1 /*
   2  * Copyright (c) 2014, 2019, 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_GC_SHARED_STRINGDEDUP_STRINGDEDUPTHREAD_HPP
  26 #define SHARE_GC_SHARED_STRINGDEDUP_STRINGDEDUPTHREAD_HPP
  27 
  28 #include "gc/shared/concurrentGCThread.hpp"
  29 #include "gc/shared/stringdedup/stringDedupStat.hpp"
  30 
  31 //
  32 // The deduplication thread is where the actual deduplication occurs. It waits for
  33 // deduplication candidates to appear on the deduplication queue, removes them from
  34 // the queue and tries to deduplicate them. It uses the deduplication hashtable to
  35 // find identical, already existing, character arrays on the heap. The thread runs
  36 // concurrently with the Java application but participates in safepoints to allow
  37 // the GC to adjust and unlink oops from the deduplication queue and table.
  38 //
  39 class StringDedupThread: public ConcurrentGCThread {
  40 protected:
  41   static StringDedupThread* _thread;
  42 
  43   StringDedupThread();
  44   ~StringDedupThread();
  45 
  46   void print_start(const StringDedupStat* last_stat);
  47   void print_end(const StringDedupStat* last_stat, const StringDedupStat* total_stat);
  48 
  49   void run_service() { this->do_deduplication(); }
  50   void stop_service();
  51 
  52   void deduplicate_shared_strings(StringDedupStat* stat);
  53 protected:
  54   virtual void do_deduplication() = 0;
  55 
  56 public:
  57   static StringDedupThread* thread();
  58 };
  59 
  60 template <typename S>
  61 class StringDedupThreadImpl : public StringDedupThread {
  62 private:
  63   StringDedupThreadImpl() { }
  64 
  65 protected:
  66   void do_deduplication();
  67 
  68 public:
  69   static void create();
  70 };
  71 
  72 #endif // SHARE_GC_SHARED_STRINGDEDUP_STRINGDEDUPTHREAD_HPP