8150013: ParNew: Prune nmethods scavengable list.

Summary: Speed up ParNew collections by pruning the list of scavengable nmethods.
Reviewed-by: jmasa, tonyp, twisti

src/share/vm/code/codeCache.cpp

@@ -336,16 +336,19 @@ void CodeCache::blobs_do(CodeBlobClosure* f) {
 }
 
 // Walk the list of methods which might contain non-perm oops.
-void CodeCache::scavenge_root_nmethods_do(CodeBlobClosure* f) {
+void CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure* f) {
   assert_locked_or_safepoint(CodeCache_lock);
 
   if (UseG1GC) {
     return;
   }
 
+  const bool fix_relocations = f->fix_relocations();
   debug_only(mark_scavenge_root_nmethods());
 
-  for (nmethod* cur = scavenge_root_nmethods(); cur != NULL; cur = cur->scavenge_root_link()) {
+  nmethod* prev = NULL;
+  nmethod* cur = scavenge_root_nmethods();
+  while (cur != NULL) {
     debug_only(cur->clear_scavenge_root_marked());
     assert(cur->scavenge_root_not_marked(), "");
     assert(cur->on_scavenge_root_list(), "else shouldn't be on this list");
@@ -360,6 +363,18 @@ void CodeCache::scavenge_root_nmethods_do(CodeBlobClosure* f) {
       // Perform cur->oops_do(f), maybe just once per nmethod.
       f->do_code_blob(cur);
     }
+    nmethod* const next = cur->scavenge_root_link();
+    // The scavengable nmethod list must contain all methods with scavengable
+    // oops. It is safe to include more nmethod on the list, but we do not
+    // expect any live non-scavengable nmethods on the list.
+    if (fix_relocations) {
+      if (!is_live || !cur->detect_scavenge_root_oops()) {
+        unlink_scavenge_root_nmethod(cur, prev);
+      } else {
+        prev = cur;
+      }
+    }
+    cur = next;
   }
 
   // Check for stray marks.
@@ -379,6 +394,24 @@ void CodeCache::add_scavenge_root_nmethod(nmethod* nm) {
   print_trace("add_scavenge_root", nm);
 }
 
+void CodeCache::unlink_scavenge_root_nmethod(nmethod* nm, nmethod* prev) {
+  assert_locked_or_safepoint(CodeCache_lock);
+
+  assert((prev == NULL && scavenge_root_nmethods() == nm) ||
+         (prev != NULL && prev->scavenge_root_link() == nm), "precondition");
+
+  assert(!UseG1GC, "G1 does not use the scavenge_root_nmethods list");
+
+  print_trace("unlink_scavenge_root", nm);
+  if (prev == NULL) {
+    set_scavenge_root_nmethods(nm->scavenge_root_link());
+  } else {
+    prev->set_scavenge_root_link(nm->scavenge_root_link());
+  }
+  nm->set_scavenge_root_link(NULL);
+  nm->clear_on_scavenge_root_list();
+}
+
 void CodeCache::drop_scavenge_root_nmethod(nmethod* nm) {
   assert_locked_or_safepoint(CodeCache_lock);
 
@@ -387,20 +420,13 @@ void CodeCache::drop_scavenge_root_nmethod(nmethod* nm) {
   }
 
   print_trace("drop_scavenge_root", nm);
-  nmethod* last = NULL;
-  nmethod* cur = scavenge_root_nmethods();
-  while (cur != NULL) {
-    nmethod* next = cur->scavenge_root_link();
+  nmethod* prev = NULL;
+  for (nmethod* cur = scavenge_root_nmethods(); cur != NULL; cur = cur->scavenge_root_link()) {
     if (cur == nm) {
-      if (last != NULL)
-            last->set_scavenge_root_link(next);
-      else  set_scavenge_root_nmethods(next);
-      nm->set_scavenge_root_link(NULL);
-      nm->clear_on_scavenge_root_list();
+      unlink_scavenge_root_nmethod(cur, prev);
       return;
     }
-    last = cur;
-    cur = next;
+    prev = cur;
   }
   assert(false, "should have been on list");
 }
@@ -429,11 +455,7 @@ void CodeCache::prune_scavenge_root_nmethods() {
     } else {
       // Prune it from the list, so we don't have to look at it any more.
       print_trace("prune_scavenge_root", cur);
-      cur->set_scavenge_root_link(NULL);
-      cur->clear_on_scavenge_root_list();
-      if (last != NULL)
-            last->set_scavenge_root_link(next);
-      else  set_scavenge_root_nmethods(next);
+      unlink_scavenge_root_nmethod(cur, last);
     }
     cur = next;
   }

src/share/vm/code/codeCache.hpp

 /*
- * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -65,6 +65,10 @@ class CodeCache : AllStatic {
 
   static int _codemem_full_count;
 
+  static void set_scavenge_root_nmethods(nmethod* nm) { _scavenge_root_nmethods = nm; }
+  static void prune_scavenge_root_nmethods();
+  static void unlink_scavenge_root_nmethod(nmethod* nm, nmethod* prev);
+
  public:
 
   // Initialization
@@ -135,13 +139,17 @@ class CodeCache : AllStatic {
   // to "true" iff some code got unloaded.
   static void do_unloading(BoolObjectClosure* is_alive, bool unloading_occurred);
   static void asserted_non_scavengable_nmethods_do(CodeBlobClosure* f = NULL) PRODUCT_RETURN;
-  static void scavenge_root_nmethods_do(CodeBlobClosure* f);
+
+  // Apply f to every live code blob in scavengable nmethods. Prune nmethods
+  // from the list of scavengable nmethods if f->fix_relocations() and a nmethod
+  // no longer has scavengable oops.  If f->fix_relocations(), then f must copy
+  // objects to their new location immediately to avoid fixing nmethods on the
+  // basis of the old object locations.
+  static void scavenge_root_nmethods_do(CodeBlobToOopClosure* f);
 
   static nmethod* scavenge_root_nmethods()          { return _scavenge_root_nmethods; }
-  static void set_scavenge_root_nmethods(nmethod* nm) { _scavenge_root_nmethods = nm; }
   static void add_scavenge_root_nmethod(nmethod* nm);
   static void drop_scavenge_root_nmethod(nmethod* nm);
-  static void prune_scavenge_root_nmethods();
 
   // Printing/debugging
   static void print();                           // prints summary

src/share/vm/code/nmethod.cpp

@@ -1392,7 +1392,6 @@ void nmethod::make_unloaded(BoolObjectClosure* is_alive, oop cause) {
   assert(_method == NULL, "Tautology");
 
   set_osr_link(NULL);
-  //set_scavenge_root_link(NULL); // done by prune_scavenge_root_nmethods
   NMethodSweeper::report_state_change(this);
 }
 

src/share/vm/gc_implementation/parallelScavenge/psScavenge.cpp

 /*
- * Copyright (c) 2002, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -636,12 +636,6 @@ bool PSScavenge::invoke_no_policy() {
 
     NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
 
-    {
-      GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer, _gc_tracer.gc_id());
-
-      CodeCache::prune_scavenge_root_nmethods();
-    }
-
     // Re-verify object start arrays
     if (VerifyObjectStartArray &&
         VerifyAfterGC) {

src/share/vm/memory/genCollectedHeap.cpp

 /*
- * Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -619,7 +619,7 @@ void GenCollectedHeap::process_roots(bool activate_scope,
                                      OopClosure* weak_roots,
                                      CLDClosure* strong_cld_closure,
                                      CLDClosure* weak_cld_closure,
-                                     CodeBlobClosure* code_roots) {
+                                     CodeBlobToOopClosure* code_roots) {
   StrongRootsScope srs(this, activate_scope);
 
   // General roots.
@@ -638,7 +638,7 @@ void GenCollectedHeap::process_roots(bool activate_scope,
   // Don't process them if they will be processed during the ClassLoaderDataGraph phase.
   CLDClosure* roots_from_clds_p = (strong_cld_closure != weak_cld_closure) ? strong_cld_closure : NULL;
   // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
-  CodeBlobClosure* roots_from_code_p = (so & SO_AllCodeCache) ? NULL : code_roots;
+  CodeBlobToOopClosure* roots_from_code_p = (so & SO_AllCodeCache) ? NULL : code_roots;
 
   Threads::possibly_parallel_oops_do(strong_roots, roots_from_clds_p, roots_from_code_p);
 

src/share/vm/memory/genCollectedHeap.hpp

 /*
- * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -416,7 +416,7 @@ public:
                      OopClosure* weak_roots,
                      CLDClosure* strong_cld_closure,
                      CLDClosure* weak_cld_closure,
-                     CodeBlobClosure* code_roots);
+                     CodeBlobToOopClosure* code_roots);
 
   void gen_process_roots(int level,
                          bool younger_gens_as_roots,

src/share/vm/memory/iterator.hpp

 /*
- * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -291,9 +291,12 @@ class CodeBlobToOopClosure : public CodeBlobClosure {
  protected:
   void do_nmethod(nmethod* nm);
  public:
+  // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
+  // patching nmethods with the old locations.
   CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
   virtual void do_code_blob(CodeBlob* cb);
 
+  bool fix_relocations() const { return _fix_relocations; }
   const static bool FixRelocations = true;
 };