Re: [PATCH v4 00/14] mpt3sas driver NVMe support:
From: Martin K. Petersen
Date: Thu Aug 31 2017 - 23:23:32 EST
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