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 <pabeni@redhat.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2020-09-14 10:01:17 +02:00 committed by David S. Miller
parent 4596a2c1b7
commit d5f49190de
2 changed files with 105 additions and 24 deletions

View File

@ -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 = max(tcp_sk(ssk)->snd_wnd, *sndbuf);
if (subflow->backup) {
if (!backup)
backup = ssk;
continue;
}
return ssk;
*sndbuf = msk->first->sk_sndbuf;
return sk_stream_memory_free(msk->first) ? msk->first : NULL;
}
return backup;
/* 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 (!sk_stream_memory_free(subflow->tcp_sock))
continue;
pace = READ_ONCE(ssk->sk_pacing_rate);
if (!pace)
continue;
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;
}
}
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 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
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;

View File

@ -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);