From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Petlund Subject: [net-next PATCH v4 2/3] net: TCP thin linear timeouts Date: Tue, 16 Feb 2010 15:40:41 +0100 Message-ID: <4B7AAE69.8020701@simula.no> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: =?ISO-8859-1?Q?Ilpo_J=E4rvinen?= , Eric Dumazet , Arnd Hannemann , LKML , shemminger@vyatta.com, David Miller , william.allen.simpson@gmail.com, damian@tvk.rwth-aachen.de, "Eric W. Biederman" To: "netdev@vger.kernel.org" Return-path: Received: from mail-forward1.uio.no ([129.240.10.70]:59205 "EHLO mail-forward1.uio.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755519Ab0BPOko (ORCPT ); Tue, 16 Feb 2010 09:40:44 -0500 Received: from exim by mail-out1.uio.no with local-bsmtp (Exim 4.69) (envelope-from ) id 1NhObS-0001dz-Nv for netdev@vger.kernel.org; Tue, 16 Feb 2010 15:40:42 +0100 Sender: netdev-owner@vger.kernel.org List-ID: Major changes: -Renamed variables, ioctl and sysctl. -Added sysctl documentation. -Removed redundant allocation. Signed-off-by: Andreas Petlund --- Documentation/networking/ip-sysctl.txt | 12 ++++++++++++ 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 | 20 +++++++++++++++++++- 6 files changed, 52 insertions(+), 1 deletions(-) diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 2dc7a1d..f147310 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -487,6 +487,18 @@ tcp_dma_copybreak - INTEGER and CONFIG_NET_DMA is enabled. Default: 4096 +tcp_thin_linear_timeouts - BOOLEAN + Enable dynamic triggering of linear timeouts for thin streams. + If set, a check is performed upon retransmission by timeout to + determine if the stream is thin (less than 4 packets in flight). + As long as the stream is found to be thin, up to 6 linear + timeouts may be performed before exponential backoff mode is + initiated. This improves retransmission latency for + non-aggressive thin streams, often found to be time-dependent. + For more information on thin streams, see + Documentation/networking/tcp-thin.txt + Default: 0 + UDP variables: udp_mem - vector of 3 INTEGERs: min, pressure, max diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 7fee8a4..42885af 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_LINEAR_TIMEOUTS 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_lto : 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..be49356 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_LINEAR_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_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..e6a2460 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_thin_linear_timeouts", + .data = &sysctl_tcp_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..a159c0d 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_LINEAR_TIMEOUTS: + if (val < 0 || val > 1) + err = -EINVAL; + else + tp->thin_lto = 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..00f7caa 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_thin_linear_timeouts __read_mostly; static void tcp_write_timer(unsigned long); static void tcp_delack_timer(unsigned long); @@ -415,7 +416,24 @@ 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_LINEAR_RETRIES before initiating + * exponential backoff behaviour to avoid continue hammering + * linear-timeout retransmissions into a black hole*/ + if (sk->sk_state == TCP_ESTABLISHED && + (tp->thin_lto || sysctl_tcp_thin_linear_timeouts) && + tcp_stream_is_thin(sk) && + icsk->icsk_retransmits <= TCP_THIN_LINEAR_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); -- 1.6.3.3