[ewg] Status of SDP? (and ib_sdp patch for Linux-3.4.x)

[Doug Ledford]

On 04/23/2012 01:25 PM, richard Croucher wrote:
> What's makes SDP so useful and why is will be sorely missed is that it
> does not require users to refactor existing TCP socket code, or even be
> in possession of the source code for that matter.

Neither does IPoIB, and there are no legal questions about the usability
of IPoIB.

>   Simply preloading
> libsdp is all need to do to convert that old, cranky tcp program to run
> (almost) native over InfiniBand. 

SDP and IPoIB are not that far apart on a well tuned IPoIB setup.

> SDP is used as a wire protocol rather than a API.  There are several
> contending API's out there, including Bob Russell's Extended Socket API
> which could be candidates, but I would like to see the concept of the
> preload preserved. It's been a powerful factor in getting InfiniBand
> adoption.

It's been a nice stop gap measure to help those apps that needed a boost
larger than IPoIB (although not greatly so) while waiting on a native
RDMA version of the application.  If the app truly needed the
performance of RDMA, they had plenty of time to port over to it.  If
they didn't deem porting important enough, then they should be able to
exist with just IPoIB.  There is very little impetus to maintain two
versions of software to make sockets based apps work on RDMA fabrics
when the relative gain of one over the other isn't that high and it has
legal encumbrances to negate the positive performance benefit.

-- 
Doug Ledford <dledford at redhat.com>
              GPG KeyID: 0E572FDD
	      http://people.redhat.com/dledford


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