net: TCP thin dupack
Subsystems (3)
PATCH 3/3 net: TCP thin dupack
This patch enables fast retransmissions after one dupACK for TCP if the stream is identified as thin. This will reduce latencies for thin streams that are not able to trigger fast retransmissions due to high packet interarrival time. This mechanism is only active if enabled by iocontrol or syscontrol and the stream is identified as thin.
Signed-off-by Andreas Petlund <[email protected]>
--- include/linux/tcp.h | 4 +++- include/net/tcp.h | 1 + net/ipv4/sysctl_net_ipv4.c | 8 ++++++++ net/ipv4/tcp.c | 5 +++++ net/ipv4/tcp_input.c | 8 ++++++++ 5 files changed, 25 insertions(+), 1 deletions(-)
include/linux/tcp.h +3 -1
@@ -97,6 +97,7 @@ enum {#define TCP_CONGESTION 13/* Congestion control algorithm */ #define TCP_MD5SIG 14/* TCP MD5 Signature (RFC2385) */ #define TCP_THIN_RM_EXPB 15/* Remove exp. backoff for thin streams*/ +#define TCP_THIN_DUPACK 16/* Fast retrans. after 1 dupack */ #define TCPI_OPT_TIMESTAMPS 1#define TCPI_OPT_SACK 2
@@ -301,7 +302,8 @@ struct tcp_sock {u8 frto_counter;/* Number of new acks after RTO */ u8 nonagle;/* Disable Nagle algorithm? */ u8 thin_rm_expb:1, /* Remove exp. backoff for thin streams */ - thin_undef : 7; + thin_dupack : 1,/* Fast retransmit on first dupack */ + thin_undef : 6;/* RTT measurement */ u32 srtt;/* smoothed round trip time << 3 */
include/net/tcp.h +1 -0
@@ -238,6 +238,7 @@ 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_force_thin_rm_expb; +extern int sysctl_tcp_force_thin_dupack;extern atomic_t tcp_memory_allocated;extern struct percpu_counter tcp_sockets_allocated;
net/ipv4/sysctl_net_ipv4.c +8 -0
@@ -721,6 +721,14 @@ static struct ctl_table ipv4_table[] = { .proc_handler = proc_dointvec }, { + .ctl_name = CTL_UNNUMBERED, + .procname = "tcp_force_thin_dupack", + .data = &sysctl_tcp_force_thin_dupack, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec + }, + { .ctl_name = CTL_UNNUMBERED, .procname = "udp_mem", .data = &sysctl_udp_mem,
net/ipv4/tcp.c +5 -0
@@ -2139,6 +2139,11 @@ static int do_tcp_setsockopt(struct sock *sk, int level, tp->thin_rm_expb =1 ;break ; +case TCP_THIN_DUPACK : +if (val) + tp->thin_dupack =1 ; +break ; +case TCP_CORK :/* When set indicates to always queue non-full frames. * Later the user clears this option and we transmit
net/ipv4/tcp_input.c +8 -0
@@ -89,6 +89,8 @@ int sysctl_tcp_frto __read_mostly = 2;int sysctl_tcp_frto_response__read_mostly ;int sysctl_tcp_nometrics_save__read_mostly ; +int sysctl_tcp_force_thin_dupack__read_mostly ; +int sysctl_tcp_moderate_rcvbuf__read_mostly =1 ;int sysctl_tcp_abc__read_mostly ;
@@ -2447,6 +2449,12 @@ static int tcp_time_to_recover(struct sock *sk)return 1 ; } +/* If a thin stream is detected, retransmit after first +* received dupack */ +if ((tp->thin_dupack || sysctl_tcp_force_thin_dupack) && +tcp_dupack_heurestics (tp) >1 &&tcp_stream_is_thin (tp)) +return 1 ; +return 0 ; }
Signature · 1 line
1.6.0.4
include/linux/tcp.h enum { · line 101
Quoted 10 lines · Andreas Petlund
include/linux/tcp.h +1
-0@@ -97,6 +97,7 @@ enum {#define TCP_CONGESTION 13/* Congestion control algorithm */ #define TCP_MD5SIG 14/* TCP MD5 Signature (RFC2385) */ #define TCP_THIN_RM_EXPB 15/* Remove exp. backoff for thin streams*/ +#define TCP_THIN_DUPACK 16/* Fast retrans. after 1 dupack */
I've not had the chance to examine the rest, but I've been poking at a patch series that's used 15 for over a year, so could you try 16 and 17?
Den 28. okt. 2009 kl. 03.43 skrev William Allen Simpson:
Quoted 14 lines
Quoted 11 lines · Andreas Petlund
include/linux/tcp.h +1
-0@@ -97,6 +97,7 @@ enum {#define TCP_CONGESTION 13/* Congestion control algorithm */ #define TCP_MD5SIG 14/* TCP MD5 Signature (RFC2385) */ #define TCP_THIN_RM_EXPB 15/* Remove exp. backoff for thin streams*/ +#define TCP_THIN_DUPACK 16/* Fast retrans. after 1 dupack */
I've not had the chance to examine the rest, but I've been poking at a patch series that's used 15 for over a year, so could you try 16 and 17?
Thank you for the feedback. I will address this in the next patch iteration.
Quoted 100 lines · Andreas Petlund
This patch enables fast retransmissions after one dupACK for TCP if the stream is identified as thin. This will reduce latencies for thin streams that are not able to trigger fast retransmissions due to high packet interarrival time. This mechanism is only active if enabled by iocontrol or syscontrol and the stream is identified as thin.
Signed-off-by Andreas Petlund <[email protected]>--- include/linux/tcp.h | 4 +++- include/net/tcp.h | 1 + net/ipv4/sysctl_net_ipv4.c | 8 ++++++++ net/ipv4/tcp.c | 5 +++++ net/ipv4/tcp_input.c | 8 ++++++++ 5 files changed, 25 insertions(+), 1 deletions(-)include/linux/tcp.h +3
-1@@ -97,6 +97,7 @@ enum {#define TCP_CONGESTION 13/* Congestion control algorithm */ #define TCP_MD5SIG 14/* TCP MD5 Signature (RFC2385) */ #define TCP_THIN_RM_EXPB 15/* Remove exp. backoff for thin streams*/ +#define TCP_THIN_DUPACK 16/* Fast retrans. after 1 dupack */ #define TCPI_OPT_TIMESTAMPS 1#define TCPI_OPT_SACK 2@@ -301,7 +302,8 @@ struct tcp_sock {u8 frto_counter;/* Number of new acks after RTO */ u8 nonagle;/* Disable Nagle algorithm? */ u8 thin_rm_expb:1, /* Remove exp. backoff for thin streams */ - thin_undef : 7; + thin_dupack : 1,/* Fast retransmit on first dupack */ + thin_undef : 6;/* RTT measurement */ u32 srtt;/* smoothed round trip time << 3 */ include/net/tcp.h +1
-0@@ -238,6 +238,7 @@ 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_force_thin_rm_expb; +extern int sysctl_tcp_force_thin_dupack;extern atomic_t tcp_memory_allocated;extern struct percpu_counter tcp_sockets_allocated;net/ipv4/sysctl_net_ipv4.c +8
-0@@ -721,6 +721,14 @@ static struct ctl_table ipv4_table[] = { .proc_handler = proc_dointvec }, { + .ctl_name = CTL_UNNUMBERED, + .procname = "tcp_force_thin_dupack", + .data = &sysctl_tcp_force_thin_dupack, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec + }, + { .ctl_name = CTL_UNNUMBERED, .procname = "udp_mem", .data = &sysctl_udp_mem,net/ipv4/tcp.c +5
-0@@ -2139,6 +2139,11 @@ static int do_tcp_setsockopt(struct sock *sk, int level, tp->thin_rm_expb =1 ;break ; +case TCP_THIN_DUPACK : +if (val) + tp->thin_dupack =1 ; +break ; +case TCP_CORK :/* When set indicates to always queue non-full frames. * Later the user clears this option and we transmit net/ipv4/tcp_input.c +2
-0@@ -89,6 +89,8 @@ int sysctl_tcp_frto __read_mostly = 2;int sysctl_tcp_frto_response__read_mostly ;int sysctl_tcp_nometrics_save__read_mostly ; +int sysctl_tcp_force_thin_dupack__read_mostly ; +int sysctl_tcp_moderate_rcvbuf__read_mostly =1 ;int sysctl_tcp_abc__read_mostly ;@@ -2447,6 +2449,12 @@ static int tcp_time_to_recover(struct sock *sk)return 1 ;
net/ipv4/tcp_input.c static int tcp_time_to_recover(struct sock *sk) · line 2459
Quoted 10 lines
net/ipv4/tcp_input.c +6
-0} +/* If a thin stream is detected, retransmit after first +* received dupack */ +if ((tp->thin_dupack || sysctl_tcp_force_thin_dupack) && +tcp_dupack_heurestics (tp) >1 &&tcp_stream_is_thin (tp)) +return 1 ; +return 0 ; }
Have you tested it? ...I doubt this will work like you say and retransmit something when the window is small. ...Besides, you should have built this patch on top of the function rename you submitted earlier as after DaveM applied that this will no longer even compile...
Signature · 1 line
i.