aoqi@0: /*
aoqi@0:  * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  *
aoqi@0:  */
aoqi@0: 
aoqi@0: #include "precompiled.hpp"
aoqi@0: #include "classfile/javaClasses.hpp"
aoqi@0: #include "gc_implementation/g1/g1StringDedupQueue.hpp"
aoqi@0: #include "memory/gcLocker.hpp"
aoqi@0: #include "runtime/mutexLocker.hpp"
aoqi@0: #include "utilities/stack.inline.hpp"
aoqi@0: 
aoqi@0: G1StringDedupQueue* G1StringDedupQueue::_queue = NULL;
aoqi@0: const size_t        G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue
aoqi@0: const size_t        G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue
aoqi@0: 
aoqi@0: G1StringDedupQueue::G1StringDedupQueue() :
aoqi@0:   _cursor(0),
aoqi@0:   _cancel(false),
aoqi@0:   _empty(true),
aoqi@0:   _dropped(0) {
aoqi@0:   _nqueues = MAX2(ParallelGCThreads, (size_t)1);
aoqi@0:   _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC);
aoqi@0:   for (size_t i = 0; i < _nqueues; i++) {
aoqi@0:     new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: G1StringDedupQueue::~G1StringDedupQueue() {
aoqi@0:   ShouldNotReachHere();
aoqi@0: }
aoqi@0: 
aoqi@0: void G1StringDedupQueue::create() {
aoqi@0:   assert(_queue == NULL, "One string deduplication queue allowed");
aoqi@0:   _queue = new G1StringDedupQueue();
aoqi@0: }
aoqi@0: 
aoqi@0: void G1StringDedupQueue::wait() {
aoqi@0:   MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
aoqi@0:   while (_queue->_empty && !_queue->_cancel) {
aoqi@0:     ml.wait(Mutex::_no_safepoint_check_flag);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: void G1StringDedupQueue::cancel_wait() {
aoqi@0:   MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
aoqi@0:   _queue->_cancel = true;
aoqi@0:   ml.notify();
aoqi@0: }
aoqi@0: 
aoqi@0: void G1StringDedupQueue::push(uint worker_id, oop java_string) {
aoqi@0:   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
aoqi@0:   assert(worker_id < _queue->_nqueues, "Invalid queue");
aoqi@0: 
aoqi@0:   // Push and notify waiter
aoqi@0:   G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id];
aoqi@0:   if (!worker_queue.is_full()) {
aoqi@0:     worker_queue.push(java_string);
aoqi@0:     if (_queue->_empty) {
aoqi@0:       MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
aoqi@0:       if (_queue->_empty) {
aoqi@0:         // Mark non-empty and notify waiter
aoqi@0:         _queue->_empty = false;
aoqi@0:         ml.notify();
aoqi@0:       }
aoqi@0:     }
aoqi@0:   } else {
aoqi@0:     // Queue is full, drop the string and update the statistics
aoqi@0:     Atomic::inc_ptr(&_queue->_dropped);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: oop G1StringDedupQueue::pop() {
aoqi@0:   assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint");
aoqi@0:   No_Safepoint_Verifier nsv;
aoqi@0: 
aoqi@0:   // Try all queues before giving up
aoqi@0:   for (size_t tries = 0; tries < _queue->_nqueues; tries++) {
aoqi@0:     // The cursor indicates where we left of last time
aoqi@0:     G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor];
aoqi@0:     while (!queue->is_empty()) {
aoqi@0:       oop obj = queue->pop();
aoqi@0:       // The oop we pop can be NULL if it was marked
aoqi@0:       // dead. Just ignore those and pop the next oop.
aoqi@0:       if (obj != NULL) {
aoqi@0:         return obj;
aoqi@0:       }
aoqi@0:     }
aoqi@0: 
aoqi@0:     // Try next queue
aoqi@0:     _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues;
aoqi@0:   }
aoqi@0: 
aoqi@0:   // Mark empty
aoqi@0:   _queue->_empty = true;
aoqi@0: 
aoqi@0:   return NULL;
aoqi@0: }
aoqi@0: 
aoqi@0: void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) {
aoqi@0:   // A worker thread first claims a queue, which ensures exclusive
aoqi@0:   // access to that queue, then continues to process it.
aoqi@0:   for (;;) {
aoqi@0:     // Grab next queue to scan
aoqi@0:     size_t queue = cl->claim_queue();
aoqi@0:     if (queue >= _queue->_nqueues) {
aoqi@0:       // End of queues
aoqi@0:       break;
aoqi@0:     }
aoqi@0: 
aoqi@0:     // Scan the queue
aoqi@0:     unlink_or_oops_do(cl, queue);
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) {
aoqi@0:   assert(queue < _queue->_nqueues, "Invalid queue");
aoqi@0:   StackIterator<oop, mtGC> iter(_queue->_queues[queue]);
aoqi@0:   while (!iter.is_empty()) {
aoqi@0:     oop* p = iter.next_addr();
aoqi@0:     if (*p != NULL) {
aoqi@0:       if (cl->is_alive(*p)) {
aoqi@0:         cl->keep_alive(p);
aoqi@0:       } else {
aoqi@0:         // Clear dead reference
aoqi@0:         *p = NULL;
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: void G1StringDedupQueue::print_statistics(outputStream* st) {
aoqi@0:   st->print_cr(
aoqi@0:     "   [Queue]\n"
aoqi@0:     "      [Dropped: "UINTX_FORMAT"]", _queue->_dropped);
aoqi@0: }
aoqi@0: 
aoqi@0: void G1StringDedupQueue::verify() {
aoqi@0:   for (size_t i = 0; i < _queue->_nqueues; i++) {
aoqi@0:     StackIterator<oop, mtGC> iter(_queue->_queues[i]);
aoqi@0:     while (!iter.is_empty()) {
aoqi@0:       oop obj = iter.next();
aoqi@0:       if (obj != NULL) {
aoqi@0:         guarantee(Universe::heap()->is_in_reserved(obj), "Object must be on the heap");
aoqi@0:         guarantee(!obj->is_forwarded(), "Object must not be forwarded");
aoqi@0:         guarantee(java_lang_String::is_instance(obj), "Object must be a String");
aoqi@0:       }
aoqi@0:     }
aoqi@0:   }
aoqi@0: }