Re: VI_GM_FAST_RDMA

Hi,

On Wed, 2004-05-19 at 05:14, Ting Zheng wrote:
> I am programming GM-VI now and I heard, there is a special option: 
> VI_GM_FAST_RDMA for compiling, so that the efficiency of RDMA opertaions 
> could be improved.
> What should I pay attention to, if I use this option?

If you compile with  -DVI_GM_FAST_RDMA,  yes the RDMA write operations
wil be faster.  However, there will be no remote memory handle checking
(as required by the spec), and you will fail a couple of tests in the VI
Intel Conformance Test Suite.

VI-GM is required to pass the VI Intel Conformance Test Suite; thus we
do advertise this shortcut.

For further details, refer to the following Myrinet FAQ entry (and
specifically this excerpt)

  http://www.myri.com/cgi-bin/fom?file=178

True RDMA operations in VI-GM are not possible with GM because GM has no
concept of memory handle protection. This concept should be added to the
GM firmware to avoid the rendez-vous, checking the remote memory handle
directly on the Myrinet card on the remote side.

There is no plan to add this functionality to GM.

Feel free to contact us at [email protected] if you have further questions.

Susan
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Susan Blackford
Member of Technical Staff
Myricom Inc.
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