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

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Date:	Fri, 25 May 2012 08:22:18 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	Denys Fedoryshchenko <denys@...p.net.lb>, netdev@...r.kernel.org
Subject: Re: Strange latency spikes/TX network stalls on Sun Fire
 X4150(x86) and e1000e

On Thu, 2012-05-24 at 23:01 -0700, Tom Herbert wrote:
> I think there is a potential problem in that netdev_tx_completed could
> be called multiple times for the same interrupt, for example if napi
> poll routine completes it's budget and is scheduled again and some new
> packets are completed.  We're looking at a solution to this.
> 
> Denys, can you try to increase the netdev budget to see if that has an effect?

TX completion has no budget, I am not sure what you mean.

e1000e driver indeed has a limit : It cannot clean more than
tx_ring->count frames per e1000_clean_tx_irq() invocation.

But with BQL, this should not happen ?

# ethtool -g eth0
Ring parameters for eth0:
Pre-set maximums:
RX:		4096
RX Mini:	0
RX Jumbo:	0
TX:		4096
Current hardware settings:
RX:		256
RX Mini:	0
RX Jumbo:	0
TX:		256


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