Quoting Momchil Velikov (velco@fadata.bg):
> >>>>> "John" == John Stoffel <stoffel@casc.com> writes:
>
> Momchil> Memory overhead due to allocator overhead is of no concern with the
> Momchil> slab allocator. What matters most is probably the overhead of the
> Momchil> radix tree nodes themselves, compared to the two pointers in struct
> Momchil> page with the hash table approach. rat-4 variant ought to have less
> Momchil> overhead compared to rat-7 at the expense of deeper/higher tree. I
> Momchil> have no figures for the actual memory usage though. For small files it
> Momchil> should be negligible, i.e. one radix tree node, 68 or 516 bytes for
> Momchil> rat-4 or rat-7, for a file of size up to 65536 or 524288 bytes. The
> Momchil> worst case would be very large file with a few cached pages with
> Momchil> offsets uniformly distributed across the whole file, that is having
> Momchil> deep tree with only one page hanging off each leaf node.
>
> John> Isn't this a good place to use AVL trees then, since they balance
> John> automatically? Admittedly, it may be more overhead than we want in
> John> the case where the tree is balanced by default anyway.
>
> The widespread opinion is that binary trees are generally way too deep
> compared to radix trees, so searches have larger cache footprint.
I've posted this before -- my cache-optimized skip list solves the
problem of balanced-tree cache footprint. It uses cacheline-sized
nodes and per-node locking to avoid false-sharing and increase
concurrency. The memory usage for the skip list is also less than
the red-black tree for trees larger than several hundred nodes.
I posted a graph on space consumption (using the Linux vm_area_struct to
calculate space overhead) at:
http://prdownloads.sourceforge.net/skiplist/slrb_space.gif
There are also results for concurrency and performance as a function
of node size.
-josh
-- PRCS version control system http://sourceforge.net/projects/prcs Xdelta storage & transport http://sourceforge.net/projects/xdelta Need a concurrent skip list? http://sourceforge.net/projects/skiplist - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu Jan 31 2002 - 21:01:33 EST
