7145569: G1: optimize nmethods scanning

Summary: Add a list of nmethods to the RSet for a region that contain references into the region. Skip scanning the code cache during root scanning and scan the nmethod lists during RSet scanning instead.
Reviewed-by: tschatzl, brutisso, mgerdin, twisti, kvn

src/share/vm/c1/c1_Runtime1.cpp

@@ -915,16 +915,6 @@ JRT_ENTRY(void, Runtime1::patch_code(JavaThread* thread, Runtime1::StubID stub_i
     // Return to the now deoptimized frame.
   }
 
-  // If we are patching in a non-perm oop, make sure the nmethod
-  // is on the right list.
-  if (ScavengeRootsInCode && mirror.not_null() && mirror()->is_scavengable()) {
-    MutexLockerEx ml_code (CodeCache_lock, Mutex::_no_safepoint_check_flag);
-    nmethod* nm = CodeCache::find_nmethod(caller_frame.pc());
-    guarantee(nm != NULL, "only nmethods can contain non-perm oops");
-    if (!nm->on_scavenge_root_list())
-      CodeCache::add_scavenge_root_nmethod(nm);
-  }
-
   // Now copy code back
 
   {
@@ -1125,6 +1115,21 @@ JRT_ENTRY(void, Runtime1::patch_code(JavaThread* thread, Runtime1::StubID stub_i
       }
     }
   }
+
+  // If we are patching in a non-perm oop, make sure the nmethod
+  // is on the right list.
+  if (ScavengeRootsInCode && mirror.not_null() && mirror()->is_scavengable()) {
+    MutexLockerEx ml_code (CodeCache_lock, Mutex::_no_safepoint_check_flag);
+    nmethod* nm = CodeCache::find_nmethod(caller_frame.pc());
+    guarantee(nm != NULL, "only nmethods can contain non-perm oops");
+    if (!nm->on_scavenge_root_list()) {
+      CodeCache::add_scavenge_root_nmethod(nm);
+    }
+
+    // Since we've patched some oops in the nmethod,
+    // (re)register it with the heap.
+    Universe::heap()->register_nmethod(nm);
+  }
 JRT_END
 
 //

src/share/vm/code/nmethod.cpp

@@ -687,6 +687,7 @@ nmethod::nmethod(
     code_buffer->copy_values_to(this);
     if (ScavengeRootsInCode && detect_scavenge_root_oops()) {
       CodeCache::add_scavenge_root_nmethod(this);
+      Universe::heap()->register_nmethod(this);
     }
     debug_only(verify_scavenge_root_oops());
     CodeCache::commit(this);
@@ -881,6 +882,7 @@ nmethod::nmethod(
     dependencies->copy_to(this);
     if (ScavengeRootsInCode && detect_scavenge_root_oops()) {
       CodeCache::add_scavenge_root_nmethod(this);
+      Universe::heap()->register_nmethod(this);
     }
     debug_only(verify_scavenge_root_oops());
 
@@ -1300,6 +1302,13 @@ bool nmethod::make_not_entrant_or_zombie(unsigned int state) {
   methodHandle the_method(method());
   No_Safepoint_Verifier nsv;
 
+  // during patching, depending on the nmethod state we must notify the GC that
+  // code has been unloaded, unregistering it. We cannot do this right while
+  // holding the Patching_lock because we need to use the CodeCache_lock. This
+  // would be prone to deadlocks.
+  // This flag is used to remember whether we need to later lock and unregister.
+  bool nmethod_needs_unregister = false;
+
   {
     // invalidate osr nmethod before acquiring the patching lock since
     // they both acquire leaf locks and we don't want a deadlock.
@@ -1332,6 +1341,13 @@ bool nmethod::make_not_entrant_or_zombie(unsigned int state) {
       inc_decompile_count();
     }
 
+    // If the state is becoming a zombie, signal to unregister the nmethod with
+    // the heap.
+    // This nmethod may have already been unloaded during a full GC.
+    if ((state == zombie) && !is_unloaded()) {
+      nmethod_needs_unregister = true;
+    }
+
     // Change state
     _state = state;
 
@@ -1367,6 +1383,9 @@ bool nmethod::make_not_entrant_or_zombie(unsigned int state) {
       // safepoint can sneak in, otherwise the oops used by the
       // dependency logic could have become stale.
       MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+      if (nmethod_needs_unregister) {
+        Universe::heap()->unregister_nmethod(this);
+      }
       flush_dependencies(NULL);
     }
 
@@ -1817,21 +1836,10 @@ void nmethod::metadata_do(void f(Metadata*)) {
   if (_method != NULL) f(_method);
 }
 
-
-// This method is called twice during GC -- once while
-// tracing the "active" nmethods on thread stacks during
-// the (strong) marking phase, and then again when walking
-// the code cache contents during the weak roots processing
-// phase. The two uses are distinguished by means of the
-// 'do_strong_roots_only' flag, which is true in the first
-// case. We want to walk the weak roots in the nmethod
-// only in the second case. The weak roots in the nmethod
-// are the oops in the ExceptionCache and the InlineCache
-// oops.
-void nmethod::oops_do(OopClosure* f, bool do_strong_roots_only) {
+void nmethod::oops_do(OopClosure* f, bool allow_zombie) {
   // make sure the oops ready to receive visitors
-  assert(!is_zombie() && !is_unloaded(),
-         "should not call follow on zombie or unloaded nmethod");
+  assert(allow_zombie || !is_zombie(), "should not call follow on zombie nmethod");
+  assert(!is_unloaded(), "should not call follow on unloaded nmethod");
 
   // If the method is not entrant or zombie then a JMP is plastered over the
   // first few bytes.  If an oop in the old code was there, that oop

src/share/vm/code/nmethod.hpp

@@ -566,7 +566,7 @@ public:
   void preserve_callee_argument_oops(frame fr, const RegisterMap *reg_map,
                                      OopClosure* f);
   void oops_do(OopClosure* f) { oops_do(f, false); }
-  void oops_do(OopClosure* f, bool do_strong_roots_only);
+  void oops_do(OopClosure* f, bool allow_zombie);
   bool detect_scavenge_root_oops();
   void verify_scavenge_root_oops() PRODUCT_RETURN;
 

src/share/vm/gc_implementation/g1/concurrentMark.cpp

@@ -4529,7 +4529,7 @@ G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
     _total_prev_live_bytes(0), _total_next_live_bytes(0),
     _hum_used_bytes(0), _hum_capacity_bytes(0),
     _hum_prev_live_bytes(0), _hum_next_live_bytes(0),
-    _total_remset_bytes(0) {
+    _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   MemRegion g1_committed = g1h->g1_committed();
   MemRegion g1_reserved = g1h->g1_reserved();
@@ -4553,9 +4553,11 @@ G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
                 G1PPRL_BYTE_H_FORMAT
                 G1PPRL_BYTE_H_FORMAT
                 G1PPRL_DOUBLE_H_FORMAT
+                G1PPRL_BYTE_H_FORMAT
                 G1PPRL_BYTE_H_FORMAT,
                 "type", "address-range",
-                "used", "prev-live", "next-live", "gc-eff", "remset");
+                "used", "prev-live", "next-live", "gc-eff",
+                "remset", "code-roots");
   _out->print_cr(G1PPRL_LINE_PREFIX
                 G1PPRL_TYPE_H_FORMAT
                 G1PPRL_ADDR_BASE_H_FORMAT
@@ -4563,9 +4565,11 @@ G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
                 G1PPRL_BYTE_H_FORMAT
                 G1PPRL_BYTE_H_FORMAT
                 G1PPRL_DOUBLE_H_FORMAT
+                G1PPRL_BYTE_H_FORMAT
                 G1PPRL_BYTE_H_FORMAT,
                 "", "",
-                "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)", "(bytes)");
+                "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
+                "(bytes)", "(bytes)");
 }
 
 // It takes as a parameter a reference to one of the _hum_* fields, it
@@ -4608,6 +4612,8 @@ bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
   size_t next_live_bytes = r->next_live_bytes();
   double gc_eff          = r->gc_efficiency();
   size_t remset_bytes    = r->rem_set()->mem_size();
+  size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
+
   if (r->used() == 0) {
     type = "FREE";
   } else if (r->is_survivor()) {
@@ -4642,6 +4648,7 @@ bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
   _total_prev_live_bytes += prev_live_bytes;
   _total_next_live_bytes += next_live_bytes;
   _total_remset_bytes    += remset_bytes;
+  _total_strong_code_roots_bytes += strong_code_roots_bytes;
 
   // Print a line for this particular region.
   _out->print_cr(G1PPRL_LINE_PREFIX
@@ -4651,9 +4658,11 @@ bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
                  G1PPRL_BYTE_FORMAT
                  G1PPRL_BYTE_FORMAT
                  G1PPRL_DOUBLE_FORMAT
+                 G1PPRL_BYTE_FORMAT
                  G1PPRL_BYTE_FORMAT,
                  type, bottom, end,
-                 used_bytes, prev_live_bytes, next_live_bytes, gc_eff , remset_bytes);
+                 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
+                 remset_bytes, strong_code_roots_bytes);
 
   return false;
 }
@@ -4669,7 +4678,8 @@ G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
                  G1PPRL_SUM_MB_PERC_FORMAT("used")
                  G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
                  G1PPRL_SUM_MB_PERC_FORMAT("next-live")
-                 G1PPRL_SUM_MB_FORMAT("remset"),
+                 G1PPRL_SUM_MB_FORMAT("remset")
+                 G1PPRL_SUM_MB_FORMAT("code-roots"),
                  bytes_to_mb(_total_capacity_bytes),
                  bytes_to_mb(_total_used_bytes),
                  perc(_total_used_bytes, _total_capacity_bytes),
@@ -4677,6 +4687,7 @@ G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
                  perc(_total_prev_live_bytes, _total_capacity_bytes),
                  bytes_to_mb(_total_next_live_bytes),
                  perc(_total_next_live_bytes, _total_capacity_bytes),
-                 bytes_to_mb(_total_remset_bytes));
+                 bytes_to_mb(_total_remset_bytes),
+                 bytes_to_mb(_total_strong_code_roots_bytes));
   _out->cr();
 }

src/share/vm/gc_implementation/g1/concurrentMark.hpp

@@ -1257,6 +1257,9 @@ private:
   // Accumulator for the remembered set size
   size_t _total_remset_bytes;
 
+  // Accumulator for strong code roots memory size
+  size_t _total_strong_code_roots_bytes;
+
   static double perc(size_t val, size_t total) {
     if (total == 0) {
       return 0.0;

src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp

@@ -46,6 +46,7 @@
 // may combine concurrent marking with parallel, incremental compaction of
 // heap subsets that will yield large amounts of garbage.
 
+// Forward declarations
 class HeapRegion;
 class HRRSCleanupTask;
 class GenerationSpec;
@@ -69,6 +70,7 @@ class STWGCTimer;
 class G1NewTracer;
 class G1OldTracer;
 class EvacuationFailedInfo;
+class nmethod;
 
 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
@@ -163,18 +165,6 @@ public:
     : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
 };
 
-// The G1 STW is alive closure.
-// An instance is embedded into the G1CH and used as the
-// (optional) _is_alive_non_header closure in the STW
-// reference processor. It is also extensively used during
-// reference processing during STW evacuation pauses.
-class G1STWIsAliveClosure: public BoolObjectClosure {
-  G1CollectedHeap* _g1;
-public:
-  G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
-  bool do_object_b(oop p);
-};
-
 class SurvivorGCAllocRegion : public G1AllocRegion {
 protected:
   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
@@ -193,6 +183,18 @@ public:
   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 };
 
+// The G1 STW is alive closure.
+// An instance is embedded into the G1CH and used as the
+// (optional) _is_alive_non_header closure in the STW
+// reference processor. It is also extensively used during
+// reference processing during STW evacuation pauses.
+class G1STWIsAliveClosure: public BoolObjectClosure {
+  G1CollectedHeap* _g1;
+public:
+  G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
+  bool do_object_b(oop p);
+};
+
 class RefineCardTableEntryClosure;
 
 class G1CollectedHeap : public SharedHeap {
@@ -1549,42 +1551,6 @@ public:
 
   virtual jlong millis_since_last_gc();
 
-  // Perform any cleanup actions necessary before allowing a verification.
-  virtual void prepare_for_verify();
-
-  // Perform verification.
-
-  // vo == UsePrevMarking  -> use "prev" marking information,
-  // vo == UseNextMarking -> use "next" marking information
-  // vo == UseMarkWord    -> use the mark word in the object header
-  //
-  // NOTE: Only the "prev" marking information is guaranteed to be
-  // consistent most of the time, so most calls to this should use
-  // vo == UsePrevMarking.
-  // Currently, there is only one case where this is called with
-  // vo == UseNextMarking, which is to verify the "next" marking
-  // information at the end of remark.
-  // Currently there is only one place where this is called with
-  // vo == UseMarkWord, which is to verify the marking during a
-  // full GC.
-  void verify(bool silent, VerifyOption vo);
-
-  // Override; it uses the "prev" marking information
-  virtual void verify(bool silent);
-
-  virtual void print_on(outputStream* st) const;
-  virtual void print_extended_on(outputStream* st) const;
-  virtual void print_on_error(outputStream* st) const;
-
-  virtual void print_gc_threads_on(outputStream* st) const;
-  virtual void gc_threads_do(ThreadClosure* tc) const;
-
-  // Override
-  void print_tracing_info() const;
-
-  // The following two methods are helpful for debugging RSet issues.
-  void print_cset_rsets() PRODUCT_RETURN;
-  void print_all_rsets() PRODUCT_RETURN;
 
   // Convenience function to be used in situations where the heap type can be
   // asserted to be this type.
@@ -1661,13 +1627,86 @@ public:
     else return is_obj_ill(obj, hr);
   }
 
+  bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
+  HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
+  bool is_marked(oop obj, VerifyOption vo);
+  const char* top_at_mark_start_str(VerifyOption vo);
+
+  ConcurrentMark* concurrent_mark() const { return _cm; }
+
+  // Refinement
+
+  ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
+
+  // The dirty cards region list is used to record a subset of regions
+  // whose cards need clearing. The list if populated during the
+  // remembered set scanning and drained during the card table
+  // cleanup. Although the methods are reentrant, population/draining
+  // phases must not overlap. For synchronization purposes the last
+  // element on the list points to itself.
+  HeapRegion* _dirty_cards_region_list;
+  void push_dirty_cards_region(HeapRegion* hr);
+  HeapRegion* pop_dirty_cards_region();
+
+  // Optimized nmethod scanning support routines
+
+  // Register the given nmethod with the G1 heap
+  virtual void register_nmethod(nmethod* nm);
+
+  // Unregister the given nmethod from the G1 heap
+  virtual void unregister_nmethod(nmethod* nm);
+
+  // Migrate the nmethods in the code root lists of the regions
+  // in the collection set to regions in to-space. In the event
+  // of an evacuation failure, nmethods that reference objects
+  // that were not successfullly evacuated are not migrated.
+  void migrate_strong_code_roots();
+
+  // During an initial mark pause, mark all the code roots that
+  // point into regions *not* in the collection set.
+  void mark_strong_code_roots(uint worker_id);
+
+  // Rebuild the stong code root lists for each region
+  // after a full GC
+  void rebuild_strong_code_roots();
+
+  // Verification
+
+  // The following is just to alert the verification code
+  // that a full collection has occurred and that the
+  // remembered sets are no longer up to date.
+  bool _full_collection;
+  void set_full_collection() { _full_collection = true;}
+  void clear_full_collection() {_full_collection = false;}
+  bool full_collection() {return _full_collection;}
+
+  // Perform any cleanup actions necessary before allowing a verification.
+  virtual void prepare_for_verify();
+
+  // Perform verification.
+
+  // vo == UsePrevMarking  -> use "prev" marking information,
+  // vo == UseNextMarking -> use "next" marking information
+  // vo == UseMarkWord    -> use the mark word in the object header
+  //
+  // NOTE: Only the "prev" marking information is guaranteed to be
+  // consistent most of the time, so most calls to this should use
+  // vo == UsePrevMarking.
+  // Currently, there is only one case where this is called with
+  // vo == UseNextMarking, which is to verify the "next" marking
+  // information at the end of remark.
+  // Currently there is only one place where this is called with
+  // vo == UseMarkWord, which is to verify the marking during a
+  // full GC.
+  void verify(bool silent, VerifyOption vo);
+
+  // Override; it uses the "prev" marking information
+  virtual void verify(bool silent);
+
   // The methods below are here for convenience and dispatch the
   // appropriate method depending on value of the given VerifyOption
-  // parameter. The options for that parameter are:
-  //
-  // vo == UsePrevMarking -> use "prev" marking information,
-  // vo == UseNextMarking -> use "next" marking information,
-  // vo == UseMarkWord    -> use mark word from object header
+  // parameter. The values for that parameter, and their meanings,
+  // are the same as those above.
 
   bool is_obj_dead_cond(const oop obj,
                         const HeapRegion* hr,
@@ -1692,31 +1731,21 @@ public:
     return false; // keep some compilers happy
   }
 
-  bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
-  HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
-  bool is_marked(oop obj, VerifyOption vo);
-  const char* top_at_mark_start_str(VerifyOption vo);
+  // Printing
 
-  // The following is just to alert the verification code
-  // that a full collection has occurred and that the
-  // remembered sets are no longer up to date.
-  bool _full_collection;
-  void set_full_collection() { _full_collection = true;}
-  void clear_full_collection() {_full_collection = false;}
-  bool full_collection() {return _full_collection;}
+  virtual void print_on(outputStream* st) const;
+  virtual void print_extended_on(outputStream* st) const;
+  virtual void print_on_error(outputStream* st) const;
 
-  ConcurrentMark* concurrent_mark() const { return _cm; }
-  ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
+  virtual void print_gc_threads_on(outputStream* st) const;
+  virtual void gc_threads_do(ThreadClosure* tc) const;
 
-  // The dirty cards region list is used to record a subset of regions
-  // whose cards need clearing. The list if populated during the
-  // remembered set scanning and drained during the card table
-  // cleanup. Although the methods are reentrant, population/draining
-  // phases must not overlap. For synchronization purposes the last
-  // element on the list points to itself.
-  HeapRegion* _dirty_cards_region_list;
-  void push_dirty_cards_region(HeapRegion* hr);
-  HeapRegion* pop_dirty_cards_region();
+  // Override
+  void print_tracing_info() const;
+
+  // The following two methods are helpful for debugging RSet issues.
+  void print_cset_rsets() PRODUCT_RETURN;
+  void print_all_rsets() PRODUCT_RETURN;
 
 public:
   void stop_conc_gc_threads();

src/share/vm/gc_implementation/g1/g1GCPhaseTimes.cpp

@@ -161,6 +161,8 @@ G1GCPhaseTimes::G1GCPhaseTimes(uint max_gc_threads) :
   _last_update_rs_times_ms(_max_gc_threads, "%.1lf"),
   _last_update_rs_processed_buffers(_max_gc_threads, "%d"),
   _last_scan_rs_times_ms(_max_gc_threads, "%.1lf"),
+  _last_strong_code_root_scan_times_ms(_max_gc_threads, "%.1lf"),
+  _last_strong_code_root_mark_times_ms(_max_gc_threads, "%.1lf"),
   _last_obj_copy_times_ms(_max_gc_threads, "%.1lf"),
   _last_termination_times_ms(_max_gc_threads, "%.1lf"),
   _last_termination_attempts(_max_gc_threads, SIZE_FORMAT),
@@ -182,6 +184,8 @@ void G1GCPhaseTimes::note_gc_start(uint active_gc_threads) {
   _last_update_rs_times_ms.reset();
   _last_update_rs_processed_buffers.reset();
   _last_scan_rs_times_ms.reset();
+  _last_strong_code_root_scan_times_ms.reset();
+  _last_strong_code_root_mark_times_ms.reset();
   _last_obj_copy_times_ms.reset();
   _last_termination_times_ms.reset();
   _last_termination_attempts.reset();
@@ -197,6 +201,8 @@ void G1GCPhaseTimes::note_gc_end() {
   _last_update_rs_times_ms.verify();
   _last_update_rs_processed_buffers.verify();
   _last_scan_rs_times_ms.verify();
+  _last_strong_code_root_scan_times_ms.verify();
+  _last_strong_code_root_mark_times_ms.verify();
   _last_obj_copy_times_ms.verify();
   _last_termination_times_ms.verify();
   _last_termination_attempts.verify();
@@ -210,6 +216,8 @@ void G1GCPhaseTimes::note_gc_end() {
                                _last_satb_filtering_times_ms.get(i) +
                                _last_update_rs_times_ms.get(i) +
                                _last_scan_rs_times_ms.get(i) +
+                               _last_strong_code_root_scan_times_ms.get(i) +
+                               _last_strong_code_root_mark_times_ms.get(i) +
                                _last_obj_copy_times_ms.get(i) +
                                _last_termination_times_ms.get(i);
 
@@ -239,6 +247,9 @@ double G1GCPhaseTimes::accounted_time_ms() {
     // Now subtract the time taken to fix up roots in generated code
     misc_time_ms += _cur_collection_code_root_fixup_time_ms;
 
+    // Strong code root migration time
+    misc_time_ms += _cur_strong_code_root_migration_time_ms;
+
     // Subtract the time taken to clean the card table from the
     // current value of "other time"
     misc_time_ms += _cur_clear_ct_time_ms;
@@ -257,9 +268,13 @@ void G1GCPhaseTimes::print(double pause_time_sec) {
     if (_last_satb_filtering_times_ms.sum() > 0.0) {
       _last_satb_filtering_times_ms.print(2, "SATB Filtering (ms)");
     }
+    if (_last_strong_code_root_mark_times_ms.sum() > 0.0) {
+     _last_strong_code_root_mark_times_ms.print(2, "Code Root Marking (ms)");
+    }
     _last_update_rs_times_ms.print(2, "Update RS (ms)");
       _last_update_rs_processed_buffers.print(3, "Processed Buffers");
     _last_scan_rs_times_ms.print(2, "Scan RS (ms)");
+    _last_strong_code_root_scan_times_ms.print(2, "Code Root Scanning (ms)");
     _last_obj_copy_times_ms.print(2, "Object Copy (ms)");
     _last_termination_times_ms.print(2, "Termination (ms)");
     if (G1Log::finest()) {
@@ -273,12 +288,17 @@ void G1GCPhaseTimes::print(double pause_time_sec) {
     if (_last_satb_filtering_times_ms.sum() > 0.0) {
       _last_satb_filtering_times_ms.print(1, "SATB Filtering (ms)");
     }
+    if (_last_strong_code_root_mark_times_ms.sum() > 0.0) {
+      _last_strong_code_root_mark_times_ms.print(1, "Code Root Marking (ms)");
+    }
     _last_update_rs_times_ms.print(1, "Update RS (ms)");
       _last_update_rs_processed_buffers.print(2, "Processed Buffers");
     _last_scan_rs_times_ms.print(1, "Scan RS (ms)");
+    _last_strong_code_root_scan_times_ms.print(1, "Code Root Scanning (ms)");
     _last_obj_copy_times_ms.print(1, "Object Copy (ms)");
   }
   print_stats(1, "Code Root Fixup", _cur_collection_code_root_fixup_time_ms);
+  print_stats(1, "Code Root Migration", _cur_strong_code_root_migration_time_ms);
   print_stats(1, "Clear CT", _cur_clear_ct_time_ms);
   double misc_time_ms = pause_time_sec * MILLIUNITS - accounted_time_ms();
   print_stats(1, "Other", misc_time_ms);

src/share/vm/gc_implementation/g1/g1GCPhaseTimes.hpp

@@ -119,6 +119,8 @@ class G1GCPhaseTimes : public CHeapObj<mtGC> {
   WorkerDataArray<double> _last_update_rs_times_ms;
   WorkerDataArray<int>    _last_update_rs_processed_buffers;
   WorkerDataArray<double> _last_scan_rs_times_ms;
+  WorkerDataArray<double> _last_strong_code_root_scan_times_ms;
+  WorkerDataArray<double> _last_strong_code_root_mark_times_ms;
   WorkerDataArray<double> _last_obj_copy_times_ms;
   WorkerDataArray<double> _last_termination_times_ms;
   WorkerDataArray<size_t> _last_termination_attempts;
@@ -128,6 +130,7 @@ class G1GCPhaseTimes : public CHeapObj<mtGC> {
 
   double _cur_collection_par_time_ms;
   double _cur_collection_code_root_fixup_time_ms;
+  double _cur_strong_code_root_migration_time_ms;
 
   double _cur_clear_ct_time_ms;
   double _cur_ref_proc_time_ms;
@@ -179,6 +182,14 @@ class G1GCPhaseTimes : public CHeapObj<mtGC> {
     _last_scan_rs_times_ms.set(worker_i, ms);
   }
 
+  void record_strong_code_root_scan_time(uint worker_i, double ms) {
+    _last_strong_code_root_scan_times_ms.set(worker_i, ms);
+  }
+
+  void record_strong_code_root_mark_time(uint worker_i, double ms) {
+    _last_strong_code_root_mark_times_ms.set(worker_i, ms);
+  }
+
   void record_obj_copy_time(uint worker_i, double ms) {
     _last_obj_copy_times_ms.set(worker_i, ms);
   }
@@ -208,6 +219,10 @@ class G1GCPhaseTimes : public CHeapObj<mtGC> {
     _cur_collection_code_root_fixup_time_ms = ms;
   }
 
+  void record_strong_code_root_migration_time(double ms) {
+    _cur_strong_code_root_migration_time_ms = ms;
+  }
+
   void record_ref_proc_time(double ms) {
     _cur_ref_proc_time_ms = ms;
   }
@@ -294,6 +309,14 @@ class G1GCPhaseTimes : public CHeapObj<mtGC> {
     return _last_scan_rs_times_ms.average();
   }
 
+  double average_last_strong_code_root_scan_time(){
+    return _last_strong_code_root_scan_times_ms.average();
+  }
+
+  double average_last_strong_code_root_mark_time(){
+    return _last_strong_code_root_mark_times_ms.average();
+  }
+
   double average_last_obj_copy_time() {
     return _last_obj_copy_times_ms.average();
   }

src/share/vm/gc_implementation/g1/g1RemSet.cpp

@@ -104,15 +104,25 @@ void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {
 class ScanRSClosure : public HeapRegionClosure {
   size_t _cards_done, _cards;
   G1CollectedHeap* _g1h;
+
   OopsInHeapRegionClosure* _oc;
+  CodeBlobToOopClosure* _code_root_cl;
+
   G1BlockOffsetSharedArray* _bot_shared;
   CardTableModRefBS *_ct_bs;
-  int _worker_i;
-  int _block_size;
-  bool _try_claimed;
+
+  double _strong_code_root_scan_time_sec;
+  int    _worker_i;
+  int    _block_size;
+  bool   _try_claimed;
+
 public:
-  ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :
+  ScanRSClosure(OopsInHeapRegionClosure* oc,
+                CodeBlobToOopClosure* code_root_cl,
+                int worker_i) :
     _oc(oc),
+    _code_root_cl(code_root_cl),
+    _strong_code_root_scan_time_sec(0.0),
     _cards(0),
     _cards_done(0),
     _worker_i(worker_i),
@@ -160,6 +170,12 @@ public:
                            card_start, card_start + G1BlockOffsetSharedArray::N_words);
   }
 
+  void scan_strong_code_roots(HeapRegion* r) {
+    double scan_start = os::elapsedTime();
+    r->strong_code_roots_do(_code_root_cl);
+    _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
+  }
+
   bool doHeapRegion(HeapRegion* r) {
     assert(r->in_collection_set(), "should only be called on elements of CS.");
     HeapRegionRemSet* hrrs = r->rem_set();
@@ -173,6 +189,7 @@ public:
     //   _try_claimed || r->claim_iter()
     // is true: either we're supposed to work on claimed-but-not-complete
     // regions, or we successfully claimed the region.
+
     HeapRegionRemSetIterator iter(hrrs);
     size_t card_index;
 
@@ -205,30 +222,43 @@ public:
       }
     }
     if (!_try_claimed) {
+      // Scan the strong code root list attached to the current region
+      scan_strong_code_roots(r);
+
       hrrs->set_iter_complete();
     }
     return false;
   }
+
+  double strong_code_root_scan_time_sec() {
+    return _strong_code_root_scan_time_sec;
+  }
+
   size_t cards_done() { return _cards_done;}
   size_t cards_looked_up() { return _cards;}
 };
 
-void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {
+void G1RemSet::scanRS(OopsInHeapRegionClosure* oc,
+                      CodeBlobToOopClosure* code_root_cl,
+                      int worker_i) {
   double rs_time_start = os::elapsedTime();
   HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
 
-  ScanRSClosure scanRScl(oc, worker_i);
+  ScanRSClosure scanRScl(oc, code_root_cl, worker_i);
 
   _g1->collection_set_iterate_from(startRegion, &scanRScl);
   scanRScl.set_try_claimed();
   _g1->collection_set_iterate_from(startRegion, &scanRScl);
 
-  double scan_rs_time_sec = os::elapsedTime() - rs_time_start;
+  double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)
+                            - scanRScl.strong_code_root_scan_time_sec();
 
-  assert( _cards_scanned != NULL, "invariant" );
+  assert(_cards_scanned != NULL, "invariant");
   _cards_scanned[worker_i] = scanRScl.cards_done();
 
   _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);
+  _g1p->phase_times()->record_strong_code_root_scan_time(worker_i,
+                                                         scanRScl.strong_code_root_scan_time_sec() * 1000.0);
 }
 
 // Closure used for updating RSets and recording references that
@@ -288,7 +318,8 @@ void G1RemSet::cleanupHRRS() {
 }
 
 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
-                                             int worker_i) {
+                                           CodeBlobToOopClosure* code_root_cl,
+                                           int worker_i) {
 #if CARD_REPEAT_HISTO
   ct_freq_update_histo_and_reset();
 #endif
@@ -328,7 +359,7 @@ void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,
     _g1p->phase_times()->record_update_rs_time(worker_i, 0.0);
   }
   if (G1UseParallelRSetScanning || (worker_i == 0)) {
-    scanRS(oc, worker_i);
+    scanRS(oc, code_root_cl, worker_i);
   } else {
     _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0);
   }

src/share/vm/gc_implementation/g1/g1RemSet.hpp

@@ -81,14 +81,23 @@ public:
   G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs);
   ~G1RemSet();
 
-  // Invoke "blk->do_oop" on all pointers into the CS in objects in regions
-  // outside the CS (having invoked "blk->set_region" to set the "from"
-  // region correctly beforehand.) The "worker_i" param is for the
-  // parallel case where the number of the worker thread calling this
-  // function can be helpful in partitioning the work to be done. It
-  // should be the same as the "i" passed to the calling thread's
-  // work(i) function. In the sequential case this param will be ingored.
-  void oops_into_collection_set_do(OopsInHeapRegionClosure* blk, int worker_i);
+  // Invoke "blk->do_oop" on all pointers into the collection set
+  // from objects in regions outside the collection set (having
+  // invoked "blk->set_region" to set the "from" region correctly
+  // beforehand.)
+  //
+  // Invoke code_root_cl->do_code_blob on the unmarked nmethods
+  // on the strong code roots list for each region in the
+  // collection set.
+  //
+  // The "worker_i" param is for the parallel case where the id
+  // of the worker thread calling this function can be helpful in
+  // partitioning the work to be done. It should be the same as
+  // the "i" passed to the calling thread's work(i) function.
+  // In the sequential case this param will be ignored.
+  void oops_into_collection_set_do(OopsInHeapRegionClosure* blk,
+                                   CodeBlobToOopClosure* code_root_cl,
+                                   int worker_i);
 
   // Prepare for and cleanup after an oops_into_collection_set_do
   // call.  Must call each of these once before and after (in sequential
@@ -98,7 +107,10 @@ public:
   void prepare_for_oops_into_collection_set_do();
   void cleanup_after_oops_into_collection_set_do();
 
-  void scanRS(OopsInHeapRegionClosure* oc, int worker_i);
+  void scanRS(OopsInHeapRegionClosure* oc,
+              CodeBlobToOopClosure* code_root_cl,
+              int worker_i);
+
   void updateRS(DirtyCardQueue* into_cset_dcq, int worker_i);
 
   CardTableModRefBS* ct_bs() { return _ct_bs; }

src/share/vm/gc_implementation/g1/g1RemSetSummary.cpp

@@ -127,32 +127,55 @@ void G1RemSetSummary::subtract_from(G1RemSetSummary* other) {
 
 class HRRSStatsIter: public HeapRegionClosure {
   size_t _occupied;
-  size_t _total_mem_sz;
-  size_t _max_mem_sz;
-  HeapRegion* _max_mem_sz_region;
+
+  size_t _total_rs_mem_sz;
+  size_t _max_rs_mem_sz;
+  HeapRegion* _max_rs_mem_sz_region;
+
+  size_t _total_code_root_mem_sz;
+  size_t _max_code_root_mem_sz;
+  HeapRegion* _max_code_root_mem_sz_region;
 public:
   HRRSStatsIter() :
     _occupied(0),
-    _total_mem_sz(0),
-    _max_mem_sz(0),
-    _max_mem_sz_region(NULL)
+    _total_rs_mem_sz(0),
+    _max_rs_mem_sz(0),
+    _max_rs_mem_sz_region(NULL),
+    _total_code_root_mem_sz(0),
+    _max_code_root_mem_sz(0),
+    _max_code_root_mem_sz_region(NULL)
   {}
 
   bool doHeapRegion(HeapRegion* r) {
-    size_t mem_sz = r->rem_set()->mem_size();
-    if (mem_sz > _max_mem_sz) {
-      _max_mem_sz = mem_sz;
-      _max_mem_sz_region = r;
+    HeapRegionRemSet* hrrs = r->rem_set();
+
+    // HeapRegionRemSet::mem_size() includes the
+    // size of the strong code roots
+    size_t rs_mem_sz = hrrs->mem_size();
+    if (rs_mem_sz > _max_rs_mem_sz) {
+      _max_rs_mem_sz = rs_mem_sz;
+      _max_rs_mem_sz_region = r;
+    }
+    _total_rs_mem_sz += rs_mem_sz;
+
+    size_t code_root_mem_sz = hrrs->strong_code_roots_mem_size();
+    if (code_root_mem_sz > _max_code_root_mem_sz) {
+      _max_code_root_mem_sz = code_root_mem_sz;
+      _max_code_root_mem_sz_region = r;
     }
-    _total_mem_sz += mem_sz;
-    size_t occ = r->rem_set()->occupied();
+    _total_code_root_mem_sz += code_root_mem_sz;
+
+    size_t occ = hrrs->occupied();
     _occupied += occ;
     return false;
   }
-  size_t total_mem_sz() { return _total_mem_sz; }
-  size_t max_mem_sz() { return _max_mem_sz; }
+  size_t total_rs_mem_sz() { return _total_rs_mem_sz; }
+  size_t max_rs_mem_sz() { return _max_rs_mem_sz; }
+  HeapRegion* max_rs_mem_sz_region() { return _max_rs_mem_sz_region; }
+  size_t total_code_root_mem_sz() { return _total_code_root_mem_sz; }
+  size_t max_code_root_mem_sz() { return _max_code_root_mem_sz; }
+  HeapRegion* max_code_root_mem_sz_region() { return _max_code_root_mem_sz_region; }
   size_t occupied() { return _occupied; }
-  HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; }
 };
 
 double calc_percentage(size_t numerator, size_t denominator) {
@@ -184,22 +207,33 @@ void G1RemSetSummary::print_on(outputStream* out) {
 
   HRRSStatsIter blk;
   G1CollectedHeap::heap()->heap_region_iterate(&blk);
+  // RemSet stats
   out->print_cr("  Total heap region rem set sizes = "SIZE_FORMAT"K."
                 "  Max = "SIZE_FORMAT"K.",
-                blk.total_mem_sz()/K, blk.max_mem_sz()/K);
+                blk.total_rs_mem_sz()/K, blk.max_rs_mem_sz()/K);
   out->print_cr("  Static structures = "SIZE_FORMAT"K,"
                 " free_lists = "SIZE_FORMAT"K.",
                 HeapRegionRemSet::static_mem_size() / K,
                 HeapRegionRemSet::fl_mem_size() / K);
   out->print_cr("    "SIZE_FORMAT" occupied cards represented.",
                 blk.occupied());
-  HeapRegion* max_mem_sz_region = blk.max_mem_sz_region();
-  HeapRegionRemSet* rem_set = max_mem_sz_region->rem_set();
+  HeapRegion* max_rs_mem_sz_region = blk.max_rs_mem_sz_region();
+  HeapRegionRemSet* max_rs_rem_set = max_rs_mem_sz_region->rem_set();
   out->print_cr("    Max size region = "HR_FORMAT", "
                 "size = "SIZE_FORMAT "K, occupied = "SIZE_FORMAT"K.",
-                HR_FORMAT_PARAMS(max_mem_sz_region),
-                (rem_set->mem_size() + K - 1)/K,
-                (rem_set->occupied() + K - 1)/K);
-
+                HR_FORMAT_PARAMS(max_rs_mem_sz_region),
+                (max_rs_rem_set->mem_size() + K - 1)/K,
+                (max_rs_rem_set->occupied() + K - 1)/K);
   out->print_cr("    Did %d coarsenings.", num_coarsenings());
+  // Strong code root stats
+  out->print_cr("  Total heap region code-root set sizes = "SIZE_FORMAT"K."
+                "  Max = "SIZE_FORMAT"K.",
+                blk.total_code_root_mem_sz()/K, blk.max_code_root_mem_sz()/K);
+  HeapRegion* max_code_root_mem_sz_region = blk.max_code_root_mem_sz_region();
+  HeapRegionRemSet* max_code_root_rem_set = max_code_root_mem_sz_region->rem_set();
+  out->print_cr("    Max size region = "HR_FORMAT", "
+                "size = "SIZE_FORMAT "K, num_elems = "SIZE_FORMAT".",
+                HR_FORMAT_PARAMS(max_code_root_mem_sz_region),
+                (max_code_root_rem_set->strong_code_roots_mem_size() + K - 1)/K,
+                (max_code_root_rem_set->strong_code_roots_list_length()));
 }

src/share/vm/gc_implementation/g1/g1_globals.hpp

@@ -319,7 +319,10 @@
                                                                             \
   diagnostic(bool, G1VerifyRSetsDuringFullGC, false,                        \
              "If true, perform verification of each heap region's "         \
-             "remembered set when verifying the heap during a full GC.")
+             "remembered set when verifying the heap during a full GC.")    \
+                                                                            \
+  diagnostic(bool, G1VerifyHeapRegionCodeRoots, false,                      \
+             "Verify the code root lists attached to each heap region.")
 
 G1_FLAGS(DECLARE_DEVELOPER_FLAG, DECLARE_PD_DEVELOPER_FLAG, DECLARE_PRODUCT_FLAG, DECLARE_PD_PRODUCT_FLAG, DECLARE_DIAGNOSTIC_FLAG, DECLARE_EXPERIMENTAL_FLAG, DECLARE_NOTPRODUCT_FLAG, DECLARE_MANAGEABLE_FLAG, DECLARE_PRODUCT_RW_FLAG)
 

src/share/vm/gc_implementation/g1/heapRegion.cpp

@@ -23,6 +23,7 @@
  */
 
 #include "precompiled.hpp"
+#include "code/nmethod.hpp"
 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
@@ -50,144 +51,6 @@ FilterOutOfRegionClosure::FilterOutOfRegionClosure(HeapRegion* r,
                                                    OopClosure* oc) :
   _r_bottom(r->bottom()), _r_end(r->end()), _oc(oc) { }
 
-class VerifyLiveClosure: public OopClosure {
-private:
-  G1CollectedHeap* _g1h;
-  CardTableModRefBS* _bs;
-  oop _containing_obj;
-  bool _failures;
-  int _n_failures;
-  VerifyOption _vo;
-public:
-  // _vo == UsePrevMarking -> use "prev" marking information,
-  // _vo == UseNextMarking -> use "next" marking information,
-  // _vo == UseMarkWord    -> use mark word from object header.
-  VerifyLiveClosure(G1CollectedHeap* g1h, VerifyOption vo) :
-    _g1h(g1h), _bs(NULL), _containing_obj(NULL),
-    _failures(false), _n_failures(0), _vo(vo)
-  {
-    BarrierSet* bs = _g1h->barrier_set();
-    if (bs->is_a(BarrierSet::CardTableModRef))
-      _bs = (CardTableModRefBS*)bs;
-  }
-
-  void set_containing_obj(oop obj) {
-    _containing_obj = obj;
-  }
-
-  bool failures() { return _failures; }
-  int n_failures() { return _n_failures; }
-
-  virtual void do_oop(narrowOop* p) { do_oop_work(p); }
-  virtual void do_oop(      oop* p) { do_oop_work(p); }
-
-  void print_object(outputStream* out, oop obj) {
-#ifdef PRODUCT
-    Klass* k = obj->klass();
-    const char* class_name = InstanceKlass::cast(k)->external_name();
-    out->print_cr("class name %s", class_name);
-#else // PRODUCT
-    obj->print_on(out);
-#endif // PRODUCT
-  }
-
-  template <class T>
-  void do_oop_work(T* p) {
-    assert(_containing_obj != NULL, "Precondition");
-    assert(!_g1h->is_obj_dead_cond(_containing_obj, _vo),
-           "Precondition");
-    T heap_oop = oopDesc::load_heap_oop(p);
-    if (!oopDesc::is_null(heap_oop)) {
-      oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
-      bool failed = false;
-      if (!_g1h->is_in_closed_subset(obj) || _g1h->is_obj_dead_cond(obj, _vo)) {
-        MutexLockerEx x(ParGCRareEvent_lock,
-                        Mutex::_no_safepoint_check_flag);
-
-        if (!_failures) {
-          gclog_or_tty->print_cr("");
-          gclog_or_tty->print_cr("----------");
-        }
-        if (!_g1h->is_in_closed_subset(obj)) {
-          HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
-          gclog_or_tty->print_cr("Field "PTR_FORMAT
-                                 " of live obj "PTR_FORMAT" in region "
-                                 "["PTR_FORMAT", "PTR_FORMAT")",
-                                 p, (void*) _containing_obj,
-                                 from->bottom(), from->end());
-          print_object(gclog_or_tty, _containing_obj);
-          gclog_or_tty->print_cr("points to obj "PTR_FORMAT" not in the heap",
-                                 (void*) obj);
-        } else {
-          HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
-          HeapRegion* to   = _g1h->heap_region_containing((HeapWord*)obj);
-          gclog_or_tty->print_cr("Field "PTR_FORMAT
-                                 " of live obj "PTR_FORMAT" in region "
-                                 "["PTR_FORMAT", "PTR_FORMAT")",
-                                 p, (void*) _containing_obj,
-                                 from->bottom(), from->end());
-          print_object(gclog_or_tty, _containing_obj);
-          gclog_or_tty->print_cr("points to dead obj "PTR_FORMAT" in region "
-                                 "["PTR_FORMAT", "PTR_FORMAT")",
-                                 (void*) obj, to->bottom(), to->end());
-          print_object(gclog_or_tty, obj);
-        }
-        gclog_or_tty->print_cr("----------");
-        gclog_or_tty->flush();
-        _failures = true;
-        failed = true;
-        _n_failures++;
-      }
-
-      if (!_g1h->full_collection() || G1VerifyRSetsDuringFullGC) {
-        HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
-        HeapRegion* to   = _g1h->heap_region_containing(obj);
-        if (from != NULL && to != NULL &&
-            from != to &&
-            !to->isHumongous()) {
-          jbyte cv_obj = *_bs->byte_for_const(_containing_obj);
-          jbyte cv_field = *_bs->byte_for_const(p);
-          const jbyte dirty = CardTableModRefBS::dirty_card_val();
-
-          bool is_bad = !(from->is_young()
-                          || to->rem_set()->contains_reference(p)
-                          || !G1HRRSFlushLogBuffersOnVerify && // buffers were not flushed
-                              (_containing_obj->is_objArray() ?
-                                  cv_field == dirty
-                               : cv_obj == dirty || cv_field == dirty));
-          if (is_bad) {
-            MutexLockerEx x(ParGCRareEvent_lock,
-                            Mutex::_no_safepoint_check_flag);
-
-            if (!_failures) {
-              gclog_or_tty->print_cr("");
-              gclog_or_tty->print_cr("----------");
-            }
-            gclog_or_tty->print_cr("Missing rem set entry:");
-            gclog_or_tty->print_cr("Field "PTR_FORMAT" "
-                                   "of obj "PTR_FORMAT", "
-                                   "in region "HR_FORMAT,
-                                   p, (void*) _containing_obj,
-                                   HR_FORMAT_PARAMS(from));
-            _containing_obj->print_on(gclog_or_tty);
-            gclog_or_tty->print_cr("points to obj "PTR_FORMAT" "
-                                   "in region "HR_FORMAT,
-                                   (void*) obj,
-                                   HR_FORMAT_PARAMS(to));
-            obj->print_on(gclog_or_tty);
-            gclog_or_tty->print_cr("Obj head CTE = %d, field CTE = %d.",
-                          cv_obj, cv_field);
-            gclog_or_tty->print_cr("----------");
-            gclog_or_tty->flush();
-            _failures = true;
-            if (!failed) _n_failures++;
-          }
-        }
-      }
-    }
-  }
-};
-
 template<class ClosureType>
 HeapWord* walk_mem_region_loop(ClosureType* cl, G1CollectedHeap* g1h,
                                HeapRegion* hr,
@@ -368,7 +231,7 @@ void HeapRegion::hr_clear(bool par, bool clear_space) {
   if (!par) {
     // If this is parallel, this will be done later.
     HeapRegionRemSet* hrrs = rem_set();
-    if (hrrs != NULL) hrrs->clear();
+    hrrs->clear();
     _claimed = InitialClaimValue;
   }
   zero_marked_bytes();
@@ -505,6 +368,7 @@ HeapRegion::HeapRegion(uint hrs_index,
     _rem_set(NULL), _recorded_rs_length(0), _predicted_elapsed_time_ms(0),
     _predicted_bytes_to_copy(0)
 {
+  _rem_set = new HeapRegionRemSet(sharedOffsetArray, this);
   _orig_end = mr.end();
   // Note that initialize() will set the start of the unmarked area of the
   // region.
@@ -512,8 +376,6 @@ HeapRegion::HeapRegion(uint hrs_index,
   set_top(bottom());
   set_saved_mark();
 
-  _rem_set =  new HeapRegionRemSet(sharedOffsetArray, this);
-
   assert(HeapRegionRemSet::num_par_rem_sets() > 0, "Invariant.");
 }
 
@@ -733,6 +595,160 @@ oops_on_card_seq_iterate_careful(MemRegion mr,
   return NULL;
 }
 
+// Code roots support
+
+void HeapRegion::add_strong_code_root(nmethod* nm) {
+  HeapRegionRemSet* hrrs = rem_set();
+  hrrs->add_strong_code_root(nm);
+}
+
+void HeapRegion::remove_strong_code_root(nmethod* nm) {
+  HeapRegionRemSet* hrrs = rem_set();
+  hrrs->remove_strong_code_root(nm);
+}
+
+void HeapRegion::migrate_strong_code_roots() {
+  assert(in_collection_set(), "only collection set regions");
+  assert(!isHumongous(), "not humongous regions");
+
+  HeapRegionRemSet* hrrs = rem_set();
+  hrrs->migrate_strong_code_roots();
+}
+
+void HeapRegion::strong_code_roots_do(CodeBlobClosure* blk) const {
+  HeapRegionRemSet* hrrs = rem_set();
+  hrrs->strong_code_roots_do(blk);
+}
+
+class VerifyStrongCodeRootOopClosure: public OopClosure {
+  const HeapRegion* _hr;
+  nmethod* _nm;
+  bool _failures;
+  bool _has_oops_in_region;
+
+  template <class T> void do_oop_work(T* p) {
+    T heap_oop = oopDesc::load_heap_oop(p);
+    if (!oopDesc::is_null(heap_oop)) {
+      oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
+
+      // Note: not all the oops embedded in the nmethod are in the
+      // current region. We only look at those which are.
+      if (_hr->is_in(obj)) {
+        // Object is in the region. Check that its less than top
+        if (_hr->top() <= (HeapWord*)obj) {
+          // Object is above top
+          gclog_or_tty->print_cr("Object "PTR_FORMAT" in region "
+                                 "["PTR_FORMAT", "PTR_FORMAT") is above "
+                                 "top "PTR_FORMAT,
+                                 obj, _hr->bottom(), _hr->end(), _hr->top());
+          _failures = true;
+          return;
+        }
+        // Nmethod has at least one oop in the current region
+        _has_oops_in_region = true;
+      }
+    }
+  }
+
+public:
+  VerifyStrongCodeRootOopClosure(const HeapRegion* hr, nmethod* nm):
+    _hr(hr), _failures(false), _has_oops_in_region(false) {}
+
+  void do_oop(narrowOop* p) { do_oop_work(p); }
+  void do_oop(oop* p)       { do_oop_work(p); }
+
+  bool failures()           { return _failures; }
+  bool has_oops_in_region() { return _has_oops_in_region; }
+};
+
+class VerifyStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
+  const HeapRegion* _hr;
+  bool _failures;
+public:
+  VerifyStrongCodeRootCodeBlobClosure(const HeapRegion* hr) :
+    _hr(hr), _failures(false) {}
+
+  void do_code_blob(CodeBlob* cb) {
+    nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
+    if (nm != NULL) {
+      // Verify that the nemthod is live
+      if (!nm->is_alive()) {
+        gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has dead nmethod "
+                               PTR_FORMAT" in its strong code roots",
+                               _hr->bottom(), _hr->end(), nm);
+        _failures = true;
+      } else {
+        VerifyStrongCodeRootOopClosure oop_cl(_hr, nm);
+        nm->oops_do(&oop_cl);
+        if (!oop_cl.has_oops_in_region()) {
+          gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has nmethod "
+                                 PTR_FORMAT" in its strong code roots "
+                                 "with no pointers into region",
+                                 _hr->bottom(), _hr->end(), nm);
+          _failures = true;
+        } else if (oop_cl.failures()) {
+          gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] has other "
+                                 "failures for nmethod "PTR_FORMAT,
+                                 _hr->bottom(), _hr->end(), nm);
+          _failures = true;
+        }
+      }
+    }
+  }
+
+  bool failures()       { return _failures; }
+};
+
+void HeapRegion::verify_strong_code_roots(VerifyOption vo, bool* failures) const {
+  if (!G1VerifyHeapRegionCodeRoots) {
+    // We're not verifying code roots.
+    return;
+  }
+  if (vo == VerifyOption_G1UseMarkWord) {
+    // Marking verification during a full GC is performed after class
+    // unloading, code cache unloading, etc so the strong code roots
+    // attached to each heap region are in an inconsistent state. They won't
+    // be consistent until the strong code roots are rebuilt after the
+    // actual GC. Skip verifying the strong code roots in this particular
+    // time.
+    assert(VerifyDuringGC, "only way to get here");
+    return;
+  }
+
+  HeapRegionRemSet* hrrs = rem_set();
+  int strong_code_roots_length = hrrs->strong_code_roots_list_length();
+
+  // if this region is empty then there should be no entries
+  // on its strong code root list
+  if (is_empty()) {
+    if (strong_code_roots_length > 0) {
+      gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is empty "
+                             "but has "INT32_FORMAT" code root entries",
+                             bottom(), end(), strong_code_roots_length);
+      *failures = true;
+    }
+    return;
+  }
+
+  // An H-region should have an empty strong code root list
+  if (isHumongous()) {
+    if (strong_code_roots_length > 0) {
+      gclog_or_tty->print_cr("region ["PTR_FORMAT","PTR_FORMAT"] is humongous "
+                             "but has "INT32_FORMAT" code root entries",
+                             bottom(), end(), strong_code_roots_length);
+      *failures = true;
+    }
+    return;
+  }
+
+  VerifyStrongCodeRootCodeBlobClosure cb_cl(this);
+  strong_code_roots_do(&cb_cl);
+
+  if (cb_cl.failures()) {
+    *failures = true;
+  }
+}
+
 void HeapRegion::print() const { print_on(gclog_or_tty); }
 void HeapRegion::print_on(outputStream* st) const {
   if (isHumongous()) {
@@ -761,10 +777,143 @@ void HeapRegion::print_on(outputStream* st) const {
   G1OffsetTableContigSpace::print_on(st);
 }
 
-void HeapRegion::verify() const {
-  bool dummy = false;
-  verify(VerifyOption_G1UsePrevMarking, /* failures */ &dummy);
-}
+class VerifyLiveClosure: public OopClosure {
+private:
+  G1CollectedHeap* _g1h;
+  CardTableModRefBS* _bs;
+  oop _containing_obj;
+  bool _failures;
+  int _n_failures;
+  VerifyOption _vo;
+public:
+  // _vo == UsePrevMarking -> use "prev" marking information,
+  // _vo == UseNextMarking -> use "next" marking information,
+  // _vo == UseMarkWord    -> use mark word from object header.
+  VerifyLiveClosure(G1CollectedHeap* g1h, VerifyOption vo) :
+    _g1h(g1h), _bs(NULL), _containing_obj(NULL),
+    _failures(false), _n_failures(0), _vo(vo)
+  {
+    BarrierSet* bs = _g1h->barrier_set();
+    if (bs->is_a(BarrierSet::CardTableModRef))
+      _bs = (CardTableModRefBS*)bs;
+  }
+
+  void set_containing_obj(oop obj) {
+    _containing_obj = obj;
+  }
+
+  bool failures() { return _failures; }
+  int n_failures() { return _n_failures; }
+
+  virtual void do_oop(narrowOop* p) { do_oop_work(p); }
+  virtual void do_oop(      oop* p) { do_oop_work(p); }
+
+  void print_object(outputStream* out, oop obj) {
+#ifdef PRODUCT
+    Klass* k = obj->klass();
+    const char* class_name = InstanceKlass::cast(k)->external_name();
+    out->print_cr("class name %s", class_name);
+#else // PRODUCT
+    obj->print_on(out);
+#endif // PRODUCT
+  }
+
+  template <class T>
+  void do_oop_work(T* p) {
+    assert(_containing_obj != NULL, "Precondition");
+    assert(!_g1h->is_obj_dead_cond(_containing_obj, _vo),
+           "Precondition");
+    T heap_oop = oopDesc::load_heap_oop(p);
+    if (!oopDesc::is_null(heap_oop)) {
+      oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
+      bool failed = false;
+      if (!_g1h->is_in_closed_subset(obj) || _g1h->is_obj_dead_cond(obj, _vo)) {
+        MutexLockerEx x(ParGCRareEvent_lock,
+                        Mutex::_no_safepoint_check_flag);
+
+        if (!_failures) {
+          gclog_or_tty->print_cr("");
+          gclog_or_tty->print_cr("----------");
+        }
+        if (!_g1h->is_in_closed_subset(obj)) {
+          HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
+          gclog_or_tty->print_cr("Field "PTR_FORMAT
+                                 " of live obj "PTR_FORMAT" in region "
+                                 "["PTR_FORMAT", "PTR_FORMAT")",
+                                 p, (void*) _containing_obj,
+                                 from->bottom(), from->end());
+          print_object(gclog_or_tty, _containing_obj);
+          gclog_or_tty->print_cr("points to obj "PTR_FORMAT" not in the heap",
+                                 (void*) obj);
+        } else {
+          HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
+          HeapRegion* to   = _g1h->heap_region_containing((HeapWord*)obj);
+          gclog_or_tty->print_cr("Field "PTR_FORMAT
+                                 " of live obj "PTR_FORMAT" in region "
+                                 "["PTR_FORMAT", "PTR_FORMAT")",
+                                 p, (void*) _containing_obj,
+                                 from->bottom(), from->end());
+          print_object(gclog_or_tty, _containing_obj);
+          gclog_or_tty->print_cr("points to dead obj "PTR_FORMAT" in region "
+                                 "["PTR_FORMAT", "PTR_FORMAT")",
+                                 (void*) obj, to->bottom(), to->end());
+          print_object(gclog_or_tty, obj);
+        }
+        gclog_or_tty->print_cr("----------");
+        gclog_or_tty->flush();
+        _failures = true;
+        failed = true;
+        _n_failures++;
+      }
+
+      if (!_g1h->full_collection() || G1VerifyRSetsDuringFullGC) {
+        HeapRegion* from = _g1h->heap_region_containing((HeapWord*)p);
+        HeapRegion* to   = _g1h->heap_region_containing(obj);
+        if (from != NULL && to != NULL &&
+            from != to &&
+            !to->isHumongous()) {
+          jbyte cv_obj = *_bs->byte_for_const(_containing_obj);
+          jbyte cv_field = *_bs->byte_for_const(p);
+          const jbyte dirty = CardTableModRefBS::dirty_card_val();
+
+          bool is_bad = !(from->is_young()
+                          || to->rem_set()->contains_reference(p)
+                          || !G1HRRSFlushLogBuffersOnVerify && // buffers were not flushed
+                              (_containing_obj->is_objArray() ?
+                                  cv_field == dirty
+                               : cv_obj == dirty || cv_field == dirty));
+          if (is_bad) {
+            MutexLockerEx x(ParGCRareEvent_lock,
+                            Mutex::_no_safepoint_check_flag);
+
+            if (!_failures) {
+              gclog_or_tty->print_cr("");
+              gclog_or_tty->print_cr("----------");
+            }
+            gclog_or_tty->print_cr("Missing rem set entry:");
+            gclog_or_tty->print_cr("Field "PTR_FORMAT" "
+                                   "of obj "PTR_FORMAT", "
+                                   "in region "HR_FORMAT,
+                                   p, (void*) _containing_obj,
+                                   HR_FORMAT_PARAMS(from));
+            _containing_obj->print_on(gclog_or_tty);
+            gclog_or_tty->print_cr("points to obj "PTR_FORMAT" "
+                                   "in region "HR_FORMAT,
+                                   (void*) obj,
+                                   HR_FORMAT_PARAMS(to));
+            obj->print_on(gclog_or_tty);
+            gclog_or_tty->print_cr("Obj head CTE = %d, field CTE = %d.",
+                          cv_obj, cv_field);
+            gclog_or_tty->print_cr("----------");
+            gclog_or_tty->flush();
+            _failures = true;
+            if (!failed) _n_failures++;
+          }
+        }
+      }
+    }
+  }
+};
 
 // This really ought to be commoned up into OffsetTableContigSpace somehow.
 // We would need a mechanism to make that code skip dead objects.
@@ -904,6 +1053,13 @@ void HeapRegion::verify(VerifyOption vo,
     *failures = true;
     return;
   }
+
+  verify_strong_code_roots(vo, failures);
+}
+
+void HeapRegion::verify() const {
+  bool dummy = false;
+  verify(VerifyOption_G1UsePrevMarking, /* failures */ &dummy);
 }
 
 // G1OffsetTableContigSpace code; copied from space.cpp.  Hope this can go

src/share/vm/gc_implementation/g1/heapRegion.hpp

@@ -52,6 +52,7 @@ class HeapRegionRemSet;
 class HeapRegionRemSetIterator;
 class HeapRegion;
 class HeapRegionSetBase;
+class nmethod;
 
 #define HR_FORMAT "%u:(%s)["PTR_FORMAT","PTR_FORMAT","PTR_FORMAT"]"
 #define HR_FORMAT_PARAMS(_hr_) \
@@ -371,7 +372,8 @@ class HeapRegion: public G1OffsetTableContigSpace {
     RebuildRSClaimValue        = 5,
     ParEvacFailureClaimValue   = 6,
     AggregateCountClaimValue   = 7,
-    VerifyCountClaimValue      = 8
+    VerifyCountClaimValue      = 8,
+    ParMarkRootClaimValue      = 9
   };
 
   inline HeapWord* par_allocate_no_bot_updates(size_t word_size) {
@@ -796,6 +798,25 @@ class HeapRegion: public G1OffsetTableContigSpace {
 
   virtual void reset_after_compaction();
 
+  // Routines for managing a list of code roots (attached to the
+  // this region's RSet) that point into this heap region.
+  void add_strong_code_root(nmethod* nm);
+  void remove_strong_code_root(nmethod* nm);
+
+  // During a collection, migrate the successfully evacuated
+  // strong code roots that referenced into this region to the
+  // new regions that they now point into. Unsuccessfully
+  // evacuated code roots are not migrated.
+  void migrate_strong_code_roots();
+
+  // Applies blk->do_code_blob() to each of the entries in
+  // the strong code roots list for this region
+  void strong_code_roots_do(CodeBlobClosure* blk) const;
+
+  // Verify that the entries on the strong code root list for this
+  // region are live and include at least one pointer into this region.
+  void verify_strong_code_roots(VerifyOption vo, bool* failures) const;
+
   void print() const;
   void print_on(outputStream* st) const;
 

src/share/vm/gc_implementation/g1/heapRegionRemSet.cpp

@@ -33,6 +33,7 @@
 #include "oops/oop.inline.hpp"
 #include "utilities/bitMap.inline.hpp"
 #include "utilities/globalDefinitions.hpp"
+#include "utilities/growableArray.hpp"
 
 class PerRegionTable: public CHeapObj<mtGC> {
   friend class OtherRegionsTable;
@@ -849,7 +850,7 @@ int HeapRegionRemSet::num_par_rem_sets() {
 
 HeapRegionRemSet::HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
                                    HeapRegion* hr)
-  : _bosa(bosa), _other_regions(hr) {
+  : _bosa(bosa), _strong_code_roots_list(NULL), _other_regions(hr) {
   reset_for_par_iteration();
 }
 
@@ -908,6 +909,12 @@ void HeapRegionRemSet::cleanup() {
 }
 
 void HeapRegionRemSet::clear() {
+  if (_strong_code_roots_list != NULL) {
+    delete _strong_code_roots_list;
+  }
+  _strong_code_roots_list = new (ResourceObj::C_HEAP, mtGC)
+                                GrowableArray<nmethod*>(10, 0, NULL, true);
+
   _other_regions.clear();
   assert(occupied() == 0, "Should be clear.");
   reset_for_par_iteration();
@@ -925,6 +932,121 @@ void HeapRegionRemSet::scrub(CardTableModRefBS* ctbs,
   _other_regions.scrub(ctbs, region_bm, card_bm);
 }
 
+
+// Code roots support
+
+void HeapRegionRemSet::add_strong_code_root(nmethod* nm) {
+  assert(nm != NULL, "sanity");
+  // Search for the code blob from the RHS to avoid
+  // duplicate entries as much as possible
+  if (_strong_code_roots_list->find_from_end(nm) < 0) {
+    // Code blob isn't already in the list
+    _strong_code_roots_list->push(nm);
+  }
+}
+
+void HeapRegionRemSet::remove_strong_code_root(nmethod* nm) {
+  assert(nm != NULL, "sanity");
+  int idx = _strong_code_roots_list->find(nm);
+  if (idx >= 0) {
+    _strong_code_roots_list->remove_at(idx);
+  }
+  // Check that there were no duplicates
+  guarantee(_strong_code_roots_list->find(nm) < 0, "duplicate entry found");
+}
+
+class NMethodMigrationOopClosure : public OopClosure {
+  G1CollectedHeap* _g1h;
+  HeapRegion* _from;
+  nmethod* _nm;
+
+  uint _num_self_forwarded;
+
+  template <class T> void do_oop_work(T* p) {
+    T heap_oop = oopDesc::load_heap_oop(p);
+    if (!oopDesc::is_null(heap_oop)) {
+      oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
+      if (_from->is_in(obj)) {
+        // Reference still points into the source region.
+        // Since roots are immediately evacuated this means that
+        // we must have self forwarded the object
+        assert(obj->is_forwarded(),
+               err_msg("code roots should be immediately evacuated. "
+                       "Ref: "PTR_FORMAT", "
+                       "Obj: "PTR_FORMAT", "
+                       "Region: "HR_FORMAT,
+                       p, (void*) obj, HR_FORMAT_PARAMS(_from)));
+        assert(obj->forwardee() == obj,
+               err_msg("not self forwarded? obj = "PTR_FORMAT, (void*)obj));
+
+        // The object has been self forwarded.
+        // Note, if we're during an initial mark pause, there is
+        // no need to explicitly mark object. It will be marked
+        // during the regular evacuation failure handling code.
+        _num_self_forwarded++;
+      } else {
+        // The reference points into a promotion or to-space region
+        HeapRegion* to = _g1h->heap_region_containing(obj);
+        to->rem_set()->add_strong_code_root(_nm);
+      }
+    }
+  }
+
+public:
+  NMethodMigrationOopClosure(G1CollectedHeap* g1h, HeapRegion* from, nmethod* nm):
+    _g1h(g1h), _from(from), _nm(nm), _num_self_forwarded(0) {}
+
+  void do_oop(narrowOop* p) { do_oop_work(p); }
+  void do_oop(oop* p)       { do_oop_work(p); }
+
+  uint retain() { return _num_self_forwarded > 0; }
+};
+
+void HeapRegionRemSet::migrate_strong_code_roots() {
+  assert(hr()->in_collection_set(), "only collection set regions");
+  assert(!hr()->isHumongous(), "not humongous regions");
+
+  ResourceMark rm;
+
+  // List of code blobs to retain for this region
+  GrowableArray<nmethod*> to_be_retained(10);
+  G1CollectedHeap* g1h = G1CollectedHeap::heap();
+
+  while (_strong_code_roots_list->is_nonempty()) {
+    nmethod *nm = _strong_code_roots_list->pop();
+    if (nm != NULL) {
+      NMethodMigrationOopClosure oop_cl(g1h, hr(), nm);
+      nm->oops_do(&oop_cl);
+      if (oop_cl.retain()) {
+        to_be_retained.push(nm);
+      }
+    }
+  }
+
+  // Now push any code roots we need to retain
+  assert(to_be_retained.is_empty() || hr()->evacuation_failed(),
+         "Retained nmethod list must be empty or "
+         "evacuation of this region failed");
+
+  while (to_be_retained.is_nonempty()) {
+    nmethod* nm = to_be_retained.pop();
+    assert(nm != NULL, "sanity");
+    add_strong_code_root(nm);
+  }
+}
+
+void HeapRegionRemSet::strong_code_roots_do(CodeBlobClosure* blk) const {
+  for (int i = 0; i < _strong_code_roots_list->length(); i += 1) {
+    nmethod* nm = _strong_code_roots_list->at(i);
+    blk->do_code_blob(nm);
+  }
+}
+
+size_t HeapRegionRemSet::strong_code_roots_mem_size() {
+  return sizeof(GrowableArray<nmethod*>) +
+         _strong_code_roots_list->max_length() * sizeof(nmethod*);
+}
+
 //-------------------- Iteration --------------------
 
 HeapRegionRemSetIterator:: HeapRegionRemSetIterator(const HeapRegionRemSet* hrrs) :

src/share/vm/gc_implementation/g1/heapRegionRemSet.hpp

@@ -37,6 +37,7 @@ class HeapRegion;
 class HeapRegionRemSetIterator;
 class PerRegionTable;
 class SparsePRT;
+class nmethod;
 
 // Essentially a wrapper around SparsePRTCleanupTask. See
 // sparsePRT.hpp for more details.
@@ -191,6 +192,10 @@ private:
   G1BlockOffsetSharedArray* _bosa;
   G1BlockOffsetSharedArray* bosa() const { return _bosa; }
 
+  // A list of code blobs (nmethods) whose code contains pointers into
+  // the region that owns this RSet.
+  GrowableArray<nmethod*>* _strong_code_roots_list;
+
   OtherRegionsTable _other_regions;
 
   enum ParIterState { Unclaimed, Claimed, Complete };
@@ -282,11 +287,13 @@ public:
   }
 
   // The actual # of bytes this hr_remset takes up.
+  // Note also includes the strong code root set.
   size_t mem_size() {
     return _other_regions.mem_size()
       // This correction is necessary because the above includes the second
       // part.
-      + sizeof(this) - sizeof(OtherRegionsTable);
+      + (sizeof(this) - sizeof(OtherRegionsTable))
+      + strong_code_roots_mem_size();
   }
 
   // Returns the memory occupancy of all static data structures associated
@@ -304,6 +311,37 @@ public:
   bool contains_reference(OopOrNarrowOopStar from) const {
     return _other_regions.contains_reference(from);
   }
+
+  // Routines for managing the list of code roots that point into
+  // the heap region that owns this RSet.
+  void add_strong_code_root(nmethod* nm);
+  void remove_strong_code_root(nmethod* nm);
+
+  // During a collection, migrate the successfully evacuated strong
+  // code roots that referenced into the region that owns this RSet
+  // to the RSets of the new regions that they now point into.
+  // Unsuccessfully evacuated code roots are not migrated.
+  void migrate_strong_code_roots();
+
+  // Applies blk->do_code_blob() to each of the entries in
+  // the strong code roots list
+  void strong_code_roots_do(CodeBlobClosure* blk) const;
+
+  // Returns the number of elements in the strong code roots list
+  int strong_code_roots_list_length() {
+    return _strong_code_roots_list->length();
+  }
+
+  // Returns true if the strong code roots contains the given
+  // nmethod.
+  bool strong_code_roots_list_contains(nmethod* nm) {
+    return _strong_code_roots_list->contains(nm);
+  }
+
+  // Returns the amount of memory, in bytes, currently
+  // consumed by the strong code roots.
+  size_t strong_code_roots_mem_size();
+
   void print() const;
 
   // Called during a stop-world phase to perform any deferred cleanups.

src/share/vm/gc_interface/collectedHeap.cpp

@@ -118,6 +118,14 @@ void CollectedHeap::print_heap_after_gc() {
   }
 }
 
+void CollectedHeap::register_nmethod(nmethod* nm) {
+  assert_locked_or_safepoint(CodeCache_lock);
+}
+
+void CollectedHeap::unregister_nmethod(nmethod* nm) {
+  assert_locked_or_safepoint(CodeCache_lock);
+}
+
 void CollectedHeap::trace_heap(GCWhen::Type when, GCTracer* gc_tracer) {
   const GCHeapSummary& heap_summary = create_heap_summary();
   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();

src/share/vm/gc_interface/collectedHeap.hpp

@@ -49,6 +49,7 @@ class MetaspaceSummary;
 class Thread;
 class ThreadClosure;
 class VirtualSpaceSummary;
+class nmethod;
 
 class GCMessage : public FormatBuffer<1024> {
  public:
@@ -603,6 +604,11 @@ class CollectedHeap : public CHeapObj<mtInternal> {
   void print_heap_before_gc();
   void print_heap_after_gc();
 
+  // Registering and unregistering an nmethod (compiled code) with the heap.
+  // Override with specific mechanism for each specialized heap type.
+  virtual void register_nmethod(nmethod* nm);
+  virtual void unregister_nmethod(nmethod* nm);
+
   void trace_heap_before_gc(GCTracer* gc_tracer);
   void trace_heap_after_gc(GCTracer* gc_tracer);
 

src/share/vm/memory/iterator.cpp

@@ -64,7 +64,7 @@ void MarkingCodeBlobClosure::do_code_blob(CodeBlob* cb) {
 }
 
 void CodeBlobToOopClosure::do_newly_marked_nmethod(nmethod* nm) {
-  nm->oops_do(_cl, /*do_strong_roots_only=*/ true);
+  nm->oops_do(_cl, /*allow_zombie=*/ false);
 }
 
 void CodeBlobToOopClosure::do_code_blob(CodeBlob* cb) {

src/share/vm/runtime/sweeper.hpp

@@ -83,6 +83,7 @@ class NMethodSweeper : public AllStatic {
   static jlong peak_disconnect_time()        { return _peak_disconnect_time; }
 
 #ifdef ASSERT
+  static bool is_sweeping(nmethod* which) { return _current == which; }
   // Keep track of sweeper activity in the ring buffer
   static void record_sweep(nmethod* nm, int line);
   static void report_events(int id, address entry);

src/share/vm/utilities/growableArray.hpp

@@ -194,6 +194,7 @@ template<class E> class GrowableArray : public GenericGrowableArray {
 
   void  clear()                 { _len = 0; }
   int   length() const          { return _len; }
+  int   max_length() const      { return _max; }
   void  trunc_to(int l)         { assert(l <= _len,"cannot increase length"); _len = l; }
   bool  is_empty() const        { return _len == 0; }
   bool  is_nonempty() const     { return _len != 0; }