tcptuning
====== Differences ====== This shows you the differences between two versions of the page.
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tcptuning [2011/04/23 00:13] sbwood |
tcptuning [2011/06/11 00:14] (current) sbwood |
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| ====== TCP Tuning ====== | ====== TCP Tuning ====== | ||
| - | |||
| By default, Centos used the following TCP parameters: | By default, Centos used the following TCP parameters: | ||
| - | <code> | + | One can use "sysctl -w" to change these parameters. In order for changes to persist after reboot, one needs to edit "/etc/sysctl.conf" (typically as root). |
| + | |||
| + | Click [[http://www.frozentux.net/ipsysctl-tutorial/ipsysctl-tutorial.html#AEN454|here]] for a description of all of these parameters. | ||
| + | |||
| + | Other helpful sites: | ||
| + | [[http://www.speedguide.net/articles/linux-tweaking-121 | SpeedGuide.net]] | ||
| + | |||
| + | [[http://www.psc.edu/networking/projects/tcptune/ | PSC High Performance]] | ||
| + | |||
| + | <code> | ||
| + | |||
| $ sysctl -a | $ sysctl -a | ||
| Line 71: | Line 80: | ||
| </code> | </code> | ||
| - | **net.core.rmem_max**: | + | **net.core.rmem_max**: Maximum TCP receive window. FasterData recommends 16MB (**16777216**) for 10G paths with a few parallel streams, or 32MB for very long end-to-end 10G or 40G paths. |
| - | **net.core.wmem_max**: | ||
| - | **net.ipv4.tcp_rmem**: | + | **net.core.wmem_max**: Maximum TCP Send Window. FasterData recommends 16MB (**16777216**) for 10G paths with a few parallel streams, or 32MB for very long end-to-end 10G or 40G paths. |
| - | **net.ipv4.tcp_wmem**: | + | **net.ipv4.tcp_rmem**: Memory reserved for TCP receive buffers (reserved memory per connection default). Format: min, default, and max number of bytes to use. FasterData recommends **4096 87380 16777216** and only changing the 3rd parameter to use more than 16MB. |
| - | **net.core.netdev_max_backlog**: | + | **net.ipv4.tcp_wmem**: Memory reserved for TCP send buffers (reserved memory per connection default). Format: min, default, and max number of bytes to use. FasterData recommends **4096 87380 16777216** and only changing the 3rd parameter to use more than 16MB. |
| + | |||
| + | **net.core.netdev_max_backlog**: FasterData recommends **30000**, and increasing for 10G or faster links. | ||
| + | |||
| + | **net.ipv4.tcp_congestion_control**: according to [[http://fasterdata.es.net/fasterdata/host-tuning/linux/expert/|FasterData]], **htcp** (Hamilton TCP) or **cubic** is better for long, high speed links. | ||
| + | |||
| + | <code> | ||
| + | sysctl -w net.core.rmem_max=16777216 | ||
| + | sysctl -w net.core.wmem_max=16777216 | ||
| + | sysctl -w net.ipv4.tcp_rmem=4096 87380 16777216 | ||
| + | sysctl -w net.ipv4.tcp_wmem=4096 87380 16777216 | ||
| + | sysctl -w net.core.netdev_max_backlog=30000 | ||
| + | sysctl -w net.ipv4.tcp_congestion_control=htcp | ||
| + | </code> | ||
| + | |||
| + | [[http://www.speedguide.net/articles/linux-tweaking-121|SpeedGuide]] also recommends the following settings: | ||
| + | <code> | ||
| + | sysctl -w net.ipv4.tcp_sack = 1 | ||
| + | sysctl -w net.ipv4.tcp_window_scaling = 1 | ||
| + | sysctl -w net.ipv4.tcp_timestamps = 0 | ||
| + | </code> | ||
| + | Although setting the tcp_timestamps = 0 is controversial (and we chose to leave it enabled): FasterData points out that some alternative congestion control protocols require accurate timestamps. | ||
| + | |||
| + | The Ethernet cards we are testing with are: | ||
| + | <code> | ||
| + | eth1: Tigon3 [partno(BCM95704A7) rev 2003 PHY(5704)] (PCI:66MHz:64-bit) 10/100/1000Base-T Ethernet 00:e0:81:2c:5e:bd | ||
| + | eth1: RXcsums[1] LinkChgREG[0] MIirq[0] ASF[0] WireSpeed[1] TSOcap[1] | ||
| + | eth1: dma_rwctrl[763f0000] dma_mask[64-bit] | ||
| + | </code> | ||
| + | |||
| + | Also, we will experiment with the MTU (using Jumbo frames of size 9000): | ||
| + | |||
| + | <code> | ||
| + | ifconfig eth1 mtu 9000 | ||
| + | </code> | ||
| + | |||
| + | And to test: | ||
| + | <code> | ||
| + | ping -M do -s 8992 192.168.0.3 | ||
| + | </code> | ||
tcptuning.1303517581.txt.gz · Last modified: 2011/04/23 00:13 by sbwood
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