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 "memory/allocation.inline.hpp"
  29 #include "memory/sharedHeap.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 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  37 
  38 void ObjPtrQueue::flush() {
  39   // Filter now to possibly save work later.  If filtering empties the
  40   // buffer then flush_impl can deallocate the buffer.
  41   filter();
  42   flush_impl();
  43 }
  44 
  45 // Return true if a SATB buffer entry refers to an object that
  46 // requires marking.
  47 //
  48 // The entry must point into the G1 heap.  In particular, it must not
  49 // be a NULL pointer.  NULL pointers are pre-filtered and never
  50 // inserted into a SATB buffer.
  51 //
  52 // An entry that is below the NTAMS pointer for the containing heap
  53 // region requires marking. Such an entry must point to a valid object.
  54 //
  55 // An entry that is at least the NTAMS pointer for the containing heap
  56 // region might be any of the following, none of which should be marked.
  57 //
  58 // * A reference to an object allocated since marking started.
  59 //   According to SATB, such objects are implicitly kept live and do
  60 //   not need to be dealt with via SATB buffer processing.
  61 //
  62 // * A reference to a young generation object. Young objects are
  63 //   handled separately and are not marked by concurrent marking.
  64 //
  65 // * A stale reference to a young generation object. If a young
  66 //   generation object reference is recorded and not filtered out
  67 //   before being moved by a young collection, the reference becomes
  68 //   stale.
  69 //
  70 // * A stale reference to an eagerly reclaimed humongous object.  If a
  71 //   humongous object is recorded and then reclaimed, the reference
  72 //   becomes stale.
  73 //
  74 // The stale reference cases are implicitly handled by the NTAMS
  75 // comparison. Because of the possibility of stale references, buffer
  76 // processing must be somewhat circumspect and not assume entries
  77 // in an unfiltered buffer refer to valid objects.
  78 
  79 inline bool requires_marking(const void* entry, G1CollectedHeap* heap) {
  80   // Includes rejection of NULL pointers.
  81   assert(heap->is_in_reserved(entry),
  82          err_msg("Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry)));
  83 
  84   HeapRegion* region = heap->heap_region_containing_raw(entry);
  85   assert(region != NULL, err_msg("No region for " PTR_FORMAT, p2i(entry)));
  86   if (entry >= region->next_top_at_mark_start()) {
  87     return false;
  88   }
  89 
  90   assert(((oop)entry)->is_oop(true /* ignore mark word */),
  91          err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry)));
  92 
  93   return true;







  94 }
  95 
  96 // This method removes entries from a SATB buffer that will not be
  97 // useful to the concurrent marking threads.  Entries are retained if
  98 // they require marking and are not already marked. Retained entries
  99 // are compacted toward the top of the buffer.
 100 
 101 void ObjPtrQueue::filter() {
 102   G1CollectedHeap* g1h = G1CollectedHeap::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, g1h) && !g1h->isMarkedNext((oop)entry)) {
 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   return should_enqueue;
 181 }
 182 
 183 void ObjPtrQueue::apply_closure_and_empty(SATBBufferClosure* cl) {
 184   assert(SafepointSynchronize::is_at_safepoint(),
 185          "SATB queues must only be processed at safepoints");
 186   if (_buf != NULL) {
 187     assert(_index % sizeof(void*) == 0, "invariant");
 188     assert(_sz % sizeof(void*) == 0, "invariant");
 189     assert(_index <= _sz, "invariant");
 190     cl->do_buffer(_buf + byte_index_to_index((int)_index),
 191                   byte_index_to_index((int)(_sz - _index)));
 192     _index = _sz;
 193   }
 194 }
 195 
 196 #ifndef PRODUCT
 197 // Helpful for debugging
 198 
 199 void ObjPtrQueue::print(const char* name) {
 200   print(name, _buf, _index, _sz);
 201 }
 202 
 203 void ObjPtrQueue::print(const char* name,
 204                         void** buf, size_t index, size_t sz) {
 205   gclog_or_tty->print_cr("  SATB BUFFER [%s] buf: " PTR_FORMAT " "
 206                          "index: " SIZE_FORMAT " sz: " SIZE_FORMAT,
 207                          name, buf, index, sz);
 208 }
 209 #endif // PRODUCT
 210 
 211 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
 212 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 213 #endif // _MSC_VER
 214 
 215 SATBMarkQueueSet::SATBMarkQueueSet() :
 216   PtrQueueSet(),
 217   _shared_satb_queue(this, true /*perm*/) { }
 218 
 219 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
 220                                   int process_completed_threshold,
 221                                   Mutex* lock) {
 222   PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
 223   _shared_satb_queue.set_lock(lock);
 224 }
 225 
 226 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
 227   t->satb_mark_queue().handle_zero_index();
 228 }
 229 
 230 #ifdef ASSERT
 231 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
 232   gclog_or_tty->print_cr("Expected SATB active state: %s",
 233                          expected_active ? "ACTIVE" : "INACTIVE");
 234   gclog_or_tty->print_cr("Actual SATB active states:");
 235   gclog_or_tty->print_cr("  Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
 236   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 237     gclog_or_tty->print_cr("  Thread \"%s\" queue: %s", t->name(),
 238                            t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE");
 239   }
 240   gclog_or_tty->print_cr("  Shared queue: %s",
 241                          shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
 242 }
 243 
 244 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
 245   // Verify queue set state
 246   if (is_active() != expected_active) {
 247     dump_active_states(expected_active);
 248     guarantee(false, "SATB queue set has an unexpected active state");
 249   }
 250 
 251   // Verify thread queue states
 252   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 253     if (t->satb_mark_queue().is_active() != expected_active) {
 254       dump_active_states(expected_active);
 255       guarantee(false, "Thread SATB queue has an unexpected active state");
 256     }
 257   }
 258 
 259   // Verify shared queue state
 260   if (shared_satb_queue()->is_active() != expected_active) {
 261     dump_active_states(expected_active);
 262     guarantee(false, "Shared SATB queue has an unexpected active state");
 263   }
 264 }
 265 #endif // ASSERT
 266 
 267 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
 268   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 269 #ifdef ASSERT
 270   verify_active_states(expected_active);
 271 #endif // ASSERT
 272   _all_active = active;
 273   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 274     t->satb_mark_queue().set_active(active);
 275   }
 276   shared_satb_queue()->set_active(active);
 277 }
 278 
 279 void SATBMarkQueueSet::filter_thread_buffers() {
 280   for(JavaThread* t = Threads::first(); t; t = t->next()) {
 281     t->satb_mark_queue().filter();
 282   }
 283   shared_satb_queue()->filter();
 284 }
 285 
 286 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {
 287   BufferNode* nd = NULL;
 288   {
 289     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 290     if (_completed_buffers_head != NULL) {
 291       nd = _completed_buffers_head;
 292       _completed_buffers_head = nd->next();
 293       if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
 294       _n_completed_buffers--;
 295       if (_n_completed_buffers == 0) _process_completed = false;
 296     }
 297   }
 298   if (nd != NULL) {
 299     void **buf = BufferNode::make_buffer_from_node(nd);
 300     // Skip over NULL entries at beginning (e.g. push end) of buffer.
 301     // Filtering can result in non-full completed buffers; see
 302     // should_enqueue_buffer.
 303     assert(_sz % sizeof(void*) == 0, "invariant");
 304     size_t limit = ObjPtrQueue::byte_index_to_index((int)_sz);
 305     for (size_t i = 0; i < limit; ++i) {
 306       if (buf[i] != NULL) {
 307         // Found the end of the block of NULLs; process the remainder.
 308         cl->do_buffer(buf + i, limit - i);
 309         break;
 310       }
 311     }
 312     deallocate_buffer(buf);
 313     return true;
 314   } else {
 315     return false;
 316   }
 317 }
 318 
 319 #ifndef PRODUCT
 320 // Helpful for debugging
 321 
 322 #define SATB_PRINTER_BUFFER_SIZE 256
 323 
 324 void SATBMarkQueueSet::print_all(const char* msg) {
 325   char buffer[SATB_PRINTER_BUFFER_SIZE];
 326   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 327 
 328   gclog_or_tty->cr();
 329   gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg);
 330 
 331   BufferNode* nd = _completed_buffers_head;
 332   int i = 0;
 333   while (nd != NULL) {
 334     void** buf = BufferNode::make_buffer_from_node(nd);
 335     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
 336     ObjPtrQueue::print(buffer, buf, 0, _sz);
 337     nd = nd->next();
 338     i += 1;
 339   }
 340 
 341   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 342     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
 343     t->satb_mark_queue().print(buffer);
 344   }
 345 
 346   shared_satb_queue()->print("Shared");
 347 
 348   gclog_or_tty->cr();
 349 }
 350 #endif // PRODUCT
 351 
 352 void SATBMarkQueueSet::abandon_partial_marking() {
 353   BufferNode* buffers_to_delete = NULL;
 354   {
 355     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 356     while (_completed_buffers_head != NULL) {
 357       BufferNode* nd = _completed_buffers_head;
 358       _completed_buffers_head = nd->next();
 359       nd->set_next(buffers_to_delete);
 360       buffers_to_delete = nd;
 361     }
 362     _completed_buffers_tail = NULL;
 363     _n_completed_buffers = 0;
 364     DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
 365   }
 366   while (buffers_to_delete != NULL) {
 367     BufferNode* nd = buffers_to_delete;
 368     buffers_to_delete = nd->next();
 369     deallocate_buffer(BufferNode::make_buffer_from_node(nd));
 370   }
 371   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 372   // So we can safely manipulate these queues.
 373   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 374     t->satb_mark_queue().reset();
 375   }
 376  shared_satb_queue()->reset();
 377 }
--- EOF ---