1/* 2 * Copyright (c) 2014, 2016, 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 "logging/log.hpp" 32#include "oops/oop.inline.hpp" 33#include "runtime/atomic.hpp" 34#include "runtime/mutexLocker.hpp" 35#include "utilities/stack.inline.hpp" 36 37G1StringDedupQueue* G1StringDedupQueue::_queue = NULL; 38const size_t G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue 39const size_t G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue 40 41G1StringDedupQueue::G1StringDedupQueue() : 42 _cursor(0), 43 _cancel(false), 44 _empty(true), 45 _dropped(0) { 46 _nqueues = ParallelGCThreads; 47 _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC); 48 for (size_t i = 0; i < _nqueues; i++) { 49 new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size); 50 } 51} 52 53G1StringDedupQueue::~G1StringDedupQueue() { 54 ShouldNotReachHere(); 55} 56 57void G1StringDedupQueue::create() { 58 assert(_queue == NULL, "One string deduplication queue allowed"); 59 _queue = new G1StringDedupQueue(); 60} 61 62void G1StringDedupQueue::wait() { 63 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); 64 while (_queue->_empty && !_queue->_cancel) { 65 ml.wait(Mutex::_no_safepoint_check_flag); 66 } 67} 68 69void G1StringDedupQueue::cancel_wait() { 70 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); 71 _queue->_cancel = true; 72 ml.notify(); 73} 74 75void G1StringDedupQueue::push(uint worker_id, oop java_string) { 76 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint"); 77 assert(worker_id < _queue->_nqueues, "Invalid queue"); 78 79 // Push and notify waiter 80 G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id]; 81 if (!worker_queue.is_full()) { 82 worker_queue.push(java_string); 83 if (_queue->_empty) { 84 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); 85 if (_queue->_empty) { 86 // Mark non-empty and notify waiter 87 _queue->_empty = false; 88 ml.notify(); 89 } 90 } 91 } else { 92 // Queue is full, drop the string and update the statistics 93 Atomic::inc_ptr(&_queue->_dropped); 94 } 95} 96 97oop G1StringDedupQueue::pop() { 98 assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint"); 99 NoSafepointVerifier nsv; 100 101 // Try all queues before giving up 102 for (size_t tries = 0; tries < _queue->_nqueues; tries++) { 103 // The cursor indicates where we left of last time 104 G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor]; 105 while (!queue->is_empty()) { 106 oop obj = queue->pop(); 107 // The oop we pop can be NULL if it was marked 108 // dead. Just ignore those and pop the next oop. 109 if (obj != NULL) { 110 return obj; 111 } 112 } 113 114 // Try next queue 115 _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues; 116 } 117 118 // Mark empty 119 _queue->_empty = true; 120 121 return NULL; 122} 123 124void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) { 125 // A worker thread first claims a queue, which ensures exclusive 126 // access to that queue, then continues to process it. 127 for (;;) { 128 // Grab next queue to scan 129 size_t queue = cl->claim_queue(); 130 if (queue >= _queue->_nqueues) { 131 // End of queues 132 break; 133 } 134 135 // Scan the queue 136 unlink_or_oops_do(cl, queue); 137 } 138} 139 140void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) { 141 assert(queue < _queue->_nqueues, "Invalid queue"); 142 StackIterator<oop, mtGC> iter(_queue->_queues[queue]); 143 while (!iter.is_empty()) { 144 oop* p = iter.next_addr(); 145 if (*p != NULL) { 146 if (cl->is_alive(*p)) { 147 cl->keep_alive(p); 148 } else { 149 // Clear dead reference 150 *p = NULL; 151 } 152 } 153 } 154} 155 156void G1StringDedupQueue::print_statistics() { 157 log_debug(gc, stringdedup)(" Queue"); 158 log_debug(gc, stringdedup)(" Dropped: " UINTX_FORMAT, _queue->_dropped); 159} 160 161void 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} 174