+++ /dev/null
-From: Alexander Duyck <alexander.h.duyck@redhat.com>
-Date: Wed, 31 Dec 2014 10:56:37 -0800
-Subject: [PATCH] fib_trie: Add functions should_inflate and should_halve
-
-This change pulls the logic for if we should inflate/halve the nodes out
-into separate functions. It also addresses what I believe is a bug where 1
-full node is all that is needed to keep a node from ever being halved.
-
-Simple script to reproduce the issue:
- modprobe dummy; ifconfig dummy0 up
- for i in `seq 0 255`; do ifconfig dummy0:$i 10.0.${i}.1/24 up; done
- ifconfig dummy0:256 10.0.255.33/16 up
- for i in `seq 0 254`; do ifconfig dummy0:$i down; done
-
-Results from /proc/net/fib_triestat
-Before:
- Local:
- Aver depth: 3.00
- Max depth: 4
- Leaves: 17
- Prefixes: 18
- Internal nodes: 11
- 1: 8 2: 2 10: 1
- Pointers: 1048
- Null ptrs: 1021
- Total size: 11 kB
-After:
- Local:
- Aver depth: 3.41
- Max depth: 5
- Leaves: 17
- Prefixes: 18
- Internal nodes: 12
- 1: 8 2: 3 3: 1
- Pointers: 36
- Null ptrs: 8
- Total size: 3 kB
-
-Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
-Signed-off-by: David S. Miller <davem@davemloft.net>
----
-
---- a/net/ipv4/fib_trie.c
-+++ b/net/ipv4/fib_trie.c
-@@ -647,12 +647,94 @@ nomem:
- return ERR_PTR(-ENOMEM);
- }
-
-+/* From "Implementing a dynamic compressed trie" by Stefan Nilsson of
-+ * the Helsinki University of Technology and Matti Tikkanen of Nokia
-+ * Telecommunications, page 6:
-+ * "A node is doubled if the ratio of non-empty children to all
-+ * children in the *doubled* node is at least 'high'."
-+ *
-+ * 'high' in this instance is the variable 'inflate_threshold'. It
-+ * is expressed as a percentage, so we multiply it with
-+ * tnode_child_length() and instead of multiplying by 2 (since the
-+ * child array will be doubled by inflate()) and multiplying
-+ * the left-hand side by 100 (to handle the percentage thing) we
-+ * multiply the left-hand side by 50.
-+ *
-+ * The left-hand side may look a bit weird: tnode_child_length(tn)
-+ * - tn->empty_children is of course the number of non-null children
-+ * in the current node. tn->full_children is the number of "full"
-+ * children, that is non-null tnodes with a skip value of 0.
-+ * All of those will be doubled in the resulting inflated tnode, so
-+ * we just count them one extra time here.
-+ *
-+ * A clearer way to write this would be:
-+ *
-+ * to_be_doubled = tn->full_children;
-+ * not_to_be_doubled = tnode_child_length(tn) - tn->empty_children -
-+ * tn->full_children;
-+ *
-+ * new_child_length = tnode_child_length(tn) * 2;
-+ *
-+ * new_fill_factor = 100 * (not_to_be_doubled + 2*to_be_doubled) /
-+ * new_child_length;
-+ * if (new_fill_factor >= inflate_threshold)
-+ *
-+ * ...and so on, tho it would mess up the while () loop.
-+ *
-+ * anyway,
-+ * 100 * (not_to_be_doubled + 2*to_be_doubled) / new_child_length >=
-+ * inflate_threshold
-+ *
-+ * avoid a division:
-+ * 100 * (not_to_be_doubled + 2*to_be_doubled) >=
-+ * inflate_threshold * new_child_length
-+ *
-+ * expand not_to_be_doubled and to_be_doubled, and shorten:
-+ * 100 * (tnode_child_length(tn) - tn->empty_children +
-+ * tn->full_children) >= inflate_threshold * new_child_length
-+ *
-+ * expand new_child_length:
-+ * 100 * (tnode_child_length(tn) - tn->empty_children +
-+ * tn->full_children) >=
-+ * inflate_threshold * tnode_child_length(tn) * 2
-+ *
-+ * shorten again:
-+ * 50 * (tn->full_children + tnode_child_length(tn) -
-+ * tn->empty_children) >= inflate_threshold *
-+ * tnode_child_length(tn)
-+ *
-+ */
-+static bool should_inflate(const struct tnode *tn)
-+{
-+ unsigned long used = tnode_child_length(tn);
-+ unsigned long threshold = used;
-+
-+ /* Keep root node larger */
-+ threshold *= node_parent(tn) ? inflate_threshold :
-+ inflate_threshold_root;
-+ used += tn->full_children;
-+ used -= tn->empty_children;
-+
-+ return tn->pos && ((50 * used) >= threshold);
-+}
-+
-+static bool should_halve(const struct tnode *tn)
-+{
-+ unsigned long used = tnode_child_length(tn);
-+ unsigned long threshold = used;
-+
-+ /* Keep root node larger */
-+ threshold *= node_parent(tn) ? halve_threshold :
-+ halve_threshold_root;
-+ used -= tn->empty_children;
-+
-+ return (tn->bits > 1) && ((100 * used) < threshold);
-+}
-+
- #define MAX_WORK 10
- static struct tnode *resize(struct trie *t, struct tnode *tn)
- {
- struct tnode *old_tn, *n = NULL;
-- int inflate_threshold_use;
-- int halve_threshold_use;
- int max_work;
-
- if (!tn)
-@@ -668,86 +750,12 @@ static struct tnode *resize(struct trie
- /* One child */
- if (tn->empty_children == (tnode_child_length(tn) - 1))
- goto one_child;
-- /*
-- * Double as long as the resulting node has a number of
-- * nonempty nodes that are above the threshold.
-- */
-
-- /*
-- * From "Implementing a dynamic compressed trie" by Stefan Nilsson of
-- * the Helsinki University of Technology and Matti Tikkanen of Nokia
-- * Telecommunications, page 6:
-- * "A node is doubled if the ratio of non-empty children to all
-- * children in the *doubled* node is at least 'high'."
-- *
-- * 'high' in this instance is the variable 'inflate_threshold'. It
-- * is expressed as a percentage, so we multiply it with
-- * tnode_child_length() and instead of multiplying by 2 (since the
-- * child array will be doubled by inflate()) and multiplying
-- * the left-hand side by 100 (to handle the percentage thing) we
-- * multiply the left-hand side by 50.
-- *
-- * The left-hand side may look a bit weird: tnode_child_length(tn)
-- * - tn->empty_children is of course the number of non-null children
-- * in the current node. tn->full_children is the number of "full"
-- * children, that is non-null tnodes with a skip value of 0.
-- * All of those will be doubled in the resulting inflated tnode, so
-- * we just count them one extra time here.
-- *
-- * A clearer way to write this would be:
-- *
-- * to_be_doubled = tn->full_children;
-- * not_to_be_doubled = tnode_child_length(tn) - tn->empty_children -
-- * tn->full_children;
-- *
-- * new_child_length = tnode_child_length(tn) * 2;
-- *
-- * new_fill_factor = 100 * (not_to_be_doubled + 2*to_be_doubled) /
-- * new_child_length;
-- * if (new_fill_factor >= inflate_threshold)
-- *
-- * ...and so on, tho it would mess up the while () loop.
-- *
-- * anyway,
-- * 100 * (not_to_be_doubled + 2*to_be_doubled) / new_child_length >=
-- * inflate_threshold
-- *
-- * avoid a division:
-- * 100 * (not_to_be_doubled + 2*to_be_doubled) >=
-- * inflate_threshold * new_child_length
-- *
-- * expand not_to_be_doubled and to_be_doubled, and shorten:
-- * 100 * (tnode_child_length(tn) - tn->empty_children +
-- * tn->full_children) >= inflate_threshold * new_child_length
-- *
-- * expand new_child_length:
-- * 100 * (tnode_child_length(tn) - tn->empty_children +
-- * tn->full_children) >=
-- * inflate_threshold * tnode_child_length(tn) * 2
-- *
-- * shorten again:
-- * 50 * (tn->full_children + tnode_child_length(tn) -
-- * tn->empty_children) >= inflate_threshold *
-- * tnode_child_length(tn)
-- *
-+ /* Double as long as the resulting node has a number of
-+ * nonempty nodes that are above the threshold.
- */
--
-- /* Keep root node larger */
--
-- if (!node_parent(tn)) {
-- inflate_threshold_use = inflate_threshold_root;
-- halve_threshold_use = halve_threshold_root;
-- } else {
-- inflate_threshold_use = inflate_threshold;
-- halve_threshold_use = halve_threshold;
-- }
--
- max_work = MAX_WORK;
-- while ((tn->full_children > 0 && max_work-- &&
-- 50 * (tn->full_children + tnode_child_length(tn)
-- - tn->empty_children)
-- >= inflate_threshold_use * tnode_child_length(tn))) {
--
-+ while (should_inflate(tn) && max_work--) {
- old_tn = tn;
- tn = inflate(t, tn);
-
-@@ -764,16 +772,11 @@ static struct tnode *resize(struct trie
- if (max_work != MAX_WORK)
- return tn;
-
-- /*
-- * Halve as long as the number of empty children in this
-+ /* Halve as long as the number of empty children in this
- * node is above threshold.
- */
--
- max_work = MAX_WORK;
-- while (tn->bits > 1 && max_work-- &&
-- 100 * (tnode_child_length(tn) - tn->empty_children) <
-- halve_threshold_use * tnode_child_length(tn)) {
--
-+ while (should_halve(tn) && max_work--) {
- old_tn = tn;
- tn = halve(t, tn);
- if (IS_ERR(tn)) {
projects / openwrt / openwrt.git / blobdiff