-stable review patch. If anyone has any objections, please let us know. --------------------- From: David S. Miller Upstream commit: 7adc3830f90df04a13366914d80a3ed407db5381 If all of the entropy is in the local and foreign addresses, but xor'ing together would cancel out that entropy, the current hash performs poorly. Suggested by Cosmin Ratiu: Basically, the situation is as follows: There is a client machine and a server machine. Both create 15000 virtual interfaces, open up a socket for each pair of interfaces and do SIP traffic. By profiling I noticed that there is a lot of time spent walking the established hash chains with this particular setup. The addresses were distributed like this: client interfaces were 198.18.0.1/16 with increments of 1 and server interfaces were 198.18.128.1/16 with increments of 1. As I said, there were 15000 interfaces. Source and destination ports were 5060 for each connection. So in this case, ports don't matter for hashing purposes, and the bits from the address pairs used cancel each other, meaning there are no differences in the whole lot of pairs, so they all end up in the same hash chain. Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Chris Wright --- include/net/inet_sock.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/include/net/inet_sock.h +++ b/include/net/inet_sock.h @@ -175,7 +175,8 @@ extern void build_ehash_secret(void); static inline unsigned int inet_ehashfn(const __be32 laddr, const __u16 lport, const __be32 faddr, const __be16 fport) { - return jhash_2words((__force __u32) laddr ^ (__force __u32) faddr, + return jhash_3words((__force __u32) laddr, + (__force __u32) faddr, ((__u32) lport) << 16 | (__force __u32)fport, inet_ehash_secret); } -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/