1 /*
   2  * Copyright (c) 2001, 2011, 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 "runtime/mutexLocker.hpp"
  31 #include "runtime/thread.hpp"
  32 
  33 // This method removes entries from an SATB buffer that will not be
  34 // useful to the concurrent marking threads. An entry is removed if it
  35 // satisfies one of the following conditions:
  36 //
  37 // * it points to an object outside the G1 heap (G1's concurrent
  38 //     marking only visits objects inside the G1 heap),
  39 // * it points to an object that has been allocated since marking
  40 //     started (according to SATB those objects do not need to be
  41 //     visited during marking), or
  42 // * it points to an object that has already been marked (no need to
  43 //     process it again).
  44 //
  45 // The rest of the entries will be retained and are compacted towards
  46 // the top of the buffer. If with this filtering we clear a large
  47 // enough chunk of the buffer we can re-use it (instead of enqueueing
  48 // it) and we can just allow the mutator to carry on executing.
  49 
  50 bool ObjPtrQueue::should_enqueue_buffer() {
  51   assert(_lock == NULL || _lock->owned_by_self(),
  52          "we should have taken the lock before calling this");
  53 
  54   // A value of 0 means "don't filter SATB buffers".
  55   if (G1SATBBufferEnqueueingThresholdPercent == 0) {
  56     return true;
  57   }
  58 
  59   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  60 
  61   // This method should only be called if there is a non-NULL buffer
  62   // that is full.
  63   assert(_index == 0, "pre-condition");
  64   assert(_buf != NULL, "pre-condition");
  65 
  66   void** buf = _buf;
  67   size_t sz = _sz;
  68 
  69   // Used for sanity checking at the end of the loop.
  70   debug_only(size_t entries = 0; size_t retained = 0;)
  71 
  72   size_t i = sz;
  73   size_t new_index = sz;
  74 
  75   // Given that we are expecting _index == 0, we could have changed
  76   // the loop condition to (i > 0). But we are using _index for
  77   // generality.
  78   while (i > _index) {
  79     assert(i > 0, "we should have at least one more entry to process");
  80     i -= oopSize;
  81     debug_only(entries += 1;)
  82     oop* p = (oop*) &buf[byte_index_to_index((int) i)];
  83     oop obj = *p;
  84     // NULL the entry so that unused parts of the buffer contain NULLs
  85     // at the end. If we are going to retain it we will copy it to its
  86     // final place. If we have retained all entries we have visited so
  87     // far, we'll just end up copying it to the same place.
  88     *p = NULL;
  89 
  90     bool retain = g1h->is_obj_ill(obj);
  91     if (retain) {
  92       assert(new_index > 0, "we should not have already filled up the buffer");
  93       new_index -= oopSize;
  94       assert(new_index >= i,
  95              "new_index should never be below i, as we alwaysr compact 'up'");
  96       oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)];
  97       assert(new_p >= p, "the destination location should never be below "
  98              "the source as we always compact 'up'");
  99       assert(*new_p == NULL,
 100              "we should have already cleared the destination location");
 101       *new_p = obj;
 102       debug_only(retained += 1;)
 103     }
 104   }
 105   size_t entries_calc = (sz - _index) / oopSize;
 106   assert(entries == entries_calc, "the number of entries we counted "
 107          "should match the number of entries we calculated");
 108   size_t retained_calc = (sz - new_index) / oopSize;
 109   assert(retained == retained_calc, "the number of retained entries we counted "
 110          "should match the number of retained entries we calculated");
 111   size_t perc = retained_calc * 100 / entries_calc;
 112   bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
 113   _index = new_index;
 114 
 115   return should_enqueue;
 116 }
 117 
 118 void ObjPtrQueue::apply_closure(ObjectClosure* cl) {
 119   if (_buf != NULL) {
 120     apply_closure_to_buffer(cl, _buf, _index, _sz);
 121     _index = _sz;
 122   }
 123 }
 124 
 125 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,
 126                                           void** buf, size_t index, size_t sz) {
 127   if (cl == NULL) return;
 128   for (size_t i = index; i < sz; i += oopSize) {
 129     oop obj = (oop)buf[byte_index_to_index((int)i)];
 130     // There can be NULL entries because of destructors.
 131     if (obj != NULL) {
 132       cl->do_object(obj);
 133     }
 134   }
 135 }
 136 
 137 #ifdef ASSERT
 138 void ObjPtrQueue::verify_oops_in_buffer() {
 139   if (_buf == NULL) return;
 140   for (size_t i = _index; i < _sz; i += oopSize) {
 141     oop obj = (oop)_buf[byte_index_to_index((int)i)];
 142     assert(obj != NULL && obj->is_oop(true /* ignore mark word */),
 143            "Not an oop");
 144   }
 145 }
 146 #endif
 147 
 148 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
 149 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 150 #endif // _MSC_VER
 151 
 152 
 153 SATBMarkQueueSet::SATBMarkQueueSet() :
 154   PtrQueueSet(),
 155   _closure(NULL), _par_closures(NULL),
 156   _shared_satb_queue(this, true /*perm*/)
 157 {}
 158 
 159 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
 160                                   int process_completed_threshold,
 161                                   Mutex* lock) {
 162   PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
 163   _shared_satb_queue.set_lock(lock);
 164   if (ParallelGCThreads > 0) {
 165     _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads);
 166   }
 167 }
 168 
 169 
 170 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
 171   DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)
 172   t->satb_mark_queue().handle_zero_index();
 173 }
 174 
 175 #ifdef ASSERT
 176 void SATBMarkQueueSet::dump_active_values(JavaThread* first,
 177                                           bool expected_active) {
 178   gclog_or_tty->print_cr("SATB queue active values for Java Threads");
 179   gclog_or_tty->print_cr(" SATB queue set: active is %s",
 180                          (is_active()) ? "TRUE" : "FALSE");
 181   gclog_or_tty->print_cr(" expected_active is %s",
 182                          (expected_active) ? "TRUE" : "FALSE");
 183   for (JavaThread* t = first; t; t = t->next()) {
 184     bool active = t->satb_mark_queue().is_active();
 185     gclog_or_tty->print_cr("  thread %s, active is %s",
 186                            t->name(), (active) ? "TRUE" : "FALSE");
 187   }
 188 }
 189 #endif // ASSERT
 190 
 191 void SATBMarkQueueSet::set_active_all_threads(bool b,
 192                                               bool expected_active) {
 193   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 194   JavaThread* first = Threads::first();
 195 
 196 #ifdef ASSERT
 197   if (_all_active != expected_active) {
 198     dump_active_values(first, expected_active);
 199 
 200     // I leave this here as a guarantee, instead of an assert, so
 201     // that it will still be compiled in if we choose to uncomment
 202     // the #ifdef ASSERT in a product build. The whole block is
 203     // within an #ifdef ASSERT so the guarantee will not be compiled
 204     // in a product build anyway.
 205     guarantee(false,
 206               "SATB queue set has an unexpected active value");
 207   }
 208 #endif // ASSERT
 209   _all_active = b;
 210 
 211   for (JavaThread* t = first; t; t = t->next()) {
 212 #ifdef ASSERT
 213     bool active = t->satb_mark_queue().is_active();
 214     if (active != expected_active) {
 215       dump_active_values(first, expected_active);
 216 
 217       // I leave this here as a guarantee, instead of an assert, so
 218       // that it will still be compiled in if we choose to uncomment
 219       // the #ifdef ASSERT in a product build. The whole block is
 220       // within an #ifdef ASSERT so the guarantee will not be compiled
 221       // in a product build anyway.
 222       guarantee(false,
 223                 "thread has an unexpected active value in its SATB queue");
 224     }
 225 #endif // ASSERT
 226     t->satb_mark_queue().set_active(b);
 227   }
 228 }
 229 
 230 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) {
 231   _closure = closure;
 232 }
 233 
 234 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) {
 235   assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition");
 236   _par_closures[i] = par_closure;
 237 }
 238 
 239 void SATBMarkQueueSet::iterate_closure_all_threads() {
 240   for(JavaThread* t = Threads::first(); t; t = t->next()) {
 241     t->satb_mark_queue().apply_closure(_closure);
 242   }
 243   shared_satb_queue()->apply_closure(_closure);
 244 }
 245 
 246 void SATBMarkQueueSet::par_iterate_closure_all_threads(int worker) {
 247   SharedHeap* sh = SharedHeap::heap();
 248   int parity = sh->strong_roots_parity();
 249 
 250   for(JavaThread* t = Threads::first(); t; t = t->next()) {
 251     if (t->claim_oops_do(true, parity)) {
 252       t->satb_mark_queue().apply_closure(_par_closures[worker]);
 253     }
 254   }
 255   // We'll have worker 0 do this one.
 256   if (worker == 0) {
 257     shared_satb_queue()->apply_closure(_par_closures[0]);
 258   }
 259 }
 260 
 261 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par,
 262                                                               int worker) {
 263   BufferNode* nd = NULL;
 264   {
 265     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 266     if (_completed_buffers_head != NULL) {
 267       nd = _completed_buffers_head;
 268       _completed_buffers_head = nd->next();
 269       if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
 270       _n_completed_buffers--;
 271       if (_n_completed_buffers == 0) _process_completed = false;
 272     }
 273   }
 274   ObjectClosure* cl = (par ? _par_closures[worker] : _closure);
 275   if (nd != NULL) {
 276     void **buf = BufferNode::make_buffer_from_node(nd);
 277     ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
 278     deallocate_buffer(buf);
 279     return true;
 280   } else {
 281     return false;
 282   }
 283 }
 284 
 285 void SATBMarkQueueSet::abandon_partial_marking() {
 286   BufferNode* buffers_to_delete = NULL;
 287   {
 288     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
 289     while (_completed_buffers_head != NULL) {
 290       BufferNode* nd = _completed_buffers_head;
 291       _completed_buffers_head = nd->next();
 292       nd->set_next(buffers_to_delete);
 293       buffers_to_delete = nd;
 294     }
 295     _completed_buffers_tail = NULL;
 296     _n_completed_buffers = 0;
 297     DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
 298   }
 299   while (buffers_to_delete != NULL) {
 300     BufferNode* nd = buffers_to_delete;
 301     buffers_to_delete = nd->next();
 302     deallocate_buffer(BufferNode::make_buffer_from_node(nd));
 303   }
 304   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
 305   // So we can safely manipulate these queues.
 306   for (JavaThread* t = Threads::first(); t; t = t->next()) {
 307     t->satb_mark_queue().reset();
 308   }
 309   shared_satb_queue()->reset();
 310 }