From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: Strange latency spikes/TX network stalls on Sun Fire
 X4150(x86) and e1000e
Date: Mon, 21 May 2012 10:40:20 +0200
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Cc: Tom Herbert <therbert@google.com>, netdev@vger.kernel.org,
	e1000-devel@lists.sourceforge.net, jeffrey.t.kirsher@intel.com,
	jesse.brandeburg@intel.com, davem@davemloft.net
To: Denys Fedoryshchenko <denys@visp.net.lb>
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On Mon, 2012-05-21 at 10:30 +0200, Eric Dumazet wrote:
> On Mon, 2012-05-21 at 11:06 +0300, Denys Fedoryshchenko wrote:
> 
> > Not sure it is a lot of time, after all it is 2 x core quad machine, 
> > should be enough fast for pings.
> > It will cause stalls on small packets even more seems.
> > 
> > Tested latest git, net-next, still the same, stalls.
> > hardware latency detector are silent by the way, so there is no 
> > significant SMI.
> > 
> 
> I am trying to reproduce your problem here with no luck yet.
> 
> I wonder of softirq are correctly scheduled on your machine
> 

By the way, fact you have 8 cpus is irrelevant.

Only one cpu has queued the NET_TX_SOFTIRQ softirq (serviced by
net_tx_action())


If this cpu is busy servicing other stuff, no other cpu will help.