Commit 21d1f11d authored by Alexander Duyck's avatar Alexander Duyck Committed by David S. Miller
Browse files

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: default avatarAlexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 12c081a5

net/ipv4/fib_trie.c

+5 −9
Original line number Diff line number Diff line
@@ -186,8 +186,6 @@ static inline unsigned long tnode_child_length(const struct tnode *tn) 
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_child(const struct tnode *tn, 
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 struct tnode *tn, const struct tnode *n) 
 */

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(struct trie *t, u32 key) 
		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(struct trie *t, u32 key, int plen) 
		}



		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 *tb, const struct flowi4 *flp, 
			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 trie *t, struct trie_stat *s) 
			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++;

			}

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