Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * 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.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "classfile/javaClasses.hpp"

 #include "gc_implementation/g1/g1StringDedupQueue.hpp"

 #include "memory/gcLocker.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "utilities/stack.inline.hpp"

 G1StringDedupQueue* G1StringDedupQueue::_queue = NULL;

 const size_t        G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue

 const size_t        G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue

 G1StringDedupQueue::G1StringDedupQueue() :

   _cursor(0),

   _empty(true),

   _dropped(0) {

   _nqueues = MAX2(ParallelGCThreads, (size_t)1);

   _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC);

   for (size_t i = 0; i < _nqueues; i++) {

     new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size);

   }

 }

 G1StringDedupQueue::~G1StringDedupQueue() {

   ShouldNotReachHere();

 }

 void G1StringDedupQueue::create() {

   assert(_queue == NULL, "One string deduplication queue allowed");

   _queue = new G1StringDedupQueue();

 }

 void G1StringDedupQueue::wait() {

   MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);

   while (_queue->_empty) {

     ml.wait(Mutex::_no_safepoint_check_flag);

   }

 }

 void G1StringDedupQueue::push(uint worker_id, oop java_string) {

   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");

   assert(worker_id < _queue->_nqueues, "Invalid queue");

   // Push and notify waiter

   G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id];

   if (!worker_queue.is_full()) {

     worker_queue.push(java_string);

     if (_queue->_empty) {

       MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);

       if (_queue->_empty) {

         // Mark non-empty and notify waiter

         _queue->_empty = false;

         ml.notify();

       }

     }

   } else {

     // Queue is full, drop the string and update the statistics

     Atomic::inc_ptr(&_queue->_dropped);

   }

 }

 oop G1StringDedupQueue::pop() {

   assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint");

   No_Safepoint_Verifier nsv;

   // Try all queues before giving up

   for (size_t tries = 0; tries < _queue->_nqueues; tries++) {

     // The cursor indicates where we left of last time

     G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor];

     while (!queue->is_empty()) {

       oop obj = queue->pop();

       // The oop we pop can be NULL if it was marked

       // dead. Just ignore those and pop the next oop.

       if (obj != NULL) {

         return obj;

       }

     }

     // Try next queue

     _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues;

   }

   // Mark empty

   _queue->_empty = true;

   return NULL;

 }

 void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) {

   // A worker thread first claims a queue, which ensures exclusive

   // access to that queue, then continues to process it.

   for (;;) {

     // Grab next queue to scan

     size_t queue = cl->claim_queue();

     if (queue >= _queue->_nqueues) {

       // End of queues

       break;

     }

     // Scan the queue

     unlink_or_oops_do(cl, queue);

   }

 }

 void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) {

   assert(queue < _queue->_nqueues, "Invalid queue");

   StackIterator<oop, mtGC> iter(_queue->_queues[queue]);

   while (!iter.is_empty()) {

     oop* p = iter.next_addr();

     if (*p != NULL) {

       if (cl->is_alive(*p)) {

         cl->keep_alive(p);

       } else {

         // Clear dead reference

         *p = NULL;

       }

     }

   }

 }

 void G1StringDedupQueue::print_statistics(outputStream* st) {

   st->print_cr(

     "   [Queue]\n"

     "      [Dropped: "UINTX_FORMAT"]", _queue->_dropped);

 }

 void G1StringDedupQueue::verify() {

   for (size_t i = 0; i < _queue->_nqueues; i++) {

     StackIterator<oop, mtGC> iter(_queue->_queues[i]);

     while (!iter.is_empty()) {

       oop obj = iter.next();

       if (obj != NULL) {

         guarantee(Universe::heap()->is_in_reserved(obj), "Object must be on the heap");

         guarantee(!obj->is_forwarded(), "Object must not be forwarded");

         guarantee(java_lang_String::is_instance(obj), "Object must be a String");

       }

     }

   }

 }