1 /* 2 * Copyright (c) 2014, 2015, 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.hpp" 28 #include "gc/g1/g1StringDedup.hpp" 29 #include "gc/g1/g1StringDedupQueue.hpp" 30 #include "gc/shared/gcLocker.hpp" 31 #include "oops/oop.inline.hpp" 32 #include "runtime/atomic.inline.hpp" 33 #include "runtime/mutexLocker.hpp" 34 #include "utilities/stack.inline.hpp" 35 36 G1StringDedupQueue* G1StringDedupQueue::_queue = NULL; 37 const size_t G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue 38 const size_t G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue 39 40 G1StringDedupQueue::G1StringDedupQueue() : 41 _cursor(0), 42 _cancel(false), 43 _empty(true), 44 _dropped(0) { 45 _nqueues = MAX2(ParallelGCThreads, (size_t)1); 46 _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC); 47 for (size_t i = 0; i < _nqueues; i++) { 48 new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size); 49 } 50 } 51 52 G1StringDedupQueue::~G1StringDedupQueue() { 53 ShouldNotReachHere(); 54 } 55 56 void G1StringDedupQueue::create() { 57 assert(_queue == NULL, "One string deduplication queue allowed"); 58 _queue = new G1StringDedupQueue(); 59 } 60 61 void G1StringDedupQueue::wait() { 62 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); 63 while (_queue->_empty && !_queue->_cancel) { 64 ml.wait(Mutex::_no_safepoint_check_flag); 65 } 66 } 67 68 void G1StringDedupQueue::cancel_wait() { 69 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); 70 _queue->_cancel = true; 71 ml.notify(); 72 } 73 74 void G1StringDedupQueue::push(uint worker_id, oop java_string) { 75 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint"); 76 assert(worker_id < _queue->_nqueues, "Invalid queue"); 77 78 // Push and notify waiter 79 G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id]; 80 if (!worker_queue.is_full()) { 81 worker_queue.push(java_string); 82 if (_queue->_empty) { 83 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); 84 if (_queue->_empty) { 85 // Mark non-empty and notify waiter 86 _queue->_empty = false; 87 ml.notify(); 88 } 89 } 90 } else { 91 // Queue is full, drop the string and update the statistics 92 Atomic::inc_ptr(&_queue->_dropped); 93 } 94 } 95 96 oop G1StringDedupQueue::pop() { 97 assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint"); 98 No_Safepoint_Verifier nsv; 99 100 // Try all queues before giving up 101 for (size_t tries = 0; tries < _queue->_nqueues; tries++) { 102 // The cursor indicates where we left of last time 103 G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor]; 104 while (!queue->is_empty()) { 105 oop obj = queue->pop(); 106 // The oop we pop can be NULL if it was marked 107 // dead. Just ignore those and pop the next oop. 108 if (obj != NULL) { 109 return obj; 110 } 111 } 112 113 // Try next queue 114 _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues; 115 } 116 117 // Mark empty 118 _queue->_empty = true; 119 120 return NULL; 121 } 122 123 void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) { 124 // A worker thread first claims a queue, which ensures exclusive 125 // access to that queue, then continues to process it. 126 for (;;) { 127 // Grab next queue to scan 128 size_t queue = cl->claim_queue(); 129 if (queue >= _queue->_nqueues) { 130 // End of queues 131 break; 132 } 133 134 // Scan the queue 135 unlink_or_oops_do(cl, queue); 136 } 137 } 138 139 void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) { 140 assert(queue < _queue->_nqueues, "Invalid queue"); 141 StackIterator<oop, mtGC> iter(_queue->_queues[queue]); 142 while (!iter.is_empty()) { 143 oop* p = iter.next_addr(); 144 if (*p != NULL) { 145 if (cl->is_alive(*p)) { 146 cl->keep_alive(p); 147 } else { 148 // Clear dead reference 149 *p = NULL; 150 } 151 } 152 } 153 } 154 155 void G1StringDedupQueue::print_statistics(outputStream* st) { 156 st->print_cr( 157 " [Queue]\n" 158 " [Dropped: "UINTX_FORMAT"]", _queue->_dropped); 159 } 160 161 void G1StringDedupQueue::verify() { 162 for (size_t i = 0; i < _queue->_nqueues; i++) { 163 StackIterator<oop, mtGC> iter(_queue->_queues[i]); 164 while (!iter.is_empty()) { 165 oop obj = iter.next(); 166 if (obj != NULL) { 167 guarantee(G1CollectedHeap::heap()->is_in_reserved(obj), "Object must be on the heap"); 168 guarantee(!obj->is_forwarded(), "Object must not be forwarded"); 169 guarantee(java_lang_String::is_instance(obj), "Object must be a String"); 170 } 171 } 172 } 173 }