• Cong Wang's avatar
    net_sched: add reverse binding for tc class · 07d79fc7
    Cong Wang authored
    TC filters when used as classifiers are bound to TC classes.
    However, there is a hidden difference when adding them in different
    orders:
    
    1. If we add tc classes before its filters, everything is fine.
       Logically, the classes exist before we specify their ID's in
       filters, it is easy to bind them together, just as in the current
       code base.
    
    2. If we add tc filters before the tc classes they bind, we have to
       do dynamic lookup in fast path. What's worse, this happens all
       the time not just once, because on fast path tcf_result is passed
       on stack, there is no way to propagate back to the one in tc filters.
    
    This hidden difference hurts performance silently if we have many tc
    classes in hierarchy.
    
    This patch intends to close this gap by doing the reverse binding when
    we create a new class, in this case we can actually search all the
    filters in its parent, match and fixup by classid. And because
    tcf_result is specific to each type of tc filter, we have to introduce
    a new ops for each filter to tell how to bind the class.
    
    Note, we still can NOT totally get rid of those class lookup in
    ->enqueue() because cgroup and flow filters have no way to determine
    the classid at setup time, they still have to go through dynamic lookup.
    
    Cc: Jamal Hadi Salim <jhs@mojatatu.com>
    Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    07d79fc7
cls_u32.c 28.4 KB