diff options
Diffstat (limited to 'target/linux/generic/patches-3.18/080-18-fib_trie-Add-tracking-value-for-suffix-length.patch')
| -rw-r--r-- | target/linux/generic/patches-3.18/080-18-fib_trie-Add-tracking-value-for-suffix-length.patch | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/target/linux/generic/patches-3.18/080-18-fib_trie-Add-tracking-value-for-suffix-length.patch b/target/linux/generic/patches-3.18/080-18-fib_trie-Add-tracking-value-for-suffix-length.patch new file mode 100644 index 0000000..6a4a45e --- /dev/null +++ b/target/linux/generic/patches-3.18/080-18-fib_trie-Add-tracking-value-for-suffix-length.patch @@ -0,0 +1,234 @@ +From: Alexander Duyck <alexander.h.duyck@redhat.com> +Date: Wed, 31 Dec 2014 10:57:08 -0800 +Subject: [PATCH] fib_trie: Add tracking value for suffix length + +This change adds a tracking value for the maximum suffix length of all +prefixes stored in any given tnode. With this value we can determine if we +need to backtrace or not based on if the suffix is greater than the pos +value. + +By doing this we can reduce the CPU overhead for lookups in the local table +as many of the prefixes there are 32b long and have a suffix length of 0 +meaning we can immediately backtrace to the root node without needing to +test any of the nodes between it and where we ended up. + +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 +@@ -96,6 +96,7 @@ struct tnode { + t_key key; + unsigned char bits; /* 2log(KEYLENGTH) bits needed */ + unsigned char pos; /* 2log(KEYLENGTH) bits needed */ ++ unsigned char slen; + struct tnode __rcu *parent; + struct rcu_head rcu; + union { +@@ -311,6 +312,7 @@ static struct tnode *leaf_new(t_key key) + * as the nodes are searched + */ + l->key = key; ++ l->slen = 0; + l->pos = 0; + /* set bits to 0 indicating we are not a tnode */ + l->bits = 0; +@@ -342,6 +344,7 @@ static struct tnode *tnode_new(t_key key + + if (tn) { + tn->parent = NULL; ++ tn->slen = pos; + tn->pos = pos; + tn->bits = bits; + tn->key = (shift < KEYLENGTH) ? (key >> shift) << shift : 0; +@@ -387,6 +390,9 @@ static void put_child(struct tnode *tn, + else if (!wasfull && isfull) + tn->full_children++; + ++ if (n && (tn->slen < n->slen)) ++ tn->slen = n->slen; ++ + rcu_assign_pointer(tn->child[i], n); + } + +@@ -635,6 +641,41 @@ static int halve(struct trie *t, struct + return 0; + } + ++static unsigned char update_suffix(struct tnode *tn) ++{ ++ unsigned char slen = tn->pos; ++ unsigned long stride, i; ++ ++ /* search though the list of children looking for nodes that might ++ * have a suffix greater than the one we currently have. This is ++ * why we start with a stride of 2 since a stride of 1 would ++ * represent the nodes with suffix length equal to tn->pos ++ */ ++ for (i = 0, stride = 0x2ul ; i < tnode_child_length(tn); i += stride) { ++ struct tnode *n = tnode_get_child(tn, i); ++ ++ if (!n || (n->slen <= slen)) ++ continue; ++ ++ /* update stride and slen based on new value */ ++ stride <<= (n->slen - slen); ++ slen = n->slen; ++ i &= ~(stride - 1); ++ ++ /* if slen covers all but the last bit we can stop here ++ * there will be nothing longer than that since only node ++ * 0 and 1 << (bits - 1) could have that as their suffix ++ * length. ++ */ ++ if ((slen + 1) >= (tn->pos + tn->bits)) ++ break; ++ } ++ ++ tn->slen = slen; ++ ++ return slen; ++} ++ + /* From "Implementing a dynamic compressed trie" by Stefan Nilsson of + * the Helsinki University of Technology and Matti Tikkanen of Nokia + * Telecommunications, page 6: +@@ -790,6 +831,19 @@ no_children: + /* drop dead node */ + tnode_free_init(tn); + tnode_free(tn); ++ return; ++ } ++ ++ /* Return if at least one deflate was run */ ++ if (max_work != MAX_WORK) ++ return; ++ ++ /* push the suffix length to the parent node */ ++ if (tn->slen > tn->pos) { ++ unsigned char slen = update_suffix(tn); ++ ++ if (tp && (slen > tp->slen)) ++ tp->slen = slen; + } + } + +@@ -818,8 +872,58 @@ static inline struct list_head *get_fa_h + return &li->falh; + } + +-static void insert_leaf_info(struct hlist_head *head, struct leaf_info *new) ++static void leaf_pull_suffix(struct tnode *l) ++{ ++ struct tnode *tp = node_parent(l); ++ ++ while (tp && (tp->slen > tp->pos) && (tp->slen > l->slen)) { ++ if (update_suffix(tp) > l->slen) ++ break; ++ tp = node_parent(tp); ++ } ++} ++ ++static void leaf_push_suffix(struct tnode *l) ++{ ++ struct tnode *tn = node_parent(l); ++ ++ /* if this is a new leaf then tn will be NULL and we can sort ++ * out parent suffix lengths as a part of trie_rebalance ++ */ ++ while (tn && (tn->slen < l->slen)) { ++ tn->slen = l->slen; ++ tn = node_parent(tn); ++ } ++} ++ ++static void remove_leaf_info(struct tnode *l, struct leaf_info *old) ++{ ++ struct hlist_node *prev; ++ ++ /* record the location of the pointer to this object */ ++ prev = rtnl_dereference(hlist_pprev_rcu(&old->hlist)); ++ ++ /* remove the leaf info from the list */ ++ hlist_del_rcu(&old->hlist); ++ ++ /* if we emptied the list this leaf will be freed and we can sort ++ * out parent suffix lengths as a part of trie_rebalance ++ */ ++ if (hlist_empty(&l->list)) ++ return; ++ ++ /* if we removed the tail then we need to update slen */ ++ if (!rcu_access_pointer(hlist_next_rcu(prev))) { ++ struct leaf_info *li = hlist_entry(prev, typeof(*li), hlist); ++ ++ l->slen = KEYLENGTH - li->plen; ++ leaf_pull_suffix(l); ++ } ++} ++ ++static void insert_leaf_info(struct tnode *l, struct leaf_info *new) + { ++ struct hlist_head *head = &l->list; + struct leaf_info *li = NULL, *last = NULL; + + if (hlist_empty(head)) { +@@ -836,6 +940,12 @@ static void insert_leaf_info(struct hlis + else + hlist_add_before_rcu(&new->hlist, &li->hlist); + } ++ ++ /* if we added to the tail node then we need to update slen */ ++ if (!rcu_access_pointer(hlist_next_rcu(&new->hlist))) { ++ l->slen = KEYLENGTH - new->plen; ++ leaf_push_suffix(l); ++ } + } + + /* rcu_read_lock needs to be hold by caller from readside */ +@@ -925,7 +1035,7 @@ static struct list_head *fib_insert_node + /* we have found a leaf. Prefixes have already been compared */ + if (IS_LEAF(n)) { + /* Case 1: n is a leaf, and prefixes match*/ +- insert_leaf_info(&n->list, li); ++ insert_leaf_info(n, li); + return fa_head; + } + +@@ -939,7 +1049,7 @@ static struct list_head *fib_insert_node + return NULL; + } + +- insert_leaf_info(&l->list, li); ++ insert_leaf_info(l, li); + + /* Case 2: n is a LEAF or a TNODE and the key doesn't match. + * +@@ -1206,7 +1316,7 @@ int fib_table_lookup(struct fib_table *t + /* only record pn and cindex if we are going to be chopping + * bits later. Otherwise we are just wasting cycles. + */ +- if (index) { ++ if (n->slen > n->pos) { + pn = n; + cindex = index; + } +@@ -1225,7 +1335,7 @@ int fib_table_lookup(struct fib_table *t + * between the key and the prefix exist in the region of + * the lsb and higher in the prefix. + */ +- if (unlikely(prefix_mismatch(key, n))) ++ if (unlikely(prefix_mismatch(key, n)) || (n->slen == n->pos)) + goto backtrace; + + /* exit out and process leaf */ +@@ -1425,7 +1535,7 @@ int fib_table_delete(struct fib_table *t + tb->tb_num_default--; + + if (list_empty(fa_head)) { +- hlist_del_rcu(&li->hlist); ++ remove_leaf_info(l, li); + free_leaf_info(li); + } + |