--- a/src/hotspot/share/gc/g1/g1CollectedHeap.cpp Sun Aug 19 20:00:57 2018 +0200
+++ b/src/hotspot/share/gc/g1/g1CollectedHeap.cpp Wed Aug 22 16:01:29 2018 +0200
@@ -70,7 +70,6 @@
#include "gc/shared/generationSpec.hpp"
#include "gc/shared/isGCActiveMark.hpp"
#include "gc/shared/oopStorageParState.hpp"
-#include "gc/shared/parallelCleaning.hpp"
#include "gc/shared/preservedMarks.inline.hpp"
#include "gc/shared/suspendibleThreadSet.hpp"
#include "gc/shared/referenceProcessor.inline.hpp"
@@ -3255,12 +3254,334 @@
undo_waste * HeapWordSize / K);
}
+class G1StringCleaningTask : public AbstractGangTask {
+private:
+ BoolObjectClosure* _is_alive;
+ G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
+ OopStorage::ParState<false /* concurrent */, false /* const */> _par_state_string;
+
+ int _initial_string_table_size;
+
+ bool _process_strings;
+ int _strings_processed;
+ int _strings_removed;
+
+ bool _process_string_dedup;
+
+public:
+ G1StringCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_string_dedup) :
+ AbstractGangTask("String Unlinking"),
+ _is_alive(is_alive),
+ _dedup_closure(is_alive, NULL, false),
+ _par_state_string(StringTable::weak_storage()),
+ _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
+ _process_string_dedup(process_string_dedup) {
+
+ _initial_string_table_size = (int) StringTable::the_table()->table_size();
+ if (process_strings) {
+ StringTable::reset_dead_counter();
+ }
+ }
+
+ ~G1StringCleaningTask() {
+ log_info(gc, stringtable)(
+ "Cleaned string table, "
+ "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
+ strings_processed(), strings_removed());
+ if (_process_strings) {
+ StringTable::finish_dead_counter();
+ }
+ }
+
+ void work(uint worker_id) {
+ int strings_processed = 0;
+ int strings_removed = 0;
+ if (_process_strings) {
+ StringTable::possibly_parallel_unlink(&_par_state_string, _is_alive, &strings_processed, &strings_removed);
+ Atomic::add(strings_processed, &_strings_processed);
+ Atomic::add(strings_removed, &_strings_removed);
+ }
+ if (_process_string_dedup) {
+ G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
+ }
+ }
+
+ size_t strings_processed() const { return (size_t)_strings_processed; }
+ size_t strings_removed() const { return (size_t)_strings_removed; }
+};
+
+class G1CodeCacheUnloadingTask {
+private:
+ static Monitor* _lock;
+
+ BoolObjectClosure* const _is_alive;
+ const bool _unloading_occurred;
+ const uint _num_workers;
+
+ // Variables used to claim nmethods.
+ CompiledMethod* _first_nmethod;
+ CompiledMethod* volatile _claimed_nmethod;
+
+ // The list of nmethods that need to be processed by the second pass.
+ CompiledMethod* volatile _postponed_list;
+ volatile uint _num_entered_barrier;
+
+ public:
+ G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
+ _is_alive(is_alive),
+ _unloading_occurred(unloading_occurred),
+ _num_workers(num_workers),
+ _first_nmethod(NULL),
+ _claimed_nmethod(NULL),
+ _postponed_list(NULL),
+ _num_entered_barrier(0)
+ {
+ CompiledMethod::increase_unloading_clock();
+ // Get first alive nmethod
+ CompiledMethodIterator iter = CompiledMethodIterator();
+ if(iter.next_alive()) {
+ _first_nmethod = iter.method();
+ }
+ _claimed_nmethod = _first_nmethod;
+ }
+
+ ~G1CodeCacheUnloadingTask() {
+ CodeCache::verify_clean_inline_caches();
+
+ CodeCache::set_needs_cache_clean(false);
+ guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
+
+ CodeCache::verify_icholder_relocations();
+ }
+
+ private:
+ void add_to_postponed_list(CompiledMethod* nm) {
+ CompiledMethod* old;
+ do {
+ old = _postponed_list;
+ nm->set_unloading_next(old);
+ } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
+ }
+
+ void clean_nmethod(CompiledMethod* nm) {
+ bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
+
+ if (postponed) {
+ // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
+ add_to_postponed_list(nm);
+ }
+
+ // Mark that this nmethod has been cleaned/unloaded.
+ // After this call, it will be safe to ask if this nmethod was unloaded or not.
+ nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
+ }
+
+ void clean_nmethod_postponed(CompiledMethod* nm) {
+ nm->do_unloading_parallel_postponed();
+ }
+
+ static const int MaxClaimNmethods = 16;
+
+ void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
+ CompiledMethod* first;
+ CompiledMethodIterator last;
+
+ do {
+ *num_claimed_nmethods = 0;
+
+ first = _claimed_nmethod;
+ last = CompiledMethodIterator(first);
+
+ if (first != NULL) {
+
+ for (int i = 0; i < MaxClaimNmethods; i++) {
+ if (!last.next_alive()) {
+ break;
+ }
+ claimed_nmethods[i] = last.method();
+ (*num_claimed_nmethods)++;
+ }
+ }
+
+ } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
+ }
+
+ CompiledMethod* claim_postponed_nmethod() {
+ CompiledMethod* claim;
+ CompiledMethod* next;
+
+ do {
+ claim = _postponed_list;
+ if (claim == NULL) {
+ return NULL;
+ }
+
+ next = claim->unloading_next();
+
+ } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
+
+ return claim;
+ }
+
+ public:
+ // Mark that we're done with the first pass of nmethod cleaning.
+ void barrier_mark(uint worker_id) {
+ MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
+ _num_entered_barrier++;
+ if (_num_entered_barrier == _num_workers) {
+ ml.notify_all();
+ }
+ }
+
+ // See if we have to wait for the other workers to
+ // finish their first-pass nmethod cleaning work.
+ void barrier_wait(uint worker_id) {
+ if (_num_entered_barrier < _num_workers) {
+ MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
+ while (_num_entered_barrier < _num_workers) {
+ ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
+ }
+ }
+ }
+
+ // Cleaning and unloading of nmethods. Some work has to be postponed
+ // to the second pass, when we know which nmethods survive.
+ void work_first_pass(uint worker_id) {
+ // The first nmethods is claimed by the first worker.
+ if (worker_id == 0 && _first_nmethod != NULL) {
+ clean_nmethod(_first_nmethod);
+ _first_nmethod = NULL;
+ }
+
+ int num_claimed_nmethods;
+ CompiledMethod* claimed_nmethods[MaxClaimNmethods];
+
+ while (true) {
+ claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
+
+ if (num_claimed_nmethods == 0) {
+ break;
+ }
+
+ for (int i = 0; i < num_claimed_nmethods; i++) {
+ clean_nmethod(claimed_nmethods[i]);
+ }
+ }
+ }
+
+ void work_second_pass(uint worker_id) {
+ CompiledMethod* nm;
+ // Take care of postponed nmethods.
+ while ((nm = claim_postponed_nmethod()) != NULL) {
+ clean_nmethod_postponed(nm);
+ }
+ }
+};
+
+Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
+
+class G1KlassCleaningTask : public StackObj {
+ volatile int _clean_klass_tree_claimed;
+ ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
+
+ public:
+ G1KlassCleaningTask() :
+ _clean_klass_tree_claimed(0),
+ _klass_iterator() {
+ }
+
+ private:
+ bool claim_clean_klass_tree_task() {
+ if (_clean_klass_tree_claimed) {
+ return false;
+ }
+
+ return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
+ }
+
+ InstanceKlass* claim_next_klass() {
+ Klass* klass;
+ do {
+ klass =_klass_iterator.next_klass();
+ } while (klass != NULL && !klass->is_instance_klass());
+
+ // this can be null so don't call InstanceKlass::cast
+ return static_cast<InstanceKlass*>(klass);
+ }
+
+public:
+
+ void clean_klass(InstanceKlass* ik) {
+ ik->clean_weak_instanceklass_links();
+ }
+
+ void work() {
+ ResourceMark rm;
+
+ // One worker will clean the subklass/sibling klass tree.
+ if (claim_clean_klass_tree_task()) {
+ Klass::clean_subklass_tree();
+ }
+
+ // All workers will help cleaning the classes,
+ InstanceKlass* klass;
+ while ((klass = claim_next_klass()) != NULL) {
+ clean_klass(klass);
+ }
+ }
+};
+
+// To minimize the remark pause times, the tasks below are done in parallel.
+class G1ParallelCleaningTask : public AbstractGangTask {
+private:
+ bool _unloading_occurred;
+ G1StringCleaningTask _string_task;
+ G1CodeCacheUnloadingTask _code_cache_task;
+ G1KlassCleaningTask _klass_cleaning_task;
+
+public:
+ // The constructor is run in the VMThread.
+ G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
+ AbstractGangTask("Parallel Cleaning"),
+ _unloading_occurred(unloading_occurred),
+ _string_task(is_alive, true, G1StringDedup::is_enabled()),
+ _code_cache_task(num_workers, is_alive, unloading_occurred),
+ _klass_cleaning_task() {
+ }
+
+ // The parallel work done by all worker threads.
+ void work(uint worker_id) {
+ // Do first pass of code cache cleaning.
+ _code_cache_task.work_first_pass(worker_id);
+
+ // Let the threads mark that the first pass is done.
+ _code_cache_task.barrier_mark(worker_id);
+
+ // Clean the Strings.
+ _string_task.work(worker_id);
+
+ // Wait for all workers to finish the first code cache cleaning pass.
+ _code_cache_task.barrier_wait(worker_id);
+
+ // Do the second code cache cleaning work, which realize on
+ // the liveness information gathered during the first pass.
+ _code_cache_task.work_second_pass(worker_id);
+
+ // Clean all klasses that were not unloaded.
+ // The weak metadata in klass doesn't need to be
+ // processed if there was no unloading.
+ if (_unloading_occurred) {
+ _klass_cleaning_task.work();
+ }
+ }
+};
+
+
void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
bool class_unloading_occurred) {
uint n_workers = workers()->active_workers();
- G1StringDedupUnlinkOrOopsDoClosure dedup_closure(is_alive, NULL, false);
- ParallelCleaningTask g1_unlink_task(is_alive, &dedup_closure, n_workers, class_unloading_occurred);
+ G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
workers()->run_task(&g1_unlink_task);
}
@@ -3272,8 +3593,7 @@
return;
}
- G1StringDedupUnlinkOrOopsDoClosure dedup_closure(is_alive, NULL, false);
- StringCleaningTask g1_unlink_task(is_alive, process_string_dedup ? &dedup_closure : NULL, process_strings);
+ G1StringCleaningTask g1_unlink_task(is_alive, process_strings, process_string_dedup);
workers()->run_task(&g1_unlink_task);
}