[nzlug] iptables problems... and ssh/tcp kernel tuning

[Glenn Enright]

On 20/02/2008, Steve Holdoway <steve at greengecko.co.nz> wrote:
> I'm having a bit of a problem with this machine. I think the root cause of the problem is this line off netstat -s:
>
> '173604 packets collapsed in receive queue due to low socket buffer' which becomes
> '185367 packets collapsed in receive queue due to low socket buffer' a couple of hours later.

net.ipv4.tcp_window_scaling = 1
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_rmem = 8192 873800 16777216
net.ipv4.tcp_wmem = 4096 655360 16777216

>The system just gets really laggy ( ping > 1 second instead of 170ms
), and throughput drops

I found the following interesting links after googling "collapsed in
receive queue". YMMV, and I'm sure you have done some similar maths,
but the article was fun to read anyway :). The vm/min_free_kbytes item
especially caught my eye. On my both my Ubuntu boxes it's set to 2495.

http://groups.google.co.uk/group/comp.protocols.tcp-ip/browse_thread/thread/2deb29908d02cc47/34a5d6c4e9d02d98
led to...
http://www.acc.umu.se/~maswan/linux-netperf.txt

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