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_implementation/g1/g1CollectedHeap.inline.hpp"
  27 #include "gc_implementation/g1/satbQueue.hpp"
  28 #include "gc_implementation/shenandoah/shenandoahHeap.inline.hpp"
  29 #include "memory/allocation.inline.hpp"
  30 #include "memory/sharedHeap.hpp"
  31 #include "oops/oop.inline.hpp"
  32 #include "runtime/mutexLocker.hpp"
  33 #include "runtime/safepoint.hpp"
  34 #include "runtime/thread.hpp"
  35 #include "runtime/vmThread.hpp"
  36 
  37 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  38 
  39 void ObjPtrQueue::flush() {
  40   // Filter now to possibly save work later.  If filtering empties the
  41   // buffer then flush_impl can deallocate the buffer.
  42   filter();
  43   flush_impl();
  44 }
  45 
  46 // Return true if a SATB buffer entry refers to an object that
  47 // requires marking.
  48 //
  49 // The entry must point into the G1 heap.  In particular, it must not
  50 // be a NULL pointer.  NULL pointers are pre-filtered and never
  51 // inserted into a SATB buffer.
  52 //
  53 // An entry that is below the NTAMS pointer for the containing heap
  54 // region requires marking. Such an entry must point to a valid object.
  55 //
  56 // An entry that is at least the NTAMS pointer for the containing heap
  57 // region might be any of the following, none of which should be marked.
  58 //
  59 // * A reference to an object allocated since marking started.
  60 //   According to SATB, such objects are implicitly kept live and do
  61 //   not need to be dealt with via SATB buffer processing.
  62 //
  63 // * A reference to a young generation object. Young objects are
  64 //   handled separately and are not marked by concurrent marking.
  65 //
  66 // * A stale reference to a young generation object. If a young
  67 //   generation object reference is recorded and not filtered out
  68 //   before being moved by a young collection, the reference becomes
  69 //   stale.
  70 //
  71 // * A stale reference to an eagerly reclaimed humongous object.  If a
  72 //   humongous object is recorded and then reclaimed, the reference
  73 //   becomes stale.
  74 //
  75 // The stale reference cases are implicitly handled by the NTAMS
  76 // comparison. Because of the possibility of stale references, buffer
  77 // processing must be somewhat circumspect and not assume entries
  78 // in an unfiltered buffer refer to valid objects.
  79 
  80 template <class HeapType>
  81 inline bool requires_marking(const void* entry, HeapType* heap) {
  82   return heap->requires_marking(entry);
  83 }









  84 
  85 void ObjPtrQueue::filter() {
  86   if (UseG1GC) {
  87     filter_impl<G1CollectedHeap>();
  88   } else if (UseShenandoahGC) {
  89     filter_impl<ShenandoahHeap>();
  90   } else {
  91     ShouldNotReachHere();
  92   }
  93 }
  94 
  95 // This method removes entries from a SATB buffer that will not be
  96 // useful to the concurrent marking threads.  Entries are retained if
  97 // they require marking and are not already marked. Retained entries
  98 // are compacted toward the top of the buffer.
  99 
 100 template <class HeapType>
 101 void ObjPtrQueue::filter_impl() {
 102   HeapType* heap = (HeapType*) Universe::heap();
 103   void** buf = _buf;
 104   size_t sz = _sz;
 105 
 106   if (buf == NULL) {
 107     // nothing to do
 108     return;
 109   }
 110 
 111   // Used for sanity checking at the end of the loop.
 112   debug_only(size_t entries = 0; size_t retained = 0;)
 113 
 114   size_t i = sz;
 115   size_t new_index = sz;
 116 
 117   while (i > _index) {
 118     assert(i > 0, "we should have at least one more entry to process");
 119     i -= oopSize;
 120     debug_only(entries += 1;)
 121     void** p = &buf[byte_index_to_index((int) i)];
 122     void* entry = *p;
 123     // NULL the entry so that unused parts of the buffer contain NULLs
 124     // at the end. If we are going to retain it we will copy it to its
 125     // final place. If we have retained all entries we have visited so
 126     // far, we'll just end up copying it to the same place.
 127     *p = NULL;
 128 
 129     if (requires_marking(entry, heap)) {
 130       assert(new_index > 0, "we should not have already filled up the buffer");
 131       new_index -= oopSize;
 132       assert(new_index >= i,
 133              "new_index should never be below i, as we alwaysr compact 'up'");
 134       void** new_p = &buf[byte_index_to_index((int) new_index)];
 135       assert(new_p >= p, "the destination location should never be below "
 136              "the source as we always compact 'up'");
 137       assert(*new_p == NULL,
 138              "we should have already cleared the destination location");
 139       *new_p = entry;
 140       debug_only(retained += 1;)
 141     }
 142   }
 143 
 144 #ifdef ASSERT
 145   size_t entries_calc = (sz - _index) / oopSize;
 146   assert(entries == entries_calc, "the number of entries we counted "
 147          "should match the number of entries we calculated");
 148   size_t retained_calc = (sz - new_index) / oopSize;
 149   assert(retained == retained_calc, "the number of retained entries we counted "
 150          "should match the number of retained entries we calculated");
 151 #endif // ASSERT
 152 
 153   _index = new_index;
 154 }
 155 
 156 // This method will first apply the above filtering to the buffer. If
 157 // post-filtering a large enough chunk of the buffer has been cleared
 158 // we can re-use the buffer (instead of enqueueing it) and we can just
 159 // allow the mutator to carry on executing using the same buffer
 160 // instead of replacing it.
 161 
 162 bool ObjPtrQueue::should_enqueue_buffer() {
 163   assert(_lock == NULL || _lock->owned_by_self(),
 164          "we should have taken the lock before calling this");
 165 
 166   // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering.
 167 
 168   // This method should only be called if there is a non-NULL buffer
 169   // that is full.
 170   assert(_index == 0, "pre-condition");
 171   assert(_buf != NULL, "pre-condition");
 172 
 173   filter();
 174 
 175   size_t sz = _sz;
 176   size_t all_entries = sz / oopSize;
 177   size_t retained_entries = (sz - _index) / oopSize;
 178   size_t perc = retained_entries * 100 / all_entries;
 179   bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
 180 
 181   if (UseShenandoahGC) {
 182     Thread* t = Thread::current();
 183     if (t->is_force_satb_flush()) {
 184       if (!should_enqueue && sz != _index) {
 185         // Non-empty buffer is compacted, and we decided not to enqueue it.
 186         // Shenandoah still wants to know about leftover work in that buffer eventually.
 187         // This avoid dealing with these leftovers during the final-mark, after the buffers
 188         // are drained completely.
 189         // TODO: This can be extended to handle G1 too
 190         should_enqueue = true;
 191       }
 192       t->set_force_satb_flush(false);
 193     }
 194   }
 195 
 196   return should_enqueue;
 197 }
 198 
 199 void ObjPtrQueue::apply_closure_and_empty(SATBBufferClosure* cl) {
 200   assert(SafepointSynchronize::is_at_safepoint(),
 201          "SATB queues must only be processed at safepoints");
 202   if (_buf != NULL) {
 203     assert(_index % sizeof(void*) == 0, "invariant");
 204     assert(_sz % sizeof(void*) == 0, "invariant");
 205     assert(_index <= _sz, "invariant");
 206     cl->do_buffer(_buf + byte_index_to_index((int)_index),
 207                   byte_index_to_index((int)(_sz - _index)));
 208     _index = _sz;
 209   }
 210 }
 211 
 212 #ifndef PRODUCT
 213 // Helpful for debugging
 214 
 215 void ObjPtrQueue::print(const char* name) {
 216   print(name, _buf, _index, _sz);
 217 }
 218 
 219 void ObjPtrQueue::print(const char* name,
 220                         void** buf, size_t index, size_t sz) {
 221   gclog_or_tty->print_cr("  SATB BUFFER [%s] buf: " PTR_FORMAT " "
 222                          "index: " SIZE_FORMAT " sz: " SIZE_FORMAT,
 223                          name, buf, index, sz);
 224 }
 225 #endif // PRODUCT
 226 
 227 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
 228 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 229 #endif // _MSC_VER
 230 
 231 SATBMarkQueueSet::SATBMarkQueueSet() :
 232   PtrQueueSet(),
 233   _shared_satb_queue(this, true /*perm*/) { }
 234 
 235 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
 236                                   int process_completed_threshold,
 237                                   Mutex* lock) {
 238   PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
 239   _shared_satb_queue.set_lock(lock);
 240 }
 241 
 242 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
 243   t->satb_mark_queue().handle_zero_index();
 244 }
 245 
 246 #ifdef ASSERT
 247 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
 248   gclog_or_tty->print_cr("Expected SATB active state: %s",
 249                          expected_active ? "ACTIVE" : "INACTIVE");
 250   gclog_or_tty->print_cr("Actual SATB active states:");
 251   gclog_or_tty->print_cr("  Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
 252   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 253     gclog_or_tty->print_cr("  Thread \"%s\" queue: %s", t->name(),
 254                            t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
 255   }
 256   gclog_or_tty->print_cr("  Shared queue: %s",
 257                          shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
 258 }
 259 
 260 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
 261   // Verify queue set state
 262   if (is_active() != expected_active) {
 263     dump_active_states(expected_active);
 264     guarantee(false, "SATB queue set has an unexpected active state");
 265   }
 266 
 267   // Verify thread queue states
 268   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 269     if (t->satb_mark_queue().is_active() != expected_active) {
 270       dump_active_states(expected_active);
 271       guarantee(false, "Thread SATB queue has an unexpected active state");
 272     }
 273   }
 274 
 275   // Verify shared queue state
 276   if (shared_satb_queue()->is_active() != expected_active) {
 277     dump_active_states(expected_active);
 278     guarantee(false, "Shared SATB queue has an unexpected active state");
 279   }
 280 }
 281 #endif // ASSERT
 282 
 283 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
 284   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 285 #ifdef ASSERT
 286   verify_active_states(expected_active);
 287 #endif // ASSERT
 288   _all_active = active;
 289   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 290     t->satb_mark_queue().set_active(active);
 291   }
 292   shared_satb_queue()->set_active(active);
 293 }
 294 
 295 void SATBMarkQueueSet::filter_thread_buffers() {
 296   for(JavaThread* t = Threads::first(); t; t = t->next()) {
 297     t->satb_mark_queue().filter();
 298   }
 299   shared_satb_queue()->filter();
 300 }
 301 
 302 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {
 303   BufferNode* nd = NULL;
 304   {
 305     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 306     if (_completed_buffers_head != NULL) {
 307       nd = _completed_buffers_head;
 308       _completed_buffers_head = nd->next();
 309       if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
 310       _n_completed_buffers--;
 311       if (_n_completed_buffers == 0) _process_completed = false;
 312     }
 313   }
 314   if (nd != NULL) {
 315     void **buf = BufferNode::make_buffer_from_node(nd);
 316     // Skip over NULL entries at beginning (e.g. push end) of buffer.
 317     // Filtering can result in non-full completed buffers; see
 318     // should_enqueue_buffer.
 319     assert(_sz % sizeof(void*) == 0, "invariant");
 320     size_t limit = ObjPtrQueue::byte_index_to_index((int)_sz);
 321     for (size_t i = 0; i < limit; ++i) {
 322       if (buf[i] != NULL) {
 323         // Found the end of the block of NULLs; process the remainder.
 324         cl->do_buffer(buf + i, limit - i);
 325         break;
 326       }
 327     }
 328     deallocate_buffer(buf);
 329     return true;
 330   } else {
 331     return false;
 332   }
 333 }
 334 
 335 #ifndef PRODUCT
 336 // Helpful for debugging
 337 
 338 #define SATB_PRINTER_BUFFER_SIZE 256
 339 
 340 void SATBMarkQueueSet::print_all(const char* msg) {
 341   char buffer[SATB_PRINTER_BUFFER_SIZE];
 342   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 343 
 344   gclog_or_tty->cr();
 345   gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
 346 
 347   BufferNode* nd = _completed_buffers_head;
 348   int i = 0;
 349   while (nd != NULL) {
 350     void** buf = BufferNode::make_buffer_from_node(nd);
 351     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
 352     ObjPtrQueue::print(buffer, buf, 0, _sz);
 353     nd = nd->next();
 354     i += 1;
 355   }
 356 
 357   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 358     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
 359     t->satb_mark_queue().print(buffer);
 360   }
 361 
 362   shared_satb_queue()->print("Shared");
 363 
 364   gclog_or_tty->cr();
 365 }
 366 #endif // PRODUCT
 367 
 368 void SATBMarkQueueSet::abandon_partial_marking() {
 369   BufferNode* buffers_to_delete = NULL;
 370   {
 371     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 372     while (_completed_buffers_head != NULL) {
 373       BufferNode* nd = _completed_buffers_head;
 374       _completed_buffers_head = nd->next();
 375       nd->set_next(buffers_to_delete);
 376       buffers_to_delete = nd;
 377     }
 378     _completed_buffers_tail = NULL;
 379     _n_completed_buffers = 0;
 380     DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
 381   }
 382   while (buffers_to_delete != NULL) {
 383     BufferNode* nd = buffers_to_delete;
 384     buffers_to_delete = nd->next();
 385     deallocate_buffer(BufferNode::make_buffer_from_node(nd));
 386   }
 387   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 388   // So we can safely manipulate these queues.
 389   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 390     t->satb_mark_queue().reset();
 391   }
 392  shared_satb_queue()->reset();
 393 }
--- EOF ---