• Wei Wang's avatar
    ipv6: convert major tx path to use RT6_LOOKUP_F_DST_NOREF · 7d9e5f42
    Wei Wang authored
    For tx path, in most cases, we still have to take refcnt on the dst
    cause the caller is caching the dst somewhere. But it still is
    beneficial to make use of RT6_LOOKUP_F_DST_NOREF flag while doing the
    route lookup. It is cause this flag prevents manipulating refcnt on
    net->ipv6.ip6_null_entry when doing fib6_rule_lookup() to traverse each
    routing table. The null_entry is a shared object and constant updates on
    it cause false sharing.
    
    We converted the current major lookup function ip6_route_output_flags()
    to make use of RT6_LOOKUP_F_DST_NOREF.
    
    Together with the change in the rx path, we see noticable performance
    boost:
    I ran synflood tests between 2 hosts under the same switch. Both hosts
    have 20G mlx NIC, and 8 tx/rx queues.
    Sender sends pure SYN flood with random src IPs and ports using trafgen.
    Receiver has a simple TCP listener on the target port.
    Both hosts have multiple custom rules:
    - For incoming packets, only local table is traversed.
    - For outgoing packets, 3 tables are traversed to find the route.
    The packet processing rate on the receiver is as follows:
    - Before the fix: 3.78Mpps
    - After the fix:  5.50Mpps
    Signed-off-by: default avatarWei Wang <weiwan@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    7d9e5f42
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