| Message ID | e22553bd881bcc3b455bad9d77b392ca3ced5c6e.1643380219.git.alibuda@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | net/smc: Optimizing performance in | expand |
On Fri, Jan 28, 2022 at 10:44:37PM +0800, D. Wythe wrote: > From: "D. Wythe" <alibuda@linux.alibaba.com> > > Current implementation does not handling backlog semantics, one > potential risk is that server will be flooded by infinite amount > connections, even if client was SMC-incapable. > > This patch works to put a limit on backlog connections, referring to the > TCP implementation, we divides SMC connections into two categories: > > 1. Half SMC connection, which includes all TCP established while SMC not > connections. > > 2. Full SMC connection, which includes all SMC established connections. > > For half SMC connection, since all half SMC connections starts with TCP > established, we can achieve our goal by put a limit before TCP > established. Refer to the implementation of TCP, this limits will based > on not only the half SMC connections but also the full connections, > which is also a constraint on full SMC connections. > > For full SMC connections, although we know exactly where it starts, it's > quite hard to put a limit before it. The easiest way is to block wait > before receive SMC confirm CLC message, while it's under protection by > smc_server_lgr_pending, a global lock, which leads this limit to the > entire host instead of a single listen socket. Another way is to drop > the full connections, but considering the cast of SMC connections, we > prefer to keep full SMC connections. > > Even so, the limits of full SMC connections still exists, see commits > about half SMC connection below. > > After this patch, the limits of backend connection shows like: > > For SMC: > > 1. Client with SMC-capability can makes 2 * backlog full SMC connections > or 1 * backlog half SMC connections and 1 * backlog full SMC > connections at most. > > 2. Client without SMC-capability can only makes 1 * backlog half TCP > connections and 1 * backlog full TCP connections. > > Signed-off-by: D. Wythe <alibuda@linux.alibaba.com> > --- > changelog: > v2: fix compile warning > --- > net/smc/af_smc.c | 43 +++++++++++++++++++++++++++++++++++++++++++ > net/smc/smc.h | 4 ++++ > 2 files changed, 47 insertions(+) > > diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c > index 1b40304..66a0e64 100644 > --- a/net/smc/af_smc.c > +++ b/net/smc/af_smc.c > @@ -73,6 +73,34 @@ static void smc_set_keepalive(struct sock *sk, int val) > smc->clcsock->sk->sk_prot->keepalive(smc->clcsock->sk, val); > } > > +static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk, struct sk_buff *skb, > + struct request_sock *req, > + struct dst_entry *dst, > + struct request_sock *req_unhash, > + bool *own_req) > +{ > + struct smc_sock *smc; > + > + smc = (struct smc_sock *)((uintptr_t)sk->sk_user_data & ~SK_USER_DATA_NOCOPY); > + > + if (READ_ONCE(sk->sk_ack_backlog) + atomic_read(&smc->smc_pendings) > > + sk->sk_max_ack_backlog) > + goto drop; > + > + if (sk_acceptq_is_full(&smc->sk)) { > + NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS); > + goto drop; > + } > + > + /* passthrough to origin syn recv sock fct */ > + return smc->ori_af_ops->syn_recv_sock(sk, skb, req, dst, req_unhash, own_req); I am wondering if there would introduce more overhead, compared with original implement? > + > +drop: > + dst_release(dst); > + tcp_listendrop(sk); > + return NULL; > +} > + > static struct smc_hashinfo smc_v4_hashinfo = { > .lock = __RW_LOCK_UNLOCKED(smc_v4_hashinfo.lock), > }; > @@ -1491,6 +1519,9 @@ static void smc_listen_out(struct smc_sock *new_smc) > struct smc_sock *lsmc = new_smc->listen_smc; > struct sock *newsmcsk = &new_smc->sk; > > + if (tcp_sk(new_smc->clcsock->sk)->syn_smc) > + atomic_dec(&lsmc->smc_pendings); > + > if (lsmc->sk.sk_state == SMC_LISTEN) { > lock_sock_nested(&lsmc->sk, SINGLE_DEPTH_NESTING); > smc_accept_enqueue(&lsmc->sk, newsmcsk); > @@ -2096,6 +2127,9 @@ static void smc_tcp_listen_work(struct work_struct *work) > if (!new_smc) > continue; > > + if (tcp_sk(new_smc->clcsock->sk)->syn_smc) > + atomic_inc(&lsmc->smc_pendings); > + > new_smc->listen_smc = lsmc; > new_smc->use_fallback = lsmc->use_fallback; > new_smc->fallback_rsn = lsmc->fallback_rsn; > @@ -2163,6 +2197,15 @@ static int smc_listen(struct socket *sock, int backlog) > smc->clcsock->sk->sk_data_ready = smc_clcsock_data_ready; > smc->clcsock->sk->sk_user_data = > (void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY); > + > + /* save origin ops */ > + smc->ori_af_ops = inet_csk(smc->clcsock->sk)->icsk_af_ops; > + > + smc->af_ops = *smc->ori_af_ops; > + smc->af_ops.syn_recv_sock = smc_tcp_syn_recv_sock; > + > + inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops; Consider to save syn_recv_sock this field only? There seems no need to save this ops all. Thank you, Tony Lu
The overhead will certainly exist, but compared with the benefits, I think it should be acceptable. If you do care, maybe we can add a switch to control it. > I am wondering if there would introduce more overhead, compared with > original implement? > >> + >> +drop: >> + dst_release(dst); >> + tcp_listendrop(sk); >> + return NULL; >> +} >> + >> static struct smc_hashinfo smc_v4_hashinfo = { >> .lock = __RW_LOCK_UNLOCKED(smc_v4_hashinfo.lock), >> }; >> @@ -1491,6 +1519,9 @@ static void smc_listen_out(struct smc_sock *new_smc) >> struct smc_sock *lsmc = new_smc->listen_smc; >> struct sock *newsmcsk = &new_smc->sk; >> >> + if (tcp_sk(new_smc->clcsock->sk)->syn_smc) >> + atomic_dec(&lsmc->smc_pendings); >> + >> if (lsmc->sk.sk_state == SMC_LISTEN) { >> lock_sock_nested(&lsmc->sk, SINGLE_DEPTH_NESTING); >> smc_accept_enqueue(&lsmc->sk, newsmcsk); >> @@ -2096,6 +2127,9 @@ static void smc_tcp_listen_work(struct work_struct *work) >> if (!new_smc) >> continue; >> >> + if (tcp_sk(new_smc->clcsock->sk)->syn_smc) >> + atomic_inc(&lsmc->smc_pendings); >> + >> new_smc->listen_smc = lsmc; >> new_smc->use_fallback = lsmc->use_fallback; >> new_smc->fallback_rsn = lsmc->fallback_rsn; >> @@ -2163,6 +2197,15 @@ static int smc_listen(struct socket *sock, int backlog) >> smc->clcsock->sk->sk_data_ready = smc_clcsock_data_ready; >> smc->clcsock->sk->sk_user_data = >> (void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY); >> + >> + /* save origin ops */ >> + smc->ori_af_ops = inet_csk(smc->clcsock->sk)->icsk_af_ops; >> + >> + smc->af_ops = *smc->ori_af_ops; >> + smc->af_ops.syn_recv_sock = smc_tcp_syn_recv_sock; >> + >> + inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops; > Only save syn_recv_sock? Maybe this comment is confusing， ‘Copy the origin ops’ is better, the origin ops is pointer to a const structure, we must copy it all, and repointer it to our structure. so the copy/save is necessary. Thanks. > Consider to save syn_recv_sock this field only? There seems no need to > save this ops all. > > Thank you, > Tony Lu
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index 1b40304..66a0e64 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -73,6 +73,34 @@ static void smc_set_keepalive(struct sock *sk, int val) smc->clcsock->sk->sk_prot->keepalive(smc->clcsock->sk, val); } +static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk, struct sk_buff *skb, + struct request_sock *req, + struct dst_entry *dst, + struct request_sock *req_unhash, + bool *own_req) +{ + struct smc_sock *smc; + + smc = (struct smc_sock *)((uintptr_t)sk->sk_user_data & ~SK_USER_DATA_NOCOPY); + + if (READ_ONCE(sk->sk_ack_backlog) + atomic_read(&smc->smc_pendings) > + sk->sk_max_ack_backlog) + goto drop; + + if (sk_acceptq_is_full(&smc->sk)) { + NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS); + goto drop; + } + + /* passthrough to origin syn recv sock fct */ + return smc->ori_af_ops->syn_recv_sock(sk, skb, req, dst, req_unhash, own_req); + +drop: + dst_release(dst); + tcp_listendrop(sk); + return NULL; +} + static struct smc_hashinfo smc_v4_hashinfo = { .lock = __RW_LOCK_UNLOCKED(smc_v4_hashinfo.lock), }; @@ -1491,6 +1519,9 @@ static void smc_listen_out(struct smc_sock *new_smc) struct smc_sock *lsmc = new_smc->listen_smc; struct sock *newsmcsk = &new_smc->sk; + if (tcp_sk(new_smc->clcsock->sk)->syn_smc) + atomic_dec(&lsmc->smc_pendings); + if (lsmc->sk.sk_state == SMC_LISTEN) { lock_sock_nested(&lsmc->sk, SINGLE_DEPTH_NESTING); smc_accept_enqueue(&lsmc->sk, newsmcsk); @@ -2096,6 +2127,9 @@ static void smc_tcp_listen_work(struct work_struct *work) if (!new_smc) continue; + if (tcp_sk(new_smc->clcsock->sk)->syn_smc) + atomic_inc(&lsmc->smc_pendings); + new_smc->listen_smc = lsmc; new_smc->use_fallback = lsmc->use_fallback; new_smc->fallback_rsn = lsmc->fallback_rsn; @@ -2163,6 +2197,15 @@ static int smc_listen(struct socket *sock, int backlog) smc->clcsock->sk->sk_data_ready = smc_clcsock_data_ready; smc->clcsock->sk->sk_user_data = (void *)((uintptr_t)smc | SK_USER_DATA_NOCOPY); + + /* save origin ops */ + smc->ori_af_ops = inet_csk(smc->clcsock->sk)->icsk_af_ops; + + smc->af_ops = *smc->ori_af_ops; + smc->af_ops.syn_recv_sock = smc_tcp_syn_recv_sock; + + inet_csk(smc->clcsock->sk)->icsk_af_ops = &smc->af_ops; + rc = kernel_listen(smc->clcsock, backlog); if (rc) { smc->clcsock->sk->sk_data_ready = smc->clcsk_data_ready; diff --git a/net/smc/smc.h b/net/smc/smc.h index bd2f3dc..0e27113 100644 --- a/net/smc/smc.h +++ b/net/smc/smc.h @@ -240,6 +240,10 @@ struct smc_sock { /* smc sock container */ bool use_fallback; /* fallback to tcp */ int fallback_rsn; /* reason for fallback */ u32 peer_diagnosis; /* decline reason from peer */ + atomic_t smc_pendings; /* pending smc connections */ + struct inet_connection_sock_af_ops af_ops; + const struct inet_connection_sock_af_ops *ori_af_ops; + /* origin af ops */ int sockopt_defer_accept; /* sockopt TCP_DEFER_ACCEPT * value