• Tom Herbert's avatar
    ipv6: Implement automatic flow label generation on transmit · cb1ce2ef
    Tom Herbert authored
    Automatically generate flow labels for IPv6 packets on transmit.
    The flow label is computed based on skb_get_hash. The flow label will
    only automatically be set when it is zero otherwise (i.e. flow label
    manager hasn't set one). This supports the transmit side functionality
    of RFC 6438.
    
    Added an IPv6 sysctl auto_flowlabels to enable/disable this behavior
    system wide, and added IPV6_AUTOFLOWLABEL socket option to enable this
    functionality per socket.
    
    By default, auto flowlabels are disabled to avoid possible conflicts
    with flow label manager, however if this feature proves useful we
    may want to enable it by default.
    
    It should also be noted that FreeBSD has already implemented automatic
    flow labels (including the sysctl and socket option). In FreeBSD,
    automatic flow labels default to enabled.
    
    Performance impact:
    
    Running super_netperf with 200 flows for TCP_RR and UDP_RR for
    IPv6. Note that in UDP case, __skb_get_hash will be called for
    every packet with explains slight regression. In the TCP case
    the hash is saved in the socket so there is no regression.
    
    Automatic flow labels disabled:
    
      TCP_RR:
        86.53% CPU utilization
        127/195/322 90/95/99% latencies
        1.40498e+06 tps
    
      UDP_RR:
        90.70% CPU utilization
        118/168/243 90/95/99% latencies
        1.50309e+06 tps
    
    Automatic flow labels enabled:
    
      TCP_RR:
        85.90% CPU utilization
        128/199/337 90/95/99% latencies
        1.40051e+06
    
      UDP_RR
        92.61% CPU utilization
        115/164/236 90/95/99% latencies
        1.4687e+06
    Signed-off-by: default avatarTom Herbert <therbert@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    cb1ce2ef
ipv6.h 25.1 KB