1 /*
   2  * Copyright (c) 2001, 2018, 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 "jvm.h"
  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/g1/g1ThreadLocalData.hpp"
  29 #include "gc/g1/satbMarkQueue.hpp"
  30 #include "gc/shared/collectedHeap.hpp"
  31 #include "memory/allocation.inline.hpp"
  32 #include "oops/oop.inline.hpp"
  33 #include "runtime/mutexLocker.hpp"
  34 #include "runtime/safepoint.hpp"
  35 #include "runtime/thread.hpp"
  36 #include "runtime/threadSMR.hpp"
  37 #include "runtime/vmThread.hpp"
  38 #include "utilities/macros.hpp"
  39 #if INCLUDE_SHENANDOAHGC
  40 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
  41 #endif
  42 
  43 SATBMarkQueue::SATBMarkQueue(SATBMarkQueueSet* qset, bool permanent) :
  44   // SATB queues are only active during marking cycles. We create
  45   // them with their active field set to false. If a thread is
  46   // created during a cycle and its SATB queue needs to be activated
  47   // before the thread starts running, we'll need to set its active
  48   // field to true. This is done in G1SBarrierSet::on_thread_attach().
  49   PtrQueue(qset, permanent, false /* active */)
  50 { }
  51 
  52 void SATBMarkQueue::flush() {
  53   // Filter now to possibly save work later.  If filtering empties the
  54   // buffer then flush_impl can deallocate the buffer.
  55   filter();
  56   flush_impl();
  57 }
  58 
  59 // Return true if a SATB buffer entry refers to an object that
  60 // requires marking.
  61 //
  62 // The entry must point into the G1 heap.  In particular, it must not
  63 // be a NULL pointer.  NULL pointers are pre-filtered and never
  64 // inserted into a SATB buffer.
  65 //
  66 // An entry that is below the NTAMS pointer for the containing heap
  67 // region requires marking. Such an entry must point to a valid object.
  68 //
  69 // An entry that is at least the NTAMS pointer for the containing heap
  70 // region might be any of the following, none of which should be marked.
  71 //
  72 // * A reference to an object allocated since marking started.
  73 //   According to SATB, such objects are implicitly kept live and do
  74 //   not need to be dealt with via SATB buffer processing.
  75 //
  76 // * A reference to a young generation object. Young objects are
  77 //   handled separately and are not marked by concurrent marking.
  78 //
  79 // * A stale reference to a young generation object. If a young
  80 //   generation object reference is recorded and not filtered out
  81 //   before being moved by a young collection, the reference becomes
  82 //   stale.
  83 //
  84 // * A stale reference to an eagerly reclaimed humongous object.  If a
  85 //   humongous object is recorded and then reclaimed, the reference
  86 //   becomes stale.
  87 //
  88 // The stale reference cases are implicitly handled by the NTAMS
  89 // comparison. Because of the possibility of stale references, buffer
  90 // processing must be somewhat circumspect and not assume entries
  91 // in an unfiltered buffer refer to valid objects.
  92 
  93 template <class HeapType>
  94 inline bool retain_entry(const void* entry, HeapType* heap) {
  95   return heap->requires_marking(entry);












  96 }
  97 
  98 void SATBMarkQueue::filter() {
  99   if (UseG1GC) {
 100     filter_impl<G1CollectedHeap>();
 101 #if INCLUDE_SHENANDOAHGC
 102   } else if (UseShenandoahGC) {
 103     filter_impl<ShenandoahHeap>();
 104 #endif
 105   } else {
 106     ShouldNotReachHere();
 107   }
 108 }
 109 
 110 // This method removes entries from a SATB buffer that will not be
 111 // useful to the concurrent marking threads.  Entries are retained if
 112 // they require marking and are not already marked. Retained entries
 113 // are compacted toward the top of the buffer.
 114 
 115 template <class HeapType>
 116 void SATBMarkQueue::filter_impl() {
 117   HeapType* heap = (HeapType*) Universe::heap();
 118   void** buf = _buf;
 119 
 120   if (buf == NULL) {
 121     // nothing to do
 122     return;
 123   }
 124 
 125   // Two-fingered compaction toward the end.
 126   void** src = &buf[index()];
 127   void** dst = &buf[capacity()];
 128   assert(src <= dst, "invariant");
 129   for ( ; src < dst; ++src) {
 130     // Search low to high for an entry to keep.
 131     void* entry = *src;
 132     if (retain_entry(entry, heap)) {
 133       // Found keeper.  Search high to low for an entry to discard.
 134       while (src < --dst) {
 135         if (!retain_entry(*dst, heap)) {
 136           *dst = entry;         // Replace discard with keeper.
 137           break;
 138         }
 139       }
 140       // If discard search failed (src == dst), the outer loop will also end.
 141     }
 142   }
 143   // dst points to the lowest retained entry, or the end of the buffer
 144   // if all the entries were filtered out.
 145   set_index(dst - buf);
 146 }
 147 
 148 // This method will first apply the above filtering to the buffer. If
 149 // post-filtering a large enough chunk of the buffer has been cleared
 150 // we can re-use the buffer (instead of enqueueing it) and we can just
 151 // allow the mutator to carry on executing using the same buffer
 152 // instead of replacing it.
 153 
 154 bool SATBMarkQueue::should_enqueue_buffer() {
 155   assert(_lock == NULL || _lock->owned_by_self(),
 156          "we should have taken the lock before calling this");
 157 
 158   // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering.
 159 
 160   // This method should only be called if there is a non-NULL buffer
 161   // that is full.
 162   assert(index() == 0, "pre-condition");
 163   assert(_buf != NULL, "pre-condition");
 164 
 165   filter();
 166 
 167   size_t cap = capacity();
 168   size_t percent_used = ((cap - index()) * 100) / cap;
 169   return percent_used > G1SATBBufferEnqueueingThresholdPercent;

 170 }
 171 
 172 void SATBMarkQueue::apply_closure_and_empty(SATBBufferClosure* cl) {
 173   assert(SafepointSynchronize::is_at_safepoint(),
 174          "SATB queues must only be processed at safepoints");
 175   if (_buf != NULL) {
 176     cl->do_buffer(&_buf[index()], size());
 177     reset();
 178   }
 179 }
 180 
 181 #ifndef PRODUCT
 182 // Helpful for debugging
 183 
 184 static void print_satb_buffer(const char* name,
 185                               void** buf,
 186                               size_t index,
 187                               size_t capacity) {
 188   tty->print_cr("  SATB BUFFER [%s] buf: " PTR_FORMAT " index: " SIZE_FORMAT
 189                 " capacity: " SIZE_FORMAT,
 190                 name, p2i(buf), index, capacity);
 191 }
 192 
 193 void SATBMarkQueue::print(const char* name) {
 194   print_satb_buffer(name, _buf, index(), capacity());
 195 }
 196 
 197 #endif // PRODUCT
 198 
 199 SATBMarkQueueSet::SATBMarkQueueSet() :
 200   PtrQueueSet(),
 201   _shared_satb_queue(this, true /* permanent */) { }
 202 
 203 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
 204                                   int process_completed_threshold,
 205                                   Mutex* lock) {
 206   PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
 207   _shared_satb_queue.set_lock(lock);
 208 }
 209 




 210 #ifdef ASSERT
 211 void SATBMarkQueueSet::dump_active_states(bool expected_active) {
 212   log_error(gc, verify)("Expected SATB active state: %s", expected_active ? "ACTIVE" : "INACTIVE");
 213   log_error(gc, verify)("Actual SATB active states:");
 214   log_error(gc, verify)("  Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE");
 215   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
 216     log_error(gc, verify)("  Thread \"%s\" queue: %s", t->name(), satb_queue_for_thread(t).is_active() ? "ACTIVE" : "INACTIVE");
 217   }
 218   log_error(gc, verify)("  Shared queue: %s", shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE");
 219 }
 220 
 221 void SATBMarkQueueSet::verify_active_states(bool expected_active) {
 222   // Verify queue set state
 223   if (is_active() != expected_active) {
 224     dump_active_states(expected_active);
 225     guarantee(false, "SATB queue set has an unexpected active state");
 226   }
 227 
 228   // Verify thread queue states
 229   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
 230     if (satb_queue_for_thread(t).is_active() != expected_active) {
 231       dump_active_states(expected_active);
 232       guarantee(false, "Thread SATB queue has an unexpected active state");
 233     }
 234   }
 235 
 236   // Verify shared queue state
 237   if (shared_satb_queue()->is_active() != expected_active) {
 238     dump_active_states(expected_active);
 239     guarantee(false, "Shared SATB queue has an unexpected active state");
 240   }
 241 }
 242 #endif // ASSERT
 243 
 244 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) {
 245   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 246 #ifdef ASSERT
 247   verify_active_states(expected_active);
 248 #endif // ASSERT
 249   _all_active = active;
 250   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
 251     satb_queue_for_thread(t).set_active(active);
 252   }
 253   shared_satb_queue()->set_active(active);
 254 }
 255 
 256 void SATBMarkQueueSet::filter_thread_buffers() {
 257   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
 258     satb_queue_for_thread(t).filter();
 259   }
 260   shared_satb_queue()->filter();
 261 }
 262 
 263 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) {
 264   BufferNode* nd = NULL;
 265   {
 266     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 267     if (_completed_buffers_head != NULL) {
 268       nd = _completed_buffers_head;
 269       _completed_buffers_head = nd->next();
 270       if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
 271       _n_completed_buffers--;
 272       if (_n_completed_buffers == 0) _process_completed = false;
 273     }
 274   }
 275   if (nd != NULL) {
 276     void **buf = BufferNode::make_buffer_from_node(nd);
 277     size_t index = nd->index();
 278     size_t size = buffer_size();
 279     assert(index <= size, "invariant");
 280     cl->do_buffer(buf + index, size - index);
 281     deallocate_buffer(nd);
 282     return true;
 283   } else {
 284     return false;
 285   }
 286 }
 287 
 288 #ifndef PRODUCT
 289 // Helpful for debugging
 290 
 291 #define SATB_PRINTER_BUFFER_SIZE 256
 292 
 293 void SATBMarkQueueSet::print_all(const char* msg) {
 294   char buffer[SATB_PRINTER_BUFFER_SIZE];
 295   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 296 
 297   tty->cr();
 298   tty->print_cr("SATB BUFFERS [%s]", msg);
 299 
 300   BufferNode* nd = _completed_buffers_head;
 301   int i = 0;
 302   while (nd != NULL) {
 303     void** buf = BufferNode::make_buffer_from_node(nd);
 304     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i);
 305     print_satb_buffer(buffer, buf, nd->index(), buffer_size());
 306     nd = nd->next();
 307     i += 1;
 308   }
 309 
 310   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
 311     jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name());
 312     satb_queue_for_thread(t).print(buffer);
 313   }
 314 
 315   shared_satb_queue()->print("Shared");
 316 
 317   tty->cr();
 318 }
 319 #endif // PRODUCT
 320 
 321 void SATBMarkQueueSet::abandon_partial_marking() {
 322   BufferNode* buffers_to_delete = NULL;
 323   {
 324     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 325     while (_completed_buffers_head != NULL) {
 326       BufferNode* nd = _completed_buffers_head;
 327       _completed_buffers_head = nd->next();
 328       nd->set_next(buffers_to_delete);
 329       buffers_to_delete = nd;
 330     }
 331     _completed_buffers_tail = NULL;
 332     _n_completed_buffers = 0;
 333     DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
 334   }
 335   while (buffers_to_delete != NULL) {
 336     BufferNode* nd = buffers_to_delete;
 337     buffers_to_delete = nd->next();
 338     deallocate_buffer(nd);
 339   }
 340   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 341   // So we can safely manipulate these queues.
 342   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) {
 343     satb_queue_for_thread(t).reset();
 344   }
 345   shared_satb_queue()->reset();
 346 }
 347 
 348 void G1SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
 349   G1ThreadLocalData::satb_mark_queue(t).handle_zero_index();
 350 }
 351 
 352 SATBMarkQueue& G1SATBMarkQueueSet::satb_queue_for_thread(Thread* t) {
 353   return G1ThreadLocalData::satb_mark_queue(t);
 354 }
 355 
--- EOF ---