changeset 19289:213031f03f61

8023021: Unnecessary clearing of the card table introduced by the fix for JDK-8023013 Reviewed-by: stefank, ehelin
author brutisso
date Thu, 15 Aug 2013 10:05:50 +0200
parents 5eb9589687dc
children 0026ec3d09e3 d247781beec7
files hotspot/src/share/vm/memory/cardTableRS.cpp hotspot/src/share/vm/memory/cardTableRS.hpp hotspot/src/share/vm/memory/genMarkSweep.cpp hotspot/src/share/vm/memory/genRemSet.hpp
diffstat 4 files changed, 17 insertions(+), 24 deletions(-) [+]
line wrap: on
line diff
--- a/hotspot/src/share/vm/memory/cardTableRS.cpp	Wed Aug 14 13:49:36 2013 +0200
+++ b/hotspot/src/share/vm/memory/cardTableRS.cpp	Thu Aug 15 10:05:50 2013 +0200
@@ -310,32 +310,27 @@
   _ct_bs->non_clean_card_iterate_possibly_parallel(sp, urasm, cl, this);
 }
 
-void CardTableRS::clear_into_younger(Generation* gen) {
-  GenCollectedHeap* gch = GenCollectedHeap::heap();
-  // Generations younger than gen have been evacuated. We can clear
-  // card table entries for gen (we know that it has no pointers
-  // to younger gens) and for those below. The card tables for
-  // the youngest gen need never be cleared.
+void CardTableRS::clear_into_younger(Generation* old_gen) {
+  assert(old_gen->level() == 1, "Should only be called for the old generation");
+  // The card tables for the youngest gen need never be cleared.
   // There's a bit of subtlety in the clear() and invalidate()
   // methods that we exploit here and in invalidate_or_clear()
   // below to avoid missing cards at the fringes. If clear() or
   // invalidate() are changed in the future, this code should
   // be revisited. 20040107.ysr
-  Generation* old_gen = gen;
   clear(old_gen->prev_used_region());
-  Generation* young_gen = gch->prev_gen(old_gen);
-  clear(young_gen->prev_used_region());
 }
 
-void CardTableRS::invalidate_or_clear(Generation* gen) {
-  // For generation gen invalidate the cards for the currently
-  // occupied part of that generation and clear the cards for the
+void CardTableRS::invalidate_or_clear(Generation* old_gen) {
+  assert(old_gen->level() == 1, "Should only be called for the old generation");
+  // Invalidate the cards for the currently occupied part of
+  // the old generation and clear the cards for the
   // unoccupied part of the generation (if any, making use
   // of that generation's prev_used_region to determine that
   // region). No need to do anything for the youngest
   // generation. Also see note#20040107.ysr above.
-  MemRegion used_mr = gen->used_region();
-  MemRegion to_be_cleared_mr = gen->prev_used_region().minus(used_mr);
+  MemRegion used_mr = old_gen->used_region();
+  MemRegion to_be_cleared_mr = old_gen->prev_used_region().minus(used_mr);
   if (!to_be_cleared_mr.is_empty()) {
     clear(to_be_cleared_mr);
   }
--- a/hotspot/src/share/vm/memory/cardTableRS.hpp	Wed Aug 14 13:49:36 2013 +0200
+++ b/hotspot/src/share/vm/memory/cardTableRS.hpp	Thu Aug 15 10:05:50 2013 +0200
@@ -142,12 +142,12 @@
   void verify_aligned_region_empty(MemRegion mr);
 
   void clear(MemRegion mr) { _ct_bs->clear(mr); }
-  void clear_into_younger(Generation* gen);
+  void clear_into_younger(Generation* old_gen);
 
   void invalidate(MemRegion mr, bool whole_heap = false) {
     _ct_bs->invalidate(mr, whole_heap);
   }
-  void invalidate_or_clear(Generation* gen);
+  void invalidate_or_clear(Generation* old_gen);
 
   static uintx ct_max_alignment_constraint() {
     return CardTableModRefBS::ct_max_alignment_constraint();
--- a/hotspot/src/share/vm/memory/genMarkSweep.cpp	Wed Aug 14 13:49:36 2013 +0200
+++ b/hotspot/src/share/vm/memory/genMarkSweep.cpp	Thu Aug 15 10:05:50 2013 +0200
@@ -121,17 +121,15 @@
     all_empty = all_empty && gch->get_gen(i)->used() == 0;
   }
   GenRemSet* rs = gch->rem_set();
+  Generation* old_gen = gch->get_gen(level);
   // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
   if (all_empty) {
     // We've evacuated all generations below us.
-    Generation* g = gch->get_gen(level);
-    rs->clear_into_younger(g);
+    rs->clear_into_younger(old_gen);
   } else {
     // Invalidate the cards corresponding to the currently used
-    // region and clear those corresponding to the evacuated region
-    // of all generations just collected.
-    rs->invalidate_or_clear(gch->get_gen(1));
-    rs->invalidate_or_clear(gch->get_gen(0));
+    // region and clear those corresponding to the evacuated region.
+    rs->invalidate_or_clear(old_gen);
   }
 
   Threads::gc_epilogue();
--- a/hotspot/src/share/vm/memory/genRemSet.hpp	Wed Aug 14 13:49:36 2013 +0200
+++ b/hotspot/src/share/vm/memory/genRemSet.hpp	Thu Aug 15 10:05:50 2013 +0200
@@ -135,7 +135,7 @@
   // younger than gen from generations gen and older.
   // The parameter clear_perm indicates if the perm_gen's
   // remembered set should also be processed/cleared.
-  virtual void clear_into_younger(Generation* gen) = 0;
+  virtual void clear_into_younger(Generation* old_gen) = 0;
 
   // Informs the RS that refs in the given "mr" may have changed
   // arbitrarily, and therefore may contain old-to-young pointers.
@@ -147,7 +147,7 @@
   // Informs the RS that refs in this generation
   // may have changed arbitrarily, and therefore may contain
   // old-to-young pointers in arbitrary locations.
-  virtual void invalidate_or_clear(Generation* gen) = 0;
+  virtual void invalidate_or_clear(Generation* old_gen) = 0;
 };
 
 #endif // SHARE_VM_MEMORY_GENREMSET_HPP