17afb853ee
also refresh generic patches for 3.14, 3.18, 3.19 and 4.0 targets might need a minor refresh as well, however, it looks like everything still applies cleanly with occasional small offsets. Signed-off-by: Daniel Golle <daniel@makrotopia.org> SVN-Revision: 44876
250 lines
8.1 KiB
Diff
250 lines
8.1 KiB
Diff
From: Alexander Duyck <alexander.h.duyck@redhat.com>
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Date: Wed, 31 Dec 2014 10:56:37 -0800
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Subject: [PATCH] fib_trie: Add functions should_inflate and should_halve
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This change pulls the logic for if we should inflate/halve the nodes out
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into separate functions. It also addresses what I believe is a bug where 1
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full node is all that is needed to keep a node from ever being halved.
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Simple script to reproduce the issue:
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modprobe dummy; ifconfig dummy0 up
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for i in `seq 0 255`; do ifconfig dummy0:$i 10.0.${i}.1/24 up; done
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ifconfig dummy0:256 10.0.255.33/16 up
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for i in `seq 0 254`; do ifconfig dummy0:$i down; done
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Results from /proc/net/fib_triestat
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Before:
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Local:
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Aver depth: 3.00
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Max depth: 4
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Leaves: 17
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Prefixes: 18
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Internal nodes: 11
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1: 8 2: 2 10: 1
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Pointers: 1048
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Null ptrs: 1021
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Total size: 11 kB
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After:
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Local:
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Aver depth: 3.41
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Max depth: 5
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Leaves: 17
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Prefixes: 18
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Internal nodes: 12
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1: 8 2: 3 3: 1
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Pointers: 36
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Null ptrs: 8
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Total size: 3 kB
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Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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--- a/net/ipv4/fib_trie.c
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+++ b/net/ipv4/fib_trie.c
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@@ -647,12 +647,94 @@ nomem:
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return ERR_PTR(-ENOMEM);
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}
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+/* From "Implementing a dynamic compressed trie" by Stefan Nilsson of
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+ * the Helsinki University of Technology and Matti Tikkanen of Nokia
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+ * Telecommunications, page 6:
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+ * "A node is doubled if the ratio of non-empty children to all
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+ * children in the *doubled* node is at least 'high'."
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+ *
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+ * 'high' in this instance is the variable 'inflate_threshold'. It
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+ * is expressed as a percentage, so we multiply it with
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+ * tnode_child_length() and instead of multiplying by 2 (since the
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+ * child array will be doubled by inflate()) and multiplying
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+ * the left-hand side by 100 (to handle the percentage thing) we
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+ * multiply the left-hand side by 50.
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+ *
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+ * The left-hand side may look a bit weird: tnode_child_length(tn)
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+ * - tn->empty_children is of course the number of non-null children
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+ * in the current node. tn->full_children is the number of "full"
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+ * children, that is non-null tnodes with a skip value of 0.
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+ * All of those will be doubled in the resulting inflated tnode, so
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+ * we just count them one extra time here.
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+ *
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+ * A clearer way to write this would be:
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+ *
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+ * to_be_doubled = tn->full_children;
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+ * not_to_be_doubled = tnode_child_length(tn) - tn->empty_children -
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+ * tn->full_children;
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+ *
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+ * new_child_length = tnode_child_length(tn) * 2;
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+ *
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+ * new_fill_factor = 100 * (not_to_be_doubled + 2*to_be_doubled) /
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+ * new_child_length;
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+ * if (new_fill_factor >= inflate_threshold)
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+ *
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+ * ...and so on, tho it would mess up the while () loop.
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+ *
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+ * anyway,
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+ * 100 * (not_to_be_doubled + 2*to_be_doubled) / new_child_length >=
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+ * inflate_threshold
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+ *
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+ * avoid a division:
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+ * 100 * (not_to_be_doubled + 2*to_be_doubled) >=
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+ * inflate_threshold * new_child_length
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+ *
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+ * expand not_to_be_doubled and to_be_doubled, and shorten:
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+ * 100 * (tnode_child_length(tn) - tn->empty_children +
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+ * tn->full_children) >= inflate_threshold * new_child_length
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+ *
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+ * expand new_child_length:
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+ * 100 * (tnode_child_length(tn) - tn->empty_children +
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+ * tn->full_children) >=
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+ * inflate_threshold * tnode_child_length(tn) * 2
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+ *
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+ * shorten again:
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+ * 50 * (tn->full_children + tnode_child_length(tn) -
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+ * tn->empty_children) >= inflate_threshold *
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+ * tnode_child_length(tn)
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+ *
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+ */
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+static bool should_inflate(const struct tnode *tn)
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+{
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+ unsigned long used = tnode_child_length(tn);
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+ unsigned long threshold = used;
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+
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+ /* Keep root node larger */
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+ threshold *= node_parent(tn) ? inflate_threshold :
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+ inflate_threshold_root;
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+ used += tn->full_children;
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+ used -= tn->empty_children;
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+
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+ return tn->pos && ((50 * used) >= threshold);
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+}
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+
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+static bool should_halve(const struct tnode *tn)
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+{
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+ unsigned long used = tnode_child_length(tn);
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+ unsigned long threshold = used;
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+
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+ /* Keep root node larger */
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+ threshold *= node_parent(tn) ? halve_threshold :
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+ halve_threshold_root;
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+ used -= tn->empty_children;
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+
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+ return (tn->bits > 1) && ((100 * used) < threshold);
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+}
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+
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#define MAX_WORK 10
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static struct tnode *resize(struct trie *t, struct tnode *tn)
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{
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struct tnode *old_tn, *n = NULL;
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- int inflate_threshold_use;
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- int halve_threshold_use;
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int max_work;
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if (!tn)
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@@ -668,86 +750,12 @@ static struct tnode *resize(struct trie
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/* One child */
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if (tn->empty_children == (tnode_child_length(tn) - 1))
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goto one_child;
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- /*
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- * Double as long as the resulting node has a number of
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- * nonempty nodes that are above the threshold.
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- */
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- /*
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- * From "Implementing a dynamic compressed trie" by Stefan Nilsson of
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- * the Helsinki University of Technology and Matti Tikkanen of Nokia
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- * Telecommunications, page 6:
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- * "A node is doubled if the ratio of non-empty children to all
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- * children in the *doubled* node is at least 'high'."
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- *
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- * 'high' in this instance is the variable 'inflate_threshold'. It
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- * is expressed as a percentage, so we multiply it with
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- * tnode_child_length() and instead of multiplying by 2 (since the
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- * child array will be doubled by inflate()) and multiplying
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- * the left-hand side by 100 (to handle the percentage thing) we
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- * multiply the left-hand side by 50.
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- *
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- * The left-hand side may look a bit weird: tnode_child_length(tn)
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- * - tn->empty_children is of course the number of non-null children
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- * in the current node. tn->full_children is the number of "full"
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- * children, that is non-null tnodes with a skip value of 0.
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- * All of those will be doubled in the resulting inflated tnode, so
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- * we just count them one extra time here.
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- *
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- * A clearer way to write this would be:
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- *
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- * to_be_doubled = tn->full_children;
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- * not_to_be_doubled = tnode_child_length(tn) - tn->empty_children -
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- * tn->full_children;
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- *
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- * new_child_length = tnode_child_length(tn) * 2;
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- *
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- * new_fill_factor = 100 * (not_to_be_doubled + 2*to_be_doubled) /
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- * new_child_length;
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- * if (new_fill_factor >= inflate_threshold)
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- *
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- * ...and so on, tho it would mess up the while () loop.
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- *
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- * anyway,
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- * 100 * (not_to_be_doubled + 2*to_be_doubled) / new_child_length >=
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- * inflate_threshold
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- *
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- * avoid a division:
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- * 100 * (not_to_be_doubled + 2*to_be_doubled) >=
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- * inflate_threshold * new_child_length
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- *
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- * expand not_to_be_doubled and to_be_doubled, and shorten:
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- * 100 * (tnode_child_length(tn) - tn->empty_children +
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- * tn->full_children) >= inflate_threshold * new_child_length
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- *
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- * expand new_child_length:
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- * 100 * (tnode_child_length(tn) - tn->empty_children +
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- * tn->full_children) >=
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- * inflate_threshold * tnode_child_length(tn) * 2
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- *
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- * shorten again:
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- * 50 * (tn->full_children + tnode_child_length(tn) -
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- * tn->empty_children) >= inflate_threshold *
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- * tnode_child_length(tn)
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- *
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+ /* Double as long as the resulting node has a number of
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+ * nonempty nodes that are above the threshold.
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*/
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-
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- /* Keep root node larger */
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-
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- if (!node_parent(tn)) {
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- inflate_threshold_use = inflate_threshold_root;
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- halve_threshold_use = halve_threshold_root;
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- } else {
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- inflate_threshold_use = inflate_threshold;
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- halve_threshold_use = halve_threshold;
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- }
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-
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max_work = MAX_WORK;
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- while ((tn->full_children > 0 && max_work-- &&
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- 50 * (tn->full_children + tnode_child_length(tn)
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- - tn->empty_children)
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- >= inflate_threshold_use * tnode_child_length(tn))) {
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-
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+ while (should_inflate(tn) && max_work--) {
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old_tn = tn;
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tn = inflate(t, tn);
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@@ -764,16 +772,11 @@ static struct tnode *resize(struct trie
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if (max_work != MAX_WORK)
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return tn;
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- /*
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- * Halve as long as the number of empty children in this
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+ /* Halve as long as the number of empty children in this
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* node is above threshold.
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*/
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-
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max_work = MAX_WORK;
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- while (tn->bits > 1 && max_work-- &&
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- 100 * (tnode_child_length(tn) - tn->empty_children) <
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- halve_threshold_use * tnode_child_length(tn)) {
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-
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+ while (should_halve(tn) && max_work--) {
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old_tn = tn;
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tn = halve(t, tn);
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if (IS_ERR(tn)) {
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