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Message-ID: <yq13787w1a3.fsf@oracle.com>
Date: Thu, 31 Aug 2017 23:22:44 -0400
From: "Martin K. Petersen" <martin.petersen@...cle.com>
To: Suganath Prabu Subramani <suganath-prabu.subramani@...adcom.com>
Cc: "Martin K. Petersen" <martin.petersen@...cle.com>,
linux-scsi@...r.kernel.org,
Sathya Prakash <Sathya.Prakash@...adcom.com>,
Kashyap Desai <kashyap.desai@...adcom.com>,
linux-kernel@...r.kernel.org,
Chaitra Basappa <chaitra.basappa@...adcom.com>,
Sreekanth Reddy <sreekanth.reddy@...adcom.com>,
linux-nvme@...ts.infradead.org
Subject: Re: [PATCH v4 00/14] mpt3sas driver NVMe support:
Hi Suganath,
> Let me explain - NVME device fast path is possible in two ways. IEEE
> SGL and PRP SGL. Due to h/w constraint we choose IEEE SGL only for
> smaller IO size. Both above is true h/w Fast Path and no firmware
> involvement.
> Agree with you. We are planning to see if we can keep only simple Fast
> Path using only PRP.
That would be great, thank you!
> Currently there is no performance issue for UNMAP translation in FW.
Good!
>> And yet patch 4 circumvents that statement by adding support for
>> encapsulated commands to bypass the FW translation...
>
> This path is not due to performance reason. User wants to interact
> with NVME drive in native NVME command for management.
Patch 4 states:
"This encapsulated NVMe command is used by applications to send direct
NVMe commands to NVMe drives or for handling unmap where the translation
at controller/firmware level is having performance issues."
--
Martin K. Petersen Oracle Linux Engineering
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