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 
  31 class Thread;
  32 class ShenandoahHeap;
  33 class ShenandoahStrDedupQueue;
  34 
  35 class ShenandoahTraversalGC : public CHeapObj<mtGC> {
  36 private:
  37   ShenandoahHeap* const _heap;
  38   ShenandoahObjToScanQueueSet* const _task_queues;
  39 
  40   // Used for buffering per-region liveness data.
  41   // Needed since ShenandoahHeapRegion uses atomics to update liveness.
  42   //
  43   // The array has max-workers elements, each of which is an array of
  44   // jushort * max_regions. The choice of jushort is not accidental:
  45   // there is a tradeoff between static/dynamic footprint that translates
  46   // into cache pressure (which is already high during marking), and
  47   // too many atomic updates. size_t/jint is too large, jbyte is too small.
  48   jushort** _liveness_local;
  49 
  50   ShenandoahHeapRegionSet _traversal_set;
  51   ShenandoahHeapRegionSet _root_regions;
  52 
  53   ShenandoahHeapRegionSetIterator _root_regions_iterator;
  54 
  55   ShenandoahConnectionMatrix* const _matrix;
  56 
  57 public:
  58   ShenandoahTraversalGC(ShenandoahHeap* heap, size_t num_regions);
  59   ~ShenandoahTraversalGC();
  60 
  61   ShenandoahHeapRegionSet* traversal_set() { return &_traversal_set; }
  62   ShenandoahHeapRegionSet* root_regions()  { return &_root_regions;}
  63 
  64   void reset();
  65   void prepare();
  66   void init_traversal_collection();
  67   void concurrent_traversal_collection();
  68   void final_traversal_collection();
  69 
  70   template <class T, bool STRING_DEDUP, bool DEGEN, bool UPDATE_MATRIX>
  71   inline void process_oop(T* p, Thread* thread, ShenandoahObjToScanQueue* queue, ShenandoahMarkingContext* const mark_context, oop base_obj);
  72 
  73   bool check_and_handle_cancelled_gc(ParallelTaskTerminator* terminator);
  74 
  75   ShenandoahObjToScanQueueSet* task_queues();
  76 
  77   jushort* get_liveness(uint worker_id);
  78   void flush_liveness(uint worker_id);
  79 
  80   void main_loop(uint worker_id, ParallelTaskTerminator* terminator);
  81 
  82 private:
  83 
  84   void prepare_regions();
  85 
  86   template <class T>
  87   void main_loop_work(T* cl, jushort* live_data, uint worker_id, ParallelTaskTerminator* terminator);
  88 
  89   void preclean_weak_refs();
  90   void weak_refs_work();
  91   void weak_refs_work_doit();
  92 
  93   void fixup_roots();
  94 };
  95 
  96 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHTRAVERSALGC_HPP