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