8367451: GenShen: Remove the option to compute age census during evacuation

Reviewed-by: kdnilsen, xpeng, phh

src/hotspot/share/gc/shenandoah/shenandoahAgeCensus.cpp

@@ -57,7 +57,7 @@ ShenandoahAgeCensus::ShenandoahAgeCensus(uint max_workers)
     // Sentinel value
     _tenuring_threshold[i] = MAX_COHORTS;
   }
-  if (ShenandoahGenerationalAdaptiveTenuring && !ShenandoahGenerationalCensusAtEvac) {
+  if (ShenandoahGenerationalAdaptiveTenuring) {
     _local_age_table = NEW_C_HEAP_ARRAY(AgeTable*, _max_workers, mtGC);
     CENSUS_NOISE(_local_noise = NEW_C_HEAP_ARRAY(ShenandoahNoiseStats, max_workers, mtGC);)
     for (uint i = 0; i < _max_workers; i++) {
@@ -152,7 +152,7 @@ void ShenandoahAgeCensus::update_census(size_t age0_pop, AgeTable* pv1, AgeTable
   prepare_for_census_update();
   assert(_global_age_table[_epoch]->is_clear(), "Dirty decks");
   CENSUS_NOISE(assert(_global_noise[_epoch].is_clear(), "Dirty decks");)
-  if (ShenandoahGenerationalAdaptiveTenuring && !ShenandoahGenerationalCensusAtEvac) {
+  if (ShenandoahGenerationalAdaptiveTenuring) {
     assert(pv1 == nullptr && pv2 == nullptr, "Error, check caller");
     // Seed cohort 0 with population that may have been missed during
     // regular census.
@@ -197,7 +197,7 @@ void ShenandoahAgeCensus::reset_global() {
 
 // Reset the local age tables, clearing any partial census.
 void ShenandoahAgeCensus::reset_local() {
-  if (!ShenandoahGenerationalAdaptiveTenuring || ShenandoahGenerationalCensusAtEvac) {
+  if (!ShenandoahGenerationalAdaptiveTenuring) {
     assert(_local_age_table == nullptr, "Error");
     return;
   }
@@ -223,7 +223,7 @@ bool ShenandoahAgeCensus::is_clear_global() {
 
 // Is local census information clear?
 bool ShenandoahAgeCensus::is_clear_local() {
-  if (!ShenandoahGenerationalAdaptiveTenuring || ShenandoahGenerationalCensusAtEvac) {
+  if (!ShenandoahGenerationalAdaptiveTenuring) {
     assert(_local_age_table == nullptr, "Error");
     return true;
   }

src/hotspot/share/gc/shenandoah/shenandoahAgeCensus.hpp

@@ -173,7 +173,7 @@ class ShenandoahAgeCensus: public CHeapObj<mtGC> {
   ~ShenandoahAgeCensus();
 
   // Return the local age table (population vector) for worker_id.
-  // Only used in the case of (ShenandoahGenerationalAdaptiveTenuring && !ShenandoahGenerationalCensusAtEvac)
+  // Only used in the case of ShenandoahGenerationalAdaptiveTenuring
   AgeTable* get_local_age_table(uint worker_id) const {
     return _local_age_table[worker_id];
   }
@@ -204,9 +204,8 @@ class ShenandoahAgeCensus: public CHeapObj<mtGC> {
 #endif // SHENANDOAH_CENSUS_NOISE
 
   // Update the census data, and compute the new tenuring threshold.
-  // This method should be called at the end of each marking (or optionally
-  // evacuation) cycle to update the tenuring threshold to be used in
-  // the next cycle.
+  // This method should be called at the end of each marking cycle to update
+  // the tenuring threshold to be used in the next cycle.
   // age0_pop is the population of Cohort 0 that may have been missed in
   // the regular census during the marking cycle, corresponding to objects
   // allocated when the concurrent marking was in progress.
@@ -231,7 +230,7 @@ class ShenandoahAgeCensus: public CHeapObj<mtGC> {
 
   // Return the net size of objects encountered (counted or skipped) in census
   // at most recent epoch.
-  size_t get_total() { return _total; }
+  size_t get_total() const { return _total; }
 #endif // !PRODUCT
 
   // Print the age census information

src/hotspot/share/gc/shenandoah/shenandoahEvacTracker.cpp

@@ -45,7 +45,7 @@ ShenandoahEvacuationStats::ShenandoahEvacuations* ShenandoahEvacuationStats::get
 }
 
 ShenandoahEvacuationStats::ShenandoahEvacuationStats()
-  : _use_age_table(ShenandoahGenerationalCensusAtEvac || !ShenandoahGenerationalAdaptiveTenuring),
+  : _use_age_table(!ShenandoahGenerationalAdaptiveTenuring),
     _age_table(nullptr) {
   if (_use_age_table) {
     _age_table = new AgeTable(false);
@@ -168,7 +168,7 @@ ShenandoahCycleStats ShenandoahEvacuationTracker::flush_cycle_to_global() {
   _mutators_global.accumulate(&mutators);
   _workers_global.accumulate(&workers);
 
-  if (ShenandoahGenerationalCensusAtEvac || !ShenandoahGenerationalAdaptiveTenuring) {
+  if (!ShenandoahGenerationalAdaptiveTenuring) {
     // Ingest mutator & worker collected population vectors into the heap's
     // global census data, and use it to compute an appropriate tenuring threshold
     // for use in the next cycle.

src/hotspot/share/gc/shenandoah/shenandoahGeneration.cpp

@@ -678,7 +678,7 @@ void ShenandoahGeneration::prepare_regions_and_collection_set(bool concurrent) {
   }
 
   // Tally the census counts and compute the adaptive tenuring threshold
-  if (is_generational && ShenandoahGenerationalAdaptiveTenuring && !ShenandoahGenerationalCensusAtEvac) {
+  if (is_generational && ShenandoahGenerationalAdaptiveTenuring) {
     // Objects above TAMS weren't included in the age census. Since they were all
     // allocated in this cycle they belong in the age 0 cohort. We walk over all
     // young regions and sum the volume of objects between TAMS and top.

src/hotspot/share/gc/shenandoah/shenandoahGenerationalHeap.cpp

@@ -357,7 +357,7 @@ oop ShenandoahGenerationalHeap::try_evacuate_object(oop p, Thread* thread, Shena
       assert(target_gen == YOUNG_GENERATION, "Error");
       // We record this census only when simulating pre-adaptive tenuring behavior, or
       // when we have been asked to record the census at evacuation rather than at mark
-      if (ShenandoahGenerationalCensusAtEvac || !ShenandoahGenerationalAdaptiveTenuring) {
+      if (!ShenandoahGenerationalAdaptiveTenuring) {
         evac_tracker()->record_age(thread, size * HeapWordSize, ShenandoahHeap::get_object_age(copy_val));
       }
     }

src/hotspot/share/gc/shenandoah/shenandoahMark.inline.hpp

@@ -118,7 +118,7 @@ inline void ShenandoahMark::count_liveness(ShenandoahLiveData* live_data, oop ob
   // Age census for objects in the young generation
   if (GENERATION == YOUNG || (GENERATION == GLOBAL && region->is_young())) {
     assert(heap->mode()->is_generational(), "Only if generational");
-    if (ShenandoahGenerationalAdaptiveTenuring && !ShenandoahGenerationalCensusAtEvac) {
+    if (ShenandoahGenerationalAdaptiveTenuring) {
       assert(region->is_young(), "Only for young objects");
       uint age = ShenandoahHeap::get_object_age(obj);
       ShenandoahAgeCensus* const census = ShenandoahGenerationalHeap::heap()->age_census();

src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp

@@ -70,10 +70,6 @@
           "many consecutive young-gen collections have been "               \
           "completed following the preceding old-gen collection.")          \
                                                                             \
-  product(bool, ShenandoahGenerationalCensusAtEvac, false, EXPERIMENTAL,    \
-          "(Generational mode only) Object age census at evacuation, "      \
-          "rather than during marking.")                                    \
-                                                                            \
   product(bool, ShenandoahGenerationalAdaptiveTenuring, true, EXPERIMENTAL, \
           "(Generational mode only) Dynamically adapt tenuring age.")       \
                                                                             \