On Tue, 8 Dec 2015, Per Hurtig wrote: > This patch implements the RTO restart modification (RTOR). When data is > ACKed, and the RTO timer is restarted, the time elapsed since the last > outstanding segment was transmitted is subtracted from the calculated RTO > value. This way, the RTO timer will expire after exactly RTO seconds, and > not RTO + RTT [+ delACK] seconds. > > This patch also implements a new sysctl (tcp_timer_restart) that is used > to control the timer restart behavior. > > Signed-off-by: Per Hurtig <per.hur...@kau.se> > --- > Documentation/networking/ip-sysctl.txt | 12 ++++++++++++ > include/net/tcp.h | 6 ++++++ > net/ipv4/sysctl_net_ipv4.c | 10 ++++++++++ > net/ipv4/tcp_input.c | 29 +++++++++++++++++++++++++++++ > 4 files changed, 57 insertions(+) > > diff --git a/Documentation/networking/ip-sysctl.txt > b/Documentation/networking/ip-sysctl.txt > index 2ea4c45..4094128 100644 > --- a/Documentation/networking/ip-sysctl.txt > +++ b/Documentation/networking/ip-sysctl.txt > @@ -591,6 +591,18 @@ tcp_syn_retries - INTEGER > with the current initial RTO of 1second. With this the final timeout > for an active TCP connection attempt will happen after 127seconds. > > +tcp_timer_restart - INTEGER > + Controls how the RTO and PTO timers are restarted (RTOR and TLPR). > + If set (per timer or combined) the timers are restarted with > + respect to the earliest outstanding segment, to not extend tail loss > + latency unnecessarily. > + Possible values: > + 0 disables RTOR and TLPR. > + 1 enables RTOR. > + 2 enables TLPR. > + 3 enables RTOR and TLPR. > + Default: 3 > + > tcp_timestamps - BOOLEAN > Enable timestamps as defined in RFC1323. > > diff --git a/include/net/tcp.h b/include/net/tcp.h > index f80e74c..833efb7 100644 > --- a/include/net/tcp.h > +++ b/include/net/tcp.h > @@ -76,6 +76,11 @@ void tcp_time_wait(struct sock *sk, int state, int timeo); > /* After receiving this amount of duplicate ACKs fast retransmit starts. */ > #define TCP_FASTRETRANS_THRESH 3 > > +/* Disable RTO Restart if the number of outstanding segments is at least. */ > +#define TCP_TIMER_RTORESTART 1 > +#define TCP_TIMER_TLPRESTART 2 > +#define TCP_RTORESTART_THRESH 4
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