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Date: Fri, 21 Aug 2009 16:10:02 +0200
From: Robert Olsson <robert@...julf.net>
To: Jens Laas <jens.laas@....uu.se>
Cc: netdev@...r.kernel.org, robert@...julf.net
Subject: [PATCH net-next-2.6] fib_trie: resize rework
Jens Laas writes:
> Here is rework and cleanup of the resize function.
>
> Some bugs we had. We were using ->parent when we should use
> node_parent(). Also we used ->parent which is not assigned by
> inflate in inflate loop.
>
> Also a fix to set thresholds to power 2 to fit halve
> and double strategy.
>
> max_resize is renamed to max_work which better indicates
> it's function.
>
> Reaching max_work is not an error, so warning is removed.
> max_work only limits amount of work done per resize.
> (limits CPU-usage, outstanding memory etc).
>
> The clean-up makes it relatively easy to add fixed sized
> root-nodes if we would like to decrease the memory pressure
> on routers with large routing tables and dynamic routing.
> If we'll need that...
>
> Its been tested with 280k routes.
>
> Work done together with Robert Olsson.
>
> Signed-off-by: Jens Låås <jens.laas@....uu.se>
Right we think is a step forward. No performance differences seen
either for lookup or insert.
Signed-off-by: Robert Olsson <robert.olsson@....uu.se>
Cheers.
--ro
PS.
We see ~7 Gbit/s simplex routing w/o route cache using packet distribution
seen on core links. Using multiQ of course
> ---
> net/ipv4/fib_trie.c | 95 ++++++++++++--------------------------------------
> 1 files changed, 23 insertions(+), 72 deletions(-)
>
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index fe3c846..291bdf5 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
> @@ -48,7 +48,7 @@
> * Patrick McHardy <kaber@...sh.net>
> */
>
> -#define VERSION "0.408"
> +#define VERSION "0.409"
>
> #include <asm/uaccess.h>
> #include <asm/system.h>
> @@ -325,10 +325,7 @@ static inline void check_tnode(const struct tnode *tn)
> static const int halve_threshold = 25;
> static const int inflate_threshold = 50;
> static const int halve_threshold_root = 15;
> -static const int inflate_threshold_root = 25;
> -
> -static int inflate_threshold_root_fix;
> -#define INFLATE_FIX_MAX 10 /* a comment in resize() */
> +static const int inflate_threshold_root = 30;
>
> static void __alias_free_mem(struct rcu_head *head)
> {
> @@ -516,14 +513,14 @@ static void tnode_put_child_reorg(struct tnode *tn, int i, struct node *n,
> rcu_assign_pointer(tn->child[i], n);
> }
>
> +#define MAX_WORK 10
> static struct node *resize(struct trie *t, struct tnode *tn)
> {
> int i;
> - int err = 0;
> struct tnode *old_tn;
> int inflate_threshold_use;
> int halve_threshold_use;
> - int max_resize;
> + int max_work;
>
> if (!tn)
> return NULL;
> @@ -538,18 +535,7 @@ static struct node *resize(struct trie *t, struct tnode *tn)
> }
> /* One child */
> if (tn->empty_children == tnode_child_length(tn) - 1)
> - for (i = 0; i < tnode_child_length(tn); i++) {
> - struct node *n;
> -
> - n = tn->child[i];
> - if (!n)
> - continue;
> -
> - /* compress one level */
> - node_set_parent(n, NULL);
> - tnode_free_safe(tn);
> - return n;
> - }
> + goto one_child;
> /*
> * Double as long as the resulting node has a number of
> * nonempty nodes that are above the threshold.
> @@ -618,15 +604,17 @@ static struct node *resize(struct trie *t, struct tnode *tn)
>
> /* Keep root node larger */
>
> - if (!tn->parent)
> - inflate_threshold_use = inflate_threshold_root +
> - inflate_threshold_root_fix;
> - else
> + if (!node_parent((struct node*) tn)) {
> + inflate_threshold_use = inflate_threshold_root;
> + halve_threshold_use = halve_threshold_root;
> + }
> + else {
> inflate_threshold_use = inflate_threshold;
> + halve_threshold_use = halve_threshold;
> + }
>
> - err = 0;
> - max_resize = 10;
> - while ((tn->full_children > 0 && max_resize-- &&
> + 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))) {
> @@ -643,47 +631,19 @@ static struct node *resize(struct trie *t, struct tnode *tn)
> }
> }
>
> - if (max_resize < 0) {
> - if (!tn->parent) {
> - /*
> - * It was observed that during large updates even
> - * inflate_threshold_root = 35 might be needed to avoid
> - * this warning; but it should be temporary, so let's
> - * try to handle this automatically.
> - */
> - if (inflate_threshold_root_fix < INFLATE_FIX_MAX)
> - inflate_threshold_root_fix++;
> - else
> - pr_warning("Fix inflate_threshold_root."
> - " Now=%d size=%d bits fix=%d\n",
> - inflate_threshold_root, tn->bits,
> - inflate_threshold_root_fix);
> - } else {
> - pr_warning("Fix inflate_threshold."
> - " Now=%d size=%d bits\n",
> - inflate_threshold, tn->bits);
> - }
> - } else if (max_resize > 3 && !tn->parent && inflate_threshold_root_fix)
> - inflate_threshold_root_fix--;
> -
> check_tnode(tn);
>
> + /* Return if at least one inflate is run */
> + if( max_work != MAX_WORK)
> + return (struct node *) tn;
> +
> /*
> * Halve as long as the number of empty children in this
> * node is above threshold.
> */
>
> -
> - /* Keep root node larger */
> -
> - if (!tn->parent)
> - halve_threshold_use = halve_threshold_root;
> - else
> - halve_threshold_use = halve_threshold;
> -
> - err = 0;
> - max_resize = 10;
> - while (tn->bits > 1 && max_resize-- &&
> + 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)) {
>
> @@ -698,19 +658,10 @@ static struct node *resize(struct trie *t, struct tnode *tn)
> }
> }
>
> - if (max_resize < 0) {
> - if (!tn->parent)
> - pr_warning("Fix halve_threshold_root."
> - " Now=%d size=%d bits\n",
> - halve_threshold_root, tn->bits);
> - else
> - pr_warning("Fix halve_threshold."
> - " Now=%d size=%d bits\n",
> - halve_threshold, tn->bits);
> - }
>
> /* Only one child remains */
> - if (tn->empty_children == tnode_child_length(tn) - 1)
> + if (tn->empty_children == tnode_child_length(tn) - 1) {
> +one_child:
> for (i = 0; i < tnode_child_length(tn); i++) {
> struct node *n;
>
> @@ -724,7 +675,7 @@ static struct node *resize(struct trie *t, struct tnode *tn)
> tnode_free_safe(tn);
> return n;
> }
> -
> + }
> return (struct node *) tn;
> }
>
> --
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