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 #ifndef SHARE_GC_SHARED_SATBMARKQUEUE_HPP

    26 #define SHARE_GC_SHARED_SATBMARKQUEUE_HPP

    27 

    28 #include "gc/shared/ptrQueue.hpp"

    29 #include "memory/allocation.hpp"

    30 

    31 class JavaThread;

    32 class SATBMarkQueueSet;

    33 

    34 // Base class for processing the contents of a SATB buffer.

    35 class SATBBufferClosure : public StackObj {

    36 protected:

    37   ~SATBBufferClosure() { }

    38 

    39 public:

    40   // Process the SATB entries in the designated buffer range.

    41   virtual void do_buffer(void** buffer, size_t size) = 0;

    42 };

    43 

    44 // A PtrQueue whose elements are (possibly stale) pointers to object heads.

    45 class SATBMarkQueue: public PtrQueue {

    46   friend class SATBMarkQueueSet;

    47 

    48 private:

    49   // Filter out unwanted entries from the buffer.

    50   inline void filter();

    51 

    52   // Removes entries from the buffer that are no longer needed.

    53   template<typename Filter>

    54   inline void apply_filter(Filter filter_out);

    55 

    56 public:

    57   SATBMarkQueue(SATBMarkQueueSet* qset, bool permanent = false);

    58 

    59   // Process queue entries and free resources.

    60   void flush();

    61 

    62   // Apply cl to the active part of the buffer.

    63   // Prerequisite: Must be at a safepoint.

    64   void apply_closure_and_empty(SATBBufferClosure* cl);

    65 

    66   // Overrides PtrQueue::should_enqueue_buffer(). See the method's

    67   // definition for more information.

    68   virtual bool should_enqueue_buffer();

    69 

    70 #ifndef PRODUCT

    71   // Helpful for debugging

    72   void print(const char* name);

    73 #endif // PRODUCT

    74 

    75   // Compiler support.

    76   static ByteSize byte_offset_of_index() {

    77     return PtrQueue::byte_offset_of_index<SATBMarkQueue>();

    78   }

    79   using PtrQueue::byte_width_of_index;

    80 

    81   static ByteSize byte_offset_of_buf() {

    82     return PtrQueue::byte_offset_of_buf<SATBMarkQueue>();

    83   }

    84   using PtrQueue::byte_width_of_buf;

    85 

    86   static ByteSize byte_offset_of_active() {

    87     return PtrQueue::byte_offset_of_active<SATBMarkQueue>();

    88   }

    89   using PtrQueue::byte_width_of_active;

    90 

    91 };

    92 

    93 class SATBMarkQueueSet: public PtrQueueSet {

    94   SATBMarkQueue _shared_satb_queue;

    95   size_t _buffer_enqueue_threshold;

    96 

    97 #ifdef ASSERT

    98   void dump_active_states(bool expected_active);

    99   void verify_active_states(bool expected_active);

   100 #endif // ASSERT

   101 

   102 protected:

   103   SATBMarkQueueSet();

   104   ~SATBMarkQueueSet() {}

   105 

   106   template<typename Filter>

   107   void apply_filter(Filter filter, SATBMarkQueue* queue) {

   108     queue->apply_filter(filter);

   109   }

   110 

   111   void initialize(Monitor* cbl_mon, Mutex* fl_lock,

   112                   int process_completed_threshold,

   113                   uint buffer_enqueue_threshold_percentage,

   114                   Mutex* lock);

   115 

   116 public:

   117   virtual SATBMarkQueue& satb_queue_for_thread(JavaThread* const t) const = 0;

   118 

   119   // Apply "set_active(active)" to all SATB queues in the set. It should be

   120   // called only with the world stopped. The method will assert that the

   121   // SATB queues of all threads it visits, as well as the SATB queue

   122   // set itself, has an active value same as expected_active.

   123   void set_active_all_threads(bool active, bool expected_active);

   124 

   125   size_t buffer_enqueue_threshold() const { return _buffer_enqueue_threshold; }

   126   virtual void filter(SATBMarkQueue* queue) = 0;

   127 

   128   // Filter all the currently-active SATB buffers.

   129   void filter_thread_buffers();

   130 

   131   // If there exists some completed buffer, pop and process it, and

   132   // return true.  Otherwise return false.  Processing a buffer

   133   // consists of applying the closure to the active range of the

   134   // buffer; the leading entries may be excluded due to filtering.

   135   bool apply_closure_to_completed_buffer(SATBBufferClosure* cl);

   136 

   137 #ifndef PRODUCT

   138   // Helpful for debugging

   139   void print_all(const char* msg);

   140 #endif // PRODUCT

   141 

   142   SATBMarkQueue* shared_satb_queue() { return &_shared_satb_queue; }

   143 

   144   // If a marking is being abandoned, reset any unprocessed log buffers.

   145   void abandon_partial_marking();

   146 };

   147 

   148 inline void SATBMarkQueue::filter() {

   149   static_cast<SATBMarkQueueSet*>(qset())->filter(this);

   150 }

   151 

   152 // Removes entries from the buffer that are no longer needed, as

   153 // determined by filter. If e is a void* entry in the buffer,

   154 // filter_out(e) must be a valid expression whose value is convertible

   155 // to bool. Entries are removed (filtered out) if the result is true,

   156 // retained if false.

   157 template<typename Filter>

   158 inline void SATBMarkQueue::apply_filter(Filter filter_out) {

   159   void** buf = this->_buf;

   160 

   161   if (buf == NULL) {

   162     // nothing to do

   163     return;

   164   }

   165 

   166   // Two-fingered compaction toward the end.

   167   void** src = &buf[this->index()];

   168   void** dst = &buf[this->capacity()];

   169   assert(src <= dst, "invariant");

   170   for ( ; src < dst; ++src) {

   171     // Search low to high for an entry to keep.

   172     void* entry = *src;

   173     if (!filter_out(entry)) {

   174       // Found keeper.  Search high to low for an entry to discard.

   175       while (src < --dst) {

   176         if (filter_out(*dst)) {

   177           *dst = entry;         // Replace discard with keeper.

   178           break;

   179         }

   180       }

   181       // If discard search failed (src == dst), the outer loop will also end.

   182     }

   183   }

   184   // dst points to the lowest retained entry, or the end of the buffer

   185   // if all the entries were filtered out.

   186   this->set_index(dst - buf);

   187 }

   188 

   189 #endif // SHARE_GC_SHARED_SATBMARKQUEUE_HPP