4360113: Evict nmethods when code cache gets full

Speculatively unload the oldest nmethods when code cache gets full.

Reviewed-by: never, kvn

hotspot/src/share/vm/code/codeCache.cpp

@@ -96,6 +96,7 @@ int CodeCache::_number_of_blobs = 0;
 int CodeCache::_number_of_nmethods_with_dependencies = 0;
 bool CodeCache::_needs_cache_clean = false;
 nmethod* CodeCache::_scavenge_root_nmethods = NULL;
+nmethod* CodeCache::_saved_nmethods = NULL;
 
 
 CodeBlob* CodeCache::first() {
@@ -395,6 +396,85 @@ void CodeCache::verify_perm_nmethods(CodeBlobClosure* f_or_null) {
 }
 #endif //PRODUCT
 
+
+nmethod* CodeCache::find_and_remove_saved_code(methodOop m) {
+  MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+  nmethod* saved = _saved_nmethods;
+  nmethod* prev = NULL;
+  while (saved != NULL) {
+    if (saved->is_in_use() && saved->method() == m) {
+      if (prev != NULL) {
+        prev->set_saved_nmethod_link(saved->saved_nmethod_link());
+      } else {
+        _saved_nmethods = saved->saved_nmethod_link();
+      }
+      assert(saved->is_speculatively_disconnected(), "shouldn't call for other nmethods");
+      saved->set_speculatively_disconnected(false);
+      saved->set_saved_nmethod_link(NULL);
+      if (PrintMethodFlushing) {
+        saved->print_on(tty, " ### nmethod is reconnected");
+      }
+      if (LogCompilation && (xtty != NULL)) {
+        ttyLocker ttyl;
+        xtty->begin_elem("nmethod_reconnected compile_id='%3d'", saved->compile_id());
+        xtty->method(methodOop(m));
+        xtty->stamp();
+        xtty->end_elem();
+      }
+      return saved;
+    }
+    prev = saved;
+    saved = saved->saved_nmethod_link();
+  }
+  return NULL;
+}
+
+void CodeCache::remove_saved_code(nmethod* nm) {
+  MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+  assert(nm->is_speculatively_disconnected(), "shouldn't call for other nmethods");
+  nmethod* saved = _saved_nmethods;
+  nmethod* prev = NULL;
+  while (saved != NULL) {
+    if (saved == nm) {
+      if (prev != NULL) {
+        prev->set_saved_nmethod_link(saved->saved_nmethod_link());
+      } else {
+        _saved_nmethods = saved->saved_nmethod_link();
+      }
+      if (LogCompilation && (xtty != NULL)) {
+        ttyLocker ttyl;
+        xtty->begin_elem("nmethod_removed compile_id='%3d'", nm->compile_id());
+        xtty->stamp();
+        xtty->end_elem();
+      }
+      return;
+    }
+    prev = saved;
+    saved = saved->saved_nmethod_link();
+  }
+  ShouldNotReachHere();
+}
+
+void CodeCache::speculatively_disconnect(nmethod* nm) {
+  assert_locked_or_safepoint(CodeCache_lock);
+  assert(nm->is_in_use() && !nm->is_speculatively_disconnected(), "should only disconnect live nmethods");
+  nm->set_saved_nmethod_link(_saved_nmethods);
+  _saved_nmethods = nm;
+  if (PrintMethodFlushing) {
+    nm->print_on(tty, " ### nmethod is speculatively disconnected");
+  }
+  if (LogCompilation && (xtty != NULL)) {
+    ttyLocker ttyl;
+    xtty->begin_elem("nmethod_disconnected compile_id='%3d'", nm->compile_id());
+    xtty->method(methodOop(nm->method()));
+    xtty->stamp();
+    xtty->end_elem();
+  }
+  nm->method()->clear_code();
+  nm->set_speculatively_disconnected(true);
+}
+
+
 void CodeCache::gc_prologue() {
   assert(!nmethod::oops_do_marking_is_active(), "oops_do_marking_epilogue must be called");
 }

hotspot/src/share/vm/code/codeCache.hpp

@@ -46,6 +46,7 @@ class CodeCache : AllStatic {
   static int _number_of_nmethods_with_dependencies;
   static bool _needs_cache_clean;
   static nmethod* _scavenge_root_nmethods;  // linked via nm->scavenge_root_link()
+  static nmethod* _saved_nmethods;          // linked via nm->saved_nmethod_look()
 
   static void verify_if_often() PRODUCT_RETURN;
 
@@ -141,11 +142,16 @@ class CodeCache : AllStatic {
   static size_t  capacity()                      { return _heap->capacity(); }
   static size_t  max_capacity()                  { return _heap->max_capacity(); }
   static size_t  unallocated_capacity()          { return _heap->unallocated_capacity(); }
+  static bool    needs_flushing()                { return unallocated_capacity() < CodeCacheFlushingMinimumFreeSpace; }
 
   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 nmethod* find_and_remove_saved_code(methodOop m);
+  static void remove_saved_code(nmethod* nm);
+  static void speculatively_disconnect(nmethod* nm);
+
   // Deoptimization
   static int  mark_for_deoptimization(DepChange& changes);
 #ifdef HOTSWAP

hotspot/src/share/vm/code/nmethod.cpp

@@ -587,6 +587,7 @@ nmethod::nmethod(
     _osr_link                = NULL;
     _scavenge_root_link      = NULL;
     _scavenge_root_state     = 0;
+    _saved_nmethod_link      = NULL;
     _compiler                = NULL;
     // We have no exception handler or deopt handler make the
     // values something that will never match a pc like the nmethod vtable entry
@@ -1033,7 +1034,7 @@ void nmethod::cleanup_inline_caches() {
         if( cb != NULL && cb->is_nmethod() ) {
           nmethod* nm = (nmethod*)cb;
           // Clean inline caches pointing to both zombie and not_entrant methods
-          if (!nm->is_in_use()) ic->set_to_clean();
+          if (!nm->is_in_use() || (nm->method()->code() != nm)) ic->set_to_clean();
         }
         break;
       }
@@ -1043,7 +1044,7 @@ void nmethod::cleanup_inline_caches() {
         if( cb != NULL && cb->is_nmethod() ) {
           nmethod* nm = (nmethod*)cb;
           // Clean inline caches pointing to both zombie and not_entrant methods
-          if (!nm->is_in_use()) csc->set_to_clean();
+          if (!nm->is_in_use() || (nm->method()->code() != nm)) csc->set_to_clean();
         }
         break;
       }
@@ -1312,7 +1313,8 @@ void nmethod::flush() {
   // completely deallocate this method
   EventMark m("flushing nmethod " INTPTR_FORMAT " %s", this, "");
   if (PrintMethodFlushing) {
-    tty->print_cr("*flushing nmethod " INTPTR_FORMAT ". Live blobs: %d", this, CodeCache::nof_blobs());
+    tty->print_cr("*flushing nmethod %3d/" INTPTR_FORMAT ". Live blobs:" UINT32_FORMAT "/Free CodeCache:" SIZE_FORMAT "Kb",
+        _compile_id, this, CodeCache::nof_blobs(), CodeCache::unallocated_capacity()/1024);
   }
 
   // We need to deallocate any ExceptionCache data.
@@ -1330,6 +1332,10 @@ void nmethod::flush() {
     CodeCache::drop_scavenge_root_nmethod(this);
   }
 
+  if (is_speculatively_disconnected()) {
+    CodeCache::remove_saved_code(this);
+  }
+
   ((CodeBlob*)(this))->flush();
 
   CodeCache::free(this);

hotspot/src/share/vm/code/nmethod.hpp

@@ -95,6 +95,8 @@ struct nmFlags {
   unsigned int has_unsafe_access:1;          // May fault due to unsafe access.
   unsigned int has_method_handle_invokes:1;  // Has this method MethodHandle invokes?
 
+  unsigned int speculatively_disconnected:1; // Marked for potential unload
+
   void clear();
 };
 
@@ -137,6 +139,7 @@ class nmethod : public CodeBlob {
   // To support simple linked-list chaining of nmethods:
   nmethod*  _osr_link;         // from instanceKlass::osr_nmethods_head
   nmethod*  _scavenge_root_link; // from CodeCache::scavenge_root_nmethods
+  nmethod*  _saved_nmethod_link; // from CodeCache::speculatively_disconnect
 
   static nmethod* volatile _oops_do_mark_nmethods;
   nmethod*        volatile _oops_do_mark_link;
@@ -413,6 +416,9 @@ class nmethod : public CodeBlob {
   bool  has_method_handle_invokes() const         { return flags.has_method_handle_invokes; }
   void  set_has_method_handle_invokes(bool z)     { flags.has_method_handle_invokes = z; }
 
+  bool  is_speculatively_disconnected() const     { return flags.speculatively_disconnected; }
+  void  set_speculatively_disconnected(bool z)     { flags.speculatively_disconnected = z; }
+
   int   level() const                             { return flags.level; }
   void  set_level(int newLevel)                   { check_safepoint(); flags.level = newLevel; }
 
@@ -437,6 +443,9 @@ class nmethod : public CodeBlob {
   nmethod* scavenge_root_link() const                  { return _scavenge_root_link; }
   void     set_scavenge_root_link(nmethod *n)          { _scavenge_root_link = n; }
 
+  nmethod* saved_nmethod_link() const                  { return _saved_nmethod_link; }
+  void     set_saved_nmethod_link(nmethod *n)          { _saved_nmethod_link = n; }
+
  public:
 
   // Sweeper support