1 /* 2 * Copyright (c) 2014, 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.hpp" 27 #include "gc_implementation/g1/g1StringDedupQueue.hpp" 28 #include "memory/gcLocker.hpp" 29 #include "runtime/mutexLocker.hpp" 30 #include "utilities/stack.inline.hpp" 31 32 G1StringDedupQueue* G1StringDedupQueue::_queue = NULL; 33 const size_t G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue 34 const size_t G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue 35 36 G1StringDedupQueue::G1StringDedupQueue() : 37 _cursor(0), 38 _empty(true), 39 _dropped(0) { 40 _nqueues = MAX2(ParallelGCThreads, (size_t)1); 41 _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC); 42 for (size_t i = 0; i < _nqueues; i++) { 43 new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size); 44 } 45 } 46 47 G1StringDedupQueue::~G1StringDedupQueue() { 48 ShouldNotReachHere(); 49 } 50 51 void G1StringDedupQueue::create() { 52 assert(_queue == NULL, "One string deduplication queue allowed"); 53 _queue = new G1StringDedupQueue(); 54 } 55 56 void G1StringDedupQueue::wait() { 57 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); 58 while (_queue->_empty) { 59 ml.wait(Mutex::_no_safepoint_check_flag); 60 } 61 } 62 63 void G1StringDedupQueue::push(uint worker_id, oop java_string) { 64 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint"); 65 assert(worker_id < _queue->_nqueues, "Invalid queue"); 66 67 // Push and notify waiter 68 G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id]; 69 if (!worker_queue.is_full()) { 70 worker_queue.push(java_string); 71 if (_queue->_empty) { 72 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); 73 if (_queue->_empty) { 74 // Mark non-empty and notify waiter 75 _queue->_empty = false; 76 ml.notify(); 77 } 78 } 79 } else { 80 // Queue is full, drop the string and update the statistics 81 Atomic::inc_ptr(&_queue->_dropped); 82 } 83 } 84 85 oop G1StringDedupQueue::pop() { 86 assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint"); 87 No_Safepoint_Verifier nsv; 88 89 // Try all queues before giving up 90 for (size_t tries = 0; tries < _queue->_nqueues; tries++) { 91 // The cursor indicates where we left of last time 92 G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor]; 93 while (!queue->is_empty()) { 94 oop obj = queue->pop(); 95 // The oop we pop can be NULL if it was marked 96 // dead. Just ignore those and pop the next oop. 97 if (obj != NULL) { 98 return obj; 99 } 100 } 101 102 // Try next queue 103 _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues; 104 } 105 106 // Mark empty 107 _queue->_empty = true; 108 109 return NULL; 110 } 111 112 void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) { 113 // A worker thread first claims a queue, which ensures exclusive 114 // access to that queue, then continues to process it. 115 for (;;) { 116 // Grab next queue to scan 117 size_t queue = cl->claim_queue(); 118 if (queue >= _queue->_nqueues) { 119 // End of queues 120 break; 121 } 122 123 // Scan the queue 124 unlink_or_oops_do(cl, queue); 125 } 126 } 127 128 void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) { 129 assert(queue < _queue->_nqueues, "Invalid queue"); 130 StackIterator<oop, mtGC> iter(_queue->_queues[queue]); 131 while (!iter.is_empty()) { 132 oop* p = iter.next_addr(); 133 if (*p != NULL) { 134 if (cl->is_alive(*p)) { 135 cl->keep_alive(p); 136 } else { 137 // Clear dead reference 138 *p = NULL; 139 } 140 } 141 } 142 } 143 144 void G1StringDedupQueue::print_statistics(outputStream* st) { 145 st->print_cr( 146 " [Queue]\n" 147 " [Dropped: "UINTX_FORMAT"]", _queue->_dropped); 148 } 149 150 void G1StringDedupQueue::verify() { 151 for (size_t i = 0; i < _queue->_nqueues; i++) { 152 StackIterator<oop, mtGC> iter(_queue->_queues[i]); 153 while (!iter.is_empty()) { 154 oop obj = iter.next(); 155 if (obj != NULL) { 156 guarantee(Universe::heap()->is_in_reserved(obj), "Object must be on the heap"); 157 guarantee(!obj->is_forwarded(), "Object must not be forwarded"); 158 guarantee(java_lang_String::is_instance(obj), "Object must be a String"); 159 } 160 } 161 } 162 }