Date:	Wed, 22 Sep 2010 13:35:10 -0700
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	Bernard Metzler <BMT@...ich.ibm.com>
Cc:	linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	Matthew Wilcox <matthew@....cx>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: software iwarp stack update

On Wed, 2010-09-22 at 10:19 +0200, Bernard Metzler wrote:
> Earlier this year, we announced the availability of an open source,
> full software implementation of the iWARP RDMA protocol stack - see
> my email "software iwarp stack" from March 14th at the linux-rdma list
> (http://www.mail-archive.com/linux-rdma@vger.kernel.org/msg02940.html)
> While since then working on performance and stability, we provided
> some source code updates. Current user and kernel code is available at
> gitorious.org/softiwarp. Please see the CHANGES file in the
> kernel/ directory for a summary of the most recent changes.
> 
> For more convenient testing, the latest update now allows for a
> stand-alone build of the kernel module without full kernel source
> code access. We tested the code with kernel version 2.6.34. If
> you are interested in a full software RDMA stack on Ethernet,
> please try it out.
> 
> In the hope of providing useful information, I put
> netdev@...r.kernel.org on copy. Subscribers of this list,
> please put me on private cc in case you reply or comment, since
> I am not subscribed to the list.
> We would be more than happy if you netdev folks would consider
> a hardware independent RDMA kernel service as something useful and
> potentially to be integrated into the mainline network stack.
> 
> Why might it be useful?
> A software RDMA stack makes the semantic advantages of
> asynchronous and one-sided communication available while obsoleting
> the need to deploy dedicated RDMA hardware or any protocol offloading
> (while not matching the lowest delay numbers of real RDMA hardware).
> Implementing the IETF's iWARP protocol stack on top of TCP kernel
> sockets, softiwarp integrates with the open fabrics environment
> and thus exports the RDMA kernel and user verbs interface.
> 
> The efficiency of the Linux TCP/IP network stack together with intrinsic
> advantages of the RDMA communication model (async. posting of work
> and reaping of work completions, transfer of send buffer ownership
> to the kernel which enables zero copy transmit, peer data placement
> without application scheduling, one-sided remote read operations etc.)
> can result in improved application-to-application performance and
> less CPU load, while using the unchanged kernel TCP stack.
> 
> A software RDMA stack might promote wider RDMA deployment,
> since when using the host TCP stack, it enables RDMA semantic
> independent of dedicated hardware. softiwarp peers with real
> RNICs (tested with Chelsio's T3 adapter).
> 
> softiwarp is still work in progress and we are very thankful for any
> suggestions/comments/bug reports. Please advise how we should proceed
> to bring the stack further to your attention. Would it be useful to
> provide patches against the current stable kernel version or the next
> release candidate?
> 

Hi Bernard,

So what I would recommend doing here to make things more appealing to
DaveM and other interested NetDev folks would be to clone a seperate
tree from the net-2.6.git or net-next-2.6.git repositories and include
the softiwarp/kernel.git code into a fresh 'in-kernel' clone tracking
the latest netdev code, and then keep git rebase'ing against DaveM's
last changes and update your local tree to the lastest netdev code.

Of course you will want to remove all of the 'out of tree' LINUX_VERSION
build macros and any other legacy bits to follow mainline kernel
convention for your 'in-kernel' softiwarp tree.

Best,

--nab


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