On 07.03.2018 19:43, Eric Dumazet wrote: > From: Eric Dumazet <eduma...@google.com> > > Kirill found that recently added synchronize_rcu() call in > ip6mr_sk_done() > was slowing down netns dismantle and posted a patch to use it only if > the socket > was found. > > I instead suggested to get rid of this call, and use instead > SOCK_RCU_FREE > > We might later change IPv4 side to use the same technique and unify > both stacks. IPv4 does not use synchronize_rcu() but has a call_rcu() > that could be replaced by SOCK_RCU_FREE. > > Tested: > time for i in {1..1000}; do unshare -n /bin/false;done > > Before : real 7m18.911s > After : real 10.187s > > Fixes: 8571ab479a6e ("ip6mr: Make mroute_sk rcu-based") > Signed-off-by: Eric Dumazet <eduma...@google.com> > Reported-by: Kirill Tkhai <ktk...@virtuozzo.com> > Cc: Yuval Mintz <yuv...@mellanox.com>
Reviewed-by: Kirill Tkhai <ktk...@virtuozzo.com> > --- > net/ipv6/ip6mr.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c > index > 2a38f9de45d399fafc9f4bcc662b44be17279e51..7345bd6c4b7dda39c0d73d542e9ca9a5366542ff > 100644 > --- a/net/ipv6/ip6mr.c > +++ b/net/ipv6/ip6mr.c > @@ -1443,6 +1443,7 @@ static int ip6mr_sk_init(struct mr_table *mrt, struct > sock *sk) > err = -EADDRINUSE; > } else { > rcu_assign_pointer(mrt->mroute_sk, sk); > + sock_set_flag(sk, SOCK_RCU_FREE); > net->ipv6.devconf_all->mc_forwarding++; > } > write_unlock_bh(&mrt_lock); > @@ -1472,6 +1473,10 @@ int ip6mr_sk_done(struct sock *sk) > if (sk == rtnl_dereference(mrt->mroute_sk)) { > write_lock_bh(&mrt_lock); > RCU_INIT_POINTER(mrt->mroute_sk, NULL); > + /* Note that mroute_sk had SOCK_RCU_FREE set, > + * so the RCU grace period before sk freeing > + * is guaranteed by sk_destruct() > + */ > net->ipv6.devconf_all->mc_forwarding--; > write_unlock_bh(&mrt_lock); > inet6_netconf_notify_devconf(net, RTM_NEWNETCONF, > @@ -1485,7 +1490,6 @@ int ip6mr_sk_done(struct sock *sk) > } > } > rtnl_unlock(); > - synchronize_rcu(); > > return err; > } >