4957990: Perm heap bloat in JVM

Summary: Treat ProfileData in MDO's as a source of weak, not strong, roots. Fixes the bug for stop-world collection -- the case of concurrent collection will be fixed separately.
Reviewed-by: jcoomes, jmasa, kvn, never

1 files changed, 8 insertions, 0 deletions

diff --git a/src/share/vm/memory/genMarkSweep.cpp b/src/share/vm/memory/genMarkSweep.cpp
index ba42d5d21..bfc41fb88 100644
--- a/src/share/vm/memory/genMarkSweep.cpp
+++ b/src/share/vm/memory/genMarkSweep.cpp
@@ -162,6 +162,9 @@ void GenMarkSweep::allocate_stacks() {
 
   int size = SystemDictionary::number_of_classes() * 2;
   _revisit_klass_stack = new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
+  // (#klass/k)^2 for k ~ 10 appears to be a better fit, but this will have to do for
+  // now until we have had a chance to investigate a more optimal setting.
+  _revisit_mdo_stack   = new (ResourceObj::C_HEAP) GrowableArray<DataLayout*>(2*size, true);
 
 #ifdef VALIDATE_MARK_SWEEP
   if (ValidateMarkSweep) {
@@ -206,6 +209,7 @@ void GenMarkSweep::deallocate_stacks() {
 
   delete _marking_stack;
   delete _revisit_klass_stack;
+  delete _revisit_mdo_stack;
 
 #ifdef VALIDATE_MARK_SWEEP
   if (ValidateMarkSweep) {
@@ -262,6 +266,10 @@ void GenMarkSweep::mark_sweep_phase1(int level,
   follow_weak_klass_links();
   assert(_marking_stack->is_empty(), "just drained");
 
+  // Visit memoized MDO's and clear any unmarked weak refs
+  follow_mdo_weak_refs();
+  assert(_marking_stack->is_empty(), "just drained");
+
   // Visit symbol and interned string tables and delete unmarked oops
   SymbolTable::unlink(&is_alive);
   StringTable::unlink(&is_alive);