hotspot/src/share/vm/gc/g1/g1StringDedupQueue.cpp
author pliden
Wed, 13 May 2015 15:16:06 +0200
changeset 30764 fec48bf5a827
parent 30173 hotspot/src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp@13cf7580b000
child 30876 44a71334fd94
permissions -rw-r--r--
8079792: GC directory structure cleanup Reviewed-by: brutisso, stefank, david
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/*
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 * Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 *
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 */
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#include "precompiled.hpp"
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#include "classfile/javaClasses.inline.hpp"
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#include "gc/g1/g1CollectedHeap.hpp"
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#include "gc/g1/g1StringDedup.hpp"
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#include "gc/g1/g1StringDedupQueue.hpp"
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#include "gc/shared/gcLocker.hpp"
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#include "oops/oop.inline.hpp"
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#include "runtime/atomic.inline.hpp"
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#include "runtime/mutexLocker.hpp"
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#include "utilities/stack.inline.hpp"
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G1StringDedupQueue* G1StringDedupQueue::_queue = NULL;
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const size_t        G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue
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const size_t        G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue
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G1StringDedupQueue::G1StringDedupQueue() :
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  _cursor(0),
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  _cancel(false),
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  _empty(true),
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  _dropped(0) {
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  _nqueues = MAX2(ParallelGCThreads, (size_t)1);
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  _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC);
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  for (size_t i = 0; i < _nqueues; i++) {
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    new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size);
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  }
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}
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G1StringDedupQueue::~G1StringDedupQueue() {
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  ShouldNotReachHere();
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}
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void G1StringDedupQueue::create() {
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  assert(_queue == NULL, "One string deduplication queue allowed");
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  _queue = new G1StringDedupQueue();
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}
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void G1StringDedupQueue::wait() {
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  MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
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  while (_queue->_empty && !_queue->_cancel) {
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    ml.wait(Mutex::_no_safepoint_check_flag);
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  }
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}
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void G1StringDedupQueue::cancel_wait() {
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  MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
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  _queue->_cancel = true;
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  ml.notify();
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}
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void G1StringDedupQueue::push(uint worker_id, oop java_string) {
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  assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
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  assert(worker_id < _queue->_nqueues, "Invalid queue");
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  // Push and notify waiter
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  G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id];
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  if (!worker_queue.is_full()) {
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    worker_queue.push(java_string);
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    if (_queue->_empty) {
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      MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
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      if (_queue->_empty) {
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        // Mark non-empty and notify waiter
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        _queue->_empty = false;
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        ml.notify();
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      }
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    }
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  } else {
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    // Queue is full, drop the string and update the statistics
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    Atomic::inc_ptr(&_queue->_dropped);
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  }
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}
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oop G1StringDedupQueue::pop() {
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  assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint");
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  No_Safepoint_Verifier nsv;
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  // Try all queues before giving up
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  for (size_t tries = 0; tries < _queue->_nqueues; tries++) {
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    // The cursor indicates where we left of last time
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    G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor];
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    while (!queue->is_empty()) {
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      oop obj = queue->pop();
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      // The oop we pop can be NULL if it was marked
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      // dead. Just ignore those and pop the next oop.
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      if (obj != NULL) {
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        return obj;
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      }
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    }
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    // Try next queue
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    _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues;
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  }
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  // Mark empty
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  _queue->_empty = true;
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  return NULL;
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}
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void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) {
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  // A worker thread first claims a queue, which ensures exclusive
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  // access to that queue, then continues to process it.
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  for (;;) {
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    // Grab next queue to scan
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    size_t queue = cl->claim_queue();
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    if (queue >= _queue->_nqueues) {
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      // End of queues
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      break;
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    }
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    // Scan the queue
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    unlink_or_oops_do(cl, queue);
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  }
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}
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void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) {
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  assert(queue < _queue->_nqueues, "Invalid queue");
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  StackIterator<oop, mtGC> iter(_queue->_queues[queue]);
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  while (!iter.is_empty()) {
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    oop* p = iter.next_addr();
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    if (*p != NULL) {
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      if (cl->is_alive(*p)) {
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        cl->keep_alive(p);
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      } else {
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        // Clear dead reference
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        *p = NULL;
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      }
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    }
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  }
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}
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void G1StringDedupQueue::print_statistics(outputStream* st) {
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  st->print_cr(
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    "   [Queue]\n"
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    "      [Dropped: "UINTX_FORMAT"]", _queue->_dropped);
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}
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void G1StringDedupQueue::verify() {
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  for (size_t i = 0; i < _queue->_nqueues; i++) {
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    StackIterator<oop, mtGC> iter(_queue->_queues[i]);
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    while (!iter.is_empty()) {
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      oop obj = iter.next();
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      if (obj != NULL) {
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        guarantee(G1CollectedHeap::heap()->is_in_reserved(obj), "Object must be on the heap");
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        guarantee(!obj->is_forwarded(), "Object must not be forwarded");
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        guarantee(java_lang_String::is_instance(obj), "Object must be a String");
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      }
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    }
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  }
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}