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Re: net.core.rmem / net.core.wmem



On Thu, 28 Feb 2008, Oliver Falk wrote:
Debian 4.0:
net.core.wmem_default = 109568
net.core.rmem_default = 109568
net.core.wmem_max = 131071
net.core.rmem_max = 131071

SuSE 10:
net.core.wmem_default = 262144
net.core.rmem_default = 262144
net.core.wmem_max = 2097152
net.core.rmem_max = 2097152

Fedora 8:
net.core.wmem_default = 124928
net.core.rmem_default = 124928
net.core.wmem_max = 131071
net.core.rmem_max = 131071

SuSE does set other values in sysctl.conf. There must be a reason to do
so, don't you think?

What does make sense? Does anyone have experimented with these and other
(related) values ? Does anyone have experience with sysctl values in
pure gigabit ethernet environments?

These values set the socket buffer defaults for all protocols. In practise, these values are not very interesting. The more interesting values are net.ipv4.tcp_rmem and net.ipv4.tcp_wmem which override the net.core.[rw]mem* socket buffer values for TCP.

For performance tuning especially in high-RTT environments, I'd recommend starting reading here and also looking at the references section:

http://kb.pert.geant2.net/PERTKB/LinuxOSSpecific

--
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings


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