--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/cardTableBarrierSet.cpp Sat Mar 24 01:08:35 2018 +0100
@@ -0,0 +1,192 @@
+/*
+ * 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.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc/shared/cardTableBarrierSetAssembler.hpp"
+#include "gc/shared/cardTableBarrierSet.inline.hpp"
+#include "gc/shared/collectedHeap.hpp"
+#include "gc/shared/genCollectedHeap.hpp"
+#include "gc/shared/space.inline.hpp"
+#include "logging/log.hpp"
+#include "memory/virtualspace.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/thread.hpp"
+#include "services/memTracker.hpp"
+#include "utilities/align.hpp"
+#include "utilities/macros.hpp"
+
+// This kind of "BarrierSet" allows a "CollectedHeap" to detect and
+// enumerate ref fields that have been modified (since the last
+// enumeration.)
+
+CardTableBarrierSet::CardTableBarrierSet(BarrierSetAssembler* barrier_set_assembler,
+ CardTable* card_table,
+ const BarrierSet::FakeRtti& fake_rtti) :
+ ModRefBarrierSet(barrier_set_assembler,
+ fake_rtti.add_tag(BarrierSet::CardTableBarrierSet)),
+ _defer_initial_card_mark(false),
+ _card_table(card_table)
+{}
+
+CardTableBarrierSet::CardTableBarrierSet(CardTable* card_table) :
+ ModRefBarrierSet(make_barrier_set_assembler<CardTableBarrierSetAssembler>(),
+ BarrierSet::FakeRtti(BarrierSet::CardTableBarrierSet)),
+ _defer_initial_card_mark(false),
+ _card_table(card_table)
+{}
+
+void CardTableBarrierSet::initialize() {
+ initialize_deferred_card_mark_barriers();
+}
+
+CardTableBarrierSet::~CardTableBarrierSet() {
+ delete _card_table;
+}
+
+void CardTableBarrierSet::write_ref_array_work(MemRegion mr) {
+ _card_table->dirty_MemRegion(mr);
+}
+
+void CardTableBarrierSet::invalidate(MemRegion mr) {
+ _card_table->invalidate(mr);
+}
+
+void CardTableBarrierSet::print_on(outputStream* st) const {
+ _card_table->print_on(st);
+}
+
+// Helper for ReduceInitialCardMarks. For performance,
+// compiled code may elide card-marks for initializing stores
+// to a newly allocated object along the fast-path. We
+// compensate for such elided card-marks as follows:
+// (a) Generational, non-concurrent collectors, such as
+// GenCollectedHeap(ParNew,DefNew,Tenured) and
+// ParallelScavengeHeap(ParallelGC, ParallelOldGC)
+// need the card-mark if and only if the region is
+// in the old gen, and do not care if the card-mark
+// succeeds or precedes the initializing stores themselves,
+// so long as the card-mark is completed before the next
+// scavenge. For all these cases, we can do a card mark
+// at the point at which we do a slow path allocation
+// in the old gen, i.e. in this call.
+// (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
+// in addition that the card-mark for an old gen allocated
+// object strictly follow any associated initializing stores.
+// In these cases, the memRegion remembered below is
+// used to card-mark the entire region either just before the next
+// slow-path allocation by this thread or just before the next scavenge or
+// CMS-associated safepoint, whichever of these events happens first.
+// (The implicit assumption is that the object has been fully
+// initialized by this point, a fact that we assert when doing the
+// card-mark.)
+// (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
+// G1 concurrent marking is in progress an SATB (pre-write-)barrier
+// is used to remember the pre-value of any store. Initializing
+// stores will not need this barrier, so we need not worry about
+// compensating for the missing pre-barrier here. Turning now
+// to the post-barrier, we note that G1 needs a RS update barrier
+// which simply enqueues a (sequence of) dirty cards which may
+// optionally be refined by the concurrent update threads. Note
+// that this barrier need only be applied to a non-young write,
+// but, like in CMS, because of the presence of concurrent refinement
+// (much like CMS' precleaning), must strictly follow the oop-store.
+// Thus, using the same protocol for maintaining the intended
+// invariants turns out, serendepitously, to be the same for both
+// G1 and CMS.
+//
+// For any future collector, this code should be reexamined with
+// that specific collector in mind, and the documentation above suitably
+// extended and updated.
+void CardTableBarrierSet::on_slowpath_allocation_exit(JavaThread* thread, oop new_obj) {
+#if defined(COMPILER2) || INCLUDE_JVMCI
+ if (!ReduceInitialCardMarks) {
+ return;
+ }
+ // If a previous card-mark was deferred, flush it now.
+ flush_deferred_card_mark_barrier(thread);
+ if (new_obj->is_typeArray() || _card_table->is_in_young(new_obj)) {
+ // Arrays of non-references don't need a post-barrier.
+ // The deferred_card_mark region should be empty
+ // following the flush above.
+ assert(thread->deferred_card_mark().is_empty(), "Error");
+ } else {
+ MemRegion mr((HeapWord*)new_obj, new_obj->size());
+ assert(!mr.is_empty(), "Error");
+ if (_defer_initial_card_mark) {
+ // Defer the card mark
+ thread->set_deferred_card_mark(mr);
+ } else {
+ // Do the card mark
+ invalidate(mr);
+ }
+ }
+#endif // COMPILER2 || JVMCI
+}
+
+void CardTableBarrierSet::initialize_deferred_card_mark_barriers() {
+ // Used for ReduceInitialCardMarks (when COMPILER2 or JVMCI is used);
+ // otherwise remains unused.
+#if defined(COMPILER2) || INCLUDE_JVMCI
+ _defer_initial_card_mark = is_server_compilation_mode_vm() && ReduceInitialCardMarks && can_elide_tlab_store_barriers()
+ && (DeferInitialCardMark || card_mark_must_follow_store());
+#else
+ assert(_defer_initial_card_mark == false, "Who would set it?");
+#endif
+}
+
+void CardTableBarrierSet::flush_deferred_card_mark_barrier(JavaThread* thread) {
+#if defined(COMPILER2) || INCLUDE_JVMCI
+ MemRegion deferred = thread->deferred_card_mark();
+ if (!deferred.is_empty()) {
+ assert(_defer_initial_card_mark, "Otherwise should be empty");
+ {
+ // Verify that the storage points to a parsable object in heap
+ DEBUG_ONLY(oop old_obj = oop(deferred.start());)
+ assert(!_card_table->is_in_young(old_obj),
+ "Else should have been filtered in on_slowpath_allocation_exit()");
+ assert(oopDesc::is_oop(old_obj, true), "Not an oop");
+ assert(deferred.word_size() == (size_t)(old_obj->size()),
+ "Mismatch: multiple objects?");
+ }
+ write_region(deferred);
+ // "Clear" the deferred_card_mark field
+ thread->set_deferred_card_mark(MemRegion());
+ }
+ assert(thread->deferred_card_mark().is_empty(), "invariant");
+#else
+ assert(!_defer_initial_card_mark, "Should be false");
+ assert(thread->deferred_card_mark().is_empty(), "Should be empty");
+#endif
+}
+
+void CardTableBarrierSet::on_thread_detach(JavaThread* thread) {
+ // The deferred store barriers must all have been flushed to the
+ // card-table (or other remembered set structure) before GC starts
+ // processing the card-table (or other remembered set).
+ flush_deferred_card_mark_barrier(thread);
+}
+
+bool CardTableBarrierSet::card_mark_must_follow_store() const {
+ return _card_table->scanned_concurrently();
+}