On 16/11/06, Andre Oppermann <[EMAIL PROTECTED]> wrote:
This is a patch adding automatic TCP send 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 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%.
New sysctl's are:
net.inet.tcp.sndbuf_auto=1 (enabled)
net.inet.tcp.sndbuf_inc=8192 (8K, step size)
net.inet.tcp.sndbuf_max=262144 (256K, growth limit)
The patch is available here:
http://people.freebsd.org/~andre/tcp_auto_sndbuf-20061116.diff
Any testers, especially with busy FTP servers, are very welcome.
--
Andre
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Ok I done some intitial tesing and so far looks sweet.
I set default send window to 32120 and started a fxp transfer to
another which on 64240 was limited to around 40mbit so 32120 would
normally give about 20mbit, and I previously had 128280 for 80mbit,
now with a default of 32120 and your default sndbuf settings it zoomed
along at around 80mbit.
this from debug.log shows it working.
Nov 22 06:33:33 heaven kernel: tcp_output: inc sockbuf, old 82456, new
90648, sb_cc 80272, snd_wnd 66984, sendwnd 66608
Nov 22 06:33:33 heaven kernel: tcp_output: inc sockbuf, old 90648, new
98840, sb_cc 89664, snd_wnd 72776, sendwnd 69504
Nov 22 06:33:33 heaven kernel: tcp_output: inc sockbuf, old 98840, new
107032, sb_cc 97608, snd_wnd 81464, sendwnd 73848
Nov 22 06:33:33 heaven kernel: tcp_output: inc sockbuf, old 107032,
new 115224, sb_cc 107000, snd_wnd 87256, sendwnd 76744
Nov 22 06:33:33 heaven kernel: tcp_output: inc sockbuf, old 115224,
new 123416, sb_cc 112296, snd_wnd 93048, sendwnd 79640
Nov 22 06:33:33 heaven kernel: tcp_output: inc sockbuf, old 123416,
new 131608, sb_cc 121688, snd_wnd 98840, sendwnd 82536
Nov 22 06:33:33 heaven kernel: tcp_output: inc sockbuf, old 131608,
new 139800, sb_cc 129632, snd_wnd 107528, sendwnd 86880
Nov 22 06:33:34 heaven kernel: tcp_output: inc sockbuf, old 139800,
new 147992, sb_cc 137992, snd_wnd 112944, sendwnd 110048
Nov 22 06:33:34 heaven kernel: tcp_output: inc sockbuf, old 147992,
new 156184, sb_cc 147384, snd_wnd 118736, sendwnd 112944
Nov 22 06:33:34 heaven kernel: tcp_output: inc sockbuf, old 156184,
new 164376, sb_cc 155328, snd_wnd 127424, sendwnd 114261
cant wait for the recv side of this patch.
Chris
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