Optimize fast path in inc_item_count.

diff --git a/cds/intrusive/split_list.h b/cds/intrusive/split_list.h
index 7a923dc8600e8ac4845637490b421d49f089d1ee..2d78c141de621515e0b172774885f9b69ab261eb 100644 (file)
--- a/cds/intrusive/split_list.h
+++ b/cds/intrusive/split_list.h
@@ -4,6 +4,7 @@
 #define CDSLIB_INTRUSIVE_SPLIT_LIST_H
 
 #include <cds/intrusive/details/split_list_base.h>
+#include <limits>
 
 namespace cds { namespace intrusive {
 
@@ -349,6 +350,7 @@ namespace cds { namespace intrusive {
         ordered_list_wrapper    m_List;             ///< Ordered list containing split-list items
         bucket_table            m_Buckets;          ///< bucket table
         atomics::atomic<size_t> m_nBucketCountLog2; ///< log2( current bucket count )
+        atomics::atomic<size_t> m_nMaxItemCount;    ///< number of items container can hold, before we have to resize
         item_counter            m_ItemCounter;      ///< Item counter
         hash                    m_HashFunctor;      ///< Hash functor
         stat                    m_Stat;             ///< Internal statistics
@@ -457,13 +459,28 @@ namespace cds { namespace intrusive {
             m_Buckets.bucket( 0, pNode );
         }
 
+        static size_t max_item_count( size_t nBucketCount, size_t nLoadFactor )
+        {
+            return nBucketCount * nLoadFactor;
+        }
+
         void inc_item_count()
         {
-            size_t sz = m_nBucketCountLog2.load(atomics::memory_order_relaxed);
-            if ( ( ++m_ItemCounter >> sz ) > m_Buckets.load_factor() && (static_cast<size_t>(1) << sz ) < m_Buckets.capacity() )
-            {
-                m_nBucketCountLog2.compare_exchange_strong( sz, sz + 1, memory_model::memory_order_relaxed, atomics::memory_order_relaxed );
-            }
+            size_t nMaxCount = m_nMaxItemCount.load(memory_model::memory_order_relaxed);
+            if ( ++m_ItemCounter <= nMaxCount )
+                return;
+
+            const size_t nLoadFactor = m_Buckets.load_factor();
+            size_t sz = m_nBucketCountLog2.load(memory_model::memory_order_relaxed);
+            const size_t nBucketCount = static_cast<size_t>(1) << sz;
+            if ( nMaxCount < max_item_count( nBucketCount, nLoadFactor ))
+                return; // someone already have updated m_nBucketCountLog2, so stop here
+
+            const size_t nNewMaxCount = (nBucketCount < m_Buckets.capacity()) ? max_item_count( nBucketCount << 1, nLoadFactor )
+                                                                              : std::numeric_limits<size_t>::max();
+            m_nMaxItemCount.compare_exchange_strong( nMaxCount, nNewMaxCount, memory_model::memory_order_relaxed,
+                memory_model::memory_order_relaxed );
+            m_nBucketCountLog2.compare_exchange_strong( sz, sz + 1, memory_model::memory_order_seq_cst, memory_model::memory_order_relaxed );
         }
 
         template <typename Q, typename Compare, typename Func>
@@ -587,6 +604,7 @@ namespace cds { namespace intrusive {
         */
         SplitListSet()
             : m_nBucketCountLog2(1)
+            , m_nMaxItemCount( max_item_count(2, m_Buckets.load_factor()) )
         {
             init();
         }
@@ -598,6 +616,7 @@ namespace cds { namespace intrusive {
             )
             : m_Buckets( nItemCount, nLoadFactor )
             , m_nBucketCountLog2(1)
+            , m_nMaxItemCount( max_item_count(2, m_Buckets.load_factor()) )
         {
             init();
         }

diff --git a/cds/intrusive/split_list_nogc.h b/cds/intrusive/split_list_nogc.h
index 8166312f2576f17d4b5b57577af34695f243eed4..5ae837c843c420ce935646a6221e4f9fa00cf0ae 100644 (file)
--- a/cds/intrusive/split_list_nogc.h
+++ b/cds/intrusive/split_list_nogc.h
@@ -6,6 +6,8 @@
 #include <cds/intrusive/details/split_list_base.h>
 #include <cds/gc/nogc.h>
 
+#include <limits>
+
 namespace cds { namespace intrusive {
 
     /// Split-ordered list (template specialization for gc::nogc)
@@ -144,6 +146,7 @@ namespace cds { namespace intrusive {
         ordered_list_wrapper    m_List;             ///< Ordered list containing split-list items
         bucket_table            m_Buckets;          ///< bucket table
         atomics::atomic<size_t> m_nBucketCountLog2; ///< log2( current bucket count )
+        atomics::atomic<size_t> m_nMaxItemCount;    ///< number of items container can hold, before we have to resize
         item_counter            m_ItemCounter;      ///< Item counter
         hash                    m_HashFunctor;      ///< Hash functor
         stat                    m_Stat;             ///< Internal statistics
@@ -253,13 +256,28 @@ namespace cds { namespace intrusive {
             m_Buckets.bucket( 0, pNode );
         }
 
-        void    inc_item_count()
+        static size_t max_item_count( size_t nBucketCount, size_t nLoadFactor )
+        {
+            return nBucketCount * nLoadFactor;
+        }
+
+        void inc_item_count()
         {
+            size_t nMaxCount = m_nMaxItemCount.load(memory_model::memory_order_relaxed);
+            if ( ++m_ItemCounter <= nMaxCount )
+                return;
+
+            const size_t nLoadFactor = m_Buckets.load_factor();
             size_t sz = m_nBucketCountLog2.load(memory_model::memory_order_relaxed);
-            if ( ( ++m_ItemCounter >> sz ) > m_Buckets.load_factor() && ((size_t)(1 << sz )) < m_Buckets.capacity() )
-            {
-                m_nBucketCountLog2.compare_exchange_strong( sz, sz + 1, memory_model::memory_order_relaxed, atomics::memory_order_relaxed );
-            }
+            const size_t nBucketCount = static_cast<size_t>(1) << sz;
+            if ( nMaxCount < max_item_count( nBucketCount, nLoadFactor ))
+                return; // someone already have updated m_nBucketCountLog2, so stop here
+
+            const size_t nNewMaxCount = (nBucketCount < m_Buckets.capacity()) ? max_item_count( nBucketCount << 1, nLoadFactor )
+                                                                              : std::numeric_limits<size_t>::max();
+            m_nMaxItemCount.compare_exchange_strong( nMaxCount, nNewMaxCount, memory_model::memory_order_relaxed,
+                memory_model::memory_order_relaxed );
+            m_nBucketCountLog2.compare_exchange_strong( sz, sz + 1, memory_model::memory_order_seq_cst, memory_model::memory_order_relaxed );
         }
 
         //@endcond
@@ -273,6 +291,7 @@ namespace cds { namespace intrusive {
         */
         SplitListSet()
             : m_nBucketCountLog2(1)
+            , m_nMaxItemCount( max_item_count(2, m_Buckets.load_factor()) )
         {
             init();
         }
@@ -284,6 +303,7 @@ namespace cds { namespace intrusive {
             )
             : m_Buckets( nItemCount, nLoadFactor )
             , m_nBucketCountLog2(1)
+            , m_nMaxItemCount( max_item_count(2, m_Buckets.load_factor()) )
         {
             init();
         }

diff --git a/cds/intrusive/split_list_rcu.h b/cds/intrusive/split_list_rcu.h
index 8a7916b41817e22604a169b4496e7f2a7c6da4ef..f83bd7d26c2083c20ad06db9adf8f98a808029ca 100644 (file)
--- a/cds/intrusive/split_list_rcu.h
+++ b/cds/intrusive/split_list_rcu.h
@@ -5,6 +5,7 @@
 
 #include <cds/intrusive/details/split_list_base.h>
 #include <cds/details/binary_functor_wrapper.h>
+#include <limits>
 
 namespace cds { namespace intrusive {
 
@@ -241,6 +242,7 @@ namespace cds { namespace intrusive {
         ordered_list_wrapper    m_List;             ///< Ordered list containing split-list items
         bucket_table            m_Buckets;          ///< bucket table
         atomics::atomic<size_t> m_nBucketCountLog2; ///< log2( current bucket count )
+        atomics::atomic<size_t> m_nMaxItemCount;    ///< number of items container can hold, before we have to resize
         item_counter            m_ItemCounter;      ///< Item counter
         hash                    m_HashFunctor;      ///< Hash functor
         stat                    m_Stat;             ///< Internal stattistics accumulator
@@ -350,13 +352,28 @@ namespace cds { namespace intrusive {
             m_Buckets.bucket( 0, pNode );
         }
 
-        void    inc_item_count()
+        static size_t max_item_count( size_t nBucketCount, size_t nLoadFactor )
         {
+            return nBucketCount * nLoadFactor;
+        }
+
+        void inc_item_count()
+        {
+            size_t nMaxCount = m_nMaxItemCount.load(memory_model::memory_order_relaxed);
+            if ( ++m_ItemCounter <= nMaxCount )
+                return;
+
+            const size_t nLoadFactor = m_Buckets.load_factor();
             size_t sz = m_nBucketCountLog2.load(memory_model::memory_order_relaxed);
-            if ( ( ++m_ItemCounter >> sz ) > m_Buckets.load_factor() && ((size_t)(1 << sz )) < m_Buckets.capacity() )
-            {
-                m_nBucketCountLog2.compare_exchange_strong( sz, sz + 1, memory_model::memory_order_relaxed, atomics::memory_order_relaxed );
-            }
+            const size_t nBucketCount = static_cast<size_t>(1) << sz;
+            if ( nMaxCount < max_item_count( nBucketCount, nLoadFactor ))
+                return; // someone already have updated m_nBucketCountLog2, so stop here
+
+            const size_t nNewMaxCount = (nBucketCount < m_Buckets.capacity()) ? max_item_count( nBucketCount << 1, nLoadFactor )
+                                                                              : std::numeric_limits<size_t>::max();
+            m_nMaxItemCount.compare_exchange_strong( nMaxCount, nNewMaxCount, memory_model::memory_order_relaxed,
+                memory_model::memory_order_relaxed );
+            m_nBucketCountLog2.compare_exchange_strong( sz, sz + 1, memory_model::memory_order_seq_cst, memory_model::memory_order_relaxed );
         }
 
         template <typename Q, typename Compare, typename Func>
@@ -465,6 +482,7 @@ namespace cds { namespace intrusive {
         */
         SplitListSet()
             : m_nBucketCountLog2(1)
+            , m_nMaxItemCount( max_item_count(2, m_Buckets.load_factor()) )
         {
             init();
         }
@@ -476,6 +494,7 @@ namespace cds { namespace intrusive {
             )
             : m_Buckets( nItemCount, nLoadFactor )
             , m_nBucketCountLog2(1)
+            , m_nMaxItemCount( max_item_count(2, m_Buckets.load_factor()) )
         {
             init();
         }