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hotspot/src/share/vm/gc_implementation/shared/markSweep.hpp

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+/*
+ * Copyright 1997-2007 Sun Microsystems, Inc.  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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+class ReferenceProcessor;
+
+// MarkSweep takes care of global mark-compact garbage collection for a
+// GenCollectedHeap using a four-phase pointer forwarding algorithm.  All
+// generations are assumed to support marking; those that can also support
+// compaction.
+//
+// Class unloading will only occur when a full gc is invoked.
+
+// If VALIDATE_MARK_SWEEP is defined, the -XX:+ValidateMarkSweep flag will
+// be operational, and will provide slow but comprehensive self-checks within
+// the GC.  This is not enabled by default in product or release builds,
+// since the extra call to track_adjusted_pointer() in _adjust_pointer()
+// would be too much overhead, and would disturb performance measurement.
+// However, debug builds are sometimes way too slow to run GC tests!
+#ifdef ASSERT
+#define VALIDATE_MARK_SWEEP 1
+#endif
+#ifdef VALIDATE_MARK_SWEEP
+#define VALIDATE_MARK_SWEEP_ONLY(code) code
+#else
+#define VALIDATE_MARK_SWEEP_ONLY(code)
+#endif
+
+
+// declared at end
+class PreservedMark;
+
+class MarkSweep : AllStatic {
+  //
+  // In line closure decls
+  //
+
+  class FollowRootClosure: public OopsInGenClosure{
+   public:
+    void do_oop(oop* p) { follow_root(p); }
+    virtual const bool do_nmethods() const { return true; }
+  };
+
+  class MarkAndPushClosure: public OopClosure {
+   public:
+    void do_oop(oop* p) { mark_and_push(p); }
+    virtual const bool do_nmethods() const { return true; }
+  };
+
+  class FollowStackClosure: public VoidClosure {
+   public:
+    void do_void() { follow_stack(); }
+  };
+
+  class AdjustPointerClosure: public OopsInGenClosure {
+    bool _is_root;
+   public:
+    AdjustPointerClosure(bool is_root) : _is_root(is_root) {}
+    void do_oop(oop* p) { _adjust_pointer(p, _is_root); }
+  };
+
+  // Used for java/lang/ref handling
+  class IsAliveClosure: public BoolObjectClosure {
+   public:
+    void do_object(oop p) { assert(false, "don't call"); }
+    bool do_object_b(oop p) { return p->is_gc_marked(); }
+  };
+
+  class KeepAliveClosure: public OopClosure {
+   public:
+    void do_oop(oop* p);
+  };
+
+  //
+  // Friend decls
+  //
+
+  friend class AdjustPointerClosure;
+  friend class KeepAliveClosure;
+  friend class VM_MarkSweep;
+  friend void marksweep_init();
+
+  //
+  // Vars
+  //
+ protected:
+  // Traversal stack used during phase1
+  static GrowableArray<oop>*             _marking_stack;
+  // Stack for live klasses to revisit at end of marking phase
+  static GrowableArray<Klass*>*          _revisit_klass_stack;
+
+  // Space for storing/restoring mark word
+  static GrowableArray<markOop>*         _preserved_mark_stack;
+  static GrowableArray<oop>*             _preserved_oop_stack;
+  static size_t                          _preserved_count;
+  static size_t                          _preserved_count_max;
+  static PreservedMark*                  _preserved_marks;
+
+  // Reference processing (used in ...follow_contents)
+  static ReferenceProcessor*             _ref_processor;
+
+#ifdef VALIDATE_MARK_SWEEP
+  static GrowableArray<oop*>*            _root_refs_stack;
+  static GrowableArray<oop> *            _live_oops;
+  static GrowableArray<oop> *            _live_oops_moved_to;
+  static GrowableArray<size_t>*          _live_oops_size;
+  static size_t                          _live_oops_index;
+  static size_t                          _live_oops_index_at_perm;
+  static GrowableArray<oop*>*            _other_refs_stack;
+  static GrowableArray<oop*>*            _adjusted_pointers;
+  static bool                            _pointer_tracking;
+  static bool                            _root_tracking;
+
+  // The following arrays are saved since the time of the last GC and
+  // assist in tracking down problems where someone has done an errant
+  // store into the heap, usually to an oop that wasn't properly
+  // handleized across a GC. If we crash or otherwise fail before the
+  // next GC, we can query these arrays to find out the object we had
+  // intended to do the store to (assuming it is still alive) and the
+  // offset within that object. Covered under RecordMarkSweepCompaction.
+  static GrowableArray<HeapWord*> *      _cur_gc_live_oops;
+  static GrowableArray<HeapWord*> *      _cur_gc_live_oops_moved_to;
+  static GrowableArray<size_t>*          _cur_gc_live_oops_size;
+  static GrowableArray<HeapWord*> *      _last_gc_live_oops;
+  static GrowableArray<HeapWord*> *      _last_gc_live_oops_moved_to;
+  static GrowableArray<size_t>*          _last_gc_live_oops_size;
+#endif
+
+
+  // Non public closures
+  static IsAliveClosure is_alive;
+  static KeepAliveClosure keep_alive;
+
+  // Class unloading. Update subklass/sibling/implementor links at end of marking phase.
+  static void follow_weak_klass_links();
+
+  // Debugging
+  static void trace(const char* msg) PRODUCT_RETURN;
+
+ public:
+  // Public closures
+  static FollowRootClosure follow_root_closure;
+  static MarkAndPushClosure mark_and_push_closure;
+  static FollowStackClosure follow_stack_closure;
+  static AdjustPointerClosure adjust_root_pointer_closure;
+  static AdjustPointerClosure adjust_pointer_closure;
+
+  // Reference Processing
+  static ReferenceProcessor* const ref_processor() { return _ref_processor; }
+
+  // Call backs for marking
+  static void mark_object(oop obj);
+  static void follow_root(oop* p);        // Mark pointer and follow contents. Empty marking
+
+                                          // stack afterwards.
+
+  static void mark_and_follow(oop* p);    // Mark pointer and follow contents.
+  static void _mark_and_push(oop* p);     // Mark pointer and push obj on
+                                          // marking stack.
+
+
+  static void mark_and_push(oop* p) {     // Check mark and maybe push on
+                                          // marking stack
+    // assert(Universe::is_reserved_heap((oop)p), "we should only be traversing objects here");
+    oop m = *p;
+    if (m != NULL && !m->mark()->is_marked()) {
+      _mark_and_push(p);
+    }
+  }
+
+  static void follow_stack();             // Empty marking stack.
+
+
+  static void preserve_mark(oop p, markOop mark);       // Save the mark word so it can be restored later
+  static void adjust_marks();             // Adjust the pointers in the preserved marks table
+  static void restore_marks();            // Restore the marks that we saved in preserve_mark
+
+  static void _adjust_pointer(oop* p, bool isroot);
+
+  static void adjust_root_pointer(oop* p) { _adjust_pointer(p, true); }
+  static void adjust_pointer(oop* p)      { _adjust_pointer(p, false); }
+
+#ifdef VALIDATE_MARK_SWEEP
+  static void track_adjusted_pointer(oop* p, oop newobj, bool isroot);
+  static void check_adjust_pointer(oop* p);     // Adjust this pointer
+  static void track_interior_pointers(oop obj);
+  static void check_interior_pointers();
+
+  static void reset_live_oop_tracking(bool at_perm);
+  static void register_live_oop(oop p, size_t size);
+  static void validate_live_oop(oop p, size_t size);
+  static void live_oop_moved_to(HeapWord* q, size_t size, HeapWord* compaction_top);
+  static void compaction_complete();
+
+  // Querying operation of RecordMarkSweepCompaction results.
+  // Finds and prints the current base oop and offset for a word
+  // within an oop that was live during the last GC. Helpful for
+  // tracking down heap stomps.
+  static void print_new_location_of_heap_address(HeapWord* q);
+#endif
+
+  // Call backs for class unloading
+  static void revisit_weak_klass_link(Klass* k);  // Update subklass/sibling/implementor links at end of marking.
+};
+
+
+class PreservedMark VALUE_OBJ_CLASS_SPEC {
+private:
+  oop _obj;
+  markOop _mark;
+
+public:
+  void init(oop obj, markOop mark) {
+    _obj = obj;
+    _mark = mark;
+  }
+
+  void adjust_pointer() {
+    MarkSweep::adjust_pointer(&_obj);
+  }
+
+  void restore() {
+    _obj->set_mark(_mark);
+  }
+};