Date: Fri, 15 Dec 2006 00:55:13 +0000 From: Chris <chrcoluk@gmail.com> To: "Andre Oppermann" <andre@freebsd.org> Cc: freebsd-net@freebsd.org, freebsd-current@freebsd.org Subject: Re: Automatic TCP send and receive socket buffer sizing Message-ID: <3aaaa3a0612141655x72c1905cw7fc8f415e08d70b8@mail.gmail.com> In-Reply-To: <45812CDE.7000103@freebsd.org> References: <457F2D82.6000905@freebsd.org> <3aaaa3a0612131706w5ae75edcvadd7958274a1e2e2@mail.gmail.com> <45812CDE.7000103@freebsd.org>
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On 14/12/06, Andre Oppermann <andre@freebsd.org> wrote: > Chris wrote: > > On 12/12/06, Andre Oppermann <andre@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. > > No, this patch doesn't work on 6.x. It makes changes to struct tcpcb > to add two additional fields. This requires netstat(1) to be recompiled > and is a ABI change. However I've got a number of requests for 6.x > patch so I may make one anyway. > > -- > Andre > > Please that would be great, the send patch works on 6.x flawlessly and has improved performance enormously it would be a shame to have to wait for 7.x to be production ready before I use it. Thanks Chris
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