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| /freebsd-10.1-release/sys/netinet/ | ||
| H A D | tcp_usrreq.c | diff 166405 Thu Feb 01 16:32:13 MST 2007 andre Auto sizing TCP socket buffers. 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. New sysctls 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) Tested by: many (on HEAD and RELENG_6) Approved by: re MFC after: 1 month |
| H A D | tcp_var.h | |
| H A D | tcp_reass.c | |
| H A D | tcp_input.c | diff 166405 Thu Feb 01 16:32:13 MST 2007 andre Auto sizing TCP socket buffers. 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. New sysctls 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) Tested by: many (on HEAD and RELENG_6) Approved by: re MFC after: 1 month |
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