Linux shaping packet loss

Nickola Kolev nikky at mnet.bg
Wed Dec 9 01:18:17 CST 2009


На Wed, 09 Dec 2009 06:38:31 +0000
gordon b slater <gordslater at ieee.org> написа:

> On Wed, 2009-12-09 at 08:02 +0200, Bazy wrote:
> 
> > Hi Chris,
> > 
> > Try setting txqueuelen to 1000 on the interfaces and see if you
> > still get a lot of packet loss.
> > 
> 
> Yes, good point and well worth a try. Rereading Chris's post about
> "250Mbps" and "forty queues", the "egress" could well be bumping the
> end of a default fifo line.
> 
> If 1000 is too high for your kit try pushing it upwards gradually from
> the default of 100 (?) but back off if you get drops or strangeness in
> ifconfig output on the egress i/f.

The default *is* 1000. From the ifconfig man page:

txqueuelen length

Set  the  length  of the transmit queue of the device. It is useful to
set this to small values for slower devices with a high atency (modem
links, ISDN) to prevent fast bulk transfers from disturbing interactive
traffic like telnet too much.

So, if you should touch it if and only if you want to have (supposedly)
finer grained control on queueing, as the hardware device also does
some reordering before it puts the data on the wire.

> I append grep-ped ifconfig outputs into a file every hour on a cron
> job until I'm happy that strangeness doesn't happen, they never do
> when you're watching sadly. 
> 
> TC problems aren't always about the TC itself, the physical interfaces
> are inherently part of the "system", as my long rambling 5am+
> up-all-night-over-ssh post about reseating NICs was trying to hint
> at.  
> 
> Nice one Bazy
> 
> Gord
> 
> 
> 
> 
> 


-- 
Regards,
Nickola




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