8332516: Serial: Always sample promoted bytes to avoid getting stuck in Full GCs

Reviewed-by: iwalulya, tschatzl

Author: albertnetymk

src/hotspot/share/gc/serial/serialHeap.cpp

@@ -468,7 +468,10 @@ bool SerialHeap::do_young_collection(bool clear_soft_refs) {
 
   COMPILER2_OR_JVMCI_PRESENT(DerivedPointerTable::update_pointers());
 
-  update_gc_stats(_young_gen, false);
+  // Only update stats for successful young-gc
+  if (result) {
+    _old_gen->update_promote_stats();
+  }
 
   if (should_verify && VerifyAfterGC) {
     Universe::verify("After GC");
@@ -761,6 +764,8 @@ void SerialHeap::do_full_collection_no_gc_locker(bool clear_all_soft_refs) {
   // Need to clear claim bits for the next mark.
   ClassLoaderDataGraph::clear_claimed_marks();
 
+  _old_gen->update_promote_stats();
+
   // Resize the metaspace capacity after full collections
   MetaspaceGC::compute_new_size();
 

src/hotspot/share/gc/serial/serialHeap.hpp

@@ -208,11 +208,6 @@ class SerialHeap : public CollectedHeap {
                               size_t requested_size,
                               size_t* actual_size) override;
 
-  // Update the gc statistics for each generation.
-  void update_gc_stats(Generation* current_generation, bool full) {
-    _old_gen->update_gc_stats(current_generation, full);
-  }
-
   void prepare_for_verify() override;
   void verify(VerifyOption option) override;
 

src/hotspot/share/gc/serial/tenuredGeneration.cpp

@@ -357,25 +357,15 @@ void TenuredGeneration::compute_new_size() {
          " capacity: " SIZE_FORMAT, used(), used_after_gc, capacity());
 }
 
-void TenuredGeneration::update_gc_stats(Generation* current_generation,
-                                        bool full) {
-  // If the young generation has been collected, gather any statistics
-  // that are of interest at this point.
-  bool current_is_young = SerialHeap::heap()->is_young_gen(current_generation);
-  if (!full && current_is_young) {
-    // Calculate size of data promoted from the young generation
-    // before doing the collection.
-    size_t used_before_gc = used();
-
-    // If the young gen collection was skipped, then the
-    // number of promoted bytes will be 0 and adding it to the
-    // average will incorrectly lessen the average.  It is, however,
-    // also possible that no promotion was needed.
-    if (used_before_gc >= _used_at_prologue) {
-      size_t promoted_in_bytes = used_before_gc - _used_at_prologue;
-      _avg_promoted->sample(promoted_in_bytes);
-    }
+void TenuredGeneration::update_promote_stats() {
+  size_t used_after_gc = used();
+  size_t promoted_in_bytes;
+  if (used_after_gc > _used_at_prologue) {
+    promoted_in_bytes = used_after_gc - _used_at_prologue;
+  } else {
+    promoted_in_bytes = 0;
   }
+  _avg_promoted->sample(promoted_in_bytes);
 }
 
 void TenuredGeneration::update_counters() {

src/hotspot/share/gc/serial/tenuredGeneration.hpp

@@ -154,7 +154,7 @@ class TenuredGeneration: public Generation {
 
   // Statistics
 
-  void update_gc_stats(Generation* current_generation, bool full);
+  void update_promote_stats();
 
   // Returns true if promotions of the specified amount are
   // likely to succeed without a promotion failure.