From: Paolo Abeni Date: Mon, 14 Sep 2020 08:01:17 +0000 (+0200) Subject: mptcp: allow picking different xmit subflows X-Git-Tag: microblaze-v5.11~110^2~279^2~2 X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=d5f49190def61c47b2faff170ba8fbc48bac4371;p=linux-2.6-microblaze.git mptcp: allow picking different xmit subflows Update the scheduler to less trivial heuristic: cache the last used subflow, and try to send on it a reasonably long burst of data. When the burst or the subflow send space is exhausted, pick the subflow with the lower ratio between write space and send buffer - that is, the subflow with the greater relative amount of free space. v1 -> v2: - fix 32 bit build breakage due to 64bits div - fix checkpath issues (uint64_t -> u64) Signed-off-by: Paolo Abeni Reviewed-by: Mat Martineau Signed-off-by: David S. Miller --- diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index ec9c38d3acc7..d7af96a900c4 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1031,41 +1031,105 @@ static void mptcp_nospace(struct mptcp_sock *msk) } } +static bool mptcp_subflow_active(struct mptcp_subflow_context *subflow) +{ + struct sock *ssk = mptcp_subflow_tcp_sock(subflow); + + /* can't send if JOIN hasn't completed yet (i.e. is usable for mptcp) */ + if (subflow->request_join && !subflow->fully_established) + return false; + + /* only send if our side has not closed yet */ + return ((1 << ssk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)); +} + +#define MPTCP_SEND_BURST_SIZE ((1 << 16) - \ + sizeof(struct tcphdr) - \ + MAX_TCP_OPTION_SPACE - \ + sizeof(struct ipv6hdr) - \ + sizeof(struct frag_hdr)) + +struct subflow_send_info { + struct sock *ssk; + u64 ratio; +}; + static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk, u32 *sndbuf) { + struct subflow_send_info send_info[2]; struct mptcp_subflow_context *subflow; - struct sock *sk = (struct sock *)msk; - struct sock *backup = NULL; - bool free; + int i, nr_active = 0; + struct sock *ssk; + u64 ratio; + u32 pace; - sock_owned_by_me(sk); + sock_owned_by_me((struct sock *)msk); *sndbuf = 0; if (!mptcp_ext_cache_refill(msk)) return NULL; - mptcp_for_each_subflow(msk, subflow) { - struct sock *ssk = mptcp_subflow_tcp_sock(subflow); - - free = sk_stream_is_writeable(subflow->tcp_sock); - if (!free) { - mptcp_nospace(msk); + if (__mptcp_check_fallback(msk)) { + if (!msk->first) return NULL; + *sndbuf = msk->first->sk_sndbuf; + return sk_stream_memory_free(msk->first) ? msk->first : NULL; + } + + /* re-use last subflow, if the burst allow that */ + if (msk->last_snd && msk->snd_burst > 0 && + sk_stream_memory_free(msk->last_snd) && + mptcp_subflow_active(mptcp_subflow_ctx(msk->last_snd))) { + mptcp_for_each_subflow(msk, subflow) { + ssk = mptcp_subflow_tcp_sock(subflow); + *sndbuf = max(tcp_sk(ssk)->snd_wnd, *sndbuf); } + return msk->last_snd; + } + + /* pick the subflow with the lower wmem/wspace ratio */ + for (i = 0; i < 2; ++i) { + send_info[i].ssk = NULL; + send_info[i].ratio = -1; + } + mptcp_for_each_subflow(msk, subflow) { + ssk = mptcp_subflow_tcp_sock(subflow); + if (!mptcp_subflow_active(subflow)) + continue; + nr_active += !subflow->backup; *sndbuf = max(tcp_sk(ssk)->snd_wnd, *sndbuf); - if (subflow->backup) { - if (!backup) - backup = ssk; + if (!sk_stream_memory_free(subflow->tcp_sock)) + continue; + pace = READ_ONCE(ssk->sk_pacing_rate); + if (!pace) continue; - } - return ssk; + ratio = div_u64((u64)READ_ONCE(ssk->sk_wmem_queued) << 32, + pace); + if (ratio < send_info[subflow->backup].ratio) { + send_info[subflow->backup].ssk = ssk; + send_info[subflow->backup].ratio = ratio; + } } - return backup; + pr_debug("msk=%p nr_active=%d ssk=%p:%lld backup=%p:%lld", + msk, nr_active, send_info[0].ssk, send_info[0].ratio, + send_info[1].ssk, send_info[1].ratio); + + /* pick the best backup if no other subflow is active */ + if (!nr_active) + send_info[0].ssk = send_info[1].ssk; + + if (send_info[0].ssk) { + msk->last_snd = send_info[0].ssk; + msk->snd_burst = min_t(int, MPTCP_SEND_BURST_SIZE, + sk_stream_wspace(msk->last_snd)); + return msk->last_snd; + } + return NULL; } static void ssk_check_wmem(struct mptcp_sock *msk) @@ -1160,6 +1224,10 @@ restart: break; } + /* burst can be negative, we will try move to the next subflow + * at selection time, if possible. + */ + msk->snd_burst -= ret; copied += ret; tx_ok = msg_data_left(msg); @@ -1375,6 +1443,11 @@ static bool __mptcp_move_skbs(struct mptcp_sock *msk) unsigned int moved = 0; bool done; + /* avoid looping forever below on racing close */ + if (((struct sock *)msk)->sk_state == TCP_CLOSE) + return false; + + __mptcp_flush_join_list(msk); do { struct sock *ssk = mptcp_subflow_recv_lookup(msk); @@ -1539,9 +1612,15 @@ static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk) sock_owned_by_me((const struct sock *)msk); + if (__mptcp_check_fallback(msk)) + return msk->first; + mptcp_for_each_subflow(msk, subflow) { struct sock *ssk = mptcp_subflow_tcp_sock(subflow); + if (!mptcp_subflow_active(subflow)) + continue; + /* still data outstanding at TCP level? Don't retransmit. */ if (!tcp_write_queue_empty(ssk)) return NULL; diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index cfa5e1b9521b..493bd2c13bc6 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -196,6 +196,8 @@ struct mptcp_sock { u64 write_seq; u64 ack_seq; u64 rcv_data_fin_seq; + struct sock *last_snd; + int snd_burst; atomic64_t snd_una; unsigned long timer_ival; u32 token; @@ -473,12 +475,12 @@ static inline bool before64(__u64 seq1, __u64 seq2) void mptcp_diag_subflow_init(struct tcp_ulp_ops *ops); -static inline bool __mptcp_check_fallback(struct mptcp_sock *msk) +static inline bool __mptcp_check_fallback(const struct mptcp_sock *msk) { return test_bit(MPTCP_FALLBACK_DONE, &msk->flags); } -static inline bool mptcp_check_fallback(struct sock *sk) +static inline bool mptcp_check_fallback(const struct sock *sk) { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); struct mptcp_sock *msk = mptcp_sk(subflow->conn);