truffle: src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp comparison

comparison src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp @ 1656:4e5661ba9d98

6944166: G1: explicit GCs are not always handled correctly Summary: G1 was not handling explicit GCs correctly in many ways. It does now. See the CR for the list of improvements contained in this changeset. Reviewed-by: iveresov, ysr, johnc

author	tonyp
date	Mon, 28 Jun 2010 14:13:17 -0400
parents	215576b54709
children	5cbac8938c4c

comparison

equal deleted inserted replaced

-:e7ec8cd4dd8a
+:4e5661ba9d98
 _g1->heap_region_par_iterate_chunked(&rebuild_rs, i,
 HeapRegion::RebuildRSClaimValue);
 }
 };
-void G1CollectedHeap::do_collection(bool full, bool clear_all_soft_refs,
+void G1CollectedHeap::do_collection(bool explicit_gc,
+bool clear_all_soft_refs,
 size_t word_size) {
 if (GC_locker::check_active_before_gc()) {
 return; // GC is disabled (e.g. JNI GetXXXCritical operation)
 }
 if (PrintHeapAtGC) {
 Universe::print_heap_before_gc();
 }
-if (full && DisableExplicitGC) {
-return;
-}
 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 assert(Thread::current() == VMThread::vm_thread(), "should be in vm thread");
 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
 collector_policy()->should_clear_all_soft_refs();
 {
 IsGCActiveMark x;
 // Timing
+bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc);
+assert(!system_gc || explicit_gc, "invariant");
 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
-TraceTime t(full ? "Full GC (System.gc())" : "Full GC",
+TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC",
 PrintGC, true, gclog_or_tty);
 TraceMemoryManagerStats tms(true /* fullGC */);
 double start = os::elapsedTime();
 // sets. We will also reset the GC time stamps of the regions.
 PostMCRemSetClearClosure rs_clear(mr_bs());
 heap_region_iterate(&rs_clear);
 // Resize the heap if necessary.
-resize_if_necessary_after_full_collection(full ? 0 : word_size);
+resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
 if (_cg1r->use_cache()) {
 _cg1r->clear_and_record_card_counts();
 _cg1r->clear_hot_cache();
 }
 // entire heap tagged as young.
 assert( check_young_list_empty(true /* check_heap */),
 "young list should be empty at this point");
 }
+// Update the number of full collections that have been completed.
+increment_full_collections_completed(false /* outer */);
 if (PrintHeapAtGC) {
 Universe::print_heap_after_gc();
 }
 }
 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
-do_collection(true, clear_all_soft_refs, 0);
+do_collection(true,                /* explicit_gc */
+clear_all_soft_refs,
+0                    /* word_size */);
 }
 // This code is mostly copied from TenuredGeneration.
 void
 G1CollectedHeap::
 _unclean_region_list(),
 _unclean_regions_coming(false),
 _young_list(new YoungList(this)),
 _gc_time_stamp(0),
 _surviving_young_words(NULL),
+_full_collections_completed(0),
 _in_cset_fast_test(NULL),
 _in_cset_fast_test_base(NULL),
 _dirty_cards_region_list(NULL) {
 _g1h = this; // To catch bugs.
 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
 return 0;
 }
 return car->free();
 }
+bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
+return
+((cause == GCCause::_gc_locker           && GCLockerInvokesConcurrent) ||
+(cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
+}
+void G1CollectedHeap::increment_full_collections_completed(bool outer) {
+MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
+// We have already incremented _total_full_collections at the start
+// of the GC, so total_full_collections() represents how many full
+// collections have been started.
+unsigned int full_collections_started = total_full_collections();
+// Given that this method is called at the end of a Full GC or of a
+// concurrent cycle, and those can be nested (i.e., a Full GC can
+// interrupt a concurrent cycle), the number of full collections
+// completed should be either one (in the case where there was no
+// nesting) or two (when a Full GC interrupted a concurrent cycle)
+// behind the number of full collections started.
+// This is the case for the inner caller, i.e. a Full GC.
+assert(outer ||
+(full_collections_started == _full_collections_completed + 1) ||
+(full_collections_started == _full_collections_completed + 2),
+err_msg("for inner caller: full_collections_started = %u "
+"is inconsistent with _full_collections_completed = %u",
+full_collections_started, _full_collections_completed));
+// This is the case for the outer caller, i.e. the concurrent cycle.
+assert(!outer ||
+(full_collections_started == _full_collections_completed + 1),
+err_msg("for outer caller: full_collections_started = %u "
+"is inconsistent with _full_collections_completed = %u",
+full_collections_started, _full_collections_completed));
+_full_collections_completed += 1;
+// This notify_all() will ensure that a thread that called
+// System.gc() with (with ExplicitGCInvokesConcurrent set or not)
+// and it's waiting for a full GC to finish will be woken up. It is
+// waiting in VM_G1IncCollectionPause::doit_epilogue().
+FullGCCount_lock->notify_all();
+}
 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
 assert(Thread::current()->is_VM_thread(), "Precondition#1");
 assert(Heap_lock->is_locked(), "Precondition#2");
 GCCauseSetter gcs(this, cause);
 switch (cause) {
 void G1CollectedHeap::collect(GCCause::Cause cause) {
 // The caller doesn't have the Heap_lock
 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
-int gc_count_before;
+unsigned int gc_count_before;
+unsigned int full_gc_count_before;
 {
 MutexLocker ml(Heap_lock);
 // Read the GC count while holding the Heap_lock
 gc_count_before = SharedHeap::heap()->total_collections();
+full_gc_count_before = SharedHeap::heap()->total_full_collections();
 // Don't want to do a GC until cleanup is completed.
 wait_for_cleanup_complete();
-} // We give up heap lock; VMThread::execute gets it back below
-switch (cause) {
+// We give up heap lock; VMThread::execute gets it back below
-case GCCause::_scavenge_alot: {
+}
-// Do an incremental pause, which might sometimes be abandoned.
-VM_G1IncCollectionPause op(gc_count_before, cause);
+if (should_do_concurrent_full_gc(cause)) {
+// Schedule an initial-mark evacuation pause that will start a
+// concurrent cycle.
+VM_G1IncCollectionPause op(gc_count_before,
+true, /* should_initiate_conc_mark */
+g1_policy()->max_pause_time_ms(),
+cause);
+VMThread::execute(&op);
+} else {
+if (cause == GCCause::_gc_locker
+DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
+// Schedule a standard evacuation pause.
+VM_G1IncCollectionPause op(gc_count_before,
+false, /* should_initiate_conc_mark */
+g1_policy()->max_pause_time_ms(),
+cause);
 VMThread::execute(&op);
-break;
+} else {
-}
+// Schedule a Full GC.
-default: {
+VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
-// In all other cases, we currently do a full gc.
-VM_G1CollectFull op(gc_count_before, cause);
 VMThread::execute(&op);
 }
 }
 }
 }
 }
 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
 HeapRegionClosure *cl) {
+if (r == NULL) {
+// The CSet is empty so there's nothing to do.
+return;
+}
 assert(r->in_collection_set(),
 "Start region must be a member of the collection set.");
 HeapRegion* cur = r;
 while (cur != NULL) {
 HeapRegion* next = cur->next_in_collection_set();
 "derived pointer present"));
 // always_do_update_barrier = true;
 }
 void G1CollectedHeap::do_collection_pause() {
+assert(Heap_lock->owned_by_self(), "we assume we'reholding the Heap_lock");
 // Read the GC count while holding the Heap_lock
 // we need to do this _before_ wait_for_cleanup_complete(), to
 // ensure that we do not give up the heap lock and potentially
 // pick up the wrong count
-int gc_count_before = SharedHeap::heap()->total_collections();
+unsigned int gc_count_before = SharedHeap::heap()->total_collections();
 // Don't want to do a GC pause while cleanup is being completed!
 wait_for_cleanup_complete();
 g1_policy()->record_stop_world_start();
 {
 MutexUnlocker mu(Heap_lock);  // give up heap lock, execute gets it back
-VM_G1IncCollectionPause op(gc_count_before);
+VM_G1IncCollectionPause op(gc_count_before,
+false, /* should_initiate_conc_mark */
+g1_policy()->max_pause_time_ms(),
+GCCause::_g1_inc_collection_pause);
 VMThread::execute(&op);
 }
 }
 void
 return false;
 }
 };
 void
-G1CollectedHeap::do_collection_pause_at_safepoint() {
+G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
 if (GC_locker::check_active_before_gc()) {
 return; // GC is disabled (e.g. JNI GetXXXCritical operation)
 }
 if (PrintHeapAtGC) {
 if (g1_policy()->full_young_gcs())
 strcat(verbose_str, "(young)");
 else
 strcat(verbose_str, "(partial)");
 }
-if (g1_policy()->during_initial_mark_pause())
+if (g1_policy()->during_initial_mark_pause()) {
 strcat(verbose_str, " (initial-mark)");
+// We are about to start a marking cycle, so we increment the
+// full collection counter.
+increment_total_full_collections();
+}
 // if PrintGCDetails is on, we'll print long statistics information
 // in the collector policy code, so let's not print this as the output
 // is messy if we do.
 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
 if (g1_policy()->in_young_gc_mode()) {
 assert(check_young_list_well_formed(),
 "young list should be well formed");
 }
-bool abandoned = false;
 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
 IsGCActiveMark x;
 gc_prologue(false);
 increment_total_collections(false /* full gc */);
 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
 #endif // YOUNG_LIST_VERBOSE
 // Now choose the CS. We may abandon a pause if we find no
 // region that will fit in the MMU pause.
-bool abandoned = g1_policy()->choose_collection_set();
+bool abandoned = g1_policy()->choose_collection_set(target_pause_time_ms);
 // Nothing to do if we were unable to choose a collection set.
 if (!abandoned) {
 #if G1_REM_SET_LOGGING
 gclog_or_tty->print_cr("\nAfter pause, heap:");

Mercurial > hg > truffle

comparison src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp @ 1656:4e5661ba9d98