Changes between Version 5 and Version 6 of MultiHost

Timestamp:

May 27, 2007, 7:49:45 PM (18 years ago)

Author:

davea

Comment:

--

MultiHost

@@ +1 @@
+[[PageOutline]]
+
 = Increasing server capacity =
 
@@ -59 +61 @@
 }}}
 You can run scheduling servers on multiple hosts by running an instance of the feeder on each host, and including the URLs in your master file.
+
+== Increasing network performance ==
+
+For projects using "fast" links, or even for internal networks, there
+can be some performance gains from tuning system TCP settings.
+
+
+A few links:
+http://dsd.lbl.gov/TCP-tuning/background.html
+
+http://dsd.lbl.gov/TCP-tuning/linux.html
+
+http://proj.sunet.se/E2E/tcptune.html
+
+http://www.onlamp.com/pub/a/onlamp/2005/11/17/tcp_tuning.html?page=1
+
+http://www.psc.edu/networking/projects/tcptune/
+
+http://www.acc.umu.se/~maswan/linux-netperf.txt
+
+http://datatag.web.cern.ch/datatag/howto/tcp.html
+
+http://www.aarnet.edu.au/engineering/networkdesign/mtu/local.html
+
+http://www.hep.ucl.ac.uk/~ytl/tcpip/linux/txqueuelen/
+
+And for bonding multiple links/interfaces:
+
+http://www.linux-corner.info/bonding.html
+
+http://www.devco.net/archives/2004/11/26/linux_ethernet_bonding.php
+
+
+The short story is that you can greatly improve your data transfer rate
+over long internet links by increasing the system TCP tx and rx
+window/buffer values. Note also the comments in
+http://www.onlamp.com/pub/a/onlamp/2005/11/17/tcp_tuning.html?page=1
+about software set buffer sizes.
+
+For internal networks fully under your control, you can greatly increase
+transfer rates and reduce CPU overheads by using "Jumbo packets" with an
+MTU of 9000. (Most new switches should support that. Check further
+before trying to go any larger.)
+
+{{{
+Other comments are in this example /etc/sysctl.conf (for Linux 2.6.xx):
+
+# Run "sysctl -p" to effect any changes made here
+#
+# TCP tuning
+# See:
+# http://www.onlamp.com/pub/a/onlamp/2005/11/17/tcp_tuning.html?page=1
+#
+# optimal TCP buffer size for a given network link is double the value
+for delay times bandwidth:
+# buffer size = 2 * delay * bandwidth
+# For example, assume a 100Mbits/s link between California and the
+United Kingdom, an RTT of 150ms. The optimal TCP buffer size for this
+link is 1.9MBytes
+#
+# increase TCP maximum buffer size
+# Example for 16 MBytes
+#net.core.rmem_max = 16777216
+#net.core.wmem_max = 16777216
+
+# For a 10Mbits/s link and worst case is Australia at 350ms RTT, so
+1MByte is more than enough
+# Linux 2.6.17 (later?) defaults to 4194304 max, so match that instead...
+net.core.rmem_max = 4194304
+net.core.wmem_max = 4194304
+
+# increase Linux autotuning TCP buffer limits
+# min, default, and maximum number of bytes to use
+# Example for 16 MBytes
+#net.ipv4.tcp_rmem = 4096 87380 16777216
+#net.ipv4.tcp_wmem = 4096 65536 16777216
+
+# Scaled for 4MByte:
+net.ipv4.tcp_rmem = 4096 87380 4194304
+net.ipv4.tcp_wmem = 4096 49152 4194304
+
+# Notes:
+#
+# Defaults:
+# net.ipv4.tcp_rmem = 4096        87380   174760
+# net.ipv4.tcp_wmem = 4096        16384   131072
+# net.ipv4.tcp_mem = 49152        65536   98304
+#
+# Do not adjust tcp_mem unless you know exactly what you are doing.
+# This array (in units of pages) determines how the system balances the
+# total network buffer space against all other LOWMEM memory usage. The
+# three elements are initialized at boot time to appropriate fractions
+# of the available system memory and do not need to be changed.
+#
+# You do not need to adjust rmem_default or wmem_default (at least not
+# for TCP tuning). These are the default buffer sizes for non-TCP sockets
+# (e.g. unix domain and UDP sockets).
+#
+#
+# Also use for example:
+# /sbin/ifconfig eth2 txqueuelen 2000
+#
+# The default of 1000 is inadequate for long distance, high throughput
+pipes.
+# For example, a rtt of 120ms at Gig rates, a txqueuelen of at least
+10000 is recommended.
+#
+# txqueuelen should not be set too large for slow links to avoid
+excessive latency,
+#
+# If you are seeing "TCP: drop open request" for real load (not a DDoS),
+# you need to increase tcp_max_syn_backlog (8192 worked much better than
+# 1024 on heavy webserver load).
+#
+# If you see stuff like "swapper: page allocation failure. order:0,
+mode:0x20"
+# you definately need to increase min_free_kbytes for the virtual memory.
+#
+#
+# All tcp settings listed by
+# sysctl -a | fgrep tcp
+#
+# Run "sysctl -p" to effect any changes made here
+}}}