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Subject: Re: [PATCH V6 6/9] isert: Rename IO functions to more descriptive
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To: Sagi Grimberg <sagig@dev.mellanox.co.il>,
        Christoph Hellwig <hch@infradead.org>
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From: Steve Wise <swise@opengridcomputing.com>
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Date: Sun, 26 Jul 2015 15:15:34 -0500
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On 7/26/2015 12:40 PM, Sagi Grimberg wrote:
>
>>> Ideally, the post contains a chain of all 4 registrations and the
>>> rdma_read (and an opportunistic good scsi response).
>>
>> Just to be clear: This example is for IB only, correct?  IW would
>> require rkeys with REMOTE_WRITE and 4 read wrs.
>
> My assumption is that it would depend on max_sge_rd.
>

yea.

> IB only? iWARP by definition isn't capable of doing rdma_read to
> more than one scatter? Anyway, we'll need to calculate the number
> of RDMA_READs.
>

The wire protocol limits the destination to a single stg/to/len (aka 
rkey/addr/len).  Devices/fw/sw could implement some magic to support a 
single stg/to/len that maps to a scatter gather list of stags/tos/lens.

>> And you're ignoring invalidation wrs (or read-with-inv) in the 
>> example...
>
> Yes, didn't want to inflate the example too much...