On 2019/2/22 下午6:26, Nikolay Aleksandrov wrote: > On 22/02/2019 11:20, we...@ucloud.cn wrote: >> From: wenxu <we...@ucloud.cn> >> >> Current fib_multipath_hash_policy can make hash based on the L3 or >> L4. But it only work on the outer IP. So a specific tunnel always >> has the same hash value. But a specific tunnel may contain so many >> inner connections. However there is no good way for tunnel packet. >> A specific tunnel route based on the percpu dst_cache. It will not >> lookup route table for each packet. >> >> This patch provide a based cpu id hash policy. The different >> connection run on different cpu and there will be different hash >> value for percpu dst_cache. >> >> Signed-off-by: wenxu <we...@ucloud.cn> >> --- >> net/ipv4/route.c | 6 ++++++ >> net/ipv4/sysctl_net_ipv4.c | 2 +- >> 2 files changed, 7 insertions(+), 1 deletion(-) >> > Hi, > When we had the same issue in the bonding, we added a new mode which used > the flow dissector to get the inner headers and hash on them. > I believe that is even easier nowadays, but I think people wanted to > use different hash algorithms as well and last we discussed this we > were talking about yet another bpf use to generate the hash. > Now we got bpf_set_hash() which can be used to achieve this from various > places, if you use that with hash_policy=1 (L4) then skb->hash will > be used and you can achieve any hashing that you desire. > > Cheers, > Nik > > Yes, we can set the skb->hash. But ip tunnel lookup the route table without skb.
The most important for performance issue most tunnel send work with dst_cache. The dst_cache is percpu cache. So the number of dst_entry of a specific tunnel is the cpu cores . So It's more better hash based on outer and cpu id.
