MINOR: ebtree: implement eb32sc_lookup_ge_or_first()
In the scheduler we always have to loop back to the beginning after
we don't find the last entry, so let's implement this in a new lookup
function instead. The resulting code is slightly faster, mostly due
to the fact that there's much less inlined code in the fast path.
diff --git a/ebtree/eb32sctree.c b/ebtree/eb32sctree.c
index 559c6a6..4f48d58 100644
--- a/ebtree/eb32sctree.c
+++ b/ebtree/eb32sctree.c
@@ -323,6 +323,97 @@
//}
}
+/*
+ * Find the first occurrence of the lowest key in the tree <root> which is
+ * equal to or greater than <x>, matching scope <scope>. If not found, it loops
+ * back to the beginning of the tree. NULL is returned is no key matches.
+ */
+REGPRM2 struct eb32sc_node *eb32sc_lookup_ge_or_first(struct eb_root *root, u32 x, unsigned long scope)
+{
+ struct eb32sc_node *eb32;
+ eb_troot_t *troot;
+ struct eb_root *curr;
+
+ troot = root->b[EB_LEFT];
+ if (unlikely(troot == NULL))
+ return NULL;
+
+ while (1) {
+ if ((eb_gettag(troot) == EB_LEAF)) {
+ /* We reached a leaf, which means that the whole upper
+ * parts were common. We will return either the current
+ * node or its next one if the former is too small.
+ */
+ eb32 = container_of(eb_untag(troot, EB_LEAF),
+ struct eb32sc_node, node.branches);
+ if ((eb32->leaf_s & scope) && eb32->key >= x)
+ return eb32;
+ /* return next */
+ troot = eb32->node.leaf_p;
+ break;
+ }
+ eb32 = container_of(eb_untag(troot, EB_NODE),
+ struct eb32sc_node, node.branches);
+
+ if (eb32->node.bit < 0) {
+ /* We're at the top of a dup tree. Either we got a
+ * matching value and we return the leftmost node, or
+ * we don't and we skip the whole subtree to return the
+ * next node after the subtree. Note that since we're
+ * at the top of the dup tree, we can simply return the
+ * next node without first trying to escape from the
+ * tree.
+ */
+ if ((eb32->node_s & scope) && eb32->key >= x)
+ troot = eb_dotag(&eb32->node.branches, EB_LEFT);
+ else
+ troot = eb32->node.node_p;
+ break;
+ }
+
+ if (((x ^ eb32->key) >> eb32->node.bit) >= EB_NODE_BRANCHES) {
+ /* No more common bits at all. Either this node is too
+ * large and we need to get its lowest value, or it is too
+ * small, and we need to get the next value.
+ */
+ if ((eb32->node_s & scope) && (eb32->key >> eb32->node.bit) > (x >> eb32->node.bit))
+ troot = eb_dotag(&eb32->node.branches, EB_LEFT);
+ else
+ troot = eb32->node.node_p;
+ break;
+ }
+ troot = eb32->node.branches.b[(x >> eb32->node.bit) & EB_NODE_BRANCH_MASK];
+ }
+
+ /* If we get here, it means we want to report next node after the
+ * current one which is not below. <troot> is already initialised
+ * to the parent's branches.
+ */
+ for (eb32 = NULL; !eb32; troot = eb_root_to_node(curr)->node_p) {
+ if (eb_gettag(troot) != EB_LEFT) {
+ curr = eb_untag(troot, EB_RGHT);
+ continue;
+ }
+
+ /* troot points to the branch location we're attached to by the
+ * left above, set curr to the corresponding eb_root.
+ */
+ curr = eb_untag(troot, EB_LEFT);
+
+ /* and go down by the right, but stop at the root */
+ troot = curr->b[EB_RGHT];
+ if (!eb_clrtag(troot))
+ break;
+
+ eb32 = eb32sc_walk_down_left(troot, scope);
+ }
+
+ if (!eb32)
+ eb32 = eb32sc_walk_down_left(root->b[EB_LEFT], scope);
+
+ return eb32;
+}
+
/* Removes a leaf node from the tree if it was still in it. Marks the node
* as unlinked.
*/