Date: Fri, 17 Nov 2006 11:22:09 -0800 From: Mark Atkinson <atkin901@yahoo.com> To: freebsd-net@freebsd.org Cc: freebsd-current@freebsd.org Subject: Re: Automatic TCP send socker buffer sizing Message-ID: <ejl252$luh$1@sea.gmane.org> References: <455CB311.8040301@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
Andre Oppermann 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. Did some minimal testing and it appears to apply cleanly and log: ov 17 11:15:27 ftp kernel: tcp_output: inc sockbuf, old 33304, new 41496, sb_cc 31776, snd_wnd 40544, sendwnd 20272 Nov 17 11:15:27 ftp kernel: tcp_output: inc sockbuf, old 41496, new 49688, sb_cc 38232, snd_wnd 46336, sendwnd 27512 Nov 17 11:15:27 ftp kernel: tcp_output: inc sockbuf, old 49688, new 57880, sb_cc 46960, snd_wnd 63712, sendwnd 40544 Nov 17 11:15:27 ftp kernel: tcp_output: inc sockbuf, old 57880, new 66072, sb_cc 55568, snd_wnd 63712, sendwnd 60816 Nov 17 11:15:27 ftp kernel: tcp_output: inc sockbuf, old 66072, new 74264, sb_cc 65168, snd_wnd 63712, sendwnd 63712 Nov 17 11:15:27 ftp kernel: tcp_output: inc sockbuf, old 74264, new 82456, sb_cc 65168, snd_wnd 63712, sendwnd 63712 -- Mark Atkinson atkin901@yahoo.com (!wired)?(coffee++):(wired);
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?ejl252$luh$1>