Date: Thu, 14 Dec 2006 11:52:14 +0100 From: Andre Oppermann <andre@freebsd.org> To: Chris <chrcoluk@gmail.com> Cc: freebsd-net@freebsd.org, freebsd-current@freebsd.org Subject: Re: Automatic TCP send and receive socket buffer sizing Message-ID: <45812CDE.7000103@freebsd.org> In-Reply-To: <3aaaa3a0612131706w5ae75edcvadd7958274a1e2e2@mail.gmail.com> References: <457F2D82.6000905@freebsd.org> <3aaaa3a0612131706w5ae75edcvadd7958274a1e2e2@mail.gmail.com>
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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
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