2 This file is a part of libcds - Concurrent Data Structures library
4 (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016
6 Source code repo: http://github.com/khizmax/libcds/
7 Download: http://sourceforge.net/projects/libcds/files/
9 Redistribution and use in source and binary forms, with or without
10 modification, are permitted provided that the following conditions are met:
12 * Redistributions of source code must retain the above copyright notice, this
13 list of conditions and the following disclaimer.
15 * Redistributions in binary form must reproduce the above copyright notice,
16 this list of conditions and the following disclaimer in the documentation
17 and/or other materials provided with the distribution.
19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
20 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
22 DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
23 FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
25 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
26 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
27 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 #ifndef CDSLIB_ALGO_FLAT_COMBINING_KERNEL_H
32 #define CDSLIB_ALGO_FLAT_COMBINING_KERNEL_H
34 #include <cds/algo/flat_combining/defs.h>
35 #include <cds/algo/flat_combining/wait_strategy.h>
37 #include <cds/sync/spinlock.h>
38 #include <cds/details/allocator.h>
39 #include <cds/opt/options.h>
40 #include <cds/algo/int_algo.h>
42 namespace cds { namespace algo {
44 /// @defgroup cds_flat_combining_intrusive Intrusive flat combining containers
45 /// @defgroup cds_flat_combining_container Non-intrusive flat combining containers
49 @anchor cds_flat_combining_description
50 Flat combining (FC) technique is invented by Hendler, Incze, Shavit and Tzafrir in their paper
51 [2010] <i>"Flat Combining and the Synchronization-Parallelism Tradeoff"</i>.
52 The technique converts a sequential data structure to its concurrent implementation.
53 A few structures are added to the sequential implementation: a <i>global lock</i>,
54 a <i>count</i> of the number of combining passes, and a pointer to the <i>head</i>
55 of a <i>publication list</i>. The publication list is a list of thread-local records
56 of a size proportional to the number of threads that are concurrently accessing the shared object.
58 Each thread \p t accessing the structure to perform an invocation of some method \p f()
59 on the shared object executes the following sequence of steps:
61 <li>Write the invocation opcode and parameters (if any) of the method \p f() to be applied
62 sequentially to the shared object in the <i>request</i> field of your thread local publication
63 record (there is no need to use a load-store memory barrier). The <i>request</i> field will later
64 be used to receive the response. If your thread local publication record is marked as active
65 continue to step 2, otherwise continue to step 5.</li>
66 <li>Check if the global lock is taken. If so (another thread is an active combiner), spin on the <i>request</i>
67 field waiting for a response to the invocation (one can add a yield at this point to allow other threads
68 on the same core to run). Once in a while while spinning check if the lock is still taken and that your
69 record is active (you may use any of \p wait_strategy instead of spinning). If your record is inactive proceed to step 5.
70 Once the response is available, reset the request field to null and return the response.</li>
71 <li>If the lock is not taken, attempt to acquire it and become a combiner. If you fail,
72 return to spinning in step 2.</li>
73 <li>Otherwise, you hold the lock and are a combiner.
75 <li>Increment the combining pass count by one.</li>
76 <li>Execute a \p fc_apply() by traversing the publication list from the head,
77 combining all non-null method call invocations, setting the <i>age</i> of each of these records
78 to the current <i>count</i>, applying the combined method calls to the structure D, and returning
79 responses to all the invocations. This traversal is guaranteed to be wait-free.</li>
80 <li>If the <i>count</i> is such that a cleanup needs to be performed, traverse the publication
81 list from the <i>head</i>. Starting from the second item (we always leave the item pointed to
82 by the head in the list), remove from the publication list all records whose <i>age</i> is
83 much smaller than the current <i>count</i>. This is done by removing the node and marking it
85 <li>Release the lock.</li>
87 <li>If you have no thread local publication record allocate one, marked as active. If you already
88 have one marked as inactive, mark it as active. Execute a store-load memory barrier. Proceed to insert
89 the record into the list with a successful CAS to the <i>head</i>. Then proceed to step 1.</li>
92 As the test results show, the flat combining technique is suitable for non-intrusive containers
93 like stack, queue, deque. For intrusive concurrent containers the flat combining demonstrates
94 less impressive results.
96 \ref cds_flat_combining_container "List of FC-based containers" in libcds.
98 \ref cds_flat_combining_intrusive "List of intrusive FC-based containers" in libcds.
100 namespace flat_combining {
102 /// Flat combining internal statistics
103 template <typename Counter = cds::atomicity::event_counter >
106 typedef Counter counter_type; ///< Event counter type
108 counter_type m_nOperationCount ; ///< How many operations have been performed
109 counter_type m_nCombiningCount ; ///< Combining call count
110 counter_type m_nCompactPublicationList; ///< Count of publication list compacting
111 counter_type m_nDeactivatePubRecord; ///< How many publication records were deactivated during compacting
112 counter_type m_nActivatePubRecord; ///< Count of publication record activating
113 counter_type m_nPubRecordCreated ; ///< Count of created publication records
114 counter_type m_nPubRecordDeleted ; ///< Count of deleted publication records
115 counter_type m_nPassiveWaitCall; ///< Count of passive waiting call (\p kernel::wait_for_combining())
116 counter_type m_nPassiveWaitIteration;///< Count of iteration inside passive waiting
117 counter_type m_nPassiveWaitWakeup; ///< Count of forcing wake-up of passive wait cycle
118 counter_type m_nInvokeExclusive; ///< Count of call \p kernel::invoke_exclusive()
119 counter_type m_nWakeupByNotifying; ///< How many times the passive thread be waked up by a notification
120 counter_type m_nPassiveToCombiner; ///< How many times the passive thread becomes the combiner
122 /// Returns current combining factor
124 Combining factor is how many operations perform in one combine pass:
125 <tt>combining_factor := m_nOperationCount / m_nCombiningCount</tt>
127 double combining_factor() const
129 return m_nCombiningCount.get() ? double( m_nOperationCount.get()) / m_nCombiningCount.get() : 0.0;
133 void onOperation() { ++m_nOperationCount; }
134 void onCombining() { ++m_nCombiningCount; }
135 void onCompactPublicationList() { ++m_nCompactPublicationList; }
136 void onDeactivatePubRecord() { ++m_nDeactivatePubRecord; }
137 void onActivatePubRecord() { ++m_nActivatePubRecord; }
138 void onCreatePubRecord() { ++m_nPubRecordCreated; }
139 void onDeletePubRecord() { ++m_nPubRecordDeleted; }
140 void onPassiveWait() { ++m_nPassiveWaitCall; }
141 void onPassiveWaitIteration() { ++m_nPassiveWaitIteration; }
142 void onPassiveWaitWakeup() { ++m_nPassiveWaitWakeup; }
143 void onInvokeExclusive() { ++m_nInvokeExclusive; }
144 void onWakeupByNotifying() { ++m_nWakeupByNotifying; }
145 void onPassiveToCombiner() { ++m_nPassiveToCombiner; }
150 /// Flat combining dummy internal statistics
154 void onOperation() const {}
155 void onCombining() const {}
156 void onCompactPublicationList() const {}
157 void onDeactivatePubRecord() const {}
158 void onActivatePubRecord() const {}
159 void onCreatePubRecord() const {}
160 void onDeletePubRecord() const {}
161 void onPassiveWait() const {}
162 void onPassiveWaitIteration() const {}
163 void onPassiveWaitWakeup() const {}
164 void onInvokeExclusive() const {}
165 void onWakeupByNotifying() const {}
166 void onPassiveToCombiner() const {}
170 /// Type traits of \ref kernel class
172 You can define different type traits for \ref kernel
173 by specifying your struct based on \p %traits
174 or by using \ref make_traits metafunction.
178 typedef cds::sync::spin lock_type; ///< Lock type
179 typedef cds::algo::flat_combining::wait_strategy::backoff< cds::backoff::delay_of<2>> wait_strategy; ///< Wait strategy
180 typedef CDS_DEFAULT_ALLOCATOR allocator; ///< Allocator used for TLS data (allocating \p publication_record derivatives)
181 typedef empty_stat stat; ///< Internal statistics
182 typedef opt::v::relaxed_ordering memory_model; ///< /// C++ memory ordering model
185 /// Metafunction converting option list to traits
188 - \p opt::lock_type - mutex type, default is \p cds::sync::spin
189 - \p opt::wait_strategy - wait strategy, see \p wait_strategy namespace, default is \p wait_strategy::backoff.
190 - \p opt::allocator - allocator type, default is \ref CDS_DEFAULT_ALLOCATOR
191 - \p opt::stat - internal statistics, possible type: \ref stat, \ref empty_stat (the default)
192 - \p opt::memory_model - C++ memory ordering model.
193 List of all available memory ordering see \p opt::memory_model.
194 Default is \p cds::opt::v::relaxed_ordering
196 template <typename... Options>
198 # ifdef CDS_DOXYGEN_INVOKED
199 typedef implementation_defined type ; ///< Metafunction result
201 typedef typename cds::opt::make_options<
202 typename cds::opt::find_type_traits< traits, Options... >::type
208 /// The kernel of flat combining
211 - \p PublicationRecord - a type derived from \ref publication_record
212 - \p Traits - a type traits of flat combining, default is \p flat_combining::traits.
213 \ref make_traits metafunction can be used to create type traits
215 The kernel object should be a member of a container class. The container cooperates with flat combining
216 kernel object. There are two ways to interact with the kernel:
217 - One-by-one processing the active records of the publication list. This mode provides by \p combine() function:
218 the container acquires its publication record by \p acquire_record(), fills its fields and calls
219 \p combine() function of its kernel object. If the current thread becomes a combiner, the kernel
220 calls \p fc_apply() function of the container for each active non-empty record. Then, the container
221 should release its publication record by \p release_record(). Only one pass through the publication
223 - Batch processing - \p batch_combine() function. It this mode the container obtains access
224 to entire publication list. This mode allows the container to perform an elimination, for example,
225 the stack can collide \p push() and \p pop() requests. The sequence of invocations is the following:
226 the container acquires its publication record by \p acquire_record(), fills its field and call
227 \p batch_combine() function of its kernel object. If the current thread becomes a combiner,
228 the kernel calls \p fc_process() function of the container passing two iterators pointing to
229 the begin and the end of publication list (see \ref iterator class). The iterators allow
230 multiple pass through active records of publication list. For each processed record the container
231 should call \p operation_done() function. On the end, the container should release
232 its record by \p release_record().
235 typename PublicationRecord
236 ,typename Traits = traits
241 typedef Traits traits; ///< Type traits
242 typedef typename traits::lock_type global_lock_type; ///< Global lock type
243 typedef typename traits::wait_strategy wait_strategy; ///< Wait strategy type
244 typedef typename traits::allocator allocator; ///< Allocator type (used for allocating publication_record_type data)
245 typedef typename traits::stat stat; ///< Internal statistics
246 typedef typename traits::memory_model memory_model; ///< C++ memory model
248 typedef typename wait_strategy::template make_publication_record<PublicationRecord>::type publication_record_type; ///< Publication record type
252 typedef cds::details::Allocator< publication_record_type, allocator > cxx11_allocator; ///< internal helper cds::details::Allocator
253 typedef std::lock_guard<global_lock_type> lock_guard;
257 atomics::atomic<unsigned int> m_nCount; ///< Total count of combining passes. Used as an age.
258 publication_record_type * m_pHead; ///< Head of publication list
259 boost::thread_specific_ptr< publication_record_type > m_pThreadRec; ///< Thread-local publication record
260 mutable global_lock_type m_Mutex; ///< Global mutex
261 mutable stat m_Stat; ///< Internal statistics
262 unsigned int const m_nCompactFactor; ///< Publication list compacting factor (the list will be compacted through \p %m_nCompactFactor combining passes)
263 unsigned int const m_nCombinePassCount; ///< Number of combining passes
264 wait_strategy m_waitStrategy; ///< Wait strategy
267 /// Initializes the object
269 Compact factor = 1024
271 Combiner pass count = 8
277 /// Initializes the object
279 unsigned int nCompactFactor ///< Publication list compacting factor (the list will be compacted through \p nCompactFactor combining passes)
280 ,unsigned int nCombinePassCount ///< Number of combining passes for combiner thread
284 , m_pThreadRec( tls_cleanup )
285 , m_nCompactFactor( (unsigned int)( cds::beans::ceil2( nCompactFactor ) - 1 )) // binary mask
286 , m_nCombinePassCount( nCombinePassCount )
291 /// Destroys the objects and mark all publication records as inactive
294 // mark all publication record as detached
295 for ( publication_record* p = m_pHead; p; ) {
298 publication_record * pRec = p;
299 p = p->pNext.load( memory_model::memory_order_relaxed );
300 if ( pRec->nState.load( memory_model::memory_order_acquire ) == removed )
301 free_publication_record( static_cast<publication_record_type *>( pRec ));
305 /// Gets publication list record for the current thread
307 If there is no publication record for the current thread
308 the function allocates it.
310 publication_record_type * acquire_record()
312 publication_record_type * pRec = m_pThreadRec.get();
314 // Allocate new publication record
315 pRec = cxx11_allocator().New();
316 pRec->pOwner = reinterpret_cast<void *>( this );
317 m_pThreadRec.reset( pRec );
318 m_Stat.onCreatePubRecord();
321 if ( pRec->nState.load( memory_model::memory_order_acquire ) != active )
324 assert( pRec->op() == req_EmptyRecord );
329 /// Marks publication record for the current thread as empty
330 void release_record( publication_record_type * pRec )
332 assert( pRec->is_done() );
333 pRec->nRequest.store( req_EmptyRecord, memory_model::memory_order_release );
336 /// Trying to execute operation \p nOpId
338 \p pRec is the publication record acquiring by \ref acquire_record earlier.
339 \p owner is a container that is owner of flat combining kernel object.
340 As a result the current thread can become a combiner or can wait for
341 another combiner performs \p pRec operation.
343 If the thread becomes a combiner, the kernel calls \p owner.fc_apply
344 for each active non-empty publication record.
346 template <class Container>
347 void combine( unsigned int nOpId, publication_record_type * pRec, Container& owner )
349 assert( nOpId >= req_Operation );
352 pRec->nRequest.store( nOpId, memory_model::memory_order_release );
353 m_Stat.onOperation();
355 try_combining( owner, pRec );
358 /// Trying to execute operation \p nOpId in batch-combine mode
360 \p pRec is the publication record acquiring by \p acquire_record() earlier.
361 \p owner is a container that owns flat combining kernel object.
362 As a result the current thread can become a combiner or can wait for
363 another combiner performs \p pRec operation.
365 If the thread becomes a combiner, the kernel calls \p owner.fc_process()
366 giving the container the full access over publication list. This function
367 is useful for an elimination technique if the container supports any kind of
368 that. The container can perform multiple pass through publication list.
370 \p owner.fc_process() has two arguments - forward iterators on begin and end of
371 publication list, see \ref iterator class. For each processed record the container
372 should call \p operation_done() function to mark the record as processed.
374 On the end of \p %batch_combine the \p combine() function is called
375 to process rest of publication records.
377 template <class Container>
378 void batch_combine( unsigned int nOpId, publication_record_type* pRec, Container& owner )
380 assert( nOpId >= req_Operation );
383 pRec->nRequest.store( nOpId, memory_model::memory_order_release );
384 m_Stat.onOperation();
386 try_batch_combining( owner, pRec );
389 /// Invokes \p Func in exclusive mode
391 Some operation in flat combining containers should be called in exclusive mode
392 i.e the current thread should become the combiner to process the operation.
393 The typical example is \p empty() function.
395 \p %invoke_exclusive() allows do that: the current thread becomes the combiner,
396 invokes \p f exclusively but unlike a typical usage the thread does not process any pending request.
397 Instead, after end of \p f call the current thread wakes up a pending thread if any.
399 template <typename Func>
400 void invoke_exclusive( Func f )
403 lock_guard l( m_Mutex );
406 m_waitStrategy.wakeup( *this );
407 m_Stat.onInvokeExclusive();
410 /// Marks \p rec as executed
412 This function should be called by container if \p batch_combine mode is used.
413 For usual combining (see \p combine() ) this function is excess.
415 void operation_done( publication_record& rec )
417 rec.nRequest.store( req_Response, memory_model::memory_order_release );
418 m_waitStrategy.notify( *this, static_cast<publication_record_type&>( rec ));
421 /// Internal statistics
422 stat const& statistics() const
428 // For container classes based on flat combining
429 stat& internal_statistics() const
435 /// Returns the compact factor
436 unsigned int compact_factor() const
438 return m_nCompactFactor + 1;
441 /// Returns number of combining passes for combiner thread
442 unsigned int combine_pass_count() const
444 return m_nCombinePassCount;
448 /// Publication list iterator
450 Iterators are intended for batch processing by container's
451 \p fc_process function.
452 The iterator allows iterate through active publication list.
458 publication_record_type * m_pRec;
463 iterator( publication_record_type * pRec )
471 while ( m_pRec && (m_pRec->nState.load( memory_model::memory_order_acquire ) != active
472 || m_pRec->op( memory_model::memory_order_relaxed) < req_Operation ))
474 m_pRec = static_cast<publication_record_type*>(m_pRec->pNext.load( memory_model::memory_order_acquire ));
480 /// Initializes an empty iterator object
486 iterator( iterator const& src )
487 : m_pRec( src.m_pRec )
491 iterator& operator++()
494 m_pRec = static_cast<publication_record_type *>( m_pRec->pNext.load( memory_model::memory_order_acquire ));
500 iterator operator++(int)
508 /// Dereference operator, can return \p nullptr
509 publication_record_type* operator ->()
514 /// Dereference operator, the iterator should not be an end iterator
515 publication_record_type& operator*()
521 /// Iterator equality
522 friend bool operator==( iterator it1, iterator it2 )
524 return it1.m_pRec == it2.m_pRec;
527 /// Iterator inequality
528 friend bool operator!=( iterator it1, iterator it2 )
530 return !( it1 == it2 );
534 /// Returns an iterator to the first active publication record
535 iterator begin() { return iterator(m_pHead); }
537 /// Returns an iterator to the end of publication list. Should not be dereferenced.
538 iterator end() { return iterator(); }
541 /// Gets current value of \p rec.nRequest
543 This function is intended for invoking from a wait strategy
545 int get_operation( publication_record& rec )
547 return rec.op( memory_model::memory_order_acquire );
550 /// Wakes up any waiting thread
552 This function is intended for invoking from a wait strategy
556 publication_record* pRec = m_pHead;
558 if ( pRec->nState.load( memory_model::memory_order_acquire ) == active
559 && pRec->op( memory_model::memory_order_acquire ) >= req_Operation )
561 m_waitStrategy.notify( *this, static_cast<publication_record_type&>( *pRec ));
564 pRec = pRec->pNext.load( memory_model::memory_order_acquire );
570 static void tls_cleanup( publication_record_type* pRec )
573 // pRec that is TLS data should be excluded from publication list
575 if ( pRec->pOwner ) {
577 pRec->nState.store( removed, memory_model::memory_order_release );
580 // kernel already deleted
581 free_publication_record( pRec );
586 static void free_publication_record( publication_record_type* pRec )
588 cxx11_allocator().Delete( pRec );
593 assert( m_pThreadRec.get() == nullptr );
594 publication_record_type* pRec = cxx11_allocator().New();
597 m_pThreadRec.reset( pRec );
598 m_Stat.onCreatePubRecord();
601 void publish( publication_record_type* pRec )
603 assert( pRec->nState.load( memory_model::memory_order_relaxed ) == inactive );
605 pRec->nAge.store( m_nCount.load(memory_model::memory_order_relaxed), memory_model::memory_order_release );
606 pRec->nState.store( active, memory_model::memory_order_release );
608 // Insert record to publication list
609 if ( m_pHead != static_cast<publication_record *>(pRec) ) {
610 publication_record * p = m_pHead->pNext.load(memory_model::memory_order_relaxed);
611 if ( p != static_cast<publication_record *>( pRec )) {
614 // Failed CAS changes p
615 } while ( !m_pHead->pNext.compare_exchange_weak( p, static_cast<publication_record *>(pRec),
616 memory_model::memory_order_release, atomics::memory_order_relaxed ));
617 m_Stat.onActivatePubRecord();
622 void republish( publication_record_type* pRec )
624 if ( pRec->nState.load( memory_model::memory_order_relaxed ) != active ) {
625 // The record has been excluded from publication list. Reinsert it
630 template <class Container>
631 void try_combining( Container& owner, publication_record_type* pRec )
633 if ( m_Mutex.try_lock() ) {
634 // The thread becomes a combiner
635 lock_guard l( m_Mutex, std::adopt_lock_t() );
637 // The record pRec can be excluded from publication list. Re-publish it
641 assert( pRec->op( memory_model::memory_order_relaxed ) == req_Response );
644 // There is another combiner, wait while it executes our request
645 if ( !wait_for_combining( pRec ) ) {
646 // The thread becomes a combiner
647 lock_guard l( m_Mutex, std::adopt_lock_t() );
649 // The record pRec can be excluded from publication list. Re-publish it
653 assert( pRec->op( memory_model::memory_order_relaxed ) == req_Response );
658 template <class Container>
659 void try_batch_combining( Container& owner, publication_record_type * pRec )
661 if ( m_Mutex.try_lock() ) {
662 // The thread becomes a combiner
663 lock_guard l( m_Mutex, std::adopt_lock_t() );
665 // The record pRec can be excluded from publication list. Re-publish it
668 batch_combining( owner );
669 assert( pRec->op( memory_model::memory_order_relaxed ) == req_Response );
672 // There is another combiner, wait while it executes our request
673 if ( !wait_for_combining( pRec ) ) {
674 // The thread becomes a combiner
675 lock_guard l( m_Mutex, std::adopt_lock_t() );
677 // The record pRec can be excluded from publication list. Re-publish it
680 batch_combining( owner );
681 assert( pRec->op( memory_model::memory_order_relaxed ) == req_Response );
686 template <class Container>
687 void combining( Container& owner )
689 // The thread is a combiner
690 assert( !m_Mutex.try_lock() );
692 unsigned int const nCurAge = m_nCount.fetch_add( 1, memory_model::memory_order_relaxed ) + 1;
694 unsigned int nEmptyPassCount = 0;
695 unsigned int nUsefulPassCount = 0;
696 for ( unsigned int nPass = 0; nPass < m_nCombinePassCount; ++nPass ) {
697 if ( combining_pass( owner, nCurAge ))
699 else if ( ++nEmptyPassCount > nUsefulPassCount )
703 m_Stat.onCombining();
704 if ( (nCurAge & m_nCompactFactor) == 0 )
705 compact_list( nCurAge );
708 template <class Container>
709 bool combining_pass( Container& owner, unsigned int nCurAge )
711 publication_record* pPrev = nullptr;
712 publication_record* p = m_pHead;
713 bool bOpDone = false;
715 switch ( p->nState.load( memory_model::memory_order_acquire )) {
717 if ( p->op() >= req_Operation ) {
718 p->nAge.store( nCurAge, memory_model::memory_order_release );
719 owner.fc_apply( static_cast<publication_record_type*>(p) );
720 operation_done( *p );
725 // Only m_pHead can be inactive in the publication list
726 assert( p == m_pHead );
729 // The record should be removed
730 p = unlink_and_delete_record( pPrev, p );
733 /// ??? That is impossible
737 p = p->pNext.load( memory_model::memory_order_acquire );
742 template <class Container>
743 void batch_combining( Container& owner )
745 // The thread is a combiner
746 assert( !m_Mutex.try_lock() );
748 unsigned int const nCurAge = m_nCount.fetch_add( 1, memory_model::memory_order_relaxed ) + 1;
750 for ( unsigned int nPass = 0; nPass < m_nCombinePassCount; ++nPass )
751 owner.fc_process( begin(), end() );
753 combining_pass( owner, nCurAge );
754 m_Stat.onCombining();
755 if ( (nCurAge & m_nCompactFactor) == 0 )
756 compact_list( nCurAge );
759 bool wait_for_combining( publication_record_type * pRec )
761 m_waitStrategy.prepare( *pRec );
762 m_Stat.onPassiveWait();
764 while ( pRec->op( memory_model::memory_order_acquire ) != req_Response ) {
765 // The record can be excluded from publication list. Reinsert it
768 m_Stat.onPassiveWaitIteration();
770 // Wait while operation processing
771 if ( m_waitStrategy.wait( *this, *pRec ))
772 m_Stat.onWakeupByNotifying();
774 if ( m_Mutex.try_lock() ) {
775 if ( pRec->op( memory_model::memory_order_acquire ) == req_Response ) {
779 // Wake up a pending threads
780 m_waitStrategy.wakeup( *this );
781 m_Stat.onPassiveWaitWakeup();
785 // The thread becomes a combiner
786 m_Stat.onPassiveToCombiner();
793 void compact_list( unsigned int const nCurAge )
795 // Thinning publication list
796 publication_record * pPrev = nullptr;
797 for ( publication_record * p = m_pHead; p; ) {
798 if ( p->nState.load( memory_model::memory_order_acquire ) == active
799 && p->nAge.load( memory_model::memory_order_acquire ) + m_nCompactFactor < nCurAge )
802 publication_record * pNext = p->pNext.load( memory_model::memory_order_acquire );
803 if ( pPrev->pNext.compare_exchange_strong( p, pNext,
804 memory_model::memory_order_release, atomics::memory_order_relaxed ))
806 p->nState.store( inactive, memory_model::memory_order_release );
808 m_Stat.onDeactivatePubRecord();
814 p = p->pNext.load( memory_model::memory_order_acquire );
817 m_Stat.onCompactPublicationList();
820 publication_record * unlink_and_delete_record( publication_record * pPrev, publication_record * p )
823 publication_record * pNext = p->pNext.load( memory_model::memory_order_acquire );
824 if ( pPrev->pNext.compare_exchange_strong( p, pNext,
825 memory_model::memory_order_release, atomics::memory_order_relaxed ))
827 free_publication_record( static_cast<publication_record_type *>( p ));
828 m_Stat.onDeletePubRecord();
833 m_pHead = static_cast<publication_record_type *>( p->pNext.load( memory_model::memory_order_acquire ));
834 free_publication_record( static_cast<publication_record_type *>( p ));
835 m_Stat.onDeletePubRecord();
846 template <typename PubRecord>
847 void fc_apply( PubRecord * )
852 template <typename Iterator>
853 void fc_process( Iterator, Iterator )
860 } // namespace flat_combining
861 }} // namespace cds::algo
863 #endif // #ifndef CDSLIB_ALGO_FLAT_COMBINING_KERNEL_H