[Gllug] socket buffer overrun

[Ben Fitzgerald]

On Wed, Oct 19, 2005 at 10:28:42AM +0100, Daniel P. Berrange wrote:
> On Wed, Oct 19, 2005 at 12:05:16AM +0100, Peter Grandi wrote:
Raising the 'tcp_rmem' should help, as 1GHz can theoretically do
<snip>

> The TCP receive/send buffers will auto-tune themselves. Those three
> values in tcp_rmem set the mimimum level, the initial and the max
> level. All connections start out at the initial level and then auto
> tune between the min/max limits. Thus when altering tcp_rmem/tcp_wmem
> one should typicall only change the 3 number - the max level. This
> allows connections which need it to autotune up to the higher buffer
> size, without wasting precious kernel memory on all other TCP connections
> on the box.

hi dan,

yes. we did end up doing this (though the problem is an application one
this hack works in the meantime!).

I should add that auto-tuning is not always set, at least according to:

http://www.csm.ornl.gov/~dunigan/netperf/auto.html

  "Autotuning is disabled if the application does its own setsockopt()
  for TCP's SND/RCVBUF"

The above relates to 2.4 kernel so this may have changed in 2.6?

cheers,

ben.

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