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: Fri, 25 May 2012 19:18:15 +0200
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Cc: Denys Fedoryshchenko <denys@visp.net.lb>, netdev@vger.kernel.org
To: Tom Herbert <therbert@google.com>
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On Fri, 2012-05-25 at 09:59 -0700, Tom Herbert wrote:
> > TX completion has no budget, I am not sure what you mean.
> >
> Right, it's the budget on RX that can be a factor.  TX completion is
> done from the NAPI poll routine, so if RX does not complete the NAPI
> is rescheduled and TX completion is done again for the same HW
> interrupt.
> 
> We need to remove the constraint that netdev_completed can only be
> called once per interrupt...

Not clear where is this constraint in the code.

Under heavy load, we can be in a loop situation, one cpu serving NAPI
for a bunch of devices (no more hardware interrupts are delivered since
we dont re-enable them at all)