[Users] Re: TCP packets lost?

[Vitaliy Gusev]

On 7 January 2008 13:01:24 Max Deineko wrote:
> Marcin Owsiany <marcin at owsiany.pl> wrote:
> > On Mon, Jan 07, 2008 at 07:55:43AM +0000, Max Deineko wrote:
> >> My first guess would have been that when the server is busy serving an
> >> expensive request, the tcp rcv buffer would get full and packets would
> >> get dropped.  But wouldn't tcpdump not be able to see them then?
> 
> > http://forum.openvz.org/index.php?t=msg&goto=21592
> >
> > My theory is that when the (receive buffer size / current connections)
> > is too small for the window size, then kernel gets itself into a state
> > where it's impossible to recover a connection.
> 
> Thanks a lot.  I already had found the thread and tried increasing
> tcp_rmem size, which hung the webserver completely (maybe it was a litte
> too big ;), but I'm still experimenting with the settings.
> 
> Of course there might be a problem with other server components, and I'm
> not really a networking expert, it's just that the tcp flow doesn't look
> like what I'd expect it to.

Please show files: /proc/net/netstat, /proc/net/snmp ( inside VE)

Have you seen any suspicious messages in dmesg related to this issue?

> 
> So is the behaviour I see normal or is there really something wrong at
> this level already?  Even if one assumed that userland components were
> broken and went haywire sometimes?
> 
> Thanks, Max.
> 
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-- 
Thanks,
Vitaliy Gusev