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 /*

  * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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  */

 #include "precompiled.hpp"

 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"

 #include "gc_implementation/g1/satbQueue.hpp"

 #include "memory/allocation.inline.hpp"

 #include "memory/sharedHeap.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "runtime/thread.hpp"

 #include "runtime/vmThread.hpp"

 // This method removes entries from an SATB buffer that will not be

 // useful to the concurrent marking threads. An entry is removed if it

 // satisfies one of the following conditions:

 //

 // * it points to an object outside the G1 heap (G1's concurrent

 //     marking only visits objects inside the G1 heap),

 // * it points to an object that has been allocated since marking

 //     started (according to SATB those objects do not need to be

 //     visited during marking), or

 // * it points to an object that has already been marked (no need to

 //     process it again).

 //

 // The rest of the entries will be retained and are compacted towards

 // the top of the buffer. If with this filtering we clear a large

 // enough chunk of the buffer we can re-use it (instead of enqueueing

 // it) and we can just allow the mutator to carry on executing.

 bool ObjPtrQueue::should_enqueue_buffer() {

   assert(_lock == NULL || _lock->owned_by_self(),

          "we should have taken the lock before calling this");

   // A value of 0 means "don't filter SATB buffers".

   if (G1SATBBufferEnqueueingThresholdPercent == 0) {

     return true;

   }

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   // This method should only be called if there is a non-NULL buffer

   // that is full.

   assert(_index == 0, "pre-condition");

   assert(_buf != NULL, "pre-condition");

   void** buf = _buf;

   size_t sz = _sz;

   // Used for sanity checking at the end of the loop.

   debug_only(size_t entries = 0; size_t retained = 0;)

   size_t i = sz;

   size_t new_index = sz;

   // Given that we are expecting _index == 0, we could have changed

   // the loop condition to (i > 0). But we are using _index for

   // generality.

   while (i > _index) {

     assert(i > 0, "we should have at least one more entry to process");

     i -= oopSize;

     debug_only(entries += 1;)

     oop* p = (oop*) &buf[byte_index_to_index((int) i)];

     oop obj = *p;

     // NULL the entry so that unused parts of the buffer contain NULLs

     // at the end. If we are going to retain it we will copy it to its

     // final place. If we have retained all entries we have visited so

     // far, we'll just end up copying it to the same place.

     *p = NULL;

     bool retain = g1h->is_obj_ill(obj);

     if (retain) {

       assert(new_index > 0, "we should not have already filled up the buffer");

       new_index -= oopSize;

       assert(new_index >= i,

              "new_index should never be below i, as we alwaysr compact 'up'");

       oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)];

       assert(new_p >= p, "the destination location should never be below "

              "the source as we always compact 'up'");

       assert(*new_p == NULL,

              "we should have already cleared the destination location");

       *new_p = obj;

       debug_only(retained += 1;)

     }

   }

   size_t entries_calc = (sz - _index) / oopSize;

   assert(entries == entries_calc, "the number of entries we counted "

          "should match the number of entries we calculated");

   size_t retained_calc = (sz - new_index) / oopSize;

   assert(retained == retained_calc, "the number of retained entries we counted "

          "should match the number of retained entries we calculated");

   size_t perc = retained_calc * 100 / entries_calc;

   bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;

   _index = new_index;

   return should_enqueue;

 }

 void ObjPtrQueue::apply_closure(ObjectClosure* cl) {

   if (_buf != NULL) {

     apply_closure_to_buffer(cl, _buf, _index, _sz);

     _index = _sz;

   }

 }

 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,

                                           void** buf, size_t index, size_t sz) {

   if (cl == NULL) return;

   for (size_t i = index; i < sz; i += oopSize) {

     oop obj = (oop)buf[byte_index_to_index((int)i)];

     // There can be NULL entries because of destructors.

     if (obj != NULL) {

       cl->do_object(obj);

     }

   }

 }

 #ifdef ASSERT

 void ObjPtrQueue::verify_oops_in_buffer() {

   if (_buf == NULL) return;

   for (size_t i = _index; i < _sz; i += oopSize) {

     oop obj = (oop)_buf[byte_index_to_index((int)i)];

     assert(obj != NULL && obj->is_oop(true /* ignore mark word */),

            "Not an oop");

   }

 }

 #endif

 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away

 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list

 #endif // _MSC_VER

 SATBMarkQueueSet::SATBMarkQueueSet() :

   PtrQueueSet(),

   _closure(NULL), _par_closures(NULL),

   _shared_satb_queue(this, true /*perm*/)

 {}

 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,

                                   int process_completed_threshold,

                                   Mutex* lock) {

   PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);

   _shared_satb_queue.set_lock(lock);

   if (ParallelGCThreads > 0) {

     _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads);

   }

 }

 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {

   DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)

   t->satb_mark_queue().handle_zero_index();

 }

 #ifdef ASSERT

 void SATBMarkQueueSet::dump_active_values(JavaThread* first,

                                           bool expected_active) {

   gclog_or_tty->print_cr("SATB queue active values for Java Threads");

   gclog_or_tty->print_cr(" SATB queue set: active is %s",

                          (is_active()) ? "TRUE" : "FALSE");

   gclog_or_tty->print_cr(" expected_active is %s",

                          (expected_active) ? "TRUE" : "FALSE");

   for (JavaThread* t = first; t; t = t->next()) {

     bool active = t->satb_mark_queue().is_active();

     gclog_or_tty->print_cr("  thread %s, active is %s",

                            t->name(), (active) ? "TRUE" : "FALSE");

   }

 }

 #endif // ASSERT

 void SATBMarkQueueSet::set_active_all_threads(bool b,

                                               bool expected_active) {

   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

   JavaThread* first = Threads::first();

 #ifdef ASSERT

   if (_all_active != expected_active) {

     dump_active_values(first, expected_active);

     // I leave this here as a guarantee, instead of an assert, so

     // that it will still be compiled in if we choose to uncomment

     // the #ifdef ASSERT in a product build. The whole block is

     // within an #ifdef ASSERT so the guarantee will not be compiled

     // in a product build anyway.

     guarantee(false,

               "SATB queue set has an unexpected active value");

   }

 #endif // ASSERT

   _all_active = b;

   for (JavaThread* t = first; t; t = t->next()) {

 #ifdef ASSERT

     bool active = t->satb_mark_queue().is_active();

     if (active != expected_active) {

       dump_active_values(first, expected_active);

       // I leave this here as a guarantee, instead of an assert, so

       // that it will still be compiled in if we choose to uncomment

       // the #ifdef ASSERT in a product build. The whole block is

       // within an #ifdef ASSERT so the guarantee will not be compiled

       // in a product build anyway.

       guarantee(false,

                 "thread has an unexpected active value in its SATB queue");

     }

 #endif // ASSERT

     t->satb_mark_queue().set_active(b);

   }

 }

 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) {

   _closure = closure;

 }

 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) {

   assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition");

   _par_closures[i] = par_closure;

 }

 void SATBMarkQueueSet::iterate_closure_all_threads() {

   for(JavaThread* t = Threads::first(); t; t = t->next()) {

     t->satb_mark_queue().apply_closure(_closure);

   }

   shared_satb_queue()->apply_closure(_closure);

 }

 void SATBMarkQueueSet::par_iterate_closure_all_threads(int worker) {

   SharedHeap* sh = SharedHeap::heap();

   int parity = sh->strong_roots_parity();

   for(JavaThread* t = Threads::first(); t; t = t->next()) {

     if (t->claim_oops_do(true, parity)) {

       t->satb_mark_queue().apply_closure(_par_closures[worker]);

     }

   }

   // We also need to claim the VMThread so that its parity is updated

   // otherwise the next call to Thread::possibly_parallel_oops_do inside

   // a StrongRootsScope might skip the VMThread because it has a stale

   // parity that matches the parity set by the StrongRootsScope

   //

   // Whichever worker succeeds in claiming the VMThread gets to do

   // the shared queue.

   VMThread* vmt = VMThread::vm_thread();

   if (vmt->claim_oops_do(true, parity)) {

     shared_satb_queue()->apply_closure(_par_closures[worker]);

   }

 }

 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par,

                                                               int worker) {

   BufferNode* nd = NULL;

   {

     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

     if (_completed_buffers_head != NULL) {

       nd = _completed_buffers_head;

       _completed_buffers_head = nd->next();

       if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;

       _n_completed_buffers--;

       if (_n_completed_buffers == 0) _process_completed = false;

     }

   }

   ObjectClosure* cl = (par ? _par_closures[worker] : _closure);

   if (nd != NULL) {

     void **buf = BufferNode::make_buffer_from_node(nd);

     ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);

     deallocate_buffer(buf);

     return true;

   } else {

     return false;

   }

 }

 void SATBMarkQueueSet::abandon_partial_marking() {

   BufferNode* buffers_to_delete = NULL;

   {

     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);

     while (_completed_buffers_head != NULL) {

       BufferNode* nd = _completed_buffers_head;

       _completed_buffers_head = nd->next();

       nd->set_next(buffers_to_delete);

       buffers_to_delete = nd;

     }

     _completed_buffers_tail = NULL;

     _n_completed_buffers = 0;

     DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());

   }

   while (buffers_to_delete != NULL) {

     BufferNode* nd = buffers_to_delete;

     buffers_to_delete = nd->next();

     deallocate_buffer(BufferNode::make_buffer_from_node(nd));

   }

   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");

   // So we can safely manipulate these queues.

   for (JavaThread* t = Threads::first(); t; t = t->next()) {

     t->satb_mark_queue().reset();

   }

   shared_satb_queue()->reset();

 }