netdev - Re: Bug#565404: linux-image-2.6.26-2-amd64: atl1e: TSO is broken

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Date:	Wed, 3 Apr 2013 02:00:20 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	"Huang, Xiong" <xiong@....qualcomm.com>
Cc:	Ben Hutchings <ben@...adent.org.uk>,
	Anders Boström <anders@...insight.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"565404@...s.debian.org" <565404@...s.debian.org>
Subject: Re: Bug#565404: linux-image-2.6.26-2-amd64: atl1e: TSO is broken

On Tue, Apr 02, 2013 at 10:23:54PM +0000, Huang, Xiong wrote:
> 
> > 
> > On Tue, Apr 02, 2013 at 09:51:12PM +0000, Huang, Xiong wrote:
> > > > The error vanishes as soon as I put a gso size limit of
> > > > MAX_TX_BUF_LEN in the driver. MAX_TX_BUF_LEN seems to be
> > arbitrary
> > > > set to 0x2000. I can even raise it to 0x3000 and don't see any tcp
> > > > retransmits. Do you have an advice on how to size this value (e.g. should
> > we switch to the windows values)?
> > > >
> > >
> > > Would you try 0x4000 ? because the buffer-length in TX descriptor is 14bits,
> > 0x4000 exceeds max value.
> > > Do you find any bug/issue on the code that calculate the length for each TX
> > descriptor ?
> > 
> > Setting MAX_TX_BUF_LEN to 0x4000
> > 
> > [ 8949.833750] ATL1E 0000:04:00.0 p33p1: NIC Link is Up <100 Mbps Full
> > Duplex> [ 8949.833783] IPv6: ADDRCONF(NETDEV_CHANGE): p33p1: link
> > becomes ready [ 8960.861557] ATL1E 0000:04:00.0 p33p1: PCIE DMA RW error
> > (status = 0x5000400) [ 8960.866879] ATL1E 0000:04:00.0 p33p1: NIC Link is Up
> > <100 Mbps Full Duplex> [ 8961.095266] ATL1E 0000:04:00.0 p33p1: PCIE DMA
> > RW error (status = 0x5000400) [ 8961.100791] ATL1E 0000:04:00.0 p33p1: NIC
> > Link is Up <100 Mbps Full Duplex>
> > 
> Hannes,  Thanks for your testing !
> 
>  simply revising MAX_TX_BUF_LEN to 0x4000 will cause incorrect TX configuration...
> I mean you can try to put a gso size limit of 0x4000 (or 0x5000)....

I tested both values with multi-gigabyte nfsv4 traffic and both values are ok.
If I understand you correctly 0x4000 is a safe limit?

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