/*
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* 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).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
#include "precompiled.hpp"
#include "gc/shared/cardTable.hpp"
#include "gc/shared/cardTableBarrierSetAssembler.hpp"
#include "gc/shared/cardTableBarrierSet.inline.hpp"
#include "gc/shared/collectedHeap.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"
#ifdef COMPILER1
#include "gc/shared/c1/cardTableBarrierSetC1.hpp"
#endif
#ifdef COMPILER2
#include "gc/shared/c2/cardTableBarrierSetC2.hpp"
#endif
class CardTableBarrierSetC1;
class CardTableBarrierSetC2;
// 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,
BarrierSetC1* barrier_set_c1,
BarrierSetC2* barrier_set_c2,
CardTable* card_table,
const BarrierSet::FakeRtti& fake_rtti) :
ModRefBarrierSet(barrier_set_assembler,
barrier_set_c1,
barrier_set_c2,
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>(),
make_barrier_set_c1<CardTableBarrierSetC1>(),
make_barrier_set_c2<CardTableBarrierSetC2>(),
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 COMPILER2_OR_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_OR_JVMCI
}
void CardTableBarrierSet::initialize_deferred_card_mark_barriers() {
// Used for ReduceInitialCardMarks (when COMPILER2 or JVMCI is used);
// otherwise remains unused.
#if COMPILER2_OR_JVMCI
_defer_initial_card_mark = is_server_compilation_mode_vm() && ReduceInitialCardMarks
&& (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 COMPILER2_OR_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(Thread* 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).
if (thread->is_Java_thread()) { // Only relevant for Java threads.
flush_deferred_card_mark_barrier((JavaThread*)thread);
}
}
bool CardTableBarrierSet::card_mark_must_follow_store() const {
return _card_table->scanned_concurrently();
}