diff --git a/src/hotspot/share/gc/shared/cardTableBarrierSet.hpp b/src/hotspot/share/gc/shared/cardTableBarrierSet.hpp new file mode 100644 index 0000000..7eca103 --- /dev/null +++ b/src/hotspot/share/gc/shared/cardTableBarrierSet.hpp @@ -0,0 +1,139 @@ +/* + * Copyright (c) 2000, 2018, 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_SHARED_CARDTABLEBARRIERSET_HPP +#define SHARE_VM_GC_SHARED_CARDTABLEBARRIERSET_HPP + +#include "gc/shared/modRefBarrierSet.hpp" +#include "utilities/align.hpp" + +class CardTable; + +// This kind of "BarrierSet" allows a "CollectedHeap" to detect and +// enumerate ref fields that have been modified (since the last +// enumeration.) + +// As it currently stands, this barrier is *imprecise*: when a ref field in +// an object "o" is modified, the card table entry for the card containing +// the head of "o" is dirtied, not necessarily the card containing the +// modified field itself. For object arrays, however, the barrier *is* +// precise; only the card containing the modified element is dirtied. +// Closures used to scan dirty cards should take these +// considerations into account. + +class CardTableBarrierSet: public ModRefBarrierSet { + // Some classes get to look at some private stuff. + friend class VMStructs; + protected: + + // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 + // or INCLUDE_JVMCI is being used + bool _defer_initial_card_mark; + CardTable* _card_table; + + CardTableBarrierSet(CardTable* card_table, const BarrierSet::FakeRtti& fake_rtti); + + public: + CardTableBarrierSet(CardTable* card_table); + ~CardTableBarrierSet(); + + CardTable* card_table() const { return _card_table; } + + virtual void initialize(); + + void write_region(MemRegion mr) { + invalidate(mr); + } + + protected: + void write_ref_array_work(MemRegion mr); + + public: + // Record a reference update. Note that these versions are precise! + // The scanning code has to handle the fact that the write barrier may be + // either precise or imprecise. We make non-virtual inline variants of + // these functions here for performance. + template + void write_ref_field_post(T* field, oop newVal); + + virtual void invalidate(MemRegion mr); + + // ReduceInitialCardMarks + void initialize_deferred_card_mark_barriers(); + + // If the CollectedHeap was asked to defer a store barrier above, + // this informs it to flush such a deferred store barrier to the + // remembered set. + void flush_deferred_card_mark_barrier(JavaThread* thread); + + // Can a compiler initialize a new object without store barriers? + // This permission only extends from the creation of a new object + // via a TLAB up to the first subsequent safepoint. If such permission + // is granted for this heap type, the compiler promises to call + // defer_store_barrier() below on any slow path allocation of + // a new object for which such initializing store barriers will + // have been elided. G1, like CMS, allows this, but should be + // ready to provide a compensating write barrier as necessary + // if that storage came out of a non-young region. The efficiency + // of this implementation depends crucially on being able to + // answer very efficiently in constant time whether a piece of + // storage in the heap comes from a young region or not. + // See ReduceInitialCardMarks. + virtual bool can_elide_tlab_store_barriers() const { + return true; + } + + // If a compiler is eliding store barriers for TLAB-allocated objects, + // we will be informed of a slow-path allocation by a call + // to on_slowpath_allocation_exit() below. Such a call precedes the + // initialization of the object itself, and no post-store-barriers will + // be issued. Some heap types require that the barrier strictly follows + // the initializing stores. (This is currently implemented by deferring the + // barrier until the next slow-path allocation or gc-related safepoint.) + // This interface answers whether a particular barrier type needs the card + // mark to be thus strictly sequenced after the stores. + virtual bool card_mark_must_follow_store() const; + + virtual void on_slowpath_allocation_exit(JavaThread* thread, oop new_obj); + virtual void on_thread_detach(JavaThread* thread); + + virtual void make_parsable(JavaThread* thread) { flush_deferred_card_mark_barrier(thread); } + + virtual void print_on(outputStream* st) const; + + template + class AccessBarrier: public ModRefBarrierSet::AccessBarrier {}; +}; + +template<> +struct BarrierSet::GetName { + static const BarrierSet::Name value = BarrierSet::CardTableBarrierSet; +}; + +template<> +struct BarrierSet::GetType { + typedef ::CardTableBarrierSet type; +}; + +#endif // SHARE_VM_GC_SHARED_CARDTABLEBARRIERSET_HPP