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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2010-11-18 22:04:46 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-11-19 10:06:54 -0800 |
| commit | c26aed40f4fd18f86bcc6aba557cab700b129b73 (patch) | |
| tree | e723d358ddd6facc3af4f37be02fabcf71e3e605 /net/core | |
| parent | 8c1592d68bc89248bfd0ee287648f41c1370d826 (diff) | |
| download | blackbird-op-linux-c26aed40f4fd18f86bcc6aba557cab700b129b73.tar.gz blackbird-op-linux-c26aed40f4fd18f86bcc6aba557cab700b129b73.zip | |
filter: use reciprocal divide
At compile time, we can replace the DIV_K instruction (divide by a
constant value) by a reciprocal divide.
At exec time, the expensive divide is replaced by a multiply, a less
expensive operation on most processors.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/filter.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index c0b68f7c8036..23e0a2a9a4de 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -37,6 +37,7 @@ #include <asm/uaccess.h> #include <asm/unaligned.h> #include <linux/filter.h> +#include <linux/reciprocal_div.h> enum { BPF_S_RET_K = 1, @@ -205,7 +206,7 @@ unsigned int sk_run_filter(struct sk_buff *skb, const struct sock_filter *fentry A /= X; continue; case BPF_S_ALU_DIV_K: - A /= K; + A = reciprocal_divide(A, K); continue; case BPF_S_ALU_AND_X: A &= X; @@ -506,6 +507,7 @@ int sk_chk_filter(struct sock_filter *filter, int flen) /* check for division by zero */ if (ftest->k == 0) return -EINVAL; + ftest->k = reciprocal_value(ftest->k); break; case BPF_S_LD_MEM: case BPF_S_LDX_MEM: |
