/*
* Copyright (c) 2001, 2019, 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
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*/
#include "precompiled.hpp"
#include "gc/g1/g1BufferNodeList.hpp"
#include "gc/g1/g1CardTableEntryClosure.hpp"
#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1DirtyCardQueue.hpp"
#include "gc/g1/g1FreeIdSet.hpp"
#include "gc/g1/g1RedirtyCardsQueue.hpp"
#include "gc/g1/g1RemSet.hpp"
#include "gc/g1/g1ThreadLocalData.hpp"
#include "gc/g1/heapRegionRemSet.hpp"
#include "gc/shared/suspendibleThreadSet.hpp"
#include "gc/shared/workgroup.hpp"
#include "runtime/atomic.hpp"
#include "runtime/flags/flagSetting.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/os.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/thread.inline.hpp"
#include "runtime/threadSMR.hpp"
#include "utilities/quickSort.hpp"
G1DirtyCardQueue::G1DirtyCardQueue(G1DirtyCardQueueSet* qset) :
// Dirty card queues are always active, so we create them with their
// active field set to true.
PtrQueue(qset, true /* active */)
{ }
G1DirtyCardQueue::~G1DirtyCardQueue() {
flush();
}
void G1DirtyCardQueue::handle_completed_buffer() {
assert(_buf != NULL, "precondition");
BufferNode* node = BufferNode::make_node_from_buffer(_buf, index());
G1DirtyCardQueueSet* dcqs = dirty_card_qset();
if (dcqs->process_or_enqueue_completed_buffer(node)) {
reset(); // Buffer fully processed, reset index.
} else {
allocate_buffer(); // Buffer enqueued, get a new one.
}
}
// Assumed to be zero by concurrent threads.
static uint par_ids_start() { return 0; }
G1DirtyCardQueueSet::G1DirtyCardQueueSet(Monitor* cbl_mon,
BufferNode::Allocator* allocator) :
PtrQueueSet(allocator),
_cbl_mon(cbl_mon),
_completed_buffers_head(NULL),
_completed_buffers_tail(NULL),
_num_cards(0),
_process_cards_threshold(ProcessCardsThresholdNever),
_process_completed_buffers(false),
_max_cards(MaxCardsUnlimited),
_max_cards_padding(0),
_free_ids(par_ids_start(), num_par_ids()),
_mutator_refined_cards_counters(NEW_C_HEAP_ARRAY(size_t, num_par_ids(), mtGC))
{
::memset(_mutator_refined_cards_counters, 0, num_par_ids() * sizeof(size_t));
_all_active = true;
}
G1DirtyCardQueueSet::~G1DirtyCardQueueSet() {
abandon_completed_buffers();
FREE_C_HEAP_ARRAY(size_t, _mutator_refined_cards_counters);
}
// Determines how many mutator threads can process the buffers in parallel.
uint G1DirtyCardQueueSet::num_par_ids() {
return (uint)os::initial_active_processor_count();
}
size_t G1DirtyCardQueueSet::total_mutator_refined_cards() const {
size_t sum = 0;
for (uint i = 0; i < num_par_ids(); ++i) {
sum += _mutator_refined_cards_counters[i];
}
return sum;
}
void G1DirtyCardQueueSet::handle_zero_index_for_thread(Thread* t) {
G1ThreadLocalData::dirty_card_queue(t).handle_zero_index();
}
void G1DirtyCardQueueSet::enqueue_completed_buffer(BufferNode* cbn) {
MonitorLocker ml(_cbl_mon, Mutex::_no_safepoint_check_flag);
cbn->set_next(NULL);
if (_completed_buffers_tail == NULL) {
assert(_completed_buffers_head == NULL, "Well-formedness");
_completed_buffers_head = cbn;
_completed_buffers_tail = cbn;
} else {
_completed_buffers_tail->set_next(cbn);
_completed_buffers_tail = cbn;
}
_num_cards += buffer_size() - cbn->index();
if (!process_completed_buffers() &&
(num_cards() > process_cards_threshold())) {
set_process_completed_buffers(true);
ml.notify_all();
}
verify_num_cards();
}
BufferNode* G1DirtyCardQueueSet::get_completed_buffer(size_t stop_at) {
MutexLocker x(_cbl_mon, Mutex::_no_safepoint_check_flag);
if (num_cards() <= stop_at) {
return NULL;
}
assert(num_cards() > 0, "invariant");
assert(_completed_buffers_head != NULL, "invariant");
assert(_completed_buffers_tail != NULL, "invariant");
BufferNode* bn = _completed_buffers_head;
_num_cards -= buffer_size() - bn->index();
_completed_buffers_head = bn->next();
if (_completed_buffers_head == NULL) {
assert(num_cards() == 0, "invariant");
_completed_buffers_tail = NULL;
set_process_completed_buffers(false);
}
verify_num_cards();
bn->set_next(NULL);
return bn;
}
#ifdef ASSERT
void G1DirtyCardQueueSet::verify_num_cards() const {
size_t actual = 0;
BufferNode* cur = _completed_buffers_head;
while (cur != NULL) {
actual += buffer_size() - cur->index();
cur = cur->next();
}
assert(actual == _num_cards,
"Num entries in completed buffers should be " SIZE_FORMAT " but are " SIZE_FORMAT,
_num_cards, actual);
}
#endif
void G1DirtyCardQueueSet::abandon_completed_buffers() {
BufferNode* buffers_to_delete = NULL;
{
MutexLocker x(_cbl_mon, Mutex::_no_safepoint_check_flag);
buffers_to_delete = _completed_buffers_head;
_completed_buffers_head = NULL;
_completed_buffers_tail = NULL;
_num_cards = 0;
set_process_completed_buffers(false);
}
while (buffers_to_delete != NULL) {
BufferNode* bn = buffers_to_delete;
buffers_to_delete = bn->next();
bn->set_next(NULL);
deallocate_buffer(bn);
}
}
void G1DirtyCardQueueSet::notify_if_necessary() {
MonitorLocker ml(_cbl_mon, Mutex::_no_safepoint_check_flag);
if (num_cards() > process_cards_threshold()) {
set_process_completed_buffers(true);
ml.notify_all();
}
}
// Merge lists of buffers. Notify the processing threads.
// The source queue is emptied as a result. The queues
// must share the monitor.
void G1DirtyCardQueueSet::merge_bufferlists(G1RedirtyCardsQueueSet* src) {
assert(allocator() == src->allocator(), "precondition");
const G1BufferNodeList from = src->take_all_completed_buffers();
if (from._head == NULL) return;
MutexLocker x(_cbl_mon, Mutex::_no_safepoint_check_flag);
if (_completed_buffers_tail == NULL) {
assert(_completed_buffers_head == NULL, "Well-formedness");
_completed_buffers_head = from._head;
_completed_buffers_tail = from._tail;
} else {
assert(_completed_buffers_head != NULL, "Well formedness");
_completed_buffers_tail->set_next(from._head);
_completed_buffers_tail = from._tail;
}
_num_cards += from._entry_count;
assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
_completed_buffers_head != NULL && _completed_buffers_tail != NULL,
"Sanity");
verify_num_cards();
}
G1BufferNodeList G1DirtyCardQueueSet::take_all_completed_buffers() {
MutexLocker x(_cbl_mon, Mutex::_no_safepoint_check_flag);
G1BufferNodeList result(_completed_buffers_head, _completed_buffers_tail, _num_cards);
_completed_buffers_head = NULL;
_completed_buffers_tail = NULL;
_num_cards = 0;
return result;
}
class G1RefineBufferedCards : public StackObj {
BufferNode* const _node;
CardTable::CardValue** const _node_buffer;
const size_t _node_buffer_size;
const uint _worker_id;
size_t* _total_refined_cards;
G1RemSet* const _g1rs;
static inline int compare_card(const CardTable::CardValue* p1,
const CardTable::CardValue* p2) {
return p2 - p1;
}
// Sorts the cards from start_index to _node_buffer_size in *decreasing*
// address order. Tests showed that this order is preferable to not sorting
// or increasing address order.
void sort_cards(size_t start_index) {
QuickSort::sort(&_node_buffer[start_index],
_node_buffer_size - start_index,
compare_card,
false);
}
// Returns the index to the first clean card in the buffer.
size_t clean_cards() {
const size_t start = _node->index();
assert(start <= _node_buffer_size, "invariant");
// Two-fingered compaction algorithm similar to the filtering mechanism in
// SATBMarkQueue. The main difference is that clean_card_before_refine()
// could change the buffer element in-place.
// We don't check for SuspendibleThreadSet::should_yield(), because
// cleaning and redirtying the cards is fast.
CardTable::CardValue** src = &_node_buffer[start];
CardTable::CardValue** dst = &_node_buffer[_node_buffer_size];
assert(src <= dst, "invariant");
for ( ; src < dst; ++src) {
// Search low to high for a card to keep.
if (_g1rs->clean_card_before_refine(src)) {
// Found keeper. Search high to low for a card to discard.
while (src < --dst) {
if (!_g1rs->clean_card_before_refine(dst)) {
*dst = *src; // Replace discard with keeper.
break;
}
}
// If discard search failed (src == dst), the outer loop will also end.
}
}
// dst points to the first retained clean card, or the end of the buffer
// if all the cards were discarded.
const size_t first_clean = dst - _node_buffer;
assert(first_clean >= start && first_clean <= _node_buffer_size, "invariant");
// Discarded cards are considered as refined.
*_total_refined_cards += first_clean - start;
return first_clean;
}
bool refine_cleaned_cards(size_t start_index) {
bool result = true;
size_t i = start_index;
for ( ; i < _node_buffer_size; ++i) {
if (SuspendibleThreadSet::should_yield()) {
redirty_unrefined_cards(i);
result = false;
break;
}
_g1rs->refine_card_concurrently(_node_buffer[i], _worker_id);
}
_node->set_index(i);
*_total_refined_cards += i - start_index;
return result;
}
void redirty_unrefined_cards(size_t start) {
for ( ; start < _node_buffer_size; ++start) {
*_node_buffer[start] = G1CardTable::dirty_card_val();
}
}
public:
G1RefineBufferedCards(BufferNode* node,
size_t node_buffer_size,
uint worker_id,
size_t* total_refined_cards) :
_node(node),
_node_buffer(reinterpret_cast<CardTable::CardValue**>(BufferNode::make_buffer_from_node(node))),
_node_buffer_size(node_buffer_size),
_worker_id(worker_id),
_total_refined_cards(total_refined_cards),
_g1rs(G1CollectedHeap::heap()->rem_set()) {}
bool refine() {
size_t first_clean_index = clean_cards();
if (first_clean_index == _node_buffer_size) {
_node->set_index(first_clean_index);
return true;
}
// This fence serves two purposes. First, the cards must be cleaned
// before processing the contents. Second, we can't proceed with
// processing a region until after the read of the region's top in
// collect_and_clean_cards(), for synchronization with possibly concurrent
// humongous object allocation (see comment at the StoreStore fence before
// setting the regions' tops in humongous allocation path).
// It's okay that reading region's top and reading region's type were racy
// wrto each other. We need both set, in any order, to proceed.
OrderAccess::fence();
sort_cards(first_clean_index);
return refine_cleaned_cards(first_clean_index);
}
};
bool G1DirtyCardQueueSet::refine_buffer(BufferNode* node,
uint worker_id,
size_t* total_refined_cards) {
G1RefineBufferedCards buffered_cards(node,
buffer_size(),
worker_id,
total_refined_cards);
return buffered_cards.refine();
}
#ifndef ASSERT
#define assert_fully_consumed(node, buffer_size)
#else
#define assert_fully_consumed(node, buffer_size) \
do { \
size_t _afc_index = (node)->index(); \
size_t _afc_size = (buffer_size); \
assert(_afc_index == _afc_size, \
"Buffer was not fully consumed as claimed: index: " \
SIZE_FORMAT ", size: " SIZE_FORMAT, \
_afc_index, _afc_size); \
} while (0)
#endif // ASSERT
bool G1DirtyCardQueueSet::process_or_enqueue_completed_buffer(BufferNode* node) {
if (Thread::current()->is_Java_thread()) {
// If the number of buffers exceeds the limit, make this Java
// thread do the processing itself. We don't lock to access
// buffer count or padding; it is fine to be imprecise here. The
// add of padding could overflow, which is treated as unlimited.
size_t limit = max_cards() + max_cards_padding();
if ((num_cards() > limit) && (limit >= max_cards())) {
if (mut_process_buffer(node)) {
return true;
}
}
}
enqueue_completed_buffer(node);
return false;
}
bool G1DirtyCardQueueSet::mut_process_buffer(BufferNode* node) {
uint worker_id = _free_ids.claim_par_id(); // temporarily claim an id
uint counter_index = worker_id - par_ids_start();
size_t* counter = &_mutator_refined_cards_counters[counter_index];
bool result = refine_buffer(node, worker_id, counter);
_free_ids.release_par_id(worker_id); // release the id
if (result) {
assert_fully_consumed(node, buffer_size());
}
return result;
}
bool G1DirtyCardQueueSet::refine_completed_buffer_concurrently(uint worker_id,
size_t stop_at,
size_t* total_refined_cards) {
BufferNode* node = get_completed_buffer(stop_at);
if (node == NULL) {
return false;
} else if (refine_buffer(node, worker_id, total_refined_cards)) {
assert_fully_consumed(node, buffer_size());
// Done with fully processed buffer.
deallocate_buffer(node);
return true;
} else {
// Return partially processed buffer to the queue.
enqueue_completed_buffer(node);
return true;
}
}
void G1DirtyCardQueueSet::abandon_logs() {
assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
abandon_completed_buffers();
// Since abandon is done only at safepoints, we can safely manipulate
// these queues.
struct AbandonThreadLogClosure : public ThreadClosure {
virtual void do_thread(Thread* t) {
G1ThreadLocalData::dirty_card_queue(t).reset();
}
} closure;
Threads::threads_do(&closure);
G1BarrierSet::shared_dirty_card_queue().reset();
}
void G1DirtyCardQueueSet::concatenate_logs() {
// Iterate over all the threads, if we find a partial log add it to
// the global list of logs. Temporarily turn off the limit on the number
// of outstanding buffers.
assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
size_t old_limit = max_cards();
set_max_cards(MaxCardsUnlimited);
struct ConcatenateThreadLogClosure : public ThreadClosure {
virtual void do_thread(Thread* t) {
G1DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(t);
if (!dcq.is_empty()) {
dcq.flush();
}
}
} closure;
Threads::threads_do(&closure);
G1BarrierSet::shared_dirty_card_queue().flush();
set_max_cards(old_limit);
}