From: Eric Dumazet <eric.duma...@gmail.com> Date: Tue, 06 Dec 2016 19:32:50 -0800
> From: Eric Dumazet <eduma...@google.com> > > Paolo noticed a cache line miss in UDP recvmsg() to access > sk_rxhash, sharing a cache line with sk_drops. > > sk_drops might be heavily incremented by cpus handling a flood targeting > this socket. > > We might place sk_drops on a separate cache line, but lets try > to avoid wasting 64 bytes per socket just for this, since we have > other bottlenecks to take care of. > > sock_rps_record_flow() should only access sk_rxhash for connected > flows. > > Testing sk_state for TCP_ESTABLISHED covers most of the cases for > connected sockets, for a zero cost, since system calls using > sock_rps_record_flow() also access sk->sk_prot which is on the > same cache line. > > A follow up patch will provide a static_key (Jump Label) since most > hosts do not even use RFS. > > Signed-off-by: Eric Dumazet <eduma...@google.com> > Reported-by: Paolo Abeni <pab...@redhat.com> Applied, thanks Eric.
