Revamp BList somewhat to further optimize the resizing behavior.

We now keep track of a lower bound as to when the list should scale
itself back down. When increasing the list size, we double the current,
with the lower bound set to 1/4 of the current size, not allowing it to
go any smaller than the block size. These combined allow us to do very
cheap tests to see if an operation requires a resize at all, and minimize
how often the list actually needs to be resized, since the difference in upper
and lower bounds prevents bouncing back and forth between a size in the case
of adding/removing an item while close to a boundary. All in all this should
make BList noticably more scalable when doing large numbers of add/remove
operations.



git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25946 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/os/support/List.h

@@ -56,14 +56,14 @@ class BList {
 		virtual void _ReservedList1();
 		virtual void _ReservedList2();
 
-		bool Resize(int32 count);
-
+		bool _ResizeArray(int32 count);
 	private:
 		void**	fObjectList;
-		size_t	fPhysicalSize;
+		int32	fPhysicalSize;
 		int32	fItemCount;
 		int32	fBlockSize;
-		uint32	_reserved[2];
+		int32	fResizeThreshold;
+		uint32	_reserved[1];
 };
 
 #endif // _BE_LIST_H