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

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Date:	Wed, 06 Jun 2012 19:05:04 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc:	Hiroaki SHIMODA <shimoda.hiroaki@...il.com>,
	Tom Herbert <therbert@...gle.com>,
	Denys Fedoryshchenko <denys@...p.net.lb>,
	netdev@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	jeffrey.t.kirsher@...el.com, davem@...emloft.net
Subject: Re: Strange latency spikes/TX network stalls on Sun Fire
 X4150(x86) and e1000e

On Wed, 2012-06-06 at 09:26 -0700, Jesse Brandeburg wrote:
> On Wed, 6 Jun 2012 Hiroaki SHIMODA <shimoda.hiroaki@...il.com> wrote:
> > Sorry for long delay. I'll post.
> > (I have no idea how to fix this problem as keeping TXDCTL.WTHRESH to 5)
> 
> I don't like changing WTHRESH wholesale because making the global change
> to WTHRESH on e1000e just to fix this one bug (likely specific to a
> particular chip/hardware) will adversely effect performance on many
> models supported by e1000e not demonstrating any problem.  We could
> possibly check something in for just ESB2LAN (S5000 chipset).
> 
> Other people (tom herbert) with this same chipset have been unable to
> reproduce this issue right?

Thats because Tom Herbert (and me on my T420s laptop)
dont have FLAG2_DMA_BURST in adapter->flags2

So it depends on some e1000e, not all...

You cant hold a TX completion indefinitely, this breaks BQL but also
other stuff.



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