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 #include "precompiled.hpp"
  26 #include "classfile/javaClasses.inline.hpp"
  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/g1/g1GCPhaseTimes.hpp"
  29 #include "gc/g1/g1StringDedup.hpp"
  30 #include "gc/g1/g1StringDedupQueue.hpp"
  31 #include "gc/g1/g1StringDedupStat.hpp"
  32 #include "gc/shared/stringdedup/stringDedup.inline.hpp"
  33 #include "gc/shared/stringdedup/stringDedupQueue.hpp"
  34 #include "gc/shared/stringdedup/stringDedupTable.hpp"
  35 #include "gc/shared/stringdedup/stringDedupThread.inline.hpp"
  36 #include "oops/oop.inline.hpp"
  37 #include "runtime/atomic.hpp"
  38 
  39 void G1StringDedup::initialize() {
  40   assert(UseG1GC, "String deduplication available with G1");
  41   StringDedup::initialize_impl<G1StringDedupQueue, G1StringDedupStat>();
  42 }
  43 
  44 bool G1StringDedup::is_candidate_from_mark(oop obj) {
  45   if (java_lang_String::is_instance_inlined(obj)) {
  46     bool from_young = G1CollectedHeap::heap()->heap_region_containing(obj)->is_young();
  47     if (from_young && obj->age() < StringDeduplicationAgeThreshold) {
  48       // Candidate found. String is being evacuated from young to old but has not
  49       // reached the deduplication age threshold, i.e. has not previously been a
  50       // candidate during its life in the young generation.
  51       return true;
  52     }
  53   }
  54 
  55   // Not a candidate
  56   return false;
  57 }
  58 
  59 void G1StringDedup::enqueue_from_mark(oop java_string, uint worker_id) {
  60   assert(is_enabled(), "String deduplication not enabled");
  61   if (is_candidate_from_mark(java_string)) {
  62     G1StringDedupQueue::push(worker_id, java_string);
  63   }
  64 }
  65 
  66 bool G1StringDedup::is_candidate_from_evacuation(bool from_young, bool to_young, oop obj) {
  67   if (from_young && java_lang_String::is_instance_inlined(obj)) {
  68     if (to_young && obj->age() == StringDeduplicationAgeThreshold) {
  69       // Candidate found. String is being evacuated from young to young and just
  70       // reached the deduplication age threshold.
  71       return true;
  72     }
  73     if (!to_young && obj->age() < StringDeduplicationAgeThreshold) {
  74       // Candidate found. String is being evacuated from young to old but has not
  75       // reached the deduplication age threshold, i.e. has not previously been a
  76       // candidate during its life in the young generation.
  77       return true;
  78     }
  79   }
  80 
  81   // Not a candidate
  82   return false;
  83 }
  84 
  85 void G1StringDedup::enqueue_from_evacuation(bool from_young, bool to_young, uint worker_id, oop java_string) {
  86   assert(is_enabled(), "String deduplication not enabled");
  87   if (is_candidate_from_evacuation(from_young, to_young, java_string)) {
  88     G1StringDedupQueue::push(worker_id, java_string);
  89   }
  90 }
  91