net.core.rmem / net.core.wmem

[Pekka Savola]

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