diff --git a/bricks/brick-hashset b/bricks/brick-hashset
index cb84804f6..5e8c3b90b 100644
--- a/bricks/brick-hashset
+++ b/bricks/brick-hashset
@@ -43,7 +43,8 @@ using hash::hash128_t;
 
 struct DefaultHasher
 {
-    auto hash( int64_t v ) const -> std::pair<int64_t, int64_t>
+    //    auto hash( int64_t v ) const -> std::pair<int64_t, int64_t>
+    auto hash( int64_t v ) const
     {
         return std::make_pair( v, ~v );
     }
@@ -85,7 +86,7 @@ struct FastCell : CellBase< T, Hasher >
     hash64_t _hash;
 
     template< typename Value >
-    bool is( Value v, hash64_t hash, Hasher &h ) {
+    bool is( const Value &v, hash64_t hash, Hasher &h ) {
         return _hash == hash && h.equal( _value, v );
     }
 
@@ -106,7 +107,7 @@ struct CompactCell : CellBase< T, Hasher >
     T _value;
 
     template< typename Value >
-    bool is( Value v, hash64_t, Hasher &h ) {
+    bool is( const Value &v, hash64_t, Hasher &h ) {
         return h.equal( _value, v );
     }
 
@@ -165,7 +166,7 @@ struct FastAtomicCell : CellBase< T, Hasher >
     }
 
     template< typename Value >
-    bool is( Value v, hash64_t hash, Hasher &h ) {
+    bool is( const Value &v, hash64_t hash, Hasher &h ) {
         hash |= 0x1;
         if ( ( (hash << 2) | 1) != (_hashlock | 1) )
             return false;
@@ -248,7 +249,7 @@ struct AtomicCell : CellBase< T, Hasher >
     }
 
     template< typename Value >
-    bool is( Value v, hash64_t hash, Hasher &h ) {
+    bool is( const Value &v, hash64_t hash, Hasher &h ) {
         return value.load().tag() == ( highbits( hash, Tagged< T >::tag_bits ) | 1 ) &&
             h.equal( value.load().t, v );
     }
@@ -606,7 +607,7 @@ struct _ConcurrentHashSet : HashSetBase< Cell >
     }
 
     template< typename T >
-    iterator find( T x ) {
+    iterator find( const T &x ) {
         return findHinted( x, hasher.hash( x ).first );
     }
 
@@ -641,7 +642,7 @@ struct _ConcurrentHashSet : HashSetBase< Cell >
     }
 
     template< typename T >
-    iterator findHinted( T x, hash64_t h ) {
+    iterator findHinted( const T &x, hash64_t h ) {
         while ( true ) {
             Find fr = findCell( x, h, _l.currentRow );
             switch ( fr.r ) {
@@ -661,7 +662,7 @@ struct _ConcurrentHashSet : HashSetBase< Cell >
     }
 
     template< typename T >
-    Find findCell( T v, hash64_t h, unsigned rowIndex )
+    Find findCell( const T &v, hash64_t h, unsigned rowIndex )
     {
         if ( changed( rowIndex ) )
             return Find( Resolution::Growing );
@@ -848,13 +849,20 @@ struct _ConcurrentHashSet : HashSetBase< Cell >
         } while( true );
     }
 
-    void increaseUsage() {
-        if ( ++_l.inserts == syncPoint ) {
-            _s->used.fetch_add( syncPoint, std::memory_order_relaxed );
-            _l.inserts = 0;
-        }
+    void increaseUsage()
+    {
+        if ( ++_l.inserts == syncPoint )
+            updateUsage();
     }
 
+    void updateUsage()
+    {
+        _s->used.fetch_add( _l.inserts, std::memory_order_relaxed );
+        _l.inserts = 0;
+    }
+
+    ~_ConcurrentHashSet() { updateUsage(); }
+
     explicit _ConcurrentHashSet( Hasher h = Hasher(), unsigned maxGrows = 64 )
         : Base( h ), _s( new Shared( maxGrows ) )
     {