prefetch btree nodes when walking a tree

persistent-data/block.h

@@ -55,11 +55,6 @@ namespace persistent_data {
 			      unsigned max_concurrent_locks,
 			      mode m);
 
-		enum block_type {
-			BT_SUPERBLOCK,
-			BT_NORMAL
-		};
-
 		typedef void (*put_behaviour_fn)(block_cache &, block_cache::block &);
 
 		class read_ref {
@@ -142,6 +137,7 @@ namespace persistent_data {
 
 		block_address get_nr_blocks() const;
 
+		void prefetch(block_address b) const;
 		void flush() const;
 
 

persistent-data/block.tcc

@@ -270,6 +270,13 @@ namespace persistent_data {
 		return bc_.get_nr_blocks();
 	}
 
+	template <uint32_t BlockSize>
+	void
+	block_manager<BlockSize>::prefetch(block_address b) const
+	{
+		bc_.prefetch(b);
+	}
+
 	template <uint32_t BlockSize>
 	void
 	block_manager<BlockSize>::flush() const

persistent-data/data-structures/btree.tcc

@@ -827,7 +827,10 @@ namespace persistent_data {
 
 		// FIXME: use a switch statement
 		if (o.get_type() == INTERNAL) {
-			if (v.visit_internal(loc, o))
+			if (v.visit_internal(loc, o)) {
+				for (unsigned i = 0; i < o.get_nr_entries(); i++)
+					tm_->prefetch(o.value_at(i));
+
 				for (unsigned i = 0; i < o.get_nr_entries(); i++) {
 					node_location loc2(loc);
 
@@ -836,6 +839,7 @@ namespace persistent_data {
 
 					walk_tree(v, loc2, o.value_at(i));
 				}
+			}
 
 		} else if (loc.path.size() < Levels - 1) {
 			if (v.visit_internal_leaf(loc, o))

persistent-data/transaction_manager.h

@@ -66,6 +66,10 @@ namespace persistent_data {
 			return bm_;
 		}
 
+		void prefetch(block_address b) {
+			bm_->prefetch(b);
+		}
+
 	private:
 		void add_shadow(block_address b);
 		void remove_shadow(block_address b);