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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>
This commit is contained in:
Alexander Duyck
David S. Miller
parent
cf3637bb8f
commit
f05a48198b
@ -647,34 +647,7 @@ nomem:
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return ERR_PTR(-ENOMEM);
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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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return NULL;
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pr_debug("In tnode_resize %p inflate_threshold=%d threshold=%d\n",
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tn, inflate_threshold, halve_threshold);
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/* No children */
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if (tn->empty_children > (tnode_child_length(tn) - 1))
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goto no_children;
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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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/* 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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@ -731,23 +704,58 @@ static struct tnode *resize(struct trie *t, struct tnode *tn)
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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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/* 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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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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return tn->pos && ((50 * used) >= threshold);
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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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/* 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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return (tn->bits > 1) && ((100 * used) < threshold);
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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 max_work;
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if (!tn)
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return NULL;
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pr_debug("In tnode_resize %p inflate_threshold=%d threshold=%d\n",
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tn, inflate_threshold, halve_threshold);
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/* No children */
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if (tn->empty_children > (tnode_child_length(tn) - 1))
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goto no_children;
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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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/* 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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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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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 *t, struct tnode *tn)
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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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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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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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