--- old/src/share/vm/memory/genMarkSweep.cpp	2014-10-17 16:28:44.000000000 +0200
+++ new/src/share/vm/memory/genMarkSweep.cpp	2014-10-17 16:28:44.000000000 +0200
@@ -37,6 +37,7 @@
 #include "memory/genCollectedHeap.hpp"
 #include "memory/genMarkSweep.hpp"
 #include "memory/genOopClosures.inline.hpp"
+#include "memory/generation.hpp"
 #include "memory/generation.inline.hpp"
 #include "memory/modRefBarrierSet.hpp"
 #include "memory/referencePolicy.hpp"
@@ -52,8 +53,7 @@
 #include "utilities/copy.hpp"
 #include "utilities/events.hpp"
 
-void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp, bool clear_all_softrefs) {
-  guarantee(level == 1, "We always collect both old and young.");
+void GenMarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, bool clear_all_softrefs) {
   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
 
   GenCollectedHeap* gch = GenCollectedHeap::heap();
@@ -86,11 +86,11 @@
   // Capture used regions for each generation that will be
   // subject to collection, so that card table adjustments can
   // be made intelligently (see clear / invalidate further below).
-  gch->save_used_regions(level);
+  gch->save_used_regions();
 
   allocate_stacks();
 
-  mark_sweep_phase1(level, clear_all_softrefs);
+  mark_sweep_phase1(clear_all_softrefs);
 
   mark_sweep_phase2();
 
@@ -98,7 +98,7 @@
   COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
   COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
 
-  mark_sweep_phase3(level);
+  mark_sweep_phase3();
 
   mark_sweep_phase4();
 
@@ -110,19 +110,14 @@
 
   deallocate_stacks();
 
-  // If compaction completely evacuated all generations younger than this
-  // one, then we can clear the card table.  Otherwise, we must invalidate
-  // it (consider all cards dirty).  In the future, we might consider doing
-  // compaction within generations only, and doing card-table sliding.
-  bool all_empty = true;
-  for (int i = 0; all_empty && i < level; i++) {
-    Generation* g = gch->get_gen(i);
-    all_empty = all_empty && gch->get_gen(i)->used() == 0;
-  }
+  // If compaction completely evacuated the young generation we can clear
+  // the card table.  Otherwise, we must invalidate it (consider all cards dirty).
+  // In the future, we might consider doing compaction within generations only,
+  // and doing card-table sliding.
   GenRemSet* rs = gch->rem_set();
-  Generation* old_gen = gch->get_gen(level);
+  Generation* old_gen = gch->old_gen();
   // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
-  if (all_empty) {
+  if (gch->young_gen()->used() == 0) {
     // We've evacuated all generations below us.
     rs->clear_into_younger(old_gen);
   } else {
@@ -160,7 +155,7 @@
   GenCollectedHeap* gch = GenCollectedHeap::heap();
   // Scratch request on behalf of oldest generation; will do no
   // allocation.
-  ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
+  ScratchBlock* scratch = gch->gather_scratch(gch->old_gen(), 0);
 
   // $$$ To cut a corner, we'll only use the first scratch block, and then
   // revert to malloc.
@@ -188,8 +183,7 @@
   _objarray_stack.clear(true);
 }
 
-void GenMarkSweep::mark_sweep_phase1(int level,
-                                  bool clear_all_softrefs) {
+void GenMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
   // Recursively traverse all live objects and mark them
   GCTraceTime tm("phase 1", PrintGC && Verbose, true, _gc_timer, _gc_tracer->gc_id());
   trace(" 1");
@@ -200,12 +194,12 @@
   // use OopsInGenClosure constructor which takes a generation,
   // as the Universe has not been created when the static constructors
   // are run.
-  follow_root_closure.set_orig_generation(gch->get_gen(level));
+  follow_root_closure.set_orig_generation(gch->old_gen());
 
   // Need new claim bits before marking starts.
   ClassLoaderDataGraph::clear_claimed_marks();
 
-  gch->gen_process_roots(level,
+  gch->gen_process_roots(Generation::Old,
                          false, // Younger gens are not roots.
                          true,  // activate StrongRootsScope
                          SharedHeap::SO_None,
@@ -274,7 +268,7 @@
   }
 };
 
-void GenMarkSweep::mark_sweep_phase3(int level) {
+void GenMarkSweep::mark_sweep_phase3() {
   GenCollectedHeap* gch = GenCollectedHeap::heap();
 
   // Adjust the pointers to reflect the new locations
@@ -288,9 +282,9 @@
   // use OopsInGenClosure constructor which takes a generation,
   // as the Universe has not been created when the static constructors
   // are run.
-  adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
+  adjust_pointer_closure.set_orig_generation(gch->old_gen());
 
-  gch->gen_process_roots(level,
+  gch->gen_process_roots(Generation::Old,
                          false, // Younger gens are not roots.
                          true,  // activate StrongRootsScope
                          SharedHeap::SO_AllCodeCache,