Subject: [Ips] Re: iSER parameter resources

From: "Alex Nezhinsky" <[email-masked]>
Date: Thu, 17 Mar 2005 21:02:06 +0200

Mike,

I'd like to comment on your answer to Bob's questions and proposals:
> [[mk
> The Datamover Architecture as described in the DA draft, upon 
> which the iSER/iSCSI interface is based, specify the required 
> exchanges at the datamover interface to separate the role of 
> the data mover (iSER) from the iSCSI layer.  Note that it 
> does not preclude other implementation specific exchanges 
> between the two layers to ensure correct and efficient 
> operation.  Consistent with this philosophy, I don't think it 
> is necessary to add a new operational primitive in this case 
> for the temporal control of resources at the implementation level. 
> mk]]

Two of the suggested primitives, namely Release_Control and
Send_Complete_Notify must receive a handle (of whatever nature) for the
operation reported as complete. In case of Release_Control this handle
refers to Control_Notify and its associated received PDU descriptors and
data, in case of Send_Complete_Notify it refers to Send_Control and its
associated sent PDU descriptors and data. 

Thus, if an implementation chooses to define these primitives, a new
kind of entity is introduced. This changes the way Control_Notify and
Send_Control work - now they have to communicate the handles, either the
caller supplies one, or the callee returns one. It would seem natural to
me to find these possibilities described in the corressponding
Operational Primitive sections of the DA spec, if only as a passing note
about the typical resource management problems and a (possible) way to
handle them - for example by having the aforementioned handles defined
as optional parameters (or return values) and explaining how these
parameters may be used if necessary.
  
I believe that Enable_Notify in Get_Data/Put_Data is a good example for
such parameter definition. It does not restrict implementors, while
clearly shows that there may be need to communicate completions.

Thanks,
Alexander Nezhinsky

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From: Mike Ko <[email-masked]>
Date: Thu, 17 Mar 2005 16:28:45 -0800

Alex,

The Notify_Enable qualifier for Put_Data and Get_Data is necessary because 
the requested data transfer has been transformed into RDMA operations 
which are handled by the RNIC.  Knowing when the RDMA operations are 
complete is useful to the iSCSI layer in determining when a SCSI Response 
PDU should be sent.  Note that the need for Data_Completion_Notify comes 
from the fact that R2T and SCSI Data-in PDUs have been transformed into 
RDMA operations, not because of resource management.

Mike
To:     "Mike Ko" <[email-masked]>
cc:     <[email-masked]>, "Robert D. Russell" <[email-masked]> 
Subject:        [Ips] Re: iSER parameter resources

Mike,

Thanks,
Alexander Nezhinsky