changeset 51020:ef980b9ac191

8203837: Split nmethod unloading from inline cache cleaning Summary: Refactor cleaning inline caches to after GC do_unloading. Reviewed-by: thartmann, eosterlund
author coleenp
date Wed, 02 May 2018 11:28:49 -0400
parents e4301f8c3aaa
children aad24ac930ee
files src/hotspot/share/aot/aotCompiledMethod.cpp src/hotspot/share/aot/aotCompiledMethod.hpp src/hotspot/share/code/codeCache.cpp src/hotspot/share/code/codeCache.hpp src/hotspot/share/code/compiledIC.cpp src/hotspot/share/code/compiledIC.hpp src/hotspot/share/code/compiledMethod.cpp src/hotspot/share/code/compiledMethod.hpp src/hotspot/share/code/nmethod.cpp src/hotspot/share/code/nmethod.hpp src/hotspot/share/gc/g1/g1CollectedHeap.cpp src/hotspot/share/oops/method.cpp src/hotspot/share/oops/method.hpp src/hotspot/share/runtime/arguments.cpp src/hotspot/share/runtime/globals.hpp
diffstat 15 files changed, 201 insertions(+), 244 deletions(-) [+]
line wrap: on
line diff
--- a/src/hotspot/share/aot/aotCompiledMethod.cpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/aot/aotCompiledMethod.cpp	Wed May 02 11:28:49 2018 -0400
@@ -75,7 +75,7 @@
   return (address*) ((address)fr->unextended_sp() + _meta->orig_pc_offset());
 }
 
-bool AOTCompiledMethod::do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive, bool unloading_occurred) {
+bool AOTCompiledMethod::do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive) {
   return false;
 }
 
@@ -245,7 +245,7 @@
 // more conservative than for nmethods.
 void AOTCompiledMethod::flush_evol_dependents_on(InstanceKlass* dependee) {
   if (is_java_method()) {
-    cleanup_inline_caches();
+    clear_inline_caches();
     mark_for_deoptimization();
     make_not_entrant();
   }
--- a/src/hotspot/share/aot/aotCompiledMethod.hpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/aot/aotCompiledMethod.hpp	Wed May 02 11:28:49 2018 -0400
@@ -284,8 +284,8 @@
   bool is_aot_runtime_stub() const { return _method == NULL; }
 
 protected:
-  virtual bool do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive, bool unloading_occurred);
-  virtual bool do_unloading_jvmci(bool unloading_occurred) { return false; }
+  virtual bool do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive);
+  virtual bool do_unloading_jvmci() { return false; }
 
 };
 
--- a/src/hotspot/share/code/codeCache.cpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/code/codeCache.cpp	Wed May 02 11:28:49 2018 -0400
@@ -685,8 +685,15 @@
   assert_locked_or_safepoint(CodeCache_lock);
   CompiledMethodIterator iter;
   while(iter.next_alive()) {
-    iter.method()->do_unloading(is_alive, unloading_occurred);
+    iter.method()->do_unloading(is_alive);
   }
+
+  // Now that all the unloaded nmethods are known, cleanup caches
+  // before CLDG is purged.
+  // This is another code cache walk but it is moved from gc_epilogue.
+  // G1 does a parallel walk of the nmethods so cleans them up
+  // as it goes and doesn't call this.
+  do_unloading_nmethod_caches(unloading_occurred);
 }
 
 void CodeCache::blobs_do(CodeBlobClosure* f) {
@@ -720,8 +727,11 @@
     assert(cur->on_scavenge_root_list(), "else shouldn't be on this list");
 
     bool is_live = (!cur->is_zombie() && !cur->is_unloaded());
-    if (TraceScavenge) {
-      cur->print_on(tty, is_live ? "scavenge root" : "dead scavenge root"); tty->cr();
+    LogTarget(Trace, gc, nmethod) lt;
+    if (lt.is_enabled()) {
+      LogStream ls(lt);
+      CompileTask::print(&ls, cur,
+        is_live ? "scavenge root " : "dead scavenge root", /*short_form:*/ true);
     }
     if (is_live) {
       // Perform cur->oops_do(f), maybe just once per nmethod.
@@ -892,18 +902,26 @@
 #endif
 }
 
-void CodeCache::gc_prologue() {
+void CodeCache::gc_prologue() { }
+
+void CodeCache::gc_epilogue() {
+  prune_scavenge_root_nmethods();
 }
 
-void CodeCache::gc_epilogue() {
+
+void CodeCache::do_unloading_nmethod_caches(bool class_unloading_occurred) {
   assert_locked_or_safepoint(CodeCache_lock);
-  NOT_DEBUG(if (needs_cache_clean())) {
+  // Even if classes are not unloaded, there may have been some nmethods that are
+  // unloaded because oops in them are no longer reachable.
+  NOT_DEBUG(if (needs_cache_clean() || class_unloading_occurred)) {
     CompiledMethodIterator iter;
     while(iter.next_alive()) {
       CompiledMethod* cm = iter.method();
       assert(!cm->is_unloaded(), "Tautology");
-      DEBUG_ONLY(if (needs_cache_clean())) {
-        cm->cleanup_inline_caches();
+      DEBUG_ONLY(if (needs_cache_clean() || class_unloading_occurred)) {
+        // Clean up both unloaded klasses from nmethods and unloaded nmethods
+        // from inline caches.
+        cm->unload_nmethod_caches(/*parallel*/false, class_unloading_occurred);
       }
       DEBUG_ONLY(cm->verify());
       DEBUG_ONLY(cm->verify_oop_relocations());
@@ -911,8 +929,6 @@
   }
 
   set_needs_cache_clean(false);
-  prune_scavenge_root_nmethods();
-
   verify_icholder_relocations();
 }
 
--- a/src/hotspot/share/code/codeCache.hpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/code/codeCache.hpp	Wed May 02 11:28:49 2018 -0400
@@ -168,9 +168,10 @@
   static void gc_epilogue();
   static void gc_prologue();
   static void verify_oops();
-  // If "unloading_occurred" is true, then unloads (i.e., breaks root links
+  // If any oops are not marked this method unloads (i.e., breaks root links
   // to) any unmarked codeBlobs in the cache.  Sets "marked_for_unloading"
   // to "true" iff some code got unloaded.
+  // "unloading_occurred" controls whether metadata should be cleaned because of class unloading.
   static void do_unloading(BoolObjectClosure* is_alive, bool unloading_occurred);
   static void asserted_non_scavengable_nmethods_do(CodeBlobClosure* f = NULL) PRODUCT_RETURN;
 
@@ -223,8 +224,10 @@
 
   static bool needs_cache_clean()                     { return _needs_cache_clean; }
   static void set_needs_cache_clean(bool v)           { _needs_cache_clean = v;    }
+
   static void clear_inline_caches();                  // clear all inline caches
-  static void cleanup_inline_caches();
+  static void cleanup_inline_caches();                // clean unloaded/zombie nmethods from inline caches
+  static void do_unloading_nmethod_caches(bool class_unloading_occurred);  // clean all nmethod caches for unloading, including inline caches
 
   // Returns true if an own CodeHeap for the given CodeBlobType is available
   static bool heap_available(int code_blob_type);
--- a/src/hotspot/share/code/compiledIC.cpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/code/compiledIC.cpp	Wed May 02 11:28:49 2018 -0400
@@ -552,7 +552,8 @@
 
 // ----------------------------------------------------------------------------
 
-void CompiledStaticCall::set_to_clean() {
+void CompiledStaticCall::set_to_clean(bool in_use) {
+  // in_use is unused but needed to match template function in CompiledMethod
   assert (CompiledIC_lock->is_locked() || SafepointSynchronize::is_at_safepoint(), "mt unsafe call");
   // Reset call site
   MutexLockerEx pl(SafepointSynchronize::is_at_safepoint() ? NULL : Patching_lock, Mutex::_no_safepoint_check_flag);
--- a/src/hotspot/share/code/compiledIC.hpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/code/compiledIC.hpp	Wed May 02 11:28:49 2018 -0400
@@ -358,7 +358,7 @@
   virtual address destination() const = 0;
 
   // Clean static call (will force resolving on next use)
-  void set_to_clean();
+  void set_to_clean(bool in_use = true);
 
   // Set state. The entry must be the same, as computed by compute_entry.
   // Computation and setting is split up, since the actions are separate during
--- a/src/hotspot/share/code/compiledMethod.cpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/code/compiledMethod.cpp	Wed May 02 11:28:49 2018 -0400
@@ -28,6 +28,8 @@
 #include "code/scopeDesc.hpp"
 #include "code/codeCache.hpp"
 #include "interpreter/bytecode.inline.hpp"
+#include "logging/log.hpp"
+#include "logging/logTag.hpp"
 #include "memory/resourceArea.hpp"
 #include "oops/methodData.hpp"
 #include "oops/method.inline.hpp"
@@ -222,9 +224,7 @@
                        pd->return_oop());
 }
 
-void CompiledMethod::cleanup_inline_caches(bool clean_all/*=false*/) {
-  assert_locked_or_safepoint(CompiledIC_lock);
-
+address CompiledMethod::oops_reloc_begin() const {
   // 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
   // should not get GC'd.  Skip the first few bytes of oops on
@@ -237,41 +237,7 @@
     // This shouldn't matter, since oops of non-entrant methods are never used.
     // In fact, why are we bothering to look at oops in a non-entrant method??
   }
-
-  // Find all calls in an nmethod and clear the ones that point to non-entrant,
-  // zombie and unloaded nmethods.
-  ResourceMark rm;
-  RelocIterator iter(this, low_boundary);
-  while(iter.next()) {
-    switch(iter.type()) {
-      case relocInfo::virtual_call_type:
-      case relocInfo::opt_virtual_call_type: {
-        CompiledIC *ic = CompiledIC_at(&iter);
-        // Ok, to lookup references to zombies here
-        CodeBlob *cb = CodeCache::find_blob_unsafe(ic->ic_destination());
-        if( cb != NULL && cb->is_compiled() ) {
-          CompiledMethod* nm = cb->as_compiled_method();
-          // Clean inline caches pointing to zombie, non-entrant and unloaded methods
-          if (clean_all || !nm->is_in_use() || (nm->method()->code() != nm)) ic->set_to_clean(is_alive());
-        }
-        break;
-      }
-      case relocInfo::static_call_type: {
-          CompiledStaticCall *csc = compiledStaticCall_at(iter.reloc());
-          CodeBlob *cb = CodeCache::find_blob_unsafe(csc->destination());
-          if( cb != NULL && cb->is_compiled() ) {
-            CompiledMethod* cm = cb->as_compiled_method();
-            // Clean inline caches pointing to zombie, non-entrant and unloaded methods
-            if (clean_all || !cm->is_in_use() || (cm->method()->code() != cm)) {
-              csc->set_to_clean();
-            }
-          }
-        break;
-      }
-      default:
-        break;
-    }
-  }
+  return low_boundary;
 }
 
 int CompiledMethod::verify_icholder_relocations() {
@@ -437,17 +403,15 @@
   return OrderAccess::load_acquire(&_unloading_clock);
 }
 
-// Processing of oop references should have been sufficient to keep
-// all strong references alive.  Any weak references should have been
-// cleared as well.  Visit all the metadata and ensure that it's
-// really alive.
-void CompiledMethod::verify_metadata_loaders(address low_boundary) {
+
+// static_stub_Relocations may have dangling references to
+// nmethods so trim them out here.  Otherwise it looks like
+// compiled code is maintaining a link to dead metadata.
+void CompiledMethod::clean_ic_stubs() {
 #ifdef ASSERT
-    RelocIterator iter(this, low_boundary);
-    while (iter.next()) {
-    // static_stub_Relocations may have dangling references to
-    // Method*s so trim them out here.  Otherwise it looks like
-    // compiled code is maintaining a link to dead metadata.
+  address low_boundary = oops_reloc_begin();
+  RelocIterator iter(this, low_boundary);
+  while (iter.next()) {
     address static_call_addr = NULL;
     if (iter.type() == relocInfo::opt_virtual_call_type) {
       CompiledIC* cic = CompiledIC_at(&iter);
@@ -470,8 +434,6 @@
       }
     }
   }
-  // Check that the metadata embedded in the nmethod is alive
-  metadata_do(check_class);
 #endif
 }
 
@@ -479,67 +441,43 @@
 // GC to unload an nmethod if it contains otherwise unreachable
 // oops.
 
-void CompiledMethod::do_unloading(BoolObjectClosure* is_alive, bool unloading_occurred) {
+void CompiledMethod::do_unloading(BoolObjectClosure* is_alive) {
   // Make sure the oop's ready to receive visitors
   assert(!is_zombie() && !is_unloaded(),
          "should not call follow on zombie or unloaded nmethod");
 
-  // If the method is not entrant then a JMP is plastered over the
-  // first few bytes.  If an oop in the old code was there, that oop
-  // should not get GC'd.  Skip the first few bytes of oops on
-  // not-entrant methods.
-  address low_boundary = verified_entry_point();
-  if (is_not_entrant()) {
-    low_boundary += NativeJump::instruction_size;
-    // %%% Note:  On SPARC we patch only a 4-byte trap, not a full NativeJump.
-    // (See comment above.)
-  }
+  address low_boundary = oops_reloc_begin();
 
-  // Exception cache
-  clean_exception_cache();
-
-  // If class unloading occurred we first iterate over all inline caches and
-  // clear ICs where the cached oop is referring to an unloaded klass or method.
-  // The remaining live cached oops will be traversed in the relocInfo::oop_type
-  // iteration below.
-  if (unloading_occurred) {
-    RelocIterator iter(this, low_boundary);
-    while(iter.next()) {
-      if (iter.type() == relocInfo::virtual_call_type) {
-        CompiledIC *ic = CompiledIC_at(&iter);
-        clean_ic_if_metadata_is_dead(ic);
-      }
-    }
-  }
-
-  if (do_unloading_oops(low_boundary, is_alive, unloading_occurred)) {
+  if (do_unloading_oops(low_boundary, is_alive)) {
     return;
   }
 
 #if INCLUDE_JVMCI
-  if (do_unloading_jvmci(unloading_occurred)) {
+  if (do_unloading_jvmci()) {
     return;
   }
 #endif
 
-  // Ensure that all metadata is still alive
-  verify_metadata_loaders(low_boundary);
+  // Cleanup exception cache and inline caches happens
+  // after all the unloaded methods are found.
 }
 
+// Clean references to unloaded nmethods at addr from this one, which is not unloaded.
 template <class CompiledICorStaticCall>
-static bool clean_if_nmethod_is_unloaded(CompiledICorStaticCall *ic, address addr, CompiledMethod* from) {
+static bool clean_if_nmethod_is_unloaded(CompiledICorStaticCall *ic, address addr, CompiledMethod* from,
+                                         bool parallel, bool clean_all) {
   // Ok, to lookup references to zombies here
   CodeBlob *cb = CodeCache::find_blob_unsafe(addr);
   CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
   if (nm != NULL) {
-    if (nm->unloading_clock() != CompiledMethod::global_unloading_clock()) {
+    if (parallel && nm->unloading_clock() != CompiledMethod::global_unloading_clock()) {
       // The nmethod has not been processed yet.
       return true;
     }
 
     // Clean inline caches pointing to both zombie and not_entrant methods
-    if (!nm->is_in_use() || (nm->method()->code() != nm)) {
-      ic->set_to_clean();
+    if (clean_all || !nm->is_in_use() || (nm->method()->code() != nm)) {
+      ic->set_to_clean(from->is_alive());
       assert(ic->is_clean(), "nmethod " PTR_FORMAT "not clean %s", p2i(from), from->method()->name_and_sig_as_C_string());
     }
   }
@@ -547,12 +485,14 @@
   return false;
 }
 
-static bool clean_if_nmethod_is_unloaded(CompiledIC *ic, CompiledMethod* from) {
-  return clean_if_nmethod_is_unloaded(ic, ic->ic_destination(), from);
+static bool clean_if_nmethod_is_unloaded(CompiledIC *ic, CompiledMethod* from,
+                                         bool parallel, bool clean_all = false) {
+  return clean_if_nmethod_is_unloaded(ic, ic->ic_destination(), from, parallel, clean_all);
 }
 
-static bool clean_if_nmethod_is_unloaded(CompiledStaticCall *csc, CompiledMethod* from) {
-  return clean_if_nmethod_is_unloaded(csc, csc->destination(), from);
+static bool clean_if_nmethod_is_unloaded(CompiledStaticCall *csc, CompiledMethod* from,
+                                         bool parallel, bool clean_all = false) {
+  return clean_if_nmethod_is_unloaded(csc, csc->destination(), from, parallel, clean_all);
 }
 
 bool CompiledMethod::do_unloading_parallel(BoolObjectClosure* is_alive, bool unloading_occurred) {
@@ -562,47 +502,79 @@
   assert(!is_zombie() && !is_unloaded(),
          "should not call follow on zombie or unloaded nmethod");
 
-  // If the method is not entrant then a JMP is plastered over the
-  // first few bytes.  If an oop in the old code was there, that oop
-  // should not get GC'd.  Skip the first few bytes of oops on
-  // not-entrant methods.
-  address low_boundary = verified_entry_point();
-  if (is_not_entrant()) {
-    low_boundary += NativeJump::instruction_size;
-    // %%% Note:  On SPARC we patch only a 4-byte trap, not a full NativeJump.
-    // (See comment above.)
+  address low_boundary = oops_reloc_begin();
+
+  if (do_unloading_oops(low_boundary, is_alive)) {
+    return false;
   }
 
-  // Exception cache
-  clean_exception_cache();
+#if INCLUDE_JVMCI
+  if (do_unloading_jvmci()) {
+    return false;
+  }
+#endif
 
+  return unload_nmethod_caches(/*parallel*/true, unloading_occurred);
+}
+
+// Cleans caches in nmethods that point to either classes that are unloaded
+// or nmethods that are unloaded.
+//
+// Can be called either in parallel by G1 currently or after all
+// nmethods are unloaded.  Return postponed=true in the parallel case for
+// inline caches found that point to nmethods that are not yet visited during
+// the do_unloading walk.
+bool CompiledMethod::unload_nmethod_caches(bool parallel, bool unloading_occurred) {
+
+  // Exception cache only needs to be called if unloading occurred
+  if (unloading_occurred) {
+    clean_exception_cache();
+  }
+
+  bool postponed = cleanup_inline_caches_impl(parallel, unloading_occurred, /*clean_all*/false);
+
+  // All static stubs need to be cleaned.
+  clean_ic_stubs();
+
+  // Check that the metadata embedded in the nmethod is alive
+  DEBUG_ONLY(metadata_do(check_class));
+
+  return postponed;
+}
+
+// Called to clean up after class unloading for live nmethods and from the sweeper
+// for all methods.
+bool CompiledMethod::cleanup_inline_caches_impl(bool parallel, bool unloading_occurred, bool clean_all) {
+  assert_locked_or_safepoint(CompiledIC_lock);
   bool postponed = false;
 
-  RelocIterator iter(this, low_boundary);
+  // Find all calls in an nmethod and clear the ones that point to non-entrant,
+  // zombie and unloaded nmethods.
+  RelocIterator iter(this, oops_reloc_begin());
   while(iter.next()) {
 
     switch (iter.type()) {
 
     case relocInfo::virtual_call_type:
       if (unloading_occurred) {
-        // If class unloading occurred we first iterate over all inline caches and
-        // clear ICs where the cached oop is referring to an unloaded klass or method.
+        // If class unloading occurred we first clear ICs where the cached metadata
+        // is referring to an unloaded klass or method.
         clean_ic_if_metadata_is_dead(CompiledIC_at(&iter));
       }
 
-      postponed |= clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this);
+      postponed |= clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, parallel, clean_all);
       break;
 
     case relocInfo::opt_virtual_call_type:
-      postponed |= clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this);
+      postponed |= clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, parallel, clean_all);
       break;
 
     case relocInfo::static_call_type:
-      postponed |= clean_if_nmethod_is_unloaded(compiledStaticCall_at(iter.reloc()), this);
+      postponed |= clean_if_nmethod_is_unloaded(compiledStaticCall_at(iter.reloc()), this, parallel, clean_all);
       break;
 
     case relocInfo::oop_type:
-      // handled by do_unloading_oops below
+      // handled by do_unloading_oops already
       break;
 
     case relocInfo::metadata_type:
@@ -613,19 +585,6 @@
     }
   }
 
-  if (do_unloading_oops(low_boundary, is_alive, unloading_occurred)) {
-    return postponed;
-  }
-
-#if INCLUDE_JVMCI
-  if (do_unloading_jvmci(unloading_occurred)) {
-    return postponed;
-  }
-#endif
-
-  // Ensure that all metadata is still alive
-  verify_metadata_loaders(low_boundary);
-
   return postponed;
 }
 
@@ -636,32 +595,21 @@
   assert(!is_zombie(),
          "should not call follow on zombie nmethod");
 
-  // If the method is not entrant then a JMP is plastered over the
-  // first few bytes.  If an oop in the old code was there, that oop
-  // should not get GC'd.  Skip the first few bytes of oops on
-  // not-entrant methods.
-  address low_boundary = verified_entry_point();
-  if (is_not_entrant()) {
-    low_boundary += NativeJump::instruction_size;
-    // %%% Note:  On SPARC we patch only a 4-byte trap, not a full NativeJump.
-    // (See comment above.)
-  }
-
-  RelocIterator iter(this, low_boundary);
+  RelocIterator iter(this, oops_reloc_begin());
   while(iter.next()) {
 
     switch (iter.type()) {
 
     case relocInfo::virtual_call_type:
-      clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this);
+      clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, true);
       break;
 
     case relocInfo::opt_virtual_call_type:
-      clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this);
+      clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, true);
       break;
 
     case relocInfo::static_call_type:
-      clean_if_nmethod_is_unloaded(compiledStaticCall_at(iter.reloc()), this);
+      clean_if_nmethod_is_unloaded(compiledStaticCall_at(iter.reloc()), this, true);
       break;
 
     default:
--- a/src/hotspot/share/code/compiledMethod.hpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/code/compiledMethod.hpp	Wed May 02 11:28:49 2018 -0400
@@ -331,8 +331,19 @@
 
   static address get_deopt_original_pc(const frame* fr);
 
-  // Inline cache support
-  void cleanup_inline_caches(bool clean_all = false);
+  // GC unloading support
+  // Cleans unloaded klasses and unloaded nmethods in inline caches
+  bool unload_nmethod_caches(bool parallel, bool class_unloading_occurred);
+
+  // Inline cache support for class unloading and nmethod unloading
+ private:
+  bool cleanup_inline_caches_impl(bool parallel, bool unloading_occurred, bool clean_all);
+ public:
+  bool cleanup_inline_caches(bool clean_all = false) {
+    // Serial version used by sweeper and whitebox test
+    return cleanup_inline_caches_impl(false, false, clean_all);
+  }
+
   virtual void clear_inline_caches();
   void clear_ic_stubs();
 
@@ -364,12 +375,15 @@
   void set_unloading_next(CompiledMethod* next) { _unloading_next = next; }
   CompiledMethod* unloading_next()              { return _unloading_next; }
 
+ protected:
+  address oops_reloc_begin() const;
+ private:
   void static clean_ic_if_metadata_is_dead(CompiledIC *ic);
 
-  // Check that all metadata is still alive
-  void verify_metadata_loaders(address low_boundary);
+  void clean_ic_stubs();
 
-  virtual void do_unloading(BoolObjectClosure* is_alive, bool unloading_occurred);
+ public:
+  virtual void do_unloading(BoolObjectClosure* is_alive);
   //  The parallel versions are used by G1.
   virtual bool do_unloading_parallel(BoolObjectClosure* is_alive, bool unloading_occurred);
   virtual void do_unloading_parallel_postponed();
@@ -381,9 +395,9 @@
   unsigned char unloading_clock();
 
 protected:
-  virtual bool do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive, bool unloading_occurred) = 0;
+  virtual bool do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive) = 0;
 #if INCLUDE_JVMCI
-  virtual bool do_unloading_jvmci(bool unloading_occurred) = 0;
+  virtual bool do_unloading_jvmci() = 0;
 #endif
 
 private:
--- a/src/hotspot/share/code/nmethod.cpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/code/nmethod.cpp	Wed May 02 11:28:49 2018 -0400
@@ -946,21 +946,8 @@
 void nmethod::verify_clean_inline_caches() {
   assert_locked_or_safepoint(CompiledIC_lock);
 
-  // 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
-  // should not get GC'd.  Skip the first few bytes of oops on
-  // not-entrant methods.
-  address low_boundary = verified_entry_point();
-  if (!is_in_use()) {
-    low_boundary += NativeJump::instruction_size;
-    // %%% Note:  On SPARC we patch only a 4-byte trap, not a full NativeJump.
-    // This means that the low_boundary is going to be a little too high.
-    // This shouldn't matter, since oops of non-entrant methods are never used.
-    // In fact, why are we bothering to look at oops in a non-entrant method??
-  }
-
   ResourceMark rm;
-  RelocIterator iter(this, low_boundary);
+  RelocIterator iter(this, oops_reloc_begin());
   while(iter.next()) {
     switch(iter.type()) {
       case relocInfo::virtual_call_type:
@@ -1041,13 +1028,17 @@
   flush_dependencies(/*delete_immediately*/false);
 
   // Break cycle between nmethod & method
-  LogTarget(Trace, class, unload) lt;
+  LogTarget(Trace, class, unload, nmethod) lt;
   if (lt.is_enabled()) {
     LogStream ls(lt);
-    ls.print_cr("making nmethod " INTPTR_FORMAT
-                  " unloadable, Method*(" INTPTR_FORMAT
-                  "), cause(" INTPTR_FORMAT ")",
-                  p2i(this), p2i(_method), p2i(cause));
+    ls.print("making nmethod " INTPTR_FORMAT
+             " unloadable, Method*(" INTPTR_FORMAT
+             "), cause(" INTPTR_FORMAT ") ",
+             p2i(this), p2i(_method), p2i(cause));
+     if (cause != NULL) {
+       cause->print_value_on(&ls);
+     }
+     ls.cr();
   }
   // Unlink the osr method, so we do not look this up again
   if (is_osr_method()) {
@@ -1378,17 +1369,15 @@
 
 
 // If this oop is not live, the nmethod can be unloaded.
-bool nmethod::can_unload(BoolObjectClosure* is_alive, oop* root, bool unloading_occurred) {
+bool nmethod::can_unload(BoolObjectClosure* is_alive, oop* root) {
   assert(root != NULL, "just checking");
   oop obj = *root;
   if (obj == NULL || is_alive->do_object_b(obj)) {
       return false;
   }
 
-  // If ScavengeRootsInCode is true, an nmethod might be unloaded
-  // simply because one of its constant oops has gone dead.
+  // An nmethod might be unloaded simply because one of its constant oops has gone dead.
   // No actual classes need to be unloaded in order for this to occur.
-  assert(unloading_occurred || ScavengeRootsInCode, "Inconsistency in unloading");
   make_unloaded(obj);
   return true;
 }
@@ -1466,7 +1455,7 @@
   set_unload_reported();
 }
 
-bool nmethod::unload_if_dead_at(RelocIterator* iter_at_oop, BoolObjectClosure *is_alive, bool unloading_occurred) {
+bool nmethod::unload_if_dead_at(RelocIterator* iter_at_oop, BoolObjectClosure *is_alive) {
   assert(iter_at_oop->type() == relocInfo::oop_type, "Wrong relocation type");
 
   oop_Relocation* r = iter_at_oop->oop_reloc();
@@ -1477,7 +1466,7 @@
          "oop must be found in exactly one place");
   if (r->oop_is_immediate() && r->oop_value() != NULL) {
     // Unload this nmethod if the oop is dead.
-    if (can_unload(is_alive, r->oop_addr(), unloading_occurred)) {
+    if (can_unload(is_alive, r->oop_addr())) {
       return true;;
     }
   }
@@ -1485,18 +1474,18 @@
   return false;
 }
 
-bool nmethod::do_unloading_scopes(BoolObjectClosure* is_alive, bool unloading_occurred) {
+bool nmethod::do_unloading_scopes(BoolObjectClosure* is_alive) {
   // Scopes
   for (oop* p = oops_begin(); p < oops_end(); p++) {
     if (*p == Universe::non_oop_word())  continue;  // skip non-oops
-    if (can_unload(is_alive, p, unloading_occurred)) {
+    if (can_unload(is_alive, p)) {
       return true;
     }
   }
   return false;
 }
 
-bool nmethod::do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive, bool unloading_occurred) {
+bool nmethod::do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive) {
   // Compiled code
 
   // Prevent extra code cache walk for platforms that don't have immediate oops.
@@ -1504,18 +1493,18 @@
     RelocIterator iter(this, low_boundary);
     while (iter.next()) {
       if (iter.type() == relocInfo::oop_type) {
-        if (unload_if_dead_at(&iter, is_alive, unloading_occurred)) {
+        if (unload_if_dead_at(&iter, is_alive)) {
           return true;
         }
       }
     }
   }
 
-  return do_unloading_scopes(is_alive, unloading_occurred);
+  return do_unloading_scopes(is_alive);
 }
 
 #if INCLUDE_JVMCI
-bool nmethod::do_unloading_jvmci(bool unloading_occurred) {
+bool nmethod::do_unloading_jvmci() {
   if (_jvmci_installed_code != NULL) {
     if (JNIHandles::is_global_weak_cleared(_jvmci_installed_code)) {
       if (_jvmci_installed_code_triggers_unloading) {
@@ -1533,15 +1522,9 @@
 
 // Iterate over metadata calling this function.   Used by RedefineClasses
 void nmethod::metadata_do(void f(Metadata*)) {
-  address low_boundary = verified_entry_point();
-  if (is_not_entrant()) {
-    low_boundary += NativeJump::instruction_size;
-    // %%% Note:  On SPARC we patch only a 4-byte trap, not a full NativeJump.
-    // (See comment above.)
-  }
   {
     // Visit all immediate references that are embedded in the instruction stream.
-    RelocIterator iter(this, low_boundary);
+    RelocIterator iter(this, oops_reloc_begin());
     while (iter.next()) {
       if (iter.type() == relocInfo::metadata_type ) {
         metadata_Relocation* r = iter.metadata_reloc();
@@ -1588,20 +1571,9 @@
   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
-  // should not get GC'd.  Skip the first few bytes of oops on
-  // not-entrant methods.
-  address low_boundary = verified_entry_point();
-  if (is_not_entrant()) {
-    low_boundary += NativeJump::instruction_size;
-    // %%% Note:  On SPARC we patch only a 4-byte trap, not a full NativeJump.
-    // (See comment above.)
-  }
-
   // Prevent extra code cache walk for platforms that don't have immediate oops.
   if (relocInfo::mustIterateImmediateOopsInCode()) {
-    RelocIterator iter(this, low_boundary);
+    RelocIterator iter(this, oops_reloc_begin());
 
     while (iter.next()) {
       if (iter.type() == relocInfo::oop_type ) {
@@ -1650,7 +1622,11 @@
           break;
       }
       // Mark was clear when we first saw this guy.
-      if (TraceScavenge) { print_on(tty, "oops_do, mark"); }
+      LogTarget(Trace, gc, nmethod) lt;
+      if (lt.is_enabled()) {
+        LogStream ls(lt);
+        CompileTask::print(&ls, this, "oops_do, mark", /*short_form:*/ true);
+      }
       return false;
     }
   }
@@ -1659,7 +1635,7 @@
 }
 
 void nmethod::oops_do_marking_prologue() {
-  if (TraceScavenge) { tty->print_cr("[oops_do_marking_prologue"); }
+  log_trace(gc, nmethod)("oops_do_marking_prologue");
   assert(_oops_do_mark_nmethods == NULL, "must not call oops_do_marking_prologue twice in a row");
   // We use cmpxchg instead of regular assignment here because the user
   // may fork a bunch of threads, and we need them all to see the same state.
@@ -1675,20 +1651,26 @@
     nmethod* next = cur->_oops_do_mark_link;
     cur->_oops_do_mark_link = NULL;
     DEBUG_ONLY(cur->verify_oop_relocations());
-    NOT_PRODUCT(if (TraceScavenge)  cur->print_on(tty, "oops_do, unmark"));
+
+    LogTarget(Trace, gc, nmethod) lt;
+    if (lt.is_enabled()) {
+      LogStream ls(lt);
+      CompileTask::print(&ls, cur, "oops_do, unmark", /*short_form:*/ true);
+    }
     cur = next;
   }
   nmethod* required = _oops_do_mark_nmethods;
   nmethod* observed = Atomic::cmpxchg((nmethod*)NULL, &_oops_do_mark_nmethods, required);
   guarantee(observed == required, "no races in this sequential code");
-  if (TraceScavenge) { tty->print_cr("oops_do_marking_epilogue]"); }
+  log_trace(gc, nmethod)("oops_do_marking_epilogue");
 }
 
 class DetectScavengeRoot: public OopClosure {
   bool     _detected_scavenge_root;
+  nmethod* _print_nm;
 public:
-  DetectScavengeRoot() : _detected_scavenge_root(false)
-  { NOT_PRODUCT(_print_nm = NULL); }
+  DetectScavengeRoot(nmethod* nm) : _detected_scavenge_root(false), _print_nm(nm) {}
+
   bool detected_scavenge_root() { return _detected_scavenge_root; }
   virtual void do_oop(oop* p) {
     if ((*p) != NULL && Universe::heap()->is_scavengable(*p)) {
@@ -1699,21 +1681,25 @@
   virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
 
 #ifndef PRODUCT
-  nmethod* _print_nm;
   void maybe_print(oop* p) {
-    if (_print_nm == NULL)  return;
-    if (!_detected_scavenge_root)  _print_nm->print_on(tty, "new scavenge root");
-    tty->print_cr("" PTR_FORMAT "[offset=%d] detected scavengable oop " PTR_FORMAT " (found at " PTR_FORMAT ")",
-                  p2i(_print_nm), (int)((intptr_t)p - (intptr_t)_print_nm),
-                  p2i(*p), p2i(p));
-    (*p)->print();
+    LogTarget(Trace, gc, nmethod) lt;
+    if (lt.is_enabled()) {
+      LogStream ls(lt);
+      if (!_detected_scavenge_root) {
+        CompileTask::print(&ls, _print_nm, "new scavenge root", /*short_form:*/ true);
+      }
+      ls.print("" PTR_FORMAT "[offset=%d] detected scavengable oop " PTR_FORMAT " (found at " PTR_FORMAT ") ",
+               p2i(_print_nm), (int)((intptr_t)p - (intptr_t)_print_nm),
+               p2i(*p), p2i(p));
+      (*p)->print_value_on(&ls);
+      ls.cr();
+    }
   }
 #endif //PRODUCT
 };
 
 bool nmethod::detect_scavenge_root_oops() {
-  DetectScavengeRoot detect_scavenge_root;
-  NOT_PRODUCT(if (TraceScavenge)  detect_scavenge_root._print_nm = this);
+  DetectScavengeRoot detect_scavenge_root(this);
   oops_do(&detect_scavenge_root);
   return detect_scavenge_root.detected_scavenge_root();
 }
--- a/src/hotspot/share/code/nmethod.hpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/code/nmethod.hpp	Wed May 02 11:28:49 2018 -0400
@@ -484,18 +484,18 @@
 #endif
 
  protected:
-  virtual bool do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive, bool unloading_occurred);
+  virtual bool do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive);
 #if INCLUDE_JVMCI
   // See comment for _jvmci_installed_code_triggers_unloading field.
   // Returns whether this nmethod was unloaded.
-  virtual bool do_unloading_jvmci(bool unloading_occurred);
+  virtual bool do_unloading_jvmci();
 #endif
 
  private:
-  bool do_unloading_scopes(BoolObjectClosure* is_alive, bool unloading_occurred);
+  bool do_unloading_scopes(BoolObjectClosure* is_alive);
   //  Unload a nmethod if the *root object is dead.
-  bool can_unload(BoolObjectClosure* is_alive, oop* root, bool unloading_occurred);
-  bool unload_if_dead_at(RelocIterator *iter_at_oop, BoolObjectClosure* is_alive, bool unloading_occurred);
+  bool can_unload(BoolObjectClosure* is_alive, oop* root);
+  bool unload_if_dead_at(RelocIterator *iter_at_oop, BoolObjectClosure* is_alive);
 
  public:
   void oops_do(OopClosure* f) { oops_do(f, false); }
--- a/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	Wed May 02 11:28:49 2018 -0400
@@ -3355,7 +3355,7 @@
       add_to_postponed_list(nm);
     }
 
-    // Mark that this thread has been cleaned/unloaded.
+    // Mark that this nmethod has been cleaned/unloaded.
     // After this call, it will be safe to ask if this nmethod was unloaded or not.
     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
   }
--- a/src/hotspot/share/oops/method.cpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/oops/method.cpp	Wed May 02 11:28:49 2018 -0400
@@ -449,12 +449,6 @@
   return Atomic::replace_if_null(counters, &_method_counters);
 }
 
-void Method::cleanup_inline_caches() {
-  // The current system doesn't use inline caches in the interpreter
-  // => nothing to do (keep this method around for future use)
-}
-
-
 int Method::extra_stack_words() {
   // not an inline function, to avoid a header dependency on Interpreter
   return extra_stack_entries() * Interpreter::stackElementSize;
--- a/src/hotspot/share/oops/method.hpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/oops/method.hpp	Wed May 02 11:28:49 2018 -0400
@@ -904,9 +904,6 @@
     return method_holder()->lookup_osr_nmethod(this, bci, level, match_level);
   }
 
-  // Inline cache support
-  void cleanup_inline_caches();
-
   // Find if klass for method is loaded
   bool is_klass_loaded_by_klass_index(int klass_index) const;
   bool is_klass_loaded(int refinfo_index, bool must_be_resolved = false) const;
--- a/src/hotspot/share/runtime/arguments.cpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/runtime/arguments.cpp	Wed May 02 11:28:49 2018 -0400
@@ -553,6 +553,7 @@
   { "CheckEndorsedAndExtDirs",       JDK_Version::jdk(10),     JDK_Version::jdk(11), JDK_Version::jdk(12) },
   { "DeferThrSuspendLoopCount",      JDK_Version::jdk(10),     JDK_Version::jdk(11), JDK_Version::jdk(12) },
   { "DeferPollingPageLoopCount",     JDK_Version::jdk(10),     JDK_Version::jdk(11), JDK_Version::jdk(12) },
+  { "TraceScavenge",                 JDK_Version::undefined(), JDK_Version::jdk(11), JDK_Version::jdk(12) },
   { "PermSize",                      JDK_Version::undefined(), JDK_Version::jdk(8),  JDK_Version::undefined() },
   { "MaxPermSize",                   JDK_Version::undefined(), JDK_Version::jdk(8),  JDK_Version::undefined() },
   { "SharedReadWriteSize",           JDK_Version::undefined(), JDK_Version::jdk(10), JDK_Version::undefined() },
--- a/src/hotspot/share/runtime/globals.hpp	Tue Jun 05 23:10:54 2018 +0530
+++ b/src/hotspot/share/runtime/globals.hpp	Wed May 02 11:28:49 2018 -0400
@@ -1055,9 +1055,6 @@
   develop(bool, TraceFinalizerRegistration, false,                          \
           "Trace registration of final references")                         \
                                                                             \
-  notproduct(bool, TraceScavenge, false,                                    \
-          "Trace scavenge")                                                 \
-                                                                            \
   product(bool, IgnoreEmptyClassPaths, false,                               \
           "Ignore empty path elements in -classpath")                       \
                                                                             \