1 /*
   2  * Copyright (c) 2001, 2014, 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 "memory/allocation.inline.hpp"
  29 #include "memory/sharedHeap.hpp"
  30 #include "oops/oop.inline.hpp"
  31 #include "runtime/mutexLocker.hpp"
  32 #include "runtime/thread.hpp"
  33 #include "runtime/vmThread.hpp"
  34 
  35 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  36 
  37 void ObjPtrQueue::flush() {
  38   // The buffer might contain refs into the CSet. We have to filter it
  39   // first before we flush it, otherwise we might end up with an
  40   // enqueued buffer with refs into the CSet which breaks our invariants.
  41   filter();
  42   PtrQueue::flush();
  43 }
  44 
  45 // This method removes entries from an SATB buffer that will not be
  46 // useful to the concurrent marking threads. An entry is removed if it
  47 // satisfies one of the following conditions:
  48 //
  49 // * it points to an object outside the G1 heap (G1's concurrent
  50 //     marking only visits objects inside the G1 heap),
  51 // * it points to an object that has been allocated since marking
  52 //     started (according to SATB those objects do not need to be
  53 //     visited during marking), or
  54 // * it points to an object that has already been marked (no need to
  55 //     process it again).
  56 //
  57 // The rest of the entries will be retained and are compacted towards
  58 // the top of the buffer. Note that, because we do not allow old
  59 // regions in the CSet during marking, all objects on the CSet regions
  60 // are young (eden or survivors) and therefore implicitly live. So any
  61 // references into the CSet will be removed during filtering.
  62 
  63 void ObjPtrQueue::filter() {
  64   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  65   void** buf = _buf;
  66   size_t sz = _sz;
  67 
  68   if (buf == NULL) {
  69     // nothing to do
  70     return;
  71   }
  72 
  73   // Used for sanity checking at the end of the loop.
  74   debug_only(size_t entries = 0; size_t retained = 0;)
  75 
  76   size_t i = sz;
  77   size_t new_index = sz;
  78 
  79   while (i > _index) {
  80     assert(i > 0, "we should have at least one more entry to process");
  81     i -= oopSize;
  82     debug_only(entries += 1;)
  83     oop* p = (oop*) &buf[byte_index_to_index((int) i)];
  84     oop obj = *p;
  85     // NULL the entry so that unused parts of the buffer contain NULLs
  86     // at the end. If we are going to retain it we will copy it to its
  87     // final place. If we have retained all entries we have visited so
  88     // far, we'll just end up copying it to the same place.
  89     *p = NULL;
  90 
  91     bool retain = g1h->is_obj_ill(obj);
  92     if (retain) {
  93       assert(new_index > 0, "we should not have already filled up the buffer");
  94       new_index -= oopSize;
  95       assert(new_index >= i,
  96              "new_index should never be below i, as we always compact 'up'");
  97       oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)];
  98       assert(new_p >= p, "the destination location should never be below "
  99              "the source as we always compact 'up'");
 100       assert(*new_p == NULL,
 101              "we should have already cleared the destination location");
 102       *new_p = obj;
 103       debug_only(retained += 1;)
 104     }
 105   }
 106 
 107 #ifdef ASSERT
 108   size_t entries_calc = (sz - _index) / oopSize;
 109   assert(entries == entries_calc, "the number of entries we counted "
 110          "should match the number of entries we calculated");
 111   size_t retained_calc = (sz - new_index) / oopSize;
 112   assert(retained == retained_calc, "the number of retained entries we counted "
 113          "should match the number of retained entries we calculated");
 114 #endif // ASSERT
 115 
 116   _index = new_index;
 117 }
 118 
 119 // This method will first apply the above filtering to the buffer. If
 120 // post-filtering a large enough chunk of the buffer has been cleared
 121 // we can re-use the buffer (instead of enqueueing it) and we can just
 122 // allow the mutator to carry on executing using the same buffer
 123 // instead of replacing it.
 124 
 125 bool ObjPtrQueue::should_enqueue_buffer() {
 126   assert(_lock == NULL || _lock->owned_by_self(),
 127          "we should have taken the lock before calling this");
 128 
 129   // Even if G1SATBBufferEnqueueingThresholdPercent == 0 we have to
 130   // filter the buffer given that this will remove any references into
 131   // the CSet as we currently assume that no such refs will appear in
 132   // enqueued buffers.
 133 
 134   // This method should only be called if there is a non-NULL buffer
 135   // that is full.
 136   assert(_index == 0, "pre-condition");
 137   assert(_buf != NULL, "pre-condition");
 138 
 139   filter();
 140 
 141   size_t sz = _sz;
 142   size_t all_entries = sz / oopSize;
 143   size_t retained_entries = (sz - _index) / oopSize;
 144   size_t perc = retained_entries * 100 / all_entries;
 145   bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
 146   return should_enqueue;
 147 }
 148 
 149 void ObjPtrQueue::apply_closure(ObjectClosure* cl) {
 150   if (_buf != NULL) {
 151     apply_closure_to_buffer(cl, _buf, _index, _sz);
 152   }
 153 }
 154 
 155 void ObjPtrQueue::apply_closure_and_empty(ObjectClosure* cl) {
 156   if (_buf != NULL) {
 157     apply_closure_to_buffer(cl, _buf, _index, _sz);
 158     _index = _sz;
 159   }
 160 }
 161 
 162 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,
 163                                           void** buf, size_t index, size_t sz) {
 164   if (cl == NULL) return;
 165   for (size_t i = index; i < sz; i += oopSize) {
 166     oop obj = (oop)buf[byte_index_to_index((int)i)];
 167     // There can be NULL entries because of destructors.
 168     if (obj != NULL) {
 169       cl->do_object(obj);
 170     }
 171   }
 172 }
 173 
 174 #ifndef PRODUCT
 175 // Helpful for debugging
 176 
 177 void ObjPtrQueue::print(const char* name) {
 178   print(name, _buf, _index, _sz);
 179 }
 180 
 181 void ObjPtrQueue::print(const char* name,
 182                         void** buf, size_t index, size_t sz) {
 183   gclog_or_tty->print_cr("  SATB BUFFER [%s] buf: "PTR_FORMAT" "
 184                          "index: "SIZE_FORMAT" sz: "SIZE_FORMAT,
 185                          name, buf, index, sz);
 186 }
 187 #endif // PRODUCT
 188 
 189 #ifdef ASSERT
 190 void ObjPtrQueue::verify_oops_in_buffer() {
 191   if (_buf == NULL) return;
 192   for (size_t i = _index; i < _sz; i += oopSize) {
 193     oop obj = (oop)_buf[byte_index_to_index((int)i)];
 194     assert(obj != NULL && obj->is_oop(true /* ignore mark word */),
 195            "Not an oop");
 196   }
 197 }
 198 #endif
 199 
 200 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
 201 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 202 #endif // _MSC_VER
 203 
 204 SATBMarkQueueSet::SATBMarkQueueSet() :
 205   PtrQueueSet(), _closures(NULL),
 206   _shared_satb_queue(this, true /*perm*/) { }
 207 
 208 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
 209                                   int process_completed_threshold,
 210                                   Mutex* lock) {
 211   PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
 212   _shared_satb_queue.set_lock(lock);
 213   _closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads, mtGC);
 214 }
 215 
 216 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
 217   DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)
 218   t->satb_mark_queue().handle_zero_index();
 219 }
 220 
 221 #ifdef ASSERT
 222 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
 223   gclog_or_tty->print_cr("Expected SATB active state: %s",
 224                          expected_active ? "ACTIVE" : "INACTIVE");
 225   gclog_or_tty->print_cr("Actual SATB active states:");
 226   gclog_or_tty->print_cr("  Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
 227   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 228     gclog_or_tty->print_cr("  Thread \"%s\" queue: %s", t->name(),
 229                            t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
 230   }
 231   gclog_or_tty->print_cr("  Shared queue: %s",
 232                          shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
 233 }
 234 
 235 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
 236   // Verify queue set state
 237   if (is_active() != expected_active) {
 238     dump_active_states(expected_active);
 239     guarantee(false, "SATB queue set has an unexpected active state");
 240   }
 241 
 242   // Verify thread queue states
 243   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 244     if (t->satb_mark_queue().is_active() != expected_active) {
 245       dump_active_states(expected_active);
 246       guarantee(false, "Thread SATB queue has an unexpected active state");
 247     }
 248   }
 249 
 250   // Verify shared queue state
 251   if (shared_satb_queue()->is_active() != expected_active) {
 252     dump_active_states(expected_active);
 253     guarantee(false, "Shared SATB queue has an unexpected active state");
 254   }
 255 }
 256 #endif // ASSERT
 257 
 258 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
 259   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 260 #ifdef ASSERT
 261   verify_active_states(expected_active);
 262 #endif // ASSERT
 263   _all_active = active;
 264   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 265     t->satb_mark_queue().set_active(active);
 266   }
 267   shared_satb_queue()->set_active(active);
 268 }
 269 
 270 void SATBMarkQueueSet::filter_thread_buffers() {
 271   for(JavaThread* t = Threads::first(); t; t = t->next()) {
 272     t->satb_mark_queue().filter();
 273   }
 274   shared_satb_queue()->filter();
 275 }
 276 
 277 void SATBMarkQueueSet::set_closure(uint worker, ObjectClosure* closure) {
 278   assert(_closures != NULL, "Precondition");
 279   assert(worker < ParallelGCThreads, "Worker index must be in range [0...ParallelGCThreads)");
 280   _closures[worker] = closure;
 281 }
 282 
 283 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(uint worker) {
 284   BufferNode* nd = NULL;
 285   {
 286     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 287     if (_completed_buffers_head != NULL) {
 288       nd = _completed_buffers_head;
 289       _completed_buffers_head = nd->next();
 290       if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
 291       _n_completed_buffers--;
 292       if (_n_completed_buffers == 0) _process_completed = false;
 293     }
 294   }
 295   ObjectClosure* cl = _closures[worker];
 296   if (nd != NULL) {
 297     void **buf = BufferNode::make_buffer_from_node(nd);
 298     ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
 299     deallocate_buffer(buf);
 300     return true;
 301   } else {
 302     return false;
 303   }
 304 }
 305 
 306 void SATBMarkQueueSet::iterate_completed_buffers_read_only(ObjectClosure* cl) {
 307   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 308   assert(cl != NULL, "pre-condition");
 309 
 310   BufferNode* nd = _completed_buffers_head;
 311   while (nd != NULL) {
 312     void** buf = BufferNode::make_buffer_from_node(nd);
 313     ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
 314     nd = nd->next();
 315   }
 316 }
 317 
 318 void SATBMarkQueueSet::iterate_thread_buffers_read_only(ObjectClosure* cl) {
 319   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 320   assert(cl != NULL, "pre-condition");
 321 
 322   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 323     t->satb_mark_queue().apply_closure(cl);
 324   }
 325   shared_satb_queue()->apply_closure(cl);
 326 }
 327 
 328 #ifndef PRODUCT
 329 // Helpful for debugging
 330 
 331 #define SATB_PRINTER_BUFFER_SIZE 256
 332 
 333 void SATBMarkQueueSet::print_all(const char* msg) {
 334   char buffer[SATB_PRINTER_BUFFER_SIZE];
 335   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 336 
 337   gclog_or_tty->cr();
 338   gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
 339 
 340   BufferNode* nd = _completed_buffers_head;
 341   int i = 0;
 342   while (nd != NULL) {
 343     void** buf = BufferNode::make_buffer_from_node(nd);
 344     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
 345     ObjPtrQueue::print(buffer, buf, 0, _sz);
 346     nd = nd->next();
 347     i += 1;
 348   }
 349 
 350   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 351     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
 352     t->satb_mark_queue().print(buffer);
 353   }
 354 
 355   shared_satb_queue()->print("Shared");
 356 
 357   gclog_or_tty->cr();
 358 }
 359 #endif // PRODUCT
 360 
 361 void SATBMarkQueueSet::abandon_partial_marking() {
 362   BufferNode* buffers_to_delete = NULL;
 363   {
 364     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 365     while (_completed_buffers_head != NULL) {
 366       BufferNode* nd = _completed_buffers_head;
 367       _completed_buffers_head = nd->next();
 368       nd->set_next(buffers_to_delete);
 369       buffers_to_delete = nd;
 370     }
 371     _completed_buffers_tail = NULL;
 372     _n_completed_buffers = 0;
 373     DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
 374   }
 375   while (buffers_to_delete != NULL) {
 376     BufferNode* nd = buffers_to_delete;
 377     buffers_to_delete = nd->next();
 378     deallocate_buffer(BufferNode::make_buffer_from_node(nd));
 379   }
 380   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 381   // So we can safely manipulate these queues.
 382   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 383     t->satb_mark_queue().reset();
 384   }
 385  shared_satb_queue()->reset();
 386 }