1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp Tue Mar 18 19:07:22 2014 +0100
1.3 @@ -0,0 +1,162 @@
1.4 +/*
1.5 + * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.23 + * or visit www.oracle.com if you need additional information or have any
1.24 + * questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#include "precompiled.hpp"
1.29 +#include "classfile/javaClasses.hpp"
1.30 +#include "gc_implementation/g1/g1StringDedupQueue.hpp"
1.31 +#include "memory/gcLocker.hpp"
1.32 +#include "runtime/mutexLocker.hpp"
1.33 +#include "utilities/stack.inline.hpp"
1.34 +
1.35 +G1StringDedupQueue* G1StringDedupQueue::_queue = NULL;
1.36 +const size_t G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue
1.37 +const size_t G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue
1.38 +
1.39 +G1StringDedupQueue::G1StringDedupQueue() :
1.40 + _cursor(0),
1.41 + _empty(true),
1.42 + _dropped(0) {
1.43 + _nqueues = MAX2(ParallelGCThreads, (size_t)1);
1.44 + _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC);
1.45 + for (size_t i = 0; i < _nqueues; i++) {
1.46 + new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size);
1.47 + }
1.48 +}
1.49 +
1.50 +G1StringDedupQueue::~G1StringDedupQueue() {
1.51 + ShouldNotReachHere();
1.52 +}
1.53 +
1.54 +void G1StringDedupQueue::create() {
1.55 + assert(_queue == NULL, "One string deduplication queue allowed");
1.56 + _queue = new G1StringDedupQueue();
1.57 +}
1.58 +
1.59 +void G1StringDedupQueue::wait() {
1.60 + MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
1.61 + while (_queue->_empty) {
1.62 + ml.wait(Mutex::_no_safepoint_check_flag);
1.63 + }
1.64 +}
1.65 +
1.66 +void G1StringDedupQueue::push(uint worker_id, oop java_string) {
1.67 + assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
1.68 + assert(worker_id < _queue->_nqueues, "Invalid queue");
1.69 +
1.70 + // Push and notify waiter
1.71 + G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id];
1.72 + if (!worker_queue.is_full()) {
1.73 + worker_queue.push(java_string);
1.74 + if (_queue->_empty) {
1.75 + MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
1.76 + if (_queue->_empty) {
1.77 + // Mark non-empty and notify waiter
1.78 + _queue->_empty = false;
1.79 + ml.notify();
1.80 + }
1.81 + }
1.82 + } else {
1.83 + // Queue is full, drop the string and update the statistics
1.84 + Atomic::inc_ptr(&_queue->_dropped);
1.85 + }
1.86 +}
1.87 +
1.88 +oop G1StringDedupQueue::pop() {
1.89 + assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint");
1.90 + No_Safepoint_Verifier nsv;
1.91 +
1.92 + // Try all queues before giving up
1.93 + for (size_t tries = 0; tries < _queue->_nqueues; tries++) {
1.94 + // The cursor indicates where we left of last time
1.95 + G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor];
1.96 + while (!queue->is_empty()) {
1.97 + oop obj = queue->pop();
1.98 + // The oop we pop can be NULL if it was marked
1.99 + // dead. Just ignore those and pop the next oop.
1.100 + if (obj != NULL) {
1.101 + return obj;
1.102 + }
1.103 + }
1.104 +
1.105 + // Try next queue
1.106 + _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues;
1.107 + }
1.108 +
1.109 + // Mark empty
1.110 + _queue->_empty = true;
1.111 +
1.112 + return NULL;
1.113 +}
1.114 +
1.115 +void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) {
1.116 + // A worker thread first claims a queue, which ensures exclusive
1.117 + // access to that queue, then continues to process it.
1.118 + for (;;) {
1.119 + // Grab next queue to scan
1.120 + size_t queue = cl->claim_queue();
1.121 + if (queue >= _queue->_nqueues) {
1.122 + // End of queues
1.123 + break;
1.124 + }
1.125 +
1.126 + // Scan the queue
1.127 + unlink_or_oops_do(cl, queue);
1.128 + }
1.129 +}
1.130 +
1.131 +void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) {
1.132 + assert(queue < _queue->_nqueues, "Invalid queue");
1.133 + StackIterator<oop, mtGC> iter(_queue->_queues[queue]);
1.134 + while (!iter.is_empty()) {
1.135 + oop* p = iter.next_addr();
1.136 + if (*p != NULL) {
1.137 + if (cl->is_alive(*p)) {
1.138 + cl->keep_alive(p);
1.139 + } else {
1.140 + // Clear dead reference
1.141 + *p = NULL;
1.142 + }
1.143 + }
1.144 + }
1.145 +}
1.146 +
1.147 +void G1StringDedupQueue::print_statistics(outputStream* st) {
1.148 + st->print_cr(
1.149 + " [Queue]\n"
1.150 + " [Dropped: "UINTX_FORMAT"]", _queue->_dropped);
1.151 +}
1.152 +
1.153 +void G1StringDedupQueue::verify() {
1.154 + for (size_t i = 0; i < _queue->_nqueues; i++) {
1.155 + StackIterator<oop, mtGC> iter(_queue->_queues[i]);
1.156 + while (!iter.is_empty()) {
1.157 + oop obj = iter.next();
1.158 + if (obj != NULL) {
1.159 + guarantee(Universe::heap()->is_in_reserved(obj), "Object must be on the heap");
1.160 + guarantee(!obj->is_forwarded(), "Object must not be forwarded");
1.161 + guarantee(java_lang_String::is_instance(obj), "Object must be a String");
1.162 + }
1.163 + }
1.164 + }
1.165 +}
