Mercurial > hg > truffle
diff src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp @ 17764:595c0f60d50d
8029075: String deduplication in G1
Summary: Implementation of JEP 192, http://openjdk.java.net/jeps/192
Reviewed-by: brutisso, tschatzl, coleenp
author | pliden |
---|---|
date | Tue, 18 Mar 2014 19:07:22 +0100 |
parents | |
children | 1772223a25a2 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp Tue Mar 18 19:07:22 2014 +0100 @@ -0,0 +1,162 @@ +/* + * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA + * or visit www.oracle.com if you need additional information or have any + * questions. + * + */ + +#include "precompiled.hpp" +#include "classfile/javaClasses.hpp" +#include "gc_implementation/g1/g1StringDedupQueue.hpp" +#include "memory/gcLocker.hpp" +#include "runtime/mutexLocker.hpp" +#include "utilities/stack.inline.hpp" + +G1StringDedupQueue* G1StringDedupQueue::_queue = NULL; +const size_t G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue +const size_t G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue + +G1StringDedupQueue::G1StringDedupQueue() : + _cursor(0), + _empty(true), + _dropped(0) { + _nqueues = MAX2(ParallelGCThreads, (size_t)1); + _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC); + for (size_t i = 0; i < _nqueues; i++) { + new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size); + } +} + +G1StringDedupQueue::~G1StringDedupQueue() { + ShouldNotReachHere(); +} + +void G1StringDedupQueue::create() { + assert(_queue == NULL, "One string deduplication queue allowed"); + _queue = new G1StringDedupQueue(); +} + +void G1StringDedupQueue::wait() { + MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); + while (_queue->_empty) { + ml.wait(Mutex::_no_safepoint_check_flag); + } +} + +void G1StringDedupQueue::push(uint worker_id, oop java_string) { + assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint"); + assert(worker_id < _queue->_nqueues, "Invalid queue"); + + // Push and notify waiter + G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id]; + if (!worker_queue.is_full()) { + worker_queue.push(java_string); + if (_queue->_empty) { + MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); + if (_queue->_empty) { + // Mark non-empty and notify waiter + _queue->_empty = false; + ml.notify(); + } + } + } else { + // Queue is full, drop the string and update the statistics + Atomic::inc_ptr(&_queue->_dropped); + } +} + +oop G1StringDedupQueue::pop() { + assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint"); + No_Safepoint_Verifier nsv; + + // Try all queues before giving up + for (size_t tries = 0; tries < _queue->_nqueues; tries++) { + // The cursor indicates where we left of last time + G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor]; + while (!queue->is_empty()) { + oop obj = queue->pop(); + // The oop we pop can be NULL if it was marked + // dead. Just ignore those and pop the next oop. + if (obj != NULL) { + return obj; + } + } + + // Try next queue + _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues; + } + + // Mark empty + _queue->_empty = true; + + return NULL; +} + +void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) { + // A worker thread first claims a queue, which ensures exclusive + // access to that queue, then continues to process it. + for (;;) { + // Grab next queue to scan + size_t queue = cl->claim_queue(); + if (queue >= _queue->_nqueues) { + // End of queues + break; + } + + // Scan the queue + unlink_or_oops_do(cl, queue); + } +} + +void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) { + assert(queue < _queue->_nqueues, "Invalid queue"); + StackIterator<oop, mtGC> iter(_queue->_queues[queue]); + while (!iter.is_empty()) { + oop* p = iter.next_addr(); + if (*p != NULL) { + if (cl->is_alive(*p)) { + cl->keep_alive(p); + } else { + // Clear dead reference + *p = NULL; + } + } + } +} + +void G1StringDedupQueue::print_statistics(outputStream* st) { + st->print_cr( + " [Queue]\n" + " [Dropped: "UINTX_FORMAT"]", _queue->_dropped); +} + +void G1StringDedupQueue::verify() { + for (size_t i = 0; i < _queue->_nqueues; i++) { + StackIterator<oop, mtGC> iter(_queue->_queues[i]); + while (!iter.is_empty()) { + oop obj = iter.next(); + if (obj != NULL) { + guarantee(Universe::heap()->is_in_reserved(obj), "Object must be on the heap"); + guarantee(!obj->is_forwarded(), "Object must not be forwarded"); + guarantee(java_lang_String::is_instance(obj), "Object must be a String"); + } + } + } +}