diff options
| author | Yuchung Cheng <ycheng@google.com> | 2017-07-19 15:41:26 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-07-19 16:14:10 -0700 |
| commit | bb4d991a28cc86a2dfbeefeff32911ca9f779c18 (patch) | |
| tree | 6fd415a7d0b54a9e639067375013fe8f2c3a48b7 | |
| parent | c4b2bf6b4a35348fe6d1eb06928eb68d7b9d99a9 (diff) | |
tcp: adjust tail loss probe timeout
This patch adjusts the timeout formula to schedule the TCP loss probe
(TLP). The previous formula uses 2*SRTT or 1.5*RTT + DelayACKMax if
only one packet is in flight. It keeps a lower bound of 10 msec which
is too large for short RTT connections (e.g. within a data-center).
The new formula = 2*RTT + (inflight == 1 ? 200ms : 2ticks) which
performs better for short and fast connections.
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | include/net/tcp.h | 3 | ||||
| -rw-r--r-- | net/ipv4/tcp_output.c | 17 | ||||
| -rw-r--r-- | net/ipv4/tcp_recovery.c | 2 |
3 files changed, 12 insertions, 10 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index 70483296157f..4f056ea79df2 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -139,6 +139,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo); #endif #define TCP_RTO_MAX ((unsigned)(120*HZ)) #define TCP_RTO_MIN ((unsigned)(HZ/5)) +#define TCP_TIMEOUT_MIN (2U) /* Min timeout for TCP timers in jiffies */ #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ)) /* RFC6298 2.1 initial RTO value */ #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now * used as a fallback RTO for the @@ -150,8 +151,6 @@ void tcp_time_wait(struct sock *sk, int state, int timeo); #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes * for local resources. */ -#define TCP_REO_TIMEOUT_MIN (2000) /* Min RACK reordering timeout in usec */ - #define TCP_KEEPALIVE_TIME (120*60*HZ) /* two hours */ #define TCP_KEEPALIVE_PROBES 9 /* Max of 9 keepalive probes */ #define TCP_KEEPALIVE_INTVL (75*HZ) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 4e985dea1dd2..886d874775df 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2377,7 +2377,6 @@ bool tcp_schedule_loss_probe(struct sock *sk) struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); u32 timeout, tlp_time_stamp, rto_time_stamp; - u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3); /* No consecutive loss probes. */ if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) { @@ -2406,15 +2405,19 @@ bool tcp_schedule_loss_probe(struct sock *sk) tcp_send_head(sk)) return false; - /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account + /* Probe timeout is 2*rtt. Add minimum RTO to account * for delayed ack when there's one outstanding packet. If no RTT * sample is available then probe after TCP_TIMEOUT_INIT. */ - timeout = rtt << 1 ? : TCP_TIMEOUT_INIT; - if (tp->packets_out == 1) - timeout = max_t(u32, timeout, - (rtt + (rtt >> 1) + TCP_DELACK_MAX)); - timeout = max_t(u32, timeout, msecs_to_jiffies(10)); + if (tp->srtt_us) { + timeout = usecs_to_jiffies(tp->srtt_us >> 2); + if (tp->packets_out == 1) + timeout += TCP_RTO_MIN; + else + timeout += TCP_TIMEOUT_MIN; + } else { + timeout = TCP_TIMEOUT_INIT; + } /* If RTO is shorter, just schedule TLP in its place. */ tlp_time_stamp = tcp_jiffies32 + timeout; diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c index fe9a493d0208..449cd914d58e 100644 --- a/net/ipv4/tcp_recovery.c +++ b/net/ipv4/tcp_recovery.c @@ -113,7 +113,7 @@ void tcp_rack_mark_lost(struct sock *sk) tp->rack.advanced = 0; tcp_rack_detect_loss(sk, &timeout); if (timeout) { - timeout = usecs_to_jiffies(timeout + TCP_REO_TIMEOUT_MIN); + timeout = usecs_to_jiffies(timeout) + TCP_TIMEOUT_MIN; inet_csk_reset_xmit_timer(sk, ICSK_TIME_REO_TIMEOUT, timeout, inet_csk(sk)->icsk_rto); } |