1 /*
   2  * Copyright (c) 2018, Red Hat, Inc. and/or its affiliates.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #ifndef SHARE_VM_GC_SHENANDOAH_SHENANDOAHTRAVERSALGC_HPP
  25 #define SHARE_VM_GC_SHENANDOAH_SHENANDOAHTRAVERSALGC_HPP
  26 
  27 #include "memory/allocation.hpp"
  28 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
  29 #include "gc/shenandoah/shenandoahTaskqueue.hpp"
  30 #include "gc/shenandoah/shenandoahArrayCopyTaskQueue.hpp"
  31 
  32 class Thread;
  33 class ShenandoahHeapRegionSet;
  34 class ShenandoahHeap;
  35 class ShenandoahStrDedupQueue;
  36 
  37 class ShenandoahTraversalGC : public CHeapObj<mtGC> {
  38 private:
  39   ShenandoahHeap* _heap;
  40   ShenandoahObjToScanQueueSet* _task_queues;
  41 
  42   // Used for buffering per-region liveness data.
  43   // Needed since ShenandoahHeapRegion uses atomics to update liveness.
  44   //
  45   // The array has max-workers elements, each of which is an array of
  46   // jushort * max_regions. The choice of jushort is not accidental:
  47   // there is a tradeoff between static/dynamic footprint that translates
  48   // into cache pressure (which is already high during marking), and
  49   // too many atomic updates. size_t/jint is too large, jbyte is too small.
  50   jushort** _liveness_local;
  51 
  52   ShenandoahHeapRegionSet* const _traversal_set;
  53   ShenandoahHeapRegionSet* const _root_regions;
  54 
  55   ShenandoahHeapRegionSetIterator _root_regions_iterator;
  56 
  57   ShenandoahConnectionMatrix* const _matrix;
  58 
  59   ShenandoahArrayCopyTaskQueue _arraycopy_task_queue;
  60 
  61 public:
  62   ShenandoahTraversalGC(ShenandoahHeap* heap, size_t num_regions);
  63   ~ShenandoahTraversalGC();
  64 
  65   ShenandoahHeapRegionSet* const traversal_set() const { return _traversal_set; }
  66   ShenandoahHeapRegionSet* const root_regions()  const { return _root_regions;}
  67 
  68   void reset();
  69   void prepare();
  70   void init_traversal_collection();
  71   void concurrent_traversal_collection();
  72   void final_traversal_collection();
  73 
  74   template <class T, bool STRING_DEDUP, bool DEGEN, bool UPDATE_MATRIX>
  75   inline void process_oop(T* p, Thread* thread, ShenandoahObjToScanQueue* queue, oop base_obj, ShenandoahStrDedupQueue* dq = NULL);
  76 
  77   bool check_and_handle_cancelled_gc(ParallelTaskTerminator* terminator);
  78 
  79   ShenandoahObjToScanQueueSet* task_queues();
  80 
  81   jushort* get_liveness(uint worker_id);
  82   void flush_liveness(uint worker_id);
  83 
  84   void main_loop(uint worker_id, ParallelTaskTerminator* terminator);
  85 
  86   void push_arraycopy(HeapWord* start, size_t count);
  87 
  88 private:
  89 
  90   void prepare_regions();
  91 
  92   template <class T>
  93   void main_loop_work(T* cl, jushort* live_data, uint worker_id, ParallelTaskTerminator* terminator);
  94 
  95   void preclean_weak_refs();
  96   void weak_refs_work();
  97   void weak_refs_work_doit();
  98 
  99   void fixup_roots();
 100 
 101   template <class T>
 102   bool process_arraycopy_task(T* cl);
 103 };
 104 
 105 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHTRAVERSALGC_HPP