[juneau-lug] Re: Web100 servers

On Sunday 24 September 2006 20:46, Kevin Miller wrote:

>
> Interesting.  I ran it at Santa Cruz and it said I need to increase my
> receive buffers (currently 128 Kb).  Searching around I noted that
> recent kernels (2.6.6+, mines 2.6.13+) should auto tune the buffer size.
>  Apparently it isn't.  So how do I increase the receive buffers to
> somewhere around 640 Kb?
>
> ...Kevin

That might be your DSL modem getting in the way.  Try it from work.

The settings will be in /proc/sys/net/ somewhere.

This link has a list, but it looks dated:

http://www-128.ibm.com/developerworks/linux/library/l-hisock.html

Look for "Table 1. Kernel tunable parameters for TCP/IP stack performance"

The values look like they are in bytes.

So to set your receive window size to 8MB, you'd want to 
set /proc/sys/net/ipv4/rmem_default to 1015808

(The example shown looks like 108kb.)

Except on my system (2.6.17) I don't have rmem_default.  But I do have 
tcp_rmem.

And my default values for tcp_rmem are considerably higher than the IBM 
examples:
IBM:
4096    87380   174760            (4k min, 85kb def, 170kb max)
4096    87380   4194304          (4k min, 85kb def, 4MB max)



It would take some experimenting.  Luckily "cat proc ..." lends itself to easy 
experiments.

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