--- old/src/share/vm/gc_implementation/g1/g1StringDedupQueue.hpp 2015-05-13 13:56:14.460607857 +0200 +++ /dev/null 2015-03-18 17:10:38.111854831 +0100 @@ -1,101 +0,0 @@ -/* - * 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. - * - */ - -#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1STRINGDEDUPQUEUE_HPP -#define SHARE_VM_GC_IMPLEMENTATION_G1_G1STRINGDEDUPQUEUE_HPP - -#include "memory/allocation.hpp" -#include "oops/oop.hpp" -#include "utilities/stack.hpp" - -class G1StringDedupUnlinkOrOopsDoClosure; - -// -// The deduplication queue acts as the communication channel between the stop-the-world -// mark/evacuation phase and the concurrent deduplication phase. Deduplication candidates -// found during mark/evacuation are placed on this queue for later processing in the -// deduplication thread. A queue entry is an oop pointing to a String object (as opposed -// to entries in the deduplication hashtable which points to character arrays). -// -// While users of the queue treat it as a single queue, it is implemented as a set of -// queues, one queue per GC worker thread, to allow lock-free and cache-friendly enqueue -// operations by the GC workers. -// -// The oops in the queue are treated as weak pointers, meaning the objects they point to -// can become unreachable and pruned (cleared) before being popped by the deduplication -// thread. -// -// Pushing to the queue is thread safe (this relies on each thread using a unique worker -// id), but only allowed during a safepoint. Popping from the queue is NOT thread safe -// and can only be done by the deduplication thread outside a safepoint. -// -// The StringDedupQueue_lock is only used for blocking and waking up the deduplication -// thread in case the queue is empty or becomes non-empty, respectively. This lock does -// not otherwise protect the queue content. -// -class G1StringDedupQueue : public CHeapObj { -private: - typedef Stack G1StringDedupWorkerQueue; - - static G1StringDedupQueue* _queue; - static const size_t _max_size; - static const size_t _max_cache_size; - - G1StringDedupWorkerQueue* _queues; - size_t _nqueues; - size_t _cursor; - bool _cancel; - volatile bool _empty; - - // Statistics counter, only used for logging. - uintx _dropped; - - G1StringDedupQueue(); - ~G1StringDedupQueue(); - - static void unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue); - -public: - static void create(); - - // Blocks and waits for the queue to become non-empty. - static void wait(); - - // Wakes up any thread blocked waiting for the queue to become non-empty. - static void cancel_wait(); - - // Pushes a deduplication candidate onto a specific GC worker queue. - static void push(uint worker_id, oop java_string); - - // Pops a deduplication candidate from any queue, returns NULL if - // all queues are empty. - static oop pop(); - - static void unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl); - - static void print_statistics(outputStream* st); - static void verify(); -}; - -#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1STRINGDEDUPQUEUE_HPP --- /dev/null 2015-03-18 17:10:38.111854831 +0100 +++ new/src/share/vm/gc/g1/g1StringDedupQueue.hpp 2015-05-13 13:56:14.284600554 +0200 @@ -0,0 +1,101 @@ +/* + * Copyright (c) 2014, 2015, 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. + * + */ + +#ifndef SHARE_VM_GC_G1_G1STRINGDEDUPQUEUE_HPP +#define SHARE_VM_GC_G1_G1STRINGDEDUPQUEUE_HPP + +#include "memory/allocation.hpp" +#include "oops/oop.hpp" +#include "utilities/stack.hpp" + +class G1StringDedupUnlinkOrOopsDoClosure; + +// +// The deduplication queue acts as the communication channel between the stop-the-world +// mark/evacuation phase and the concurrent deduplication phase. Deduplication candidates +// found during mark/evacuation are placed on this queue for later processing in the +// deduplication thread. A queue entry is an oop pointing to a String object (as opposed +// to entries in the deduplication hashtable which points to character arrays). +// +// While users of the queue treat it as a single queue, it is implemented as a set of +// queues, one queue per GC worker thread, to allow lock-free and cache-friendly enqueue +// operations by the GC workers. +// +// The oops in the queue are treated as weak pointers, meaning the objects they point to +// can become unreachable and pruned (cleared) before being popped by the deduplication +// thread. +// +// Pushing to the queue is thread safe (this relies on each thread using a unique worker +// id), but only allowed during a safepoint. Popping from the queue is NOT thread safe +// and can only be done by the deduplication thread outside a safepoint. +// +// The StringDedupQueue_lock is only used for blocking and waking up the deduplication +// thread in case the queue is empty or becomes non-empty, respectively. This lock does +// not otherwise protect the queue content. +// +class G1StringDedupQueue : public CHeapObj { +private: + typedef Stack G1StringDedupWorkerQueue; + + static G1StringDedupQueue* _queue; + static const size_t _max_size; + static const size_t _max_cache_size; + + G1StringDedupWorkerQueue* _queues; + size_t _nqueues; + size_t _cursor; + bool _cancel; + volatile bool _empty; + + // Statistics counter, only used for logging. + uintx _dropped; + + G1StringDedupQueue(); + ~G1StringDedupQueue(); + + static void unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue); + +public: + static void create(); + + // Blocks and waits for the queue to become non-empty. + static void wait(); + + // Wakes up any thread blocked waiting for the queue to become non-empty. + static void cancel_wait(); + + // Pushes a deduplication candidate onto a specific GC worker queue. + static void push(uint worker_id, oop java_string); + + // Pops a deduplication candidate from any queue, returns NULL if + // all queues are empty. + static oop pop(); + + static void unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl); + + static void print_statistics(outputStream* st); + static void verify(); +}; + +#endif // SHARE_VM_GC_G1_G1STRINGDEDUPQUEUE_HPP