• Robert Shearman's avatar
    mpls: reduce memory usage of routes · cf4b24f0
    Robert Shearman authored
    Nexthops for MPLS routes have a via address field sized for the
    largest via address that is expected, which is 32 bytes. This means
    that in the most common case of having ipv4 via addresses, 28 bytes of
    memory more than required are used per nexthop. In the other common
    case of an ipv6 nexthop then 16 bytes more than required are
    used. With large numbers of MPLS routes this extra memory usage could
    start to become significant.
    
    To avoid allocating memory for a maximum length via address when not
    all of it is required and to allow for ease of iterating over
    nexthops, then the via addresses are changed to be stored in the same
    memory block as the route and nexthops, but in an array after the end
    of the array of nexthops. New accessors are provided to retrieve a
    pointer to the via address.
    
    To allow for O(1) access without having to store a pointer or offset
    per nh, the via address for each nexthop is sized according to the
    maximum via address for any nexthop in the route, which is stored in a
    new route field, rt_max_alen, but this is in an existing hole in
    struct mpls_route so it doesn't increase the size of the
    structure. Each via address is ensured to be aligned to VIA_ALEN_ALIGN
    to account for architectures that don't allow unaligned accesses.
    Signed-off-by: default avatarRobert Shearman <rshearma@brocade.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    cf4b24f0
internal.h 3.4 KB