From: Alexander Duyck <alexander.h.duyck@redhat.com> Date: Wed, 31 Dec 2014 10:57:02 -0800 Subject: [PATCH] fib_trie: Remove checks for index >= tnode_child_length from tnode_get_child For some reason the compiler doesn't seem to understand that when we are in a loop that runs from tnode_child_length - 1 to 0 we don't expect the value of tn->bits to change. As such every call to tnode_get_child was rerunning tnode_chile_length which ended up consuming quite a bit of space in the resultant assembly code. I have gone though and verified that in all cases where tnode_get_child is used we are either winding though a fixed loop from tnode_child_length - 1 to 0, or are in a fastpath case where we are verifying the value by either checking for any remaining bits after shifting index by bits and testing for leaf, or by using tnode_child_length. size net/ipv4/fib_trie.o Before: text data bss dec hex filename 15506 376 8 15890 3e12 net/ipv4/fib_trie.o After: text data bss dec hex filename 14827 376 8 15211 3b6b net/ipv4/fib_trie.o 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 @@ -186,8 +186,6 @@ static inline unsigned long tnode_child_ static inline struct tnode *tnode_get_child(const struct tnode *tn, unsigned long i) { - BUG_ON(i >= tnode_child_length(tn)); - return rtnl_dereference(tn->child[i]); } @@ -195,8 +193,6 @@ static inline struct tnode *tnode_get_ch static inline struct tnode *tnode_get_child_rcu(const struct tnode *tn, unsigned long i) { - BUG_ON(i >= tnode_child_length(tn)); - return rcu_dereference_rtnl(tn->child[i]); } @@ -371,7 +367,7 @@ static inline int tnode_full(const struc */ static void put_child(struct tnode *tn, unsigned long i, struct tnode *n) { - struct tnode *chi = rtnl_dereference(tn->child[i]); + struct tnode *chi = tnode_get_child(tn, i); int isfull, wasfull; BUG_ON(i >= tnode_child_length(tn)); @@ -867,7 +863,7 @@ static struct tnode *fib_find_node(struc if (IS_LEAF(n)) break; - n = rcu_dereference_rtnl(n->child[index]); + n = tnode_get_child_rcu(n, index); } return n; @@ -934,7 +930,7 @@ static struct list_head *fib_insert_node } tp = n; - n = rcu_dereference_rtnl(n->child[index]); + n = tnode_get_child_rcu(n, index); } l = leaf_new(key); @@ -1215,7 +1211,7 @@ int fib_table_lookup(struct fib_table *t cindex = index; } - n = rcu_dereference(n->child[index]); + n = tnode_get_child_rcu(n, index); if (unlikely(!n)) goto backtrace; } @@ -1835,7 +1831,7 @@ static void trie_collect_stats(struct tr if (n->bits < MAX_STAT_DEPTH) s->nodesizes[n->bits]++; - for (i = 0; i < tnode_child_length(n); i++) { + for (i = tnode_child_length(n); i--;) { if (!rcu_access_pointer(n->child[i])) s->nullpointers++; }