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From: Gil Bloch (gil_at_[hidden])
Date: 2006-09-14 10:37:01


Gleb Natapov wrote:
> On Wed, Sep 13, 2006 at 07:50:02PM +0530, Sunil Patil wrote:
>
>> Hi,
>>
>> This is somewhat irrelevant question. It was said that in order delivery is
>> a feature of Mellanox HCA and not part of IB spec. Is this true for UD type
>> QPs also for which IB spec says that "in order delivery" is not guaranteed ?
>>
>>
> UD is unreliable datagram, Nothing is guaranteed about it. The Mellanox HCA
> guarantees inorder delivery of RDMAed data.
>

InfniBand specification guarantees no placement ordering, but delivery
ordering (messages are delivered in the order sent) for reliable
transport. For un-reliable, since some packets could be lost in the
fabric, those packet will not be delivered, thus no ordering guaranteed.
Mellanox HCAs guarantee in-order placement between packets in reliable
transports, as well as in-packet data placement (last byte of the packet
payload will be written last to the memory).
For un-reliable transport, the ordering between packets can not be
guaranteed (again, since some packets could be lost in the fabric) but
the in-packet placement ordering is guaranteed.
>
>> Regards
>> Sunil
>>
>>
>>
>>
>> On 9/13/06, Open MPI <bugs_at_[hidden]> wrote:
>>
>>> #366: OpenIB on IA64: we should disable small message RDMA
>>>
>>> -------------------------+--------------------------------------------------
>>> Reporter: jsquyres | Owner: gleb
>>> Type: defect | Status: new
>>> Priority: major | Milestone: Open MPI 1.1.2
>>> Version: trunk | Resolution:
>>> Keywords: openib, ia64 |
>>>
>>> -------------------------+--------------------------------------------------
>>> Comment (by gleb):
>>>
>>> Actually in order delivery is a feature of Mellanox HCA and not part of
>>> the IB/iWarp spec.[[BR]]
>>> See [http://openib.org/pipermail/openib-general/2006-August/025305.html]
>>> for discussion about this. So use_eager_rdma flag is a good candidate to
>>> be put in mca-btl-openib-hca-params.ini file.
>>>
>>> --
>>> Ticket URL: <http://svn.open-mpi.org/trac/ompi/ticket/366>
>>> Open MPI <http://www.open-mpi.org/>
>>>
>>> _______________________________________________
>>> bugs mailing list
>>> bugs_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/bugs
>>>
>>>
>>>
>
>
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>> devel_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>
>
> --
> Gleb.
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>