AVL trees, red-black trees, and others. Weak AVL (wavl) trees are a
recently discovered member of that class. This change replaces
red-black rebalancing with weak AVL rebalancing in the RB tree macros.
Wavl trees sit between AVL and red-black trees in terms of how
strictly balance is enforced. They have the stricter balance of AVL
trees as the tree is built - a wavl tree is an AVL tree until the
first deletion. Once removals start, wavl trees are lazier about
rebalancing than AVL trees, so that removals can be fast, but the
balance of the tree can decay to that of a red-black tree. Subsequent
insertions can push balance back toward the stricter AVL conditions.
Removing a node from a wavl tree never requires more than two
rotations, which is better than either red-black or AVL
trees. Inserting a node into a wavl tree never requires more than two
rotations, which matches red-black and AVL trees. The only
disadvantage of wavl trees to red-black trees is that more insertions
are likely to adjust the tree a bit. That's the cost of keeping the
tree more balanced.
Testing has shown that for the cases where red-black trees do worst,
wavl trees better balance leads to faster lookups, so that if lookups
outnumber insertions by a nontrivial amount, lookup time saved exceeds
the extra cost of balancing.
Reviewed by: alc, gbe, markj
Tested by: pho
Discussed with: emaste
Differential Revision: https://reviews.freebsd.org/D25480
and reinserting it back with an updated key.
This is one of dependencies for the upcoming stats(3) code.
Reviewed by: cem
Obtained from: Netflix
MFC after: 2 weeks
Sponsored by: Klara Inc, Netflix
Differential Revision: https://reviews.freebsd.org/D21786
to the traditional tree(3) RB trees, but using an array (preallocated,
linear chunk of memory) to store the tree.
This avoids allocation overhead, improves memory locality,
and makes it trivially easy to share/transfer/copy the entire tree
without the need for marshalling. The downside is that the size
is fixed at initialization time; there is no mechanism to resize
it.
This is one of the dependencies for the new stats(3) framework
(https://reviews.freebsd.org/D20477).
Reviewed by: bcr (man pages), markj
Discussed with: cem
MFC after: 2 weeks
Sponsored by: Klara Inc, Netflix
Obtained from: Netflix
Differential Revision: https://reviews.freebsd.org/D20324
This helps to reduce code size in statically linked applications.
Submitted by: Sebastian Huber <sebastian.huber@embedded-brains.de>
MFC after: 2 weeks
These are largely syntactic sugar. However, they improve code
readability where an RB_FOREACH() or RB_FOREACH_REVERSE()
traversal has been interrupted and must be resumed. Performance
is improved by avoiding unnecessary traversal from the head node.
