Improve performance on long fat networks (LFNs) #2910
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On Linux, the TCP send buffer size is increased to 32768 if it is less that this (which it normally is). This however has the effect of disabling dynamic buffer sizing, leading to a maximum available bandwidth of max_bandwidth = 262144 (bits) / round_trip_time (secs) This is not noticeable on a LAN with an RTT of around 0.5ms, but very noticeable on a WAN with an RTT of 0.25s. Comments in the config file and manpage in this area are improved, as is the logging if the parameters are actually set.
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Fixes #2905
Probably fixes #1625
Fixes #1483
Fixes #1026
On Linux, the TCP send buffer size is increased to 32768 if it is less that this (which it normally is). This however has the effect of disabling dynamic buffer sizing, leading to a maximum available bandwidth of
max_bandwidth = 262144 (bits) / round_trip_time (secs)
This is not noticeable on a LAN with an RTT of around 0.5ms, but very noticeable on a WAN with an RTT of 0.25s.
Comments in the config file and manpage in this area are improved, as is the logging if the parameters are actually set.
This change has no impact on default FreeBSD behaviour. On this platform the default TCP buffer size (
net.inet.tcp.sendspace) is 32768.