netdev - Re: Strange latency spikes/TX network stalls on Sun Fire X4150(x86) and e1000e

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Message-ID: <1337589620.3361.23.camel@edumazet-glaptop>
Date:	Mon, 21 May 2012 10:40:20 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Denys Fedoryshchenko <denys@...p.net.lb>
Cc:	Tom Herbert <therbert@...gle.com>, netdev@...r.kernel.org,
	e1000-devel@...ts.sourceforge.net, jeffrey.t.kirsher@...el.com,
	jesse.brandeburg@...el.com, davem@...emloft.net
Subject: Re: Strange latency spikes/TX network stalls on Sun Fire
 X4150(x86) and e1000e

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.



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