From: Willem de Bruijn <willemdebruijn.ker...@gmail.com> Date: Sun, 7 Jul 2019 05:34:45 -0400
> From: Willem de Bruijn <will...@google.com> > > Processes can request ipv6 flowlabels with cmsg IPV6_FLOWINFO. > If not set, by default an autogenerated flowlabel is selected. > > Explicit flowlabels require a control operation per label plus a > datapath check on every connection (every datagram if unconnected). > This is particularly expensive on unconnected sockets multiplexing > many flows, such as QUIC. > > In the common case, where no lease is exclusive, the check can be > safely elided, as both lease request and check trivially succeed. > Indeed, autoflowlabel does the same even with exclusive leases. > > Elide the check if no process has requested an exclusive lease. > > fl6_sock_lookup previously returns either a reference to a lease or > NULL to denote failure. Modify to return a real error and update > all callers. On return NULL, they can use the label and will elide > the atomic_dec in fl6_sock_release. > > This is an optimization. Robust applications still have to revert to > requesting leases if the fast path fails due to an exclusive lease. > > Changes RFC->v1: > - use static_key_false_deferred to rate limit jump label operations > - call static_key_deferred_flush to stop timers on exit > - move decrement out of RCU context > - defer optimization also if opt data is associated with a lease > - updated all fp6_sock_lookup callers, not just udp > > Signed-off-by: Willem de Bruijn <will...@google.com> Looks good, applied, thanks Willem.
