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fib_trie: Remove checks for index >= tnode_child_length from tnode_get_child

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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>
This commit is contained in:
Alexander Duyck 2014-12-31 10:57:02 -08:00 committed by David S. Miller
parent 12c081a5c8
commit 21d1f11db0
1 changed files with 5 additions and 9 deletions
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14
net/ipv4/fib_trie.c
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@ -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++;
}