src/hotspot/share/gc/g1/g1StringDedup.cpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 *
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#include "precompiled.hpp"
#include "classfile/javaClasses.inline.hpp"
#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1GCPhaseTimes.hpp"
#include "gc/g1/g1StringDedup.hpp"
#include "gc/g1/g1StringDedupQueue.hpp"
#include "gc/g1/g1StringDedupStat.hpp"
#include "gc/shared/stringdedup/stringDedup.inline.hpp"
#include "gc/shared/stringdedup/stringDedupQueue.hpp"
#include "gc/shared/stringdedup/stringDedupTable.hpp"
#include "gc/shared/stringdedup/stringDedupThread.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"

void G1StringDedup::initialize() {
  assert(UseG1GC, "String deduplication available with G1");
  StringDedup::initialize_impl<G1StringDedupQueue, G1StringDedupStat>();
}

bool G1StringDedup::is_candidate_from_mark(oop obj) {
  if (java_lang_String::is_instance_inlined(obj)) {
    bool from_young = G1CollectedHeap::heap()->heap_region_containing(obj)->is_young();
    if (from_young && obj->age() < StringDeduplicationAgeThreshold) {
      // Candidate found. String is being evacuated from young to old but has not
      // reached the deduplication age threshold, i.e. has not previously been a
      // candidate during its life in the young generation.
      return true;
    }
  }

  // Not a candidate
  return false;
}

void G1StringDedup::enqueue_from_mark(oop java_string, uint worker_id) {
  assert(is_enabled(), "String deduplication not enabled");
  if (is_candidate_from_mark(java_string)) {
    G1StringDedupQueue::push(worker_id, java_string);
  }
}

bool G1StringDedup::is_candidate_from_evacuation(bool from_young, bool to_young, oop obj) {
  if (from_young && java_lang_String::is_instance_inlined(obj)) {
    if (to_young && obj->age() == StringDeduplicationAgeThreshold) {
      // Candidate found. String is being evacuated from young to young and just
      // reached the deduplication age threshold.
      return true;
    }
    if (!to_young && obj->age() < StringDeduplicationAgeThreshold) {
      // Candidate found. String is being evacuated from young to old but has not
      // reached the deduplication age threshold, i.e. has not previously been a
      // candidate during its life in the young generation.
      return true;
    }
  }

  // Not a candidate
  return false;
}

void G1StringDedup::enqueue_from_evacuation(bool from_young, bool to_young, uint worker_id, oop java_string) {
  assert(is_enabled(), "String deduplication not enabled");
  if (is_candidate_from_evacuation(from_young, to_young, java_string)) {
    G1StringDedupQueue::push(worker_id, java_string);
  }
}