStackClosure: public VoidClosure {
uint _worker_id;
ShenandoahTaskTerminator* _terminator;
bool _reset_terminator;
public:
ShenandoahCMDrainMarkingStackClosure(uint worker_id, ShenandoahTaskTerminator* t, bool reset_terminator = false):
_worker_id(worker_id),
_terminator(t),
_reset_terminator(reset_terminator) {
}
void do_void() {
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
ShenandoahHeap* sh = ShenandoahHeap::heap();
ShenandoahConcurrentMark* scm = sh->concurrent_mark();
assert(sh->process_references(), "why else would we be here?");
ReferenceProcessor* rp = sh->ref_processor();
shenandoah_assert_rp_isalive_installed();
scm->mark_loop(_worker_id, _terminator, rp,
false, // not cancellable
false); // do not do strdedup
if (_reset_terminator) {
_terminator->reset_for_reuse();
}
}
};
class ShenandoahCMKeepAliveClosure : public OopClosure {
private:
ShenandoahObjToScanQueue* _queue;
ShenandoahHeap* _heap;
ShenandoahMarkingContext* const _mark_context;
template <class T>
inline void do_oop_work(T* p) {
ShenandoahConcurrentMark::mark_through_ref<T, NONE, NO_DEDUP>(p, _heap, _queue, _mark_context);
}
public:
ShenandoahCMKeepAliveClosure(ShenandoahObjToScanQueue* q) :
_queue(q),
_heap(ShenandoahHeap::heap()),
_mark_context(_heap->marking_context()) {}
void do_oop(narrowOop* p) { do_oop_work(p); }
void do_oop(oop* p) { do_oop_work(p); }
};
class ShenandoahCMKeepAliveUpdateClosure : public OopClosure {
private:
ShenandoahObjToScanQueue* _queue;
ShenandoahHeap* _heap;
ShenandoahMarkingContext* const _mark_context;
template <class T>
inline void do_oop_work(T* p) {
ShenandoahConcurrentMark::mark_through_ref<T, SIMPLE, NO_DEDUP>(p, _heap, _queue, _mark_context);
}
public:
ShenandoahCMKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
_queue(q),
_heap(ShenandoahHeap::heap()),
_mark_context(_heap->marking_context()) {}
void do_oop(narrowOop* p) { do_oop_work(p); }
void do_oop(oop* p) { do_oop_work(p); }
};
class ShenandoahWeakUpdateClosure : public OopClosure {
private:
ShenandoahHeap* const _heap;
template <class T>
inline void do_oop_work(T* p) {
oop o = _heap->maybe_update_with_forwarded(p);
shenandoah_assert_marked_except(p, o, o == NULL);
}
public:
ShenandoahWeakUpdateClosure() : _heap(ShenandoahHeap::heap()) {}
void do_oop(narrowOop* p) { do_oop_work(p); }
void do_oop(oop* p) { do_oop_work(p); }
};
class ShenandoahRefProcTaskProxy : public AbstractGangTask {
private:
AbstractRefProcTaskExecutor::ProcessTask& _proc_task;
ShenandoahTaskTerminator* _terminator;
public:
ShenandoahRefProcTaskProxy(AbstractRefProcTaskExecutor::ProcessTask& proc_task,
ShenandoahTaskTerminator* t) :
AbstractGangTask("Process reference objects in parallel"),
_proc_task(proc_task),
_terminator(t) {
}
void work(uint worker_id) {
ResourceMark rm;
HandleMark hm;
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
ShenandoahHeap* heap = ShenandoahHeap::heap();
ShenandoahCMDrainMarkingStackClosure complete_gc(worker_id, _terminator);
if (heap->has_forwarded_objects()) {
ShenandoahForwardedIsAliveClosure is_alive;
ShenandoahCMKeepAliveUpdateClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
_proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
} else {
ShenandoahIsAliveClosure is_alive;
ShenandoahCMKeepAliveClosure keep_alive(heap->concurrent_mark()->get_queue(worker_id));
_proc_task.work(worker_id, is_alive, keep_alive, complete_gc);
}
}
};
class ShenandoahRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
private:
WorkGang* _workers;
public:
ShenandoahRefProcTaskExecutor(WorkGang* workers) :
_workers(workers) {
}
// Executes a task using worker threads.
void execute(ProcessTask& task, uint ergo_workers) {
assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
ShenandoahHeap* heap = ShenandoahHeap::heap();
ShenandoahConcurrentMark* cm = heap->concurrent_mark();
ShenandoahPushWorkerQueuesScope scope(_workers, cm->task_queues(),
ergo_workers,
/* do_check = */ false);
uint nworkers = _workers->active_workers();
cm->task_queues()->reserve(nworkers);
ShenandoahTaskTerminator terminator(nworkers, cm->task_queues());
ShenandoahRefProcTaskProxy proc_task_proxy(task, &terminator);
_workers->run_task(&proc_task_proxy);
}
};
void ShenandoahConcurrentMark::weak_refs_work(bool full_gc) {
assert(_heap->process_references(), "sanity");
ShenandoahPhaseTimings::Phase phase_root =
full_gc ?
ShenandoahPhaseTimings::full_gc_weakrefs :
ShenandoahPhaseTimings::weakrefs;
ShenandoahGCPhase phase(phase_root);
ReferenceProcessor* rp = _heap->ref_processor();
// NOTE: We cannot shortcut on has_discovered_references() here, because
// we will miss marking JNI Weak refs then, see implementation in
// ReferenceProcessor::process_discovered_references.
weak_refs_work_doit(full_gc);
rp->verify_no_references_recorded();
assert(!rp->discovery_enabled(), "Post condition");
}
void ShenandoahConcurrentMark::weak_refs_work_doit(bool full_gc) {
ReferenceProcessor* rp = _heap->ref_processor();
ShenandoahPhaseTimings::Phase phase_process =
full_gc ?
ShenandoahPhaseTimings::full_gc_weakrefs_process :
ShenandoahPhaseTimings::weakrefs_process;
ShenandoahPhaseTimings::Phase phase_process_termination =
full_gc ?
ShenandoahPhaseTimings::full_gc_weakrefs_termination :
ShenandoahPhaseTimings::weakrefs_termination;
shenandoah_assert_rp_isalive_not_installed();
ShenandoahIsAliveSelector is_alive;
ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
WorkGang* workers = _heap->workers();
uint nworkers = workers->active_workers();
rp->setup_policy(_heap->soft_ref_policy()->should_clear_all_soft_refs());
rp->set_active_mt_degree(nworkers);
assert(task_queues()->is_empty(), "Should be empty");
// complete_gc and keep_alive closures instantiated here are only needed for
// single-threaded path in RP. They share the queue 0 for tracking work, which
// simplifies implementation. Since RP may decide to call complete_gc several
// times, we need to be able to reuse the terminator.
uint serial_worker_id = 0;
ShenandoahTaskTerminator terminator(1, task_queues());
ShenandoahCMDrainMarkingStackClosure complete_gc(serial_worker_id, &terminator, /* reset_terminator = */ true);
ShenandoahRefProcTaskExecutor executor(workers);
ReferenceProcessorPhaseTimes pt(_heap->gc_timer(), rp->num_queues());
{
ShenandoahGCPhase phase(phase_process);
ShenandoahTerminationTracker phase_term(phase_process_termination);
if (_heap->has_forwarded_objects()) {
ShenandoahCMKeepAliveUpdateClosure keep_alive(get_queue(serial_worker_id));
rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
&complete_gc, &executor,
&pt);
} else {
ShenandoahCMKeepAliveClosure keep_alive(get_queue(serial_worker_id));
rp->process_discovered_references(is_alive.is_alive_closure(), &keep_alive,
&complete_gc, &executor,
&pt);
}
pt.print_all_references();
assert(task_queues()->is_empty(), "Should be empty");
}
}
class ShenandoahCancelledGCYieldClosure : public YieldClosure {
private:
ShenandoahHeap* const _heap;
public:
ShenandoahCancelledGCYieldClosure() : _heap(ShenandoahHeap::heap()) {};
virtual bool should_return() { return _heap->cancelled_gc(); }
};
class ShenandoahPrecleanCompleteGCClosure : public VoidClosure {
public:
void do_void() {
ShenandoahHeap* sh = ShenandoahHeap::heap();
ShenandoahConcurrentMark* scm = sh->concurrent_mark();
assert(sh->process_references(), "why else would we be here?");
ShenandoahTaskTerminator terminator(1, scm->task_queues());
ReferenceProcessor* rp = sh->ref_processor();
shenandoah_assert_rp_isalive_installed();
scm->mark_loop(0, &terminator, rp,
false, // not cancellable
false); // do not do strdedup
}
};
class ShenandoahPrecleanKeepAliveUpdateClosure : public OopClosure {
private:
ShenandoahObjToScanQueue* _queue;
ShenandoahHeap* _heap;
ShenandoahMarkingContext* const _mark_context;
template <class T>
inline void do_oop_work(T* p) {
ShenandoahConcurrentMark::mark_through_ref<T, CONCURRENT, NO_DEDUP>(p, _heap, _queue, _mark_context);
}
public:
ShenandoahPrecleanKeepAliveUpdateClosure(ShenandoahObjToScanQueue* q) :
_queue(q),
_heap(ShenandoahHeap::heap()),
_mark_context(_heap->marking_context()) {}
void do_oop(narrowOop* p) { do_oop_work(p); }
void do_oop(oop* p) { do_oop_work(p); }
};
class ShenandoahPrecleanTask : public AbstractGangTask {
private:
ReferenceProcessor* _rp;
public:
ShenandoahPrecleanTask(ReferenceProcessor* rp) :
AbstractGangTask("Precleaning task"),
_rp(rp) {}
void work(uint worker_id) {
assert(worker_id == 0, "The code below is single-threaded, only one worker is expected");
ShenandoahParallelWorkerSession worker_session(worker_id);
ShenandoahHeap* sh = ShenandoahHeap::heap();
ShenandoahObjToScanQueue* q = sh->concurrent_mark()->get_queue(worker_id);
ShenandoahCancelledGCYieldClosure yield;
ShenandoahPrecleanCompleteGCClosure complete_gc;
if (sh->has_forwarded_objects()) {
ShenandoahForwardedIsAliveClosure is_alive;
ShenandoahPrecleanKeepAliveUpdateClosure keep_alive(q);
ResourceMark rm;
_rp->preclean_discovered_references(&is_alive, &keep_alive,
&complete_gc, &yield,
NULL);
} else {
ShenandoahIsAliveClosure is_alive;
ShenandoahCMKeepAliveClosure keep_alive(q);
ResourceMark rm;
_rp->preclean_discovered_references(&is_alive, &keep_alive,
&complete_gc, &yield,
NULL);
}
}
};
void ShenandoahConcurrentMark::preclean_weak_refs() {
// Pre-cleaning weak references before diving into STW makes sense at the
// end of concurrent mark. This will filter out the references which referents
// are alive. Note that ReferenceProcessor already filters out these on reference
// discovery, and the bulk of work is done here. This phase processes leftovers
// that missed the initial filtering, i.e. when referent was marked alive after
// reference was discovered by RP.
assert(_heap->process_references(), "sanity");
// Shortcut if no references were discovered to avoid winding up threads.
ReferenceProcessor* rp = _heap->ref_processor();
if (!rp->has_discovered_references()) {
return;
}
assert(task_queues()->is_empty(), "Should be empty");
ReferenceProcessorMTDiscoveryMutator fix_mt_discovery(rp, false);
shenandoah_assert_rp_isalive_not_installed();
ShenandoahIsAliveSelector is_alive;
ReferenceProcessorIsAliveMutator fix_isalive(rp, is_alive.is_alive_closure());
// Execute precleaning in the worker thread: it will give us GCLABs, String dedup
// queues and other goodies. When upstream ReferenceProcessor starts supporting
// parallel precleans, we can extend this to more threads.
WorkGang* workers = _heap->workers();
uint nworkers = workers->active_workers();
assert(nworkers == 1, "This code uses only a single worker");
task_queues()->reserve(nworkers);
ShenandoahPrecleanTask task(rp);
workers->run_task(&task);
assert(task_queues()->is_empty(), "Should be empty");
}
void ShenandoahConcurrentMark::cancel() {
// Clean up marking stacks.
ShenandoahObjToScanQueueSet* queues = task_queues();
queues->clear();
// Cancel SATB buffers.
ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
}
ShenandoahObjToScanQueue* ShenandoahConcurrentMark::get_queue(uint worker_id) {
assert(task_queues()->get_reserved() > worker_id, "No reserved queue for worker id: %d", worker_id);
return _task_queues->queue(worker_id);
}
template <bool CANCELLABLE>
void ShenandoahConcurrentMark::mark_loop_prework(uint w, ShenandoahTaskTerminator *t, ReferenceProcessor *rp,
bool strdedup) {
ShenandoahObjToScanQueue* q = get_queue(w);
jushort* ld = _heap->get_liveness_cache(w);
// TODO: We can clean up this if we figure out how to do templated oop closures that
// play nice with specialized_oop_iterators.
if (_heap->unload_classes()) {
if (_heap->has_forwarded_objects()) {
if (strdedup) {
ShenandoahMarkUpdateRefsMetadataDedupClosure cl(q, rp);
mark_loop_work<ShenandoahMarkUpdateRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
} else {
ShenandoahMarkUpdateRefsMetadataClosure cl(q, rp);
mark_loop_work<ShenandoahMarkUpdateRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
}
} else {
if (strdedup) {
ShenandoahMarkRefsMetadataDedupClosure cl(q, rp);
mark_loop_work<ShenandoahMarkRefsMetadataDedupClosure, CANCELLABLE>(&cl, ld, w, t);
} else {
ShenandoahMarkRefsMetadataClosure cl(q, rp);
mark_loop_work<ShenandoahMarkRefsMetadataClosure, CANCELLABLE>(&cl, ld, w, t);
}
}
} else {
if (_heap->has_forwarded_objects()) {
if (strdedup) {
ShenandoahMarkUpdateRefsDedupClosure cl(q, rp);
mark_loop_work<ShenandoahMarkUpdateRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
} else {
ShenandoahMarkUpdateRefsClosure cl(q, rp);
mark_loop_work<ShenandoahMarkUpdateRefsClosure, CANCELLABLE>(&cl, ld, w, t);
}
} else {
if (strdedup) {
ShenandoahMarkRefsDedupClosure cl(q, rp);
mark_loop_work<ShenandoahMarkRefsDedupClosure, CANCELLABLE>(&cl, ld, w, t);
} else {
ShenandoahMarkRefsClosure cl(q, rp);
mark_loop_work<ShenandoahMarkRefsClosure, CANCELLABLE>(&cl, ld, w, t);
}
}
}
_heap->flush_liveness_cache(w);
}
template <class T, bool CANCELLABLE>
void ShenandoahConcurrentMark::mark_loop_work(T* cl, jushort* live_data, uint worker_id, ShenandoahTaskTerminator *terminator) {
uintx stride = ShenandoahMarkLoopStride;
ShenandoahHeap* heap = ShenandoahHeap::heap();
ShenandoahObjToScanQueueSet* queues = task_queues();
ShenandoahObjToScanQueue* q;
ShenandoahMarkTask t;
/*
* Process outstanding queues, if any.
*
* There can be more queues than workers. To deal with the imbalance, we claim
* extra queues first. Since marking can push new tasks into the queue associated
* with this worker id, we come back to process this queue in the normal loop.
*/
assert(queues->get_reserved() == heap->workers()->active_workers(),
"Need to reserve proper number of queues: reserved: %u, active: %u", queues->get_reserved(), heap->workers()->active_workers());
q = queues->claim_next();
while (q != NULL) {
if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
return;
}
for (uint i = 0; i < stride; i++) {
if (q->pop(t)) {
do_task<T>(q, cl, live_data, &t);
} else {
assert(q->is_empty(), "Must be empty");
q = queues->claim_next();
break;
}
}
}
q = get_queue(worker_id);
ShenandoahSATBBufferClosure drain_satb(q);
SATBMarkQueueSet& satb_mq_set = ShenandoahBarrierSet::satb_mark_queue_set();
/*
* Normal marking loop:
*/
while (true) {
if (CANCELLABLE && heap->check_cancelled_gc_and_yield()) {
return;
}
while (satb_mq_set.completed_buffers_num() > 0) {
satb_mq_set.apply_closure_to_completed_buffer(&drain_satb);
}
uint work = 0;
for (uint i = 0; i < stride; i++) {
if (q->pop(t) ||
queues->steal(worker_id, t)) {
do_task<T>(q, cl, live_data, &t);
work++;
} else {
break;
}
}
if (work == 0) {
// No work encountered in current stride, try to terminate.
// Need to leave the STS here otherwise it might block safepoints.
ShenandoahSuspendibleThreadSetLeaver stsl(CANCELLABLE && ShenandoahSuspendibleWorkers);
ShenandoahTerminationTimingsTracker term_tracker(worker_id);
ShenandoahTerminatorTerminator tt(heap);
if (terminator->offer_termination(&tt)) return;
}
}
}
bool ShenandoahConcurrentMark::claim_codecache() {
assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
return _claimed_codecache.try_set();
}
void ShenandoahConcurrentMark::clear_claim_codecache() {
assert(ShenandoahConcurrentScanCodeRoots, "must not be called otherwise");
_claimed_codecache.unset();
}