diff options
| author | Alexander Duyck <alexander.h.duyck@redhat.com> | 2015-01-22 15:51:08 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-01-25 14:47:15 -0800 |
| commit | b3832117b4b61374fac08692f1b1a620088342dd (patch) | |
| tree | 836e0e535f9fb38c60808b21851923ff3d2744e2 /net/ipv4/fib_trie.c | |
| parent | bc579ae5f902e7a17d4a02ca32779c90604d57b9 (diff) | |
fib_trie: Use index & (~0ul << n->bits) instead of index >> n->bits
In doing performance testing and analysis of the changes I recently found
that by shifting the index I had created an unnecessary dependency.
I have updated the code so that we instead shift a mask by bits and then
just test against that as that should save us about 2 CPU cycles since we
can generate the mask while the key and pos are being processed.
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/fib_trie.c')
| -rw-r--r-- | net/ipv4/fib_trie.c | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index 281e5e00025f..dea2f80e08c3 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -961,12 +961,12 @@ static struct tnode *fib_find_node(struct trie *t, u32 key) * prefix plus zeros for the bits in the cindex. The index * is the difference between the key and this value. From * this we can actually derive several pieces of data. - * if !(index >> bits) - * we know the value is cindex - * else + * if (index & (~0ul << bits)) * we have a mismatch in skip bits and failed + * else + * we know the value is cindex */ - if (index >> n->bits) + if (index & (~0ul << n->bits)) return NULL; /* we have found a leaf. Prefixes have already been compared */ @@ -1301,12 +1301,12 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp, * prefix plus zeros for the "bits" in the prefix. The index * is the difference between the key and this value. From * this we can actually derive several pieces of data. - * if !(index >> bits) - * we know the value is child index - * else + * if (index & (~0ul << bits)) * we have a mismatch in skip bits and failed + * else + * we know the value is cindex */ - if (index >> n->bits) + if (index & (~0ul << n->bits)) break; /* we have found a leaf. Prefixes have already been compared */ |