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| author | Felix Fietkau <nbd@openwrt.org> | 2015-05-08 21:46:51 +0000 |
|---|---|---|
| committer | Felix Fietkau <nbd@openwrt.org> | 2015-05-08 21:46:51 +0000 |
| commit | dbb99e937a7a32a7f9df94b51e6bd5b7766b0825 (patch) | |
| tree | 4979de2731497a28ec7f9a3e39772e550ca7a89a /target/linux/generic/patches-3.18/080-19-fib_trie-Use-index-0ul-n-bits-instead-of-index-n-bit.patch | |
| parent | 3f4011ad367cc4bd5d0734cded64bd8527f021d9 (diff) | |
| download | upstream-dbb99e937a7a32a7f9df94b51e6bd5b7766b0825.tar.gz upstream-dbb99e937a7a32a7f9df94b51e6bd5b7766b0825.tar.bz2 upstream-dbb99e937a7a32a7f9df94b51e6bd5b7766b0825.zip | |
kernel: add accidentally left out fib trie backport patch
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
SVN-Revision: 45650
Diffstat (limited to 'target/linux/generic/patches-3.18/080-19-fib_trie-Use-index-0ul-n-bits-instead-of-index-n-bit.patch')
| -rw-r--r-- | target/linux/generic/patches-3.18/080-19-fib_trie-Use-index-0ul-n-bits-instead-of-index-n-bit.patch | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/target/linux/generic/patches-3.18/080-19-fib_trie-Use-index-0ul-n-bits-instead-of-index-n-bit.patch b/target/linux/generic/patches-3.18/080-19-fib_trie-Use-index-0ul-n-bits-instead-of-index-n-bit.patch new file mode 100644 index 0000000000..d5fc112563 --- /dev/null +++ b/target/linux/generic/patches-3.18/080-19-fib_trie-Use-index-0ul-n-bits-instead-of-index-n-bit.patch @@ -0,0 +1,52 @@ +From: Alexander Duyck <alexander.h.duyck@redhat.com> +Date: Thu, 22 Jan 2015 15:51:08 -0800 +Subject: [PATCH] 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> +--- + +--- a/net/ipv4/fib_trie.c ++++ b/net/ipv4/fib_trie.c +@@ -961,12 +961,12 @@ static struct tnode *fib_find_node(struc + * 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 *t + * 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 */ |