1 /*

     2  * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 #include "precompiled.hpp"

    26 #include "gc/g1/g1CollectedHeap.inline.hpp"

    27 #include "gc/g1/satbQueue.hpp"

    28 #include "gc/shared/collectedHeap.hpp"

    29 #include "memory/allocation.inline.hpp"

    30 #include "oops/oop.inline.hpp"

    31 #include "runtime/mutexLocker.hpp"

    32 #include "runtime/safepoint.hpp"

    33 #include "runtime/thread.hpp"

    34 #include "runtime/vmThread.hpp"

    35 

    36 void ObjPtrQueue::flush() {

    37   // Filter now to possibly save work later.  If filtering empties the

    38   // buffer then flush_impl can deallocate the buffer.

    39   filter();

    40   flush_impl();

    41 }

    42 

    43 // Return true if a SATB buffer entry refers to an object that

    44 // requires marking.

    45 //

    46 // The entry must point into the G1 heap.  In particular, it must not

    47 // be a NULL pointer.  NULL pointers are pre-filtered and never

    48 // inserted into a SATB buffer.

    49 //

    50 // An entry that is below the NTAMS pointer for the containing heap

    51 // region requires marking. Such an entry must point to a valid object.

    52 //

    53 // An entry that is at least the NTAMS pointer for the containing heap

    54 // region might be any of the following, none of which should be marked.

    55 //

    56 // * A reference to an object allocated since marking started.

    57 //   According to SATB, such objects are implicitly kept live and do

    58 //   not need to be dealt with via SATB buffer processing.

    59 //

    60 // * A reference to a young generation object. Young objects are

    61 //   handled separately and are not marked by concurrent marking.

    62 //

    63 // * A stale reference to a young generation object. If a young

    64 //   generation object reference is recorded and not filtered out

    65 //   before being moved by a young collection, the reference becomes

    66 //   stale.

    67 //

    68 // * A stale reference to an eagerly reclaimed humongous object.  If a

    69 //   humongous object is recorded and then reclaimed, the reference

    70 //   becomes stale.

    71 //

    72 // The stale reference cases are implicitly handled by the NTAMS

    73 // comparison. Because of the possibility of stale references, buffer

    74 // processing must be somewhat circumspect and not assume entries

    75 // in an unfiltered buffer refer to valid objects.

    76 

    77 inline bool requires_marking(const void* entry, G1CollectedHeap* heap) {

    78   // Includes rejection of NULL pointers.

    79   assert(heap->is_in_reserved(entry),

    80          err_msg("Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry)));

    81 

    82   HeapRegion* region = heap->heap_region_containing_raw(entry);

    83   assert(region != NULL, err_msg("No region for " PTR_FORMAT, p2i(entry)));

    84   if (entry >= region->next_top_at_mark_start()) {

    85     return false;

    86   }

    87 

    88   assert(((oop)entry)->is_oop(true /* ignore mark word */),

    89          err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry)));

    90 

    91   return true;

    92 }

    93 

    94 // This method removes entries from a SATB buffer that will not be

    95 // useful to the concurrent marking threads.  Entries are retained if

    96 // they require marking and are not already marked. Retained entries

    97 // are compacted toward the top of the buffer.

    98 

    99 void ObjPtrQueue::filter() {

   100   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   101   void** buf = _buf;

   102   size_t sz = _sz;

   103 

   104   if (buf == NULL) {

   105     // nothing to do

   106     return;

   107   }

   108 

   109   // Used for sanity checking at the end of the loop.

   110   debug_only(size_t entries = 0; size_t retained = 0;)

   111 

   112   size_t i = sz;

   113   size_t new_index = sz;

   114 

   115   while (i > _index) {

   116     assert(i > 0, "we should have at least one more entry to process");

   117     i -= oopSize;

   118     debug_only(entries += 1;)

   119     void** p = &buf[byte_index_to_index((int) i)];

   120     void* entry = *p;

   121     // NULL the entry so that unused parts of the buffer contain NULLs

   122     // at the end. If we are going to retain it we will copy it to its

   123     // final place. If we have retained all entries we have visited so

   124     // far, we'll just end up copying it to the same place.

   125     *p = NULL;

   126 

   127     if (requires_marking(entry, g1h) && !g1h->isMarkedNext((oop)entry)) {

   128       assert(new_index > 0, "we should not have already filled up the buffer");

   129       new_index -= oopSize;

   130       assert(new_index >= i,

   131              "new_index should never be below i, as we always compact 'up'");

   132       void** new_p = &buf[byte_index_to_index((int) new_index)];

   133       assert(new_p >= p, "the destination location should never be below "

   134              "the source as we always compact 'up'");

   135       assert(*new_p == NULL,

   136              "we should have already cleared the destination location");

   137       *new_p = entry;

   138       debug_only(retained += 1;)

   139     }

   140   }

   141 

   142 #ifdef ASSERT

   143   size_t entries_calc = (sz - _index) / oopSize;

   144   assert(entries == entries_calc, "the number of entries we counted "

   145          "should match the number of entries we calculated");

   146   size_t retained_calc = (sz - new_index) / oopSize;

   147   assert(retained == retained_calc, "the number of retained entries we counted "

   148          "should match the number of retained entries we calculated");

   149 #endif // ASSERT

   150 

   151   _index = new_index;

   152 }

   153 

   154 // This method will first apply the above filtering to the buffer. If

   155 // post-filtering a large enough chunk of the buffer has been cleared

   156 // we can re-use the buffer (instead of enqueueing it) and we can just

   157 // allow the mutator to carry on executing using the same buffer

   158 // instead of replacing it.

   159 

   160 bool ObjPtrQueue::should_enqueue_buffer() {

   161   assert(_lock == NULL || _lock->owned_by_self(),

   162          "we should have taken the lock before calling this");

   163 

   164   // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering.

   165 

   166   // This method should only be called if there is a non-NULL buffer

   167   // that is full.

   168   assert(_index == 0, "pre-condition");

   169   assert(_buf != NULL, "pre-condition");

   170 

   171   filter();

   172 

   173   size_t sz = _sz;

   174   size_t all_entries = sz / oopSize;

   175   size_t retained_entries = (sz - _index) / oopSize;

   176   size_t perc = retained_entries * 100 / all_entries;

   177   bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;

   178   return should_enqueue;

   179 }

   180 

   181 void ObjPtrQueue::apply_closure_and_empty(SATBBufferClosure* cl) {

   182   assert(SafepointSynchronize::is_at_safepoint(),

   183          "SATB queues must only be processed at safepoints");

   184   if (_buf != NULL) {

   185     assert(_index % sizeof(void*) == 0, "invariant");

   186     assert(_sz % sizeof(void*) == 0, "invariant");

   187     assert(_index <= _sz, "invariant");

   188     cl->do_buffer(_buf + byte_index_to_index((int)_index),

   189                   byte_index_to_index((int)(_sz - _index)));

   190     _index = _sz;

   191   }

   192 }

   193 

   194 #ifndef PRODUCT

   195 // Helpful for debugging

   196 

   197 void ObjPtrQueue::print(const char* name) {

   198   print(name, _buf, _index, _sz);

   199 }

   200 

   201 void ObjPtrQueue::print(const char* name,

   202                         void** buf, size_t index, size_t sz) {

   203   gclog_or_tty->print_cr("  SATB BUFFER [%s] buf: "PTR_FORMAT" "

   204                          "index: "SIZE_FORMAT" sz: "SIZE_FORMAT,

   205                          name, p2i(buf), index, sz);

   206 }

   207 #endif // PRODUCT

   208 

   209 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away

   210 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list

   211 #endif // _MSC_VER

   212 

   213 SATBMarkQueueSet::SATBMarkQueueSet() :

   214   PtrQueueSet(),

   215   _shared_satb_queue(this, true /*perm*/) { }

   216 

   217 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,

   218                                   int process_completed_threshold,

   219                                   Mutex* lock) {

   220   PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);

   221   _shared_satb_queue.set_lock(lock);

   222 }

   223 

   224 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {

   225   t->satb_mark_queue().handle_zero_index();

   226 }

   227 

   228 #ifdef ASSERT

   229 void SATBMarkQueueSet::dump_active_states(bool expected_active) {

   230   gclog_or_tty->print_cr("Expected SATB active state: %s",

   231                          expected_active ? "ACTIVE" : "INACTIVE");

   232   gclog_or_tty->print_cr("Actual SATB active states:");

   233   gclog_or_tty->print_cr("  Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");

   234   for (JavaThread* t = Threads::first(); t; t = t->next()) {

   235     gclog_or_tty->print_cr("  Thread \"%s\" queue: %s", t->name(),

   236                            t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");

   237   }

   238   gclog_or_tty->print_cr("  Shared queue: %s",

   239                          shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");

   240 }

   241 

   242 void SATBMarkQueueSet::verify_active_states(bool expected_active) {

   243   // Verify queue set state

   244   if (is_active() != expected_active) {

   245     dump_active_states(expected_active);

   246     guarantee(false, "SATB queue set has an unexpected active state");

   247   }

   248 

   249   // Verify thread queue states

   250   for (JavaThread* t = Threads::first(); t; t = t->next()) {

   251     if (t->satb_mark_queue().is_active() != expected_active) {

   252       dump_active_states(expected_active);

   253       guarantee(false, "Thread SATB queue has an unexpected active state");

   254     }

   255   }

   256 

   257   // Verify shared queue state

   258   if (shared_satb_queue()->is_active() != expected_active) {

   259     dump_active_states(expected_active);

   260     guarantee(false, "Shared SATB queue has an unexpected active state");

   261   }

   262 }

   263 #endif // ASSERT

   264 

   265 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {

   266   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

   267 #ifdef ASSERT

   268   verify_active_states(expected_active);

   269 #endif // ASSERT

   270   _all_active = active;

   271   for (JavaThread* t = Threads::first(); t; t = t->next()) {

   272     t->satb_mark_queue().set_active(active);

   273   }

   274   shared_satb_queue()->set_active(active);

   275 }

   276 

   277 void SATBMarkQueueSet::filter_thread_buffers() {

   278   for(JavaThread* t = Threads::first(); t; t = t->next()) {

   279     t->satb_mark_queue().filter();

   280   }

   281   shared_satb_queue()->filter();

   282 }

   283 

   284 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {

   285   BufferNode* nd = NULL;

   286   {

   287     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

   288     if (_completed_buffers_head != NULL) {

   289       nd = _completed_buffers_head;

   290       _completed_buffers_head = nd->next();

   291       if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;

   292       _n_completed_buffers--;

   293       if (_n_completed_buffers == 0) _process_completed = false;

   294     }

   295   }

   296   if (nd != NULL) {

   297     void **buf = BufferNode::make_buffer_from_node(nd);

   298     // Skip over NULL entries at beginning (e.g. push end) of buffer.

   299     // Filtering can result in non-full completed buffers; see

   300     // should_enqueue_buffer.

   301     assert(_sz % sizeof(void*) == 0, "invariant");

   302     size_t limit = ObjPtrQueue::byte_index_to_index((int)_sz);

   303     for (size_t i = 0; i < limit; ++i) {

   304       if (buf[i] != NULL) {

   305         // Found the end of the block of NULLs; process the remainder.

   306         cl->do_buffer(buf + i, limit - i);

   307         break;

   308       }

   309     }

   310     deallocate_buffer(buf);

   311     return true;

   312   } else {

   313     return false;

   314   }

   315 }

   316 

   317 #ifndef PRODUCT

   318 // Helpful for debugging

   319 

   320 #define SATB_PRINTER_BUFFER_SIZE 256

   321 

   322 void SATBMarkQueueSet::print_all(const char* msg) {

   323   char buffer[SATB_PRINTER_BUFFER_SIZE];

   324   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

   325 

   326   gclog_or_tty->cr();

   327   gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);

   328 

   329   BufferNode* nd = _completed_buffers_head;

   330   int i = 0;

   331   while (nd != NULL) {

   332     void** buf = BufferNode::make_buffer_from_node(nd);

   333     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);

   334     ObjPtrQueue::print(buffer, buf, 0, _sz);

   335     nd = nd->next();

   336     i += 1;

   337   }

   338 

   339   for (JavaThread* t = Threads::first(); t; t = t->next()) {

   340     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());

   341     t->satb_mark_queue().print(buffer);

   342   }

   343 

   344   shared_satb_queue()->print("Shared");

   345 

   346   gclog_or_tty->cr();

   347 }

   348 #endif // PRODUCT

   349 

   350 void SATBMarkQueueSet::abandon_partial_marking() {

   351   BufferNode* buffers_to_delete = NULL;

   352   {

   353     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

   354     while (_completed_buffers_head != NULL) {

   355       BufferNode* nd = _completed_buffers_head;

   356       _completed_buffers_head = nd->next();

   357       nd->set_next(buffers_to_delete);

   358       buffers_to_delete = nd;

   359     }

   360     _completed_buffers_tail = NULL;

   361     _n_completed_buffers = 0;

   362     DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());

   363   }

   364   while (buffers_to_delete != NULL) {

   365     BufferNode* nd = buffers_to_delete;

   366     buffers_to_delete = nd->next();

   367     deallocate_buffer(BufferNode::make_buffer_from_node(nd));

   368   }

   369   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

   370   // So we can safely manipulate these queues.

   371   for (JavaThread* t = Threads::first(); t; t = t->next()) {

   372     t->satb_mark_queue().reset();

   373   }

   374  shared_satb_queue()->reset();

   375 }