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
|
|
@ -647,12 +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 *t, struct tnode *tn)
|
|||
/* 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
|
||||
|
||||
/* 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)
|
||||
*
|
||||
*/
|
||||
|
||||
/* 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 *t, struct tnode *tn)
|
|||
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)) {
|
||||
|
|
|
|||
Loading…
Reference in a new issue