1 /*
   2  * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_BUFFERINGOOPCLOSURE_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_BUFFERINGOOPCLOSURE_HPP
  27 
  28 #include "memory/genOopClosures.hpp"
  29 #include "memory/generation.hpp"
  30 #include "runtime/os.hpp"
  31 #include "utilities/taskqueue.hpp"
  32 
  33 // A BufferingOops closure tries to separate out the cost of finding roots
  34 // from the cost of applying closures to them.  It maintains an array of
  35 // ref-containing locations.  Until the array is full, applying the closure
  36 // to an oop* merely records that location in the array.  Since this
  37 // closure app cost is small, an elapsed timer can approximately attribute
  38 // all of this cost to the cost of finding the roots.  When the array fills
  39 // up, the wrapped closure is applied to all elements, keeping track of
  40 // this elapsed time of this process, and leaving the array empty.
  41 // The caller must be sure to call "done" to process any unprocessed
  42 // buffered entriess.
  43 
  44 class Generation;
  45 class HeapRegion;
  46 
  47 class BufferingOopClosure: public OopClosure {
  48 protected:
  49   enum PrivateConstants {
  50     BufferLength = 1024
  51   };
  52 
  53   StarTask  _buffer[BufferLength];
  54   StarTask* _buffer_top;
  55   StarTask* _buffer_curr;
  56 
  57   OopClosure* _oc;
  58   double      _closure_app_seconds;
  59 
  60   void process_buffer () {
  61     double start = os::elapsedTime();
  62     for (StarTask* curr = _buffer; curr < _buffer_curr; ++curr) {
  63       if (curr->is_narrow()) {
  64         assert(UseCompressedOops, "Error");
  65         _oc->do_oop((narrowOop*)(*curr));
  66       } else {
  67         _oc->do_oop((oop*)(*curr));
  68       }
  69     }
  70     _buffer_curr = _buffer;
  71     _closure_app_seconds += (os::elapsedTime() - start);
  72   }
  73 
  74   template <class T> inline void do_oop_work(T* p) {
  75     if (_buffer_curr == _buffer_top) {
  76       process_buffer();
  77     }
  78     StarTask new_ref(p);
  79     *_buffer_curr = new_ref;
  80     ++_buffer_curr;
  81   }
  82 
  83 public:
  84   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
  85   virtual void do_oop(oop* p)       { do_oop_work(p); }
  86 
  87   void done () {
  88     if (_buffer_curr > _buffer) {
  89       process_buffer();
  90     }
  91   }
  92   double closure_app_seconds () {
  93     return _closure_app_seconds;
  94   }
  95   BufferingOopClosure (OopClosure *oc) :
  96     _oc(oc),
  97     _buffer_curr(_buffer), _buffer_top(_buffer + BufferLength),
  98     _closure_app_seconds(0.0) { }
  99 };
 100 
 101 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_BUFFERINGOOPCLOSURE_HPP