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Date: Fri, 12 Feb 2010 04:52:13 +0100
From: Eric Dumazet <eric.dumazet@...il.com>
To: Andreas Petlund <apetlund@...ula.no>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>,
Arnd Hannemann <hannemann@...s.rwth-aachen.de>,
LKML <linux-kernel@...r.kernel.org>, shemminger@...tta.com,
David Miller <davem@...emloft.net>,
william.allen.simpson@...il.com, damian@....rwth-aachen.de
Subject: Re: [net-next PATCH v3 2/3] net: TCP thin linear timeouts
Le jeudi 11 février 2010 à 13:07 +0100, Andreas Petlund a écrit :
> Major changes:
> -Possible to disable mechanisms by socket option
> -Socket option value boundary check
>
>
> Signed-off-by: Andreas Petlund <apetlund@...ula.no>
> ---
> include/linux/sysctl.h | 1 +
> include/linux/tcp.h | 3 +++
> include/net/tcp.h | 4 ++++
> net/ipv4/sysctl_net_ipv4.c | 7 +++++++
> net/ipv4/tcp.c | 7 +++++++
> net/ipv4/tcp_timer.c | 19 ++++++++++++++++++-
> 6 files changed, 40 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index 9f236cd..d840d75 100644
> --- a/include/linux/sysctl.h
> +++ b/include/linux/sysctl.h
> @@ -425,6 +425,7 @@ enum
> NET_TCP_ALLOWED_CONG_CONTROL=123,
> NET_TCP_MAX_SSTHRESH=124,
> NET_TCP_FRTO_RESPONSE=125,
> + NET_TCP_FORCE_THIN_LINEAR_TIMEOUTS=126,
> };
>
> enum {
> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> index 7fee8a4..67da706 100644
> --- a/include/linux/tcp.h
> +++ b/include/linux/tcp.h
> @@ -103,6 +103,7 @@ enum {
> #define TCP_CONGESTION 13 /* Congestion control algorithm */
> #define TCP_MD5SIG 14 /* TCP MD5 Signature (RFC2385) */
> #define TCP_COOKIE_TRANSACTIONS 15 /* TCP Cookie Transactions */
> +#define TCP_THIN_LT 16 /* Use linear timeouts for thin streams*/
>
> /* for TCP_INFO socket option */
> #define TCPI_OPT_TIMESTAMPS 1
> @@ -341,6 +342,8 @@ struct tcp_sock {
> u16 advmss; /* Advertised MSS */
> u8 frto_counter; /* Number of new acks after RTO */
> u8 nonagle; /* Disable Nagle algorithm? */
> + u8 thin_lt : 1,/* Use linear timeouts for thin streams */
> + thin_undef : 7;
>
> /* RTT measurement */
> u32 srtt; /* smoothed round trip time << 3 */
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index e5e2056..bc5856a 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -196,6 +196,9 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo);
> #define TCP_NAGLE_CORK 2 /* Socket is corked */
> #define TCP_NAGLE_PUSH 4 /* Cork is overridden for already queued data */
>
> +/* TCP thin-stream limits */
> +#define TCP_THIN_LT_RETRIES 6 /* After 6 linear retries, do exp. backoff */
> +
> extern struct inet_timewait_death_row tcp_death_row;
>
> /* sysctl variables for tcp */
> @@ -241,6 +244,7 @@ extern int sysctl_tcp_workaround_signed_windows;
> extern int sysctl_tcp_slow_start_after_idle;
> extern int sysctl_tcp_max_ssthresh;
> extern int sysctl_tcp_cookie_size;
> +extern int sysctl_tcp_force_thin_linear_timeouts;
>
> extern atomic_t tcp_memory_allocated;
> extern struct percpu_counter tcp_sockets_allocated;
> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
> index 7e3712c..cb2ed35 100644
> --- a/net/ipv4/sysctl_net_ipv4.c
> +++ b/net/ipv4/sysctl_net_ipv4.c
> @@ -576,6 +576,13 @@ static struct ctl_table ipv4_table[] = {
> .proc_handler = proc_dointvec
> },
> {
> + .procname = "tcp_force_thin_linear_timeouts",
> + .data = &sysctl_tcp_force_thin_linear_timeouts,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec
> + },
> + {
> .procname = "udp_mem",
> .data = &sysctl_udp_mem,
> .maxlen = sizeof(sysctl_udp_mem),
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index d5d69ea..ce9aeb0 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -2229,6 +2229,13 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
> }
> break;
>
> + case TCP_THIN_LT:
> + if (val < 0 || val > 1)
> + err = -EINVAL;
> + else
> + tp->thin_lt = val;
> + break;
> +
> case TCP_CORK:
> /* When set indicates to always queue non-full frames.
> * Later the user clears this option and we transmit
> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
> index de7d1bf..a682479 100644
> --- a/net/ipv4/tcp_timer.c
> +++ b/net/ipv4/tcp_timer.c
> @@ -29,6 +29,7 @@ int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL;
> int sysctl_tcp_retries1 __read_mostly = TCP_RETR1;
> int sysctl_tcp_retries2 __read_mostly = TCP_RETR2;
> int sysctl_tcp_orphan_retries __read_mostly;
> +int sysctl_tcp_force_thin_linear_timeouts __read_mostly;
>
> static void tcp_write_timer(unsigned long);
> static void tcp_delack_timer(unsigned long);
> @@ -415,7 +416,23 @@ void tcp_retransmit_timer(struct sock *sk)
> icsk->icsk_retransmits++;
>
> out_reset_timer:
> - icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
> + /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
> + * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
> + * might be increased if the stream oscillates between thin and thick,
> + * thus the old value might already be too high compared to the value
> + * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
> + * backoff. Limit to TCP_THIN_LT_RETRIES before initiating exponential
> + * backoff behaviour to avoid continue hammering linear-timeout
> + * retransmissions into a black hole*/
> + if ((tp->thin_lt || sysctl_tcp_force_thin_linear_timeouts) &&
> + tcp_stream_is_thin(sk) && sk->sk_state == TCP_ESTABLISHED &&
> + icsk->icsk_retransmits <= TCP_THIN_LT_RETRIES) {
> + icsk->icsk_backoff = 0;
> + icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
> + } else {
> + /* Use normal (exponential) backoff */
> + icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
> + }
> inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
> if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1))
> __sk_dst_reset(sk);
Hi Anreas
Could you include a section in Documentation/networking/ip-sysctl.txt
about tcp_force_thin_linear_timeouts setting ?
Also, you should provide some documentation to be included in man pages
(man 7 tcp), to Michael Kerrisk ( <mtk.manpages@...il.com> ), both for
tcp_force_thin_linear_timeouts and TCP_THIN_LT
(Same applies for patch 3/3 and tcp_force_thin_dupack /
TCP_THIN_DUPACK )
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