| Message ID | 20250207152830.2527578-6-edumazet@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 1280c26228bd7eb14bdecd67dedbdd871f8fdda5 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | tcp: allow to reduce max RTO | expand |
On Fri, Feb 7, 2025 at 11:30 PM Eric Dumazet <edumazet@google.com> wrote: > > Previous patch added a TCP_RTO_MAX_MS socket option > to tune a TCP socket max RTO value. > > Many setups prefer to change a per netns sysctl. > > This patch adds /proc/sys/net/ipv4/tcp_rto_max_ms > > Its initial value is 120000 (120 seconds). > > Keep in mind that a decrease of tcp_rto_max_ms > means shorter overall timeouts, unless tcp_retries2 > sysctl is increased. > > Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Jason Xing <kerneljasonxing@gmail.com> Thanks for picking up my incomplete patch/work and fulfilling it at last :) Thanks, Jason
On Fri, Feb 7, 2025 at 11:46 PM Jason Xing <kerneljasonxing@gmail.com> wrote: > > On Fri, Feb 7, 2025 at 11:30 PM Eric Dumazet <edumazet@google.com> wrote: > > > > Previous patch added a TCP_RTO_MAX_MS socket option > > to tune a TCP socket max RTO value. > > > > Many setups prefer to change a per netns sysctl. > > > > This patch adds /proc/sys/net/ipv4/tcp_rto_max_ms > > > > Its initial value is 120000 (120 seconds). > > > > Keep in mind that a decrease of tcp_rto_max_ms > > means shorter overall timeouts, unless tcp_retries2 > > sysctl is increased. > > > > Signed-off-by: Eric Dumazet <edumazet@google.com> > > Reviewed-by: Jason Xing <kerneljasonxing@gmail.com> Reviewed-by: Neal Cardwell <ncardwell@google.com> Thanks, Eric! neal
From: Eric Dumazet <edumazet@google.com> Date: Fri, 7 Feb 2025 15:28:30 +0000 > Previous patch added a TCP_RTO_MAX_MS socket option > to tune a TCP socket max RTO value. > > Many setups prefer to change a per netns sysctl. > > This patch adds /proc/sys/net/ipv4/tcp_rto_max_ms > > Its initial value is 120000 (120 seconds). > > Keep in mind that a decrease of tcp_rto_max_ms > means shorter overall timeouts, unless tcp_retries2 > sysctl is increased. > > Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 363b4950d542aa32fbf6ab1617de46a900061f82..054561f8dcae77d4183f5b7e45f671ba8979390a 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -705,6 +705,8 @@ tcp_retries2 - INTEGER seconds and is a lower bound for the effective timeout. TCP will effectively time out at the first RTO which exceeds the hypothetical timeout. + If tcp_rto_max_ms is decreased, it is recommended to also + change tcp_retries2. RFC 1122 recommends at least 100 seconds for the timeout, which corresponds to a value of at least 8. @@ -1237,6 +1239,17 @@ tcp_rto_min_us - INTEGER Default: 200000 +tcp_rto_max_ms - INTEGER + Maximal TCP retransmission timeout (in ms). + Note that TCP_RTO_MAX_MS socket option has higher precedence. + + When changing tcp_rto_max_ms, it is important to understand + that tcp_retries2 might need a change. + + Possible Values: 1000 - 120,000 + + Default: 120,000 + UDP variables ============= diff --git a/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst b/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst index de0263302f16dd815593671c4f75a93ed6f7cac4..6e7b20afd2d4984233e91d713ee9acd4b2e007f2 100644 --- a/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst +++ b/Documentation/networking/net_cachelines/netns_ipv4_sysctl.rst @@ -86,6 +86,7 @@ u8 sysctl_tcp_sack u8 sysctl_tcp_window_scaling tcp_syn_options,tcp_parse_options u8 sysctl_tcp_timestamps u8 sysctl_tcp_early_retrans read_mostly tcp_schedule_loss_probe(tcp_write_xmit) +u32 sysctl_tcp_rto_max_ms u8 sysctl_tcp_recovery tcp_fastretrans_alert u8 sysctl_tcp_thin_linear_timeouts tcp_retrans_timer(on_thin_streams) u8 sysctl_tcp_slow_start_after_idle unlikely(tcp_cwnd_validate-network-not-starved) diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index 46452da352061007d19d00fdacddd25bbe56444d..45ac125e8aebb99d4083d540c907f0d560dac0b0 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -181,6 +181,7 @@ struct netns_ipv4 { u8 sysctl_tcp_window_scaling; u8 sysctl_tcp_timestamps; int sysctl_tcp_rto_min_us; + int sysctl_tcp_rto_max_ms; u8 sysctl_tcp_recovery; u8 sysctl_tcp_thin_linear_timeouts; u8 sysctl_tcp_slow_start_after_idle; diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 42cb5dc9cb245c26f9a38f8c8c4b26b1adddca39..3a43010d726fb103beaad2b11d6797424b0c946e 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -28,6 +28,7 @@ static int tcp_adv_win_scale_max = 31; static int tcp_app_win_max = 31; static int tcp_min_snd_mss_min = TCP_MIN_SND_MSS; static int tcp_min_snd_mss_max = 65535; +static int tcp_rto_max_max = TCP_RTO_MAX_SEC * MSEC_PER_SEC; static int ip_privileged_port_min; static int ip_privileged_port_max = 65535; static int ip_ttl_min = 1; @@ -1583,6 +1584,15 @@ static struct ctl_table ipv4_net_table[] = { .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ONE, }, + { + .procname = "tcp_rto_max_ms", + .data = &init_net.ipv4.sysctl_tcp_rto_max_ms, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ONE_THOUSAND, + .extra2 = &tcp_rto_max_max, + }, }; static __net_init int ipv4_sysctl_init_net(struct net *net) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index a9b92d8bfb5644431683ec214aedd0e9756e8a0a..d01f42cf3863bd87ac0a91ab01505616a1bd4225 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -423,7 +423,7 @@ void tcp_init_sock(struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); - int rto_min_us; + int rto_min_us, rto_max_ms; tp->out_of_order_queue = RB_ROOT; sk->tcp_rtx_queue = RB_ROOT; @@ -433,8 +433,8 @@ void tcp_init_sock(struct sock *sk) icsk->icsk_rto = TCP_TIMEOUT_INIT; - /* Use a sysctl ? */ - icsk->icsk_rto_max = TCP_RTO_MAX; + rto_max_ms = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rto_max_ms); + icsk->icsk_rto_max = msecs_to_jiffies(rto_max_ms); rto_min_us = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rto_min_us); icsk->icsk_rto_min = usecs_to_jiffies(rto_min_us); diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 06fb0123d2d60e22f19ea48b73ac3668c51465a2..d1fd2128ac6cce9b845b1f8d278a194c511db87b 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -3532,6 +3532,7 @@ static int __net_init tcp_sk_init(struct net *net) net->ipv4.sysctl_tcp_pingpong_thresh = 1; net->ipv4.sysctl_tcp_rto_min_us = jiffies_to_usecs(TCP_RTO_MIN); + net->ipv4.sysctl_tcp_rto_max_ms = TCP_RTO_MAX_SEC * MSEC_PER_SEC; return 0; }
Previous patch added a TCP_RTO_MAX_MS socket option to tune a TCP socket max RTO value. Many setups prefer to change a per netns sysctl. This patch adds /proc/sys/net/ipv4/tcp_rto_max_ms Its initial value is 120000 (120 seconds). Keep in mind that a decrease of tcp_rto_max_ms means shorter overall timeouts, unless tcp_retries2 sysctl is increased. Signed-off-by: Eric Dumazet <edumazet@google.com> --- Documentation/networking/ip-sysctl.rst | 13 +++++++++++++ .../networking/net_cachelines/netns_ipv4_sysctl.rst | 1 + include/net/netns/ipv4.h | 1 + net/ipv4/sysctl_net_ipv4.c | 10 ++++++++++ net/ipv4/tcp.c | 6 +++--- net/ipv4/tcp_ipv4.c | 1 + 6 files changed, 29 insertions(+), 3 deletions(-)