Re: Automatic TCP send and receive socket buffer sizing

On 12/12/06, Andre Oppermann <andre_at_freebsd.org> wrote:
> This is a patch adding automatic TCP send and receive socket buffer sizing.
> Normally the socket buffers are static (either derived from global defaults
> or set with setsockopt) and do not adapt to real network conditions.  Two
> things happen: a) your socket buffers are too small and you can't reach the
> full potential of the network between both hosts; b) your socket buffers are
> too big and you waste a lot of kernel memory for data just sitting around.
>
> With automatic TCP send and receive socket buffers we can start with a small
> buffer and quickly grow it in parallel with the TCP congestion window to match
> real network conditions.
>
> FreeBSD has a default 32K send socket buffer.  This supports a maximal
> transfer rate of only slightly more than 2Mbit/s on a 100ms RTT trans-
> continental link.  Or at 200ms just above 1Mbit/s.  With TCP send buffer
> auto scaling and the default values below it supports 20Mbit/s at 100ms
> and 10Mbit/s at 200ms.  That's an improvement of factor 10, or 1000%.
> For the receive side it looks slightly better with a default of 64K buffer
> size.
>
> The automatic send buffer sizing patch is currently running on one half of
> the FTP.FreeBSD.ORG cluster w/o any problems so far.  Against this machine
> with the automatic receive buffer sizing patch I can download at 5.7MBytes
> per second.  Without patch it maxed out at 1.6MBytes per second as the delay
> bandwidth product became equal to the static socket buffer size without hitting
> the limits of the physical link between the machines.  My test machine is about
> 35ms from that FTP.FreeBSD.ORG and connected through a moderately loaded 100Mbit
> Internet link.
>
> New sysctl's are:
>
>  net.inet.tcp.sendbuf_auto=1      (enabled)
>  net.inet.tcp.sendbuf_inc=8192    (8K, step size)
>  net.inet.tcp.sendbuf_max=262144   (256K, growth limit)
>  net.inet.tcp.recvbuf_auto=1      (enabled)
>  net.inet.tcp.recvbuf_inc=16384           (16K, step size)
>  net.inet.tcp.recvbuf_max=262144   (256K, growth limit)
>
> The patch is available here (it may apply with some fuzz):
>
>  http://people.freebsd.org/~andre/tcp_auto_buf-20061212.diff
>
> Any tests and test reports are very welcome.
>
> --
> Andre

Hi does this patch work on 6.x? I used the send patch on 6.x and works
great please make a 6.x patch thank you and I will happily test.

Chris