diff options
| -rw-r--r-- | Documentation/networking/dccp.txt | 3 | ||||
| -rw-r--r-- | net/dccp/ccids/Kconfig | 31 | ||||
| -rw-r--r-- | net/dccp/ccids/ccid3.c | 11 | ||||
| -rw-r--r-- | net/dccp/ccids/ccid3.h | 2 |
4 files changed, 9 insertions, 38 deletions
diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt index cdb6492..271d524 100644 --- a/Documentation/networking/dccp.txt +++ b/Documentation/networking/dccp.txt @@ -174,6 +174,9 @@ Per-route rto_min support > ip route change 10.0.0.0/24 rto_min 250j dev wlan0 > ip route add 10.0.0.254/32 rto_min 800j dev wlan0 > ip route show dev wlan0 + CCID-3 also supports the rto_min setting: it is used to define the lower + bound for the expiry of the nofeedback timer. This can be useful on LANs + with very low RTTs (e.g., loopback, Gbit ethernet). Notes diff --git a/net/dccp/ccids/Kconfig b/net/dccp/ccids/Kconfig index 8408398..0581143 100644 --- a/net/dccp/ccids/Kconfig +++ b/net/dccp/ccids/Kconfig @@ -47,37 +47,6 @@ config IP_DCCP_CCID3_DEBUG If in doubt, say N. -config IP_DCCP_CCID3_RTO - int "Use higher bound for nofeedback timer" - default 100 - depends on IP_DCCP_CCID3 && EXPERIMENTAL - ---help--- - Use higher lower bound for nofeedback timer expiration. - - The TFRC nofeedback timer normally expires after the maximum of 4 - RTTs and twice the current send interval (RFC 3448, 4.3). On LANs - with a small RTT this can mean a high processing load and reduced - performance, since then the nofeedback timer is triggered very - frequently. - - This option enables to set a higher lower bound for the nofeedback - value. Values in units of milliseconds can be set here. - - A value of 0 disables this feature by enforcing the value specified - in RFC 3448. The following values have been suggested as bounds for - experimental use: - * 16-20ms to match the typical multimedia inter-frame interval - * 100ms as a reasonable compromise [default] - * 1000ms corresponds to the lower TCP RTO bound (RFC 2988, 2.4) - - The default of 100ms is a compromise between a large value for - efficient DCCP implementations, and a small value to avoid disrupting - the network in times of congestion. - - The purpose of the nofeedback timer is to slow DCCP down when there - is serious network congestion: experimenting with larger values should - therefore not be performed on WANs. - config IP_DCCP_TFRC_LIB def_bool y if IP_DCCP_CCID3 diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index 4340672..278e170 100644 --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -460,13 +460,12 @@ done_computing_x: sk->sk_write_space(sk); /* - * Update timeout interval for the nofeedback timer. - * We use a configuration option to increase the lower bound. - * This can help avoid triggering the nofeedback timer too - * often ('spinning') on LANs with small RTTs. + * Update timeout interval for the nofeedback timer. In order to control + * rate halving on networks with very low RTTs (<= 1 ms), use per-route + * tunable RTAX_RTO_MIN value as the lower bound. */ - hc->tx_t_rto = max_t(u32, 4 * hc->tx_rtt, (CONFIG_IP_DCCP_CCID3_RTO * - (USEC_PER_SEC / 1000))); + hc->tx_t_rto = max_t(u32, 4 * hc->tx_rtt, + USEC_PER_SEC/HZ * tcp_rto_min(sk)); /* * Schedule no feedback timer to expire in * max(t_RTO, 2 * s/X) = max(t_RTO, 2 * t_ipi) diff --git a/net/dccp/ccids/ccid3.h b/net/dccp/ccids/ccid3.h index b186424..b7e569c 100644 --- a/net/dccp/ccids/ccid3.h +++ b/net/dccp/ccids/ccid3.h @@ -42,7 +42,7 @@ #include "lib/tfrc.h" #include "../ccid.h" -/* Two seconds as per RFC 3448 4.2 */ +/* Two seconds as per RFC 5348, 4.2 */ #define TFRC_INITIAL_TIMEOUT (2 * USEC_PER_SEC) /* In usecs - half the scheduling granularity as per RFC3448 4.6 */ |
